Thoracoabdominal aortic aneurysms (TAAA) involve the aorta in the chest and abdomen. As such, major branch arteries to the head, arms, spinal cord, intestines, and kidneys may originate from the aneurysm. An endovascular repair of a TAAA is only possible if blood flow to these critical arteries is preserved. Hybrid procedures offer one option, but a more direct approach involves the use of a branched endograft. However, the complex anatomy associated with the supra-aortic vessels is particularly difficult to accommodate with branched endograft devices. [ 17 ]  Dr. Timothy Chuter pioneered this approach, with a completely endovascular solution. After partial deployment of the main body of an endograft, separate endograft limbs are deployed from the main body to each major aortic branch. This procedure is long, technically difficult, and currently only performed in a few centers.
When the aneurysm begins above the renal arteries, neither fenestrated endografts nor "EndoAnchoring" of an infrarenal endograft is useful (an open surgical repair may be necessary). Alternatively, a "branched" endograft may be used. A branched endograft has graft limbs that branch off of the main portion of the device to directly provide blood flow to the kidneys or the visceral arteries. [ 18 ] [ 19 ]


On occasion, there is inadequate length or quality of the proximal or distal aortic neck. In these cases, a fully minimally invasive option is not possible. One solution, however, is a hybrid repair, which combines an open surgical bypass with EVAR or TEVAR. In hybrid procedures, the endograft is positioned over major aortic branches. While such a position would normally cause problems from disruption of blood flow to the covered branches (renal, visceral, or branches to the head or arms), the prior placement of bypass grafts to these critical vessels allowed the deployment of the endograft at a level that would otherwise not be possible. [ citation needed ]


If a patient has calcified or narrow femoral arteries that prohibit the introduction of the endograft transfemorally, an iliac conduit may be used. This is typically a piece of PTFE that is sewn directly to the iliac arteries, which are exposed via an open retroperitoneal approach. The endograft is then introduced into the aorta through the conduit. [ citation needed ]


In patients with thoracic aortic disease involving the arch and descending aorta, it is not always possible to perform a completely endovascular repair. This is because head vessels of the aortic arch supplying blood to the brain cannot be covered and for this reason, there is often an inadequate landing zone for stent-graft delivery. A hybrid repair strategy offers a reasonable choice for treating such patients. A commonly used hybrid repair procedure is the "frozen elephant trunk repair". [ 20 ]  This technique involves midline sternotomy. The aortic arch is transected and the stent-graft device is delivered in an ante-grade fashion in the descending aorta. The aortic arch is subsequently reconstructed and the proximal portion of the stent-graft device is then directly sutured into the surgical graft. Patients with anomalies of the arch and some disease extension into the descending aorta are often ideal candidates. Studies have reported successful use of hybrid techniques for treating Kommerell diverticulum [ 21 ]  and descending aneurysms in patients with previous coarctation repairs. [ 22 ] [ 23 ]


In addition, hybrid techniques combining both open and endovascular repair are also used in managing emergency complications in the aortic arch, such as retrograde ascending dissection and endoleaks from previous stent grafting of descending aorta. A "reverse frozen elephant trunk repair" is shown to be particularly effective. [ 24 ]


The complications of EVAR can be divided into those that are related to the repair procedure and those related to the endograft device. For example, a  myocardial infarction  that occurs immediately after the repair is normally related to the procedure and not the device. By contrast, the development of an endoleak from degeneration of endograft fabric would be a device-related complication. [ 19 ]


Durability and problems such as 'endoleaks' may require careful surveillance and adjuvant procedures to ensure the success of the EVAR or EVAR/hybrid procedure. CT angiography (CTA) imaging has, in particular, made a key contribution to planning, success, durability in this complex area of vascular surgery. [ citation needed ]


A major cause of complications in EVAR is the failure of the seal between the proximal, infra-renal aneurysm neck and the endovascular graft. [ 27 ] [ 28 ] [ 29 ]  Risk of this form of failure is especially elevated in adverse or challenging proximal neck anatomies, where this seal could be compromised by unsuitable geometric fit between the graft and vessel wall, as well as instability of the anatomy. [ 30 ] [ 31 ] [ 32 ]  New recent techniques have been introduced to address these risks by utilizing a segment of the supra-renal portion of the aorta to increase the sealing zone, such as with fenestrated EVAR, chimneys and snorkels. [ 33 ]  These techniques may be suitable in certain patients with qualifying factors, e.g., configuration of renal arteries, renal function.  However, these are more complex procedures than standard EVAR and may be subject to further complications. [ 34 ] [ 35 ] [ 36 ]


An approach that directly augments the fixation and sealing between the graft and aorta to mimic the stability of a surgical anastomosis is EndoAnchoring. [ 37 ] [ 38 ]  EndoAnchors are small, helically shaped implants that directly lock the graft to the aortic wall with the goal to prevent complications of the seal, especially in adverse neck anatomies. [ 39 ] [ 40 ]  These EndoAnchors may also be used to treat identified leaks between the graft and proximal neck. [ 41 ] [ 42 ] [ 43 ]


Arterial dissection, contrast-induced kidney failure, thromboembolizaton,  ischemic colitis , groin  hematoma , wound infection, type II endoleaks, myocardial infarction, congestive heart failure, cardiac arrhythmias, respiratory failure. [ citation needed ]


Endograft migration, aneurysm rupture, graft limb stenosis/kinking, type I/III/IV endoleaks, stent graft thrombosis, or infection. [ 44 ]  Device infection occurs in 1-5% of aortic prosthesis placements and is a life-threatening complication. [ 45 ]


An endoleak is a leak into the aneurysm sac after endovascular repair. Five types of endoleaks exist: [ 14 ]


Type I and III leaks are considered high-pressure leaks and are more concerning than other leak types. Depending on the aortic anatomy, they may require further intervention to treat. Type II leaks are common and often can be left untreated unless the aneurysm sac continues to expand after EVAR. [ 46 ]


Spinal cord injury is a devastating complication after aortic surgery, specifically for thoracoabdominal aortic aneurysm repair; severe injury could lead to urine and fecal incontinence, paresthesia and even paraplegia. [ 47 ]  The risk varies between studies with two metanalysis demonstrating a pooled incidence of spinal cord injury 2.2% [ 48 ]  and 11%. [ 49 ]  Predictive factors include increasing extent of coverage, hypogastric artery occlusion, prior aortic repair and perioperative hypotension. [ 50 ]  Spinal cord injury related to aortic repair occurs due to impaired blood flow to the spine after coverage of blood vessels, important to the blood circulation of the spine, namely intercostal- and lumbar arteries. [ 51 ]  Neuromonitoring appears to be effective in detecting perioperative spinal cord injury risk during TEVAR. While the incidence of spinal cord injury remains variable, identification of risk factors may guide clinical decisions, particularly in high-risk procedures. [ 52 ]  A few methods exist for potentially reversing spinal cord injury, if it arises, elevated blood pressure, increased oxygenation, blood transfusion and cerebrospinal fluid drainage.


Cerebrospinal fluid drainage is one of the adjunct methods used to reverse spinal cord injury. With increased drainage of spinal fluid, the intrathecal pressure decreases which allows for increase blood perfusion to the spine, possibly reversing the ischemic injury of the spinal tissue due to lessened blood supply. The benefits of this procedure have been established in open aortic repair [ 53 ]  and suggested in endovascular aortic repair. [ 47 ]


As compared to the traditional aortic repair, standard recovery after EVAR is faster with earlier ambulation. However, there is still risk of spinal cord injury early after the procedure. Patients who have undergone EVAR typically spend one night in the hospital to be monitored, although it has been suggested that EVAR can be performed as a same-day procedure. [ 54 ]


Patients are advised to slowly return to normal activity. There are no specific activity restrictions after EVAR, however, patients typically are seen by their surgeon within one month after EVAR to begin post-EVAR surveillance. [ citation needed ]


There is limited research looking at patients' experience of recovery after more complex and staged EVAR for thoracoabdominal aortic diseases. One qualitative study found that patients with complex aortic diseases struggle with physical and psychological setbacks, continuing years after their operations. [ 55 ]


Dr.  Juan C. Parodi  introduced the minimally-invasive endovascular aneurysm repair (EVAR) to the world and performed the first successful endovascular repair of an abdominal aortic aneurysm on 7 September 1990 in Buenos Aires on a friend of  Carlos Menem , the then President of Argentina. The first device was simple, according to Parodi: "It was a graft I designed with expandable ends, the extra-large Palmaz stent, a Teflon sheath with a valve, a wire, and the valvuloplasty balloon, which I took from the cardiologists." Parodi's first patient lived for nine years after the procedure and died from pancreatic cancer. [ 56 ] [ 57 ]
The first EVAR performed in the United States was in 1992 by Drs.  Frank Veith ,  Michael Marin ,  Juan Parodi  and  Claudio Schonholz  at  Montefiore Medical Center  affiliated with  Albert Einstein College of Medicine . [ citation needed ]


The modern endovascular device used to repair abdominal aortic aneurysms, which is bifurcated and modular, was pioneered and first employed by Dr. Timothy Chuter while a fellow at the  University of Rochester . [ 58 ]  The first clinical series of his device was published from Nottingham in 1994. [ 59 ]  The first endovascular repair of a ruptured abdominal aortic aneurysm was also reported from Nottingham in 1994. [ 60 ]


By 2003, four devices were on the market in the United States. [ 61 ]  Each of these devices has since been either abandoned or further refined to improve its characteristics  in vivo .


Women are known to have smaller aortas on average than men, so are potential candidates for AAA treatment at smaller maximum aneurysm diameters than men. [ citation needed ]


As immunosuppressive medications are known to increase the rate of aneurysm growth, transplant candidates are AAA repair candidates at smaller maximum aneurysm diameters than the general population. [ citation needed ]


Due to the expense associated with EVAR stent-graft devices and their specificity to human aortic anatomy, EVAR is not used in other animals. [ citation needed ]


Endovascular coiling  is an  endovascular  treatment for  intracranial aneurysms  and  bleeding  throughout the body. The procedure reduces blood circulation to an aneurysm or blood vessel through the implantation of detachable platinum wires, with the clinician inserting one or more into the blood vessel or aneurysm until it is determined that blood flow is no longer occurring within the space. It is one of two main treatments for cerebral  aneurysms, the other being  surgical clipping .


Endovascular coiling is typically used to treat  cerebral aneurysms . The main goal is prevention of rupture in unruptured aneurysms, and prevention of rebleeding in ruptured aneurysms by limiting blood circulation to the aneurysm space. Clinically, packing density is recommended to be 20-30% or more of the aneurysm's volume, typically requiring deployment of multiple wires. [ 1 ]  Higher volumes may be difficult due to the delicate nature of the aneurysm; intraoperative rupture rates are as high as 7.6% for this procedure. [ 2 ]  In ruptured aneurysms, coiling is performed quickly after rupture because of the high risk of rebleeding within the first few weeks after initial rupture. The patients most suitable for endovascular coiling are those with aneurysms with a small neck size (preferably <4 mm), luminal diameter <25 mm and those that are distinct from the parent vessel. [ 3 ]  Larger aneurysms are subject to compaction of coils, due to both looser packing densities (more coils are needed) and increased blood flow. Coil compaction renders them unsuitable as they are incapable of stemming blood flow. [ 4 ]  However, technological advances have made coiling of many other aneurysms possible as well.


A number of studies have questioned the efficacy of endovascular coiling over the more traditional surgical clipping. Most concerns involve the chance of later bleeds or other recanalization. [ 5 ] [ 6 ] [ 7 ]  Due to its less invasive nature, endovascular coiling usually presents faster recovery times than surgical clipping, with one study finding a significant decrease in probability of death or dependency compared to a neurosurgical population. [ 8 ]  Complication rates for coiling as well are generally found to be lower than microsurgery (11.7% and 17.6% for coiling and microsurgery, respectively). Despite this, intraoperative rupture rates for coiling have been documented as being as high as 7.6%. [ 2 ]  Clinical results are found to be similar at a two-month and one year follow-up between coiling and neurosurgery. [ 9 ]


Reported recurrence rates are quite varied, with rates between 20 and 50% of aneurysms recurring within one year of coiling, and with the recurrence rate increasing with time. [ 2 ] [ 10 ]  These results are similar to those previously reported by other endovascular groups. [ 11 ]  Other studies have questioned whether new matrix coils work better than bare platinum coils. [ 12 ]


The  International Subarachnoid Aneurysm Trial  tested the efficacy of endovascular coiling against the traditional micro-surgical clipping. The study initially found very favorable results for coiling, however its results and methodology were criticized. Since the study's release in 2002, and again in 2005, some studies have found higher recurrence rates with coiling, while others have concluded that there is no clear consensus between which procedure is preferred. [ 13 ]


Risks of endovascular coiling include  stroke , aneurysm rupture during the procedure and aneurysm recurrence and rupture after the procedure. [ 3 ]  Additionally in some patients coiling may not be successful. In general, coiling is only performed when the risk of aneurysm rupture is higher than the risks of the procedure itself.


Similar to patients who experience neurosurgical procedures, coiling results in an increase in resting energy expenditure, albeit at a slightly reduced rate than their neurosurgery counterpart. This can lead to malnutrition if steps are not taken to compensate for the increased metabolic rate. [ 14 ]


The treatment works by promoting blood clotting ( thrombosis ) in the aneurysm, eventually sealing it from the blood flow. This is accomplished by decreasing the amount of blood flow going into the aneurysm, increasing the residence time of the blood (thereby lowering the velocity) in the aneurysm space and reducing the  wall shear stress  of the aneurysm wall. This change in the blood flow, or  hemodynamics , is ultimately dependent on several factors, including:


While these factors are crucial to the success of the procedure, thrombosis ultimately is dependent on biological processes, with the coiling only providing the appropriate conditions for the process to occur, and hopefully closing the aneurysm.


Endovascular coiling is usually performed by an  interventional neuroradiologist  or neurosurgeon with the patient under general anaesthesia. The whole procedure is performed under  fluoroscopic imaging  guidance. A guiding catheter is inserted through the femoral artery and advanced to a site close to the aneurysm after which angiography is performed to localize and assess the aneurysm. After this, a microcatheter is navigated into the aneurysm.


The treatment uses detachable coils made of platinum that are inserted into the aneurysm using the microcatheter. A variety of coils are available, including Guglielmi Detachable Coils (GDC) which are platinum, Matrix coils which are coated with a biopolymer, and hydrogel coated coils. Coils are also available in a variety of diameters, lengths, and cross sections. [ 16 ]  A coil is first inserted along the aneurysm wall to create a frame, with the core then being filled with more coils. [ 17 ]  A series of progressively smaller coils may also be used. Success is determined by injecting a contrast dye into parent artery and qualitatively determining if dye is flowing into the aneurysm space during fluoroscopy. If no flow is observed, the procedure is considered completed. [ 2 ]  In the case of wide-necked aneurysms a  stent  may be used. [ 18 ]


Endovascular coiling was a developed through the synthesis of a number of innovations that took place between 1970 and 1990 in the field of electronics, neurosurgery, and  interventional radiology . [ 4 ]  While the procedure itself has been and continues to be compared to surgical clipping, the development of the concept and procedure has resulted in it becoming the gold standard at many centers. [ 4 ]


The first documented technique of using metal coils to induce thrombosis was accomplished by Mullan in 1974. Copper coils were inserted into a giant aneurysm through externally puncturing the aneurysm wall via craniotomy. Five patients died, with ten having satisfactory process. [ 19 ]  It did not gain popularity due to the specialized equipment required, in addition to the technique being unsuitable for many types of aneurysms. [ 4 ]  Later, in 1980, similar techniques were developed by Alksne and Smith using iron suspended in  methyl methacrylate  in a limited set of patients. There were no deaths in 22 consecutive cases with low morbidity. [ 20 ]  This technique also did not gain traction due to advances in clipping. [ 4 ]


As a means of avoiding invasive methods, early endovascular interventions involved the usage of detachable and nondetachable  balloon catheters  to occlude the aneurysm while preserving the  parent artery . [ 21 ]  Despite the innovative approach, the aneurysms were often found to adapt to the shape of the balloon itself resulting in higher incidents of aneurysm rupture. This procedure was deemed "uncontrollable" due to its high morbidity and mortality rate, but it demonstrated that the endovascular approach was feasible for many aneurysms. [ 4 ]  Endovascular coils would later be used in 1989 by Hilal et al., but these were short, stiff coils that offered no control, preventing dense packing of the aneurysm. [ 22 ]  Controllable microguidewire systems were later used. [ 4 ]


In 1983 the use of electrically induced thrombosis for intracranial aneurysms was described for the first time. [ 23 ]  A stainless steel electrode  supplied a positive current to the aneurysm to stimulate electrothrombosis. Minimal occlusion was achieved, but the researchers discovered that the erosion of the electrode due to  electrolysis  would be useful as a detachment system. [ 4 ]  Detachable coils were constructed from a platinum coil soldered to a stainless steel delivery wire, first described in 1991 by Guglielmi et al. [ 3 ]  When combined with a controllable microguide wire system, multiple coils could be inserted to fully pack an aneurysm. [ 4 ]


Given the complexity of modeling the vasculature, much research has been devoted towards modeling the hemodynamics of an aneurysm before and after an intervention. Techniques such as  particle image velocimetry  (PIV) and  computational fluid dynamics / finite element analysis  (CFD/FEA) have yielded results that have influenced the direction of research, but no model to date has been able to account for all factors present. [ 2 ] [ 24 ] [ 25 ]  Advantages of the  in-silico  research method include flexibility of selecting variables, but one comparative study has found that simulations tend to over-emphasis results compared to PIV, and are more beneficial for trends than exact values. [ 25 ]


Medical images, particularly  CT angiography , can be used to generate 3D reconstructions of patient specific anatomy. When combined with CFD/FEA, hemodynamics can be estimated in patient specific simulations, giving the clinician greater predictive tools for surgical planning and outcome evaluation to best promote thrombus formation. [ 26 ] [ 27 ]  However, most computer models use many assumptions for simplicity, including rigid walls (non-elastic) for vasculature, substituting a porous medium in place of physical coil representations, and  navier-stokes  for fluid behavior. However, new predictive models are being developed as computational power increases, including algorithms for simulations of coil behavior in-vivo. [ 16 ]


Ethylene vinyl alcohol  ( EVOH ) is a formal  copolymer  of  ethylene  and  vinyl alcohol .  Because the latter  monomer  mainly exists as its  tautomer   acetaldehyde , the copolymer is prepared by polymerization of ethylene and  vinyl acetate  to give the  ethylene vinyl acetate  (EVA) copolymer followed by hydrolysis.  EVOH copolymer is defined by the mole % ethylene content: lower ethylene content grades have higher barrier properties; higher ethylene content grades have lower temperatures for  extrusion .


The  plastic  resin is commonly used as an oxygen barrier in  food packaging .  It is better than other plastics at keeping air out and flavors in, is highly transparent, weather resistant, oil and solvent resistant, flexible, moldable, recyclable, and printable.  Its drawback is that it is difficult to make and therefore more expensive than other food packaging.  Instead of making an entire package out of EVOH, manufacturers keep costs down by coextruding or laminating it as a thin layer between cardboard, foil, or other plastics. [ 1 ] [ 2 ]


It is also used as a hydrocarbon barrier in plastic fuel tanks and pipes.


Because of the high capital cost to build an EVOH plant, and the complexity of making a food grade product, only a few companies produce EVOH:


Kuraray  produces EVOH resin under the name "EVAL," with a 10,000 ton plant in Okayama, Japan; a 58,000 ton plant in the U.S. (near Houston, TX) under its subsidiary Kuraray America; and a 35,000 ton plant in Belgium under its subsidiary EVAL Europe. [ 3 ]


Nippon Gohsei produces EVOH under the trade name Soarnol.  It has production sites in Mizushima, Japan; La Porte, Texas in the USA; and at  Salt End ,  Hull , England. [ 4 ]


Chang Chun Petrochemical produces EVOH under the trade name EVASIN.  It has a single site in Taipei, Taiwan.


Due to its strong barrier against gasses (especially oxygen), odors and flavours, [ 5 ]  food packaging manufacturers use EVOH in their packaging structure to extend the shelf life of food products. [ 6 ]


A downside of EVOH is its relatively high moisture sensitivity, meaning that the barrier capabilities of EVOH decrease in environments with high humidity. [ 7 ]  As such, EVOH is often applied within a multilayer film. Here, one or more inside layers contain EVOH, but the outside layers consist of a different plastic that is less sensitive to moisture, such as  polyethylene .


EVOH is used in a liquid embolic system in  interventional radiology , e.g. in  Onyx . [ 8 ]  Dissolved in  dimethyl sulfoxide  (DMSO) and mixed with a radiopaque substance, ethylene vinyl alcohol copolymer is used to  embolize   blood vessels .


Hemorrhoidal artery embolization  (HAE, or hemorrhoid artery embolization) is a non-surgical treatment of internal  hemorrhoids. [ 1 ]


The procedure involves blocking the abnormal blood flow to the rectal (hemorrhoidal) arteries using microcoils and/or  microparticles  to decrease the size of the hemorrhoids and improve hemorrhoid related symptoms, especially bleeding. [ 2 ]  It is a  minimally invasive therapy  that can be performed as an outpatient procedure. [ 3 ]


HAE begins when a  catheter  is inserted into the femoral or radial artery through a small incision. The catheter is then carefully navigated through the arterial system with  x-ray  guidance until it reaches the branches of the  superior rectal artery  that supply blood to the hemorrhoidal plexus. [ 3 ]  Once in position,  microparticles  and/or microcoils are injected through the catheter to block these arteries, thereby reducing the blood supply to the hemorrhoids. This causes the hemorrhoidal tissue to shrink over time, alleviating symptoms such as pain, bleeding, and swelling. [ 1 ] [ 2 ] [ 4 ]  Post-procedure, patients are monitored for a brief period to ensure stability before being discharged with instructions for managing any minor discomfort or symptoms that may occur during the recovery period.


HAE offers several benefits as a minimally invasive treatment for symptomatic hemorrhoids. Firstly, HAE effectively reduces blood flow to the hemorrhoidal tissue, leading to significant shrinkage and resolution of symptoms such as pain, bleeding, and prolapse. [ 2 ] [ 4 ]  This approach has been shown to provide long-lasting relief comparable to surgical methods but with potentially lower complication rates and faster recovery times. [ 5 ]  Additionally, HAE is associated with minimal post-procedural pain and allows for quicker return to daily activities, making it an attractive option for patients seeking less invasive treatment options. [ 5 ]  Moreover, its safety profile and efficacy have been supported by clinical trials, demonstrating its potential as a preferred alternative for managing hemorrhoidal disease. [ 6 ] [ 7 ] [ 8 ]  HAE is very effective at stopping bleeding related symptom with success rate of approximately 90%. [ 9 ]


The incidence of adverse events with HAE is very low. Rare arterial access site complications may occur. [ 2 ]   Although minor anal discomfort can occur in a minority of patients, there have been no reports of anorectal complications when embolization is performed primarily with microcoils [ 2 ]


Hepatic artery embolization , also known as  trans-arterial embolization (TAE) , is one of the several therapeutic methods to treat primary liver tumors or  metastases  to the liver. The  embolization  therapy can reduce the size of the tumor, and decrease the tumor's impact such its hormone production, effectively decreasing symptoms. The treatment was initially developed in the early 1970s. [ 1 ]  The  several types of hepatic artery treatments are based on the observation that tumor cells get nearly all their nutrients from the hepatic artery, while the normal cells of the liver get about 70-80 percent of their nutrients and 50% their oxygen supply from the portal vein, and thus can survive with the hepatic artery effectively blocked. [ 2 ]  In practice, hepatic artery embolization occludes the blood flow to the tumors, [ 3 ]  achieving significant tumor shrinkage in over 80% of people. [ 3 ]  Shrinkage rates vary. [ 4 ] [ 5 ]


The  several types of  hepatic artery  treatments are based on the observation that  tumor cells  get nearly all their nutrients from the hepatic artery, while the normal cells of the liver get about 70-80 percent of their nutrients and 50% their oxygen supply from the  portal vein , and thus can survive with the hepatic artery effectively blocked. [ 2 ]  In practice,  hepatic artery embolization is an option if the neoplastic growth is mainly within the liver. [ 6 ]  By occluding the blood supply to the tumors, [ 3 ]  achieving significant tumor shrinkage in over 80% of people. [ 3 ]  Shrinkage rates vary. [ 4 ]  The therapy can effectively decrease symptoms by reducing the size of the tumor, or by decreasing the tumor's impact, for example by decreasing the tumor's production of  hormones . [ 7 ]


Primary liver tumors, metastatic  neuroendocrine tumors  to the liver [ 8 ]  and other  metastases  to the liver [ 9 ] [ 10 ]  may be considered for therapy directed via the hepatic artery.


The percutaneous  Seldinger technique  introduces a  catheter , which is a thin flexible tube made of medical grade material, into the  hepatic artery  under radiological control. [ 11 ] [ 12 ]  This approach was developed for  metastatic   neuroendocrine tumors  in the early 1970s. [ 1 ]  Tumor cells get over 90% of their nutrients from the hepatic artery, [ 1 ]  while the normal cells of the liver get about 70-80 percent of their nutrients and 50% their oxygen supply from the portal vein, and thus can survive with the hepatic artery effectively blocked. [ 1 ] [ 2 ]  Once the catheter is carefully placed in the artery or in a selected branch, the blood flow can be occluded by injecting various items, such as plastic particles, glue, metal coils, foam, or by deploying a balloon. [ 11 ]  Additional considerations and procedural details have been reviewed. [ 1 ] [ 13 ]


In hepatic artery chemotherapy (HAC), chemotherapy agents are given into the hepatic artery, often by steady infusion over hours or even days. Compared with systemic chemotherapy, a higher proportion of the chemotherapy agents is (in theory) delivered to the lesions in the liver. [ 14 ] [ 15 ]


Hepatic artery chemoembolization (HACE), sometimes called  transarterial chemoembolization  (TACE), combines hepatic artery embolization with hepatic artery chemo infusion. In one method, embospheres bound with chemotherapy agents injected into the hepatic artery, lodge in downstream capillaries. The spheres not only block blood flow to the lesions but by halting the chemotherapy agents in the neighborhood of the lesions, they provide a much better targeting leverage than chemo infusion provides.


Image-guided radiation therapy  (IGRT) is the process of frequent  imaging , during a course of  radiation treatment , used to direct the treatment, position the patient, and compare to the pre-therapy imaging from the  treatment plan . [ 1 ]  Immediately prior to, or during, a treatment fraction, the patient is localized in the treatment room in the same position as planned from the reference imaging dataset. An example of IGRT would include comparison of a  cone beam computed tomography  (CBCT) dataset, acquired on the treatment machine, with the  computed tomography  (CT) dataset from planning. IGRT would also include matching planar kilovoltage (kV) radiographs or megavoltage (MV) images with digital reconstructed radiographs (DRRs) from the planning CT.


This process is distinct from the use of imaging to delineate targets and organs in the planning process of radiation therapy. However, there is a connection between the imaging processes as IGRT relies directly on the imaging modalities from planning as the reference coordinates for localizing the patient. The variety of medical imaging technologies used in planning includes  x-ray computed tomography  (CT),  magnetic resonance imaging  (MRI), and  positron emission tomography  (PET) among others.


IGRT can help to reduce errors in set-up and positioning, allow the margins around target tissue when planning to be reduced, and enable treatment to be adapted during its course, with the aim of overall improving outcomes. [ 2 ] [ 3 ]


The goal of the IGRT process is to improve the accuracy of the radiation field placement, and to reduce the exposure of healthy tissue during radiation treatments. In years past, larger planning target volume (PTV) margins were used to compensate for localization errors during treatment. [ 4 ]  This resulted in healthy human tissues receiving unnecessary doses of radiation during treatment. PTV margins are the most widely used method to account for geometric uncertainties. By improving accuracy through IGRT, radiation is decreased to surrounding healthy tissues, allowing for increased radiation to the tumour for control. [ 4 ]


Currently, certain radiation therapy techniques employ the process of  intensity-modulated radiotherapy (IMRT) . This form of radiation treatment uses computers and linear accelerators to sculpt a three-dimensional radiation dose map, specific to the target's location, shape and motion characteristics. Because of the level of precision required for  IMRT , detailed data must be gathered about tumour locations. The single most important area of innovation in clinical practice is the reduction of the planning target volume margins around the location. The ability to avoid more normal tissue (and thus potentially employ dose escalation strategies) is a direct by-product of the ability to execute therapy with the most accuracy. [ 4 ]


Modern, advanced radiotherapy techniques such as proton and charged particle radiotherapy enable superior precision in the dose delivery and spatial distribution of the effective dose. Today, those possibilities add new challenges to IGRT, concerning required accuracy and reliability. [ 5 ]  Suitable approaches are therefore a matter of intense research.


IGRT increases the amount of data collected throughout the course of therapy. Over the course of time, whether for an individual or a population of patients, this information will allow for the continued assessment and further refinement of treatment techniques. The clinical benefit for the patient is the ability to monitor and adapt to changes that may occur during the course of radiation treatment. Such changes can include tumor shrinkage or expansion, or changes in shape of the tumor and surrounding anatomy. [ 4 ]


The precision of IGRT is significantly improved when technologies that were originally developed for  image-guided surgery , such as the  N-localizer [ 6 ]  and Sturm-Pastyr localizer, [ 7 ]  are used in conjunction with these medical imaging technologies. SRT provides a Non-Surgical Alternative for Non-Melanoma Skin Cancer & an Effective Solution for Keloids.


Sensus Healthcare is a manufacturer and distributor of this device With a compact 30”x30” footprint, the mobile unit delivers a precise and calibrated dose of SRT that penetrates only five millimeters below the skin’s surface—making it one of the safest and most effective alternative cancer treatments available. Unlike more powerful radiotherapy devices, the SRT-100™ carefully destroys malignant skin cancer cells while preserving healthy tissue.


Radiation therapy is a local treatment that is designed to treat the defined tumour and spare the surrounding normal tissue from receiving doses above specified dose tolerances. There are many factors that may contribute to differences between the planned dose distribution and the delivered dose distribution. One such factor is uncertainty in patient position on the treatment unit. IGRT is a component of the radiation therapy process that incorporates imaging coordinates from the treatment plan to be delivered in order to ensure the patient is properly aligned in the treatment room. [ 8 ]


The localization information provided through IGRT approaches can also be used to facilitate robust treatment planning strategies and enable patient modelling, which is beyond the scope of this article. [ citation needed ]


In general, at the time of 'planning' (whether a clinical mark up or a full simulation) the intended area for treatment is outlined by the radiation oncologist. Once the area of treatment was determined, marks were placed on the skin. The purpose of the ink marks was to align and position the patient daily for treatment to improve reproducibility of field placement. By aligning the markings with the radiation field (or its representation) in the radiation therapy treatment room, the correct placement of the treatment field could be identified. [ 8 ]


Over time, with improvement in technology – light fields with cross hairs, isocentric lasers – and with the shift to the practice of 'tattooing' – a procedure where ink markings are replaced with a permanent mark by the application of ink just under the first layer of skin using a needle in documented locations - the reproducibility of the patient's setup improved. [ 9 ]


Portal imaging is the acquisition of images using a radiation beam that is being used for giving radiation treatment to a patient. [ 10 ]  If not all of the radiation beam is absorbed or scattered in the patient, the portion that passes through may be measured and used to produce images of the patient.


It is difficult to establish the initial use of portal imaging to define radiation field placement. From the early days of radiation therapy,  X-rays  or  gamma rays  were used to develop large format radiographic films for inspection. With the introduction of  cobalt-60  machines in the 1950s, radiation went deeper inside the body, but with lower contrast and poor subjective visibility. Today, using advancements in digital imaging devices, the use of electronic portal imaging has developed into both a tool for accurate field placement and as a quality assurance tool for review by radiation oncologists during check film reviews. [ 8 ]


Electronic portal imaging is the process of using digital imaging, such as a CCD video camera, liquid ion chamber and amorphous silicon flat panel detectors to create a digital image with improved quality and contrast over traditional portal imaging. The benefit of the system is the ability to capture images, for review and guidance, digitally. [ 11 ]  These systems are in use throughout clinical practice. [ 12 ]  Current reviews of Electronic Portal Imaging Devices (EPID) show acceptable results in imaging irradiations and in most clinical practice, provide sufficiently large fields-of-view. kV is not a portal imaging feature. [ 4 ]


Fluoroscopy is an imaging technique that uses a fluoroscope, in coordination with either a screen or image-capturing device to create real-time images of patients' internal structures.


Digital X-ray equipment mounted in the radiation treatment device is often used to picture the patient’s internal anatomy at time before or during treatment, which then can be compared to the original planning CT series. Usage of an orthogonal set-up of two radiographic axes is common, to provide means for highly accurate patient position verification. [ 5 ]


A medical imaging method employing tomography where digital geometry processing is used to generate a three-dimensional image of the internal structures of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation. CT produces a volume of data, which can be manipulated, through a process known as windowing, in order to demonstrate various structures based on their ability to attenuate and prevent transmission of the incident X-ray beam.


With the growing recognition of the utility of CT imaging in using guidance strategies to match treatment volume position and treatment field placement, several systems have been designed that place an actual conventional 2-D CT machine in the treatment room alongside the treatment linear accelerator. The advantage is that the conventional CT provides accurate measure of tissue attenuation, which is important for dose calculation (e.g. CT on rails). [ 8 ]


Cone-beam   computed tomography  (CBCT) based image guided systems have been integrated with medical linear accelerators to great success. With improvements in flat-panel technology, CBCT has been able to provide volumetric imaging, and allows for radiographic or fluoroscopic monitoring throughout the treatment process. Cone beam CT acquires many projections over the entire volume of interest in each projection. Using reconstruction strategies pioneered by Feldkamp, the 2D projections are reconstructed into a 3D volume analogous to the CT planning dataset.


Megavoltage computed tomography  (MVCT) is a medical imaging technique that uses the Megavoltage range of X-rays to create an image of bony structures or surrogate structures within the body. The original rational for MVCT was spurred by the need for accurate density estimates for treatment planning. Both patient and target structure localization were secondary uses. A test unit using a single linear detector, consisting of 75 cadmium tungstate crystals, was mounted on the linear accelerator gantry. [ citation needed ]  The test results indicated a spatial resolution of .5mm, and a contrast resolution of 5% using this method. While another approach could involve integrating the system directly into the MLA [ clarification needed ] , it would limit the number of revolutions to a number prohibitive to regular use. [ citation needed ]


Optical tracking entails the use of a camera to relay positional information of objects within its inherent coordinate system by means of a subset of the electromagnetic spectrum of wavelengths spanning ultra-violet, visible, and infrared light. Optical navigation has been in use for the last 10 years within  image-guided surgery  (neurosurgery, ENT, and orthopaedic) and has increased in prevalence within radiotherapy to provide real-time feedback through visual cues on graphical user interfaces (GUIs). For the latter, a method of calibration is used to align the camera's native coordinate system with that of the isocentric reference frame of the radiation treatment delivery room.  Optically tracked tools are then used to identify the positions of patient reference set-up points and these are compared to their location within the planning CT coordinate system. A computation based on least-squares methodology is performed using these two sets of coordinates to determine a treatment couch translation that will result in the alignment of the patient's planned isocenter with that of the treatment room. These tools can also be used for intra-fraction monitoring of patient position by placing an optically tracked tool on a region of interest to either initiate radiation delivery (i.e. gating regimes) or action (i.e. repositioning). Alternatively, products such as AlignRT (from Vision RT) allow for real time feedback by imaging the patient directly and tracking the skin surface of the patient.


The first clinically active MRI-guided radiation therapy machine, the ViewRay device, was installed in St. Louis, MO, at the  Alvin J. Siteman Cancer Center  at Barnes-Jewish Hospital and Washington University School of Medicine. Treatment of the first patients was announced in February 2014. [ 13 ]  Other radiation therapy machines which incorporate real-time MRI tracking of tumors are currently in development. MRI-guided radiation therapy enables clinicians to see a patient's internal anatomy in real-time using continual soft-tissue imaging and allows them to keep the radiation beams on target when the tumour moves during treatment. [ 14 ]


Ultrasound is used for daily patient setup. It is useful for soft tissue such as the breast and prostate. The BAT (Best Nomos) and Clarity (Elekta) systems are the two main systems currently being used. The Clarity system has been further developed to enable intra-fraction prostate motion tracking via trans-perineal imaging.


While not IGRT per se, electromagnetic transponder systems seek to serve exactly the same clinical function as CBCT or kV X-ray, yet provide for more temporally continuous analysis of setup error analogous to that of the optical tracking strategies. Hence, this technology (although entailing the use of no "images") is usually classified as an IGRT approach.


There are two basic correction strategies used while determining the most beneficial patient position and beam structure: on-line and off-line correction. Both serve their purposes in the clinical setting, and have their own merits. Generally, a combination of the both strategies is employed. Often, a patient will receive corrections to their treatment via on-line strategies during their first radiation session, and physicians make subsequent adjustments off-line during check film rounds. [ 4 ]


The On-line strategy makes adjustment to patient and beam position during the treatment process, based on continuously updated information throughout the procedure. [ 8 ]  The on-line approach requires a high-level of integration of both software and hardware. The advantage of this strategy is a reduction in both systematic and random errors. An example is the use of a marker-based program in the treatment of prostate cancer at Princess Margaret Hospital. Gold markers are implanted into the prostate to provide a surrogate position of the gland. Prior to each day's treatment, portal imaging system results are returned. If the center of the mass has moved greater than 3mm, then the couch is readjusted and a subsequent reference image is created. [ 4 ]  Other clinics correct for any positional errors, never allowing for >1 mm error in any measured axes.


The Off-line strategy determines the best patient position through accumulated data gathered during treatment sessions, almost always initial treatments. Physicians and staff measure the accuracy of treatment and devise treatment guidelines during using information from the images. The strategy requires greater coordination than on-line strategies. However, the use of off-line strategies does reduce the risk of systematic error. The risk of random error may still persist, however.


An  inferior vena cava filter  is a  medical device  made of metal that is  implanted  by  vascular surgeons  or  interventional radiologists  into the  inferior vena cava  to prevent a life-threatening  pulmonary embolism  (PE) or  venous thromboembolism  (VTE). [ 2 ] [ 3 ]


The filter is designed to trap a  blood clot  and prevent its travel to the  lung  where it would form a pulmonary embolism. [ 4 ] [ 3 ]  Their effectiveness and safety profile is well established, and they may be used when  anticoagulant treatment  is not sufficient. [ 5 ]


Results from the PREPIC study and other studies which have shown many long-term complications of IVC filters led to the introduction of retrievable IVC filters. [ 6 ]  The first retrievable IVC filters were approved by FDA in 2003 and 2004. [ 7 ]


In 2012, the  American College of Chest Physicians  recommended IVC filters for those with  contraindications  to  anticoagulation  who either have acute PE or acute  proximal deep vein thrombosis  (above the knee). [ 8 ] [ 9 ]


The first IVC filter was created by  Kazi Mobin-Uddin  who published his findings in 1969 in the  New England Journal of Medicine . [ 10 ] [ 11 ] [ 12 ] [ 13 ]  The Mobin-Uddin filter was later replaced by the Greenfield filter developed by  Lazar Greenfield  which had a lower rate of filter related complications. [ 12 ]


While the ability to retrieve a filter does exist for many models, it cannot be guaranteed that all cases of filter placement will allow for, or be indicated for retrieval.  Thus, the requirements and indications for permanent placement of filters is used to decide on when to use both permanent and temporary IVC filters. [ 14 ]


Long-term risk factors must be considered as well, to include life expectancy of more than six months following insertion, and the ability of the patient to comply with anticoagulation therapy. [ 5 ]  The decision to use a filter that is temporary vs permanent basically is tied to the expected duration of time that protection is needed to prevent pulmonary emboli from passing to the heart and lungs. One such guideline is outlined below: [ 14 ]


While many  studies have been done on the efficacy of Vena Cava filters, there still have not been any major studies done on the actual placement and removal of the filters regarding standard guidelines.  Which is why the Society of Interventional Radiology created a multidisciplinary panel that developed the following guidelines to see if someone qualifies for implantation: [ citation needed ]


These are patients that should strongly consider having IVC filter placement, as they are at greatest risk of pulmonary embolus.


This is a maybe category; normally it represents patients who could benefit from an IVC filter, but may be just fine without one as well. [ citation needed ]


These are usually very controversial reasons to do an IVC filter, and most radiologists and doctors generally will not recommend an IVC filter if other options are available instead.


There is no current published data confirming the benefit of removing an IVC.  Because of this, the Society of Interventional Radiology created a multidisciplinary panel that developed the following guidelines to see if someone qualifies for removal: [ 5 ]


An IVC filter, just by doing its job properly (catching embolic material), can eventually fill up with embolic material and cause a circulatory impairment that may warrant revision with vascular surgery (new filter, stent additions, or otherwise). A representative case has been reported in science journalism of the type that reports interesting unusual causes and solutions of symptoms; [ 16 ]  in this instance, the symptom was  orthostatic hypotension . [ 16 ]  Physicians speculate that this problem is uncommon but nonetheless worth consideration in differential diagnosis. [ 16 ]


In those with initial acute proximal DVT or acute PE who had IVC filters placed instead of  anticoagulation , and who have their risk of bleeding resolve, the  American College of Chest Physicians  suggested, in 2012, that they receive a standard course of  anticoagulation . [ 8 ] [ 9 ]  While IVC filters are associated with a long term risk of DVT, [ 17 ]  they are not, alone, reason enough to maintain extended anticoagulation. [ 8 ] [ 9 ]


The main function of a vena cava filter is to prevent death from massive pulmonary emboli.  Long-term clinical follow-up studies have shown that this is accomplished in 96% of cases having a standard stainless-steel Greenfield filter. [ 18 ]


In August, 2010, the FDA released an Initial Communication on the Risk and Adverse events associated with Long Term use of an inferior vena cava filter. [ 19 ]    Over a period of about 5 years, they identify 921 events.  While not the majority of cases, that number still represents a statistical significance of the use of long-term IVCs.


Of these IVC filter side effects, 328 involved device migration, 146 involved embolizations after detachment of device components, 70 involved perforation of the IVC, and 56 involved filter fracture. Much of the medical community believes that this large number of adverse events is related to the heart filter remaining in place for longer than necessary.


Common issues relating to failure, to include death (the other 4% of cases) include:


While these side effects are not common (less than 10-20% of patients), many do report issues stemming from the placement and complication of the IVC while inside of the body. [ 20 ]


Numerous small published articles and case studies report describe similar issues to the above.  Most notably:


Even though the cases above are the exception, and not the rule, most radiologists object to doing prophylactic filter insertions in patients who do not have thromboembolic diseases. [ 32 ]  For the most part, whenever possible, interventional radiologists would rather start the patient on anticoagulants than use an IVC, even if requested or referred via a doctor. [ 33 ]


While most IVC filters are made of non-ferromagnetic materials, there are a few types that are weakly ferromagnetic. Accordingly, IVC filters fall under the MRI Safe and MRI Conditional categories depending mostly on type of material used during construction.  Rarely will one find an MRI Not Safe IVC filter, as most of the steel, and other ferromagnetic material devices have been discontinued via the FDA. [ citation needed ]


IVC filters are attached to the vena cava via hooks on their ends. Some are compression springs, which compress outward onto the side wall of the vena cava; however, they still have small hooks that retain their location.  These hooks aid in the anchoring and healing process, as they allow the tissues to 'ingrow' around them, securing the IVC in place.  It is unlikely, then, after 4 to 6 weeks of healing, that an MRI of 1.5 tesla, up to 3 tesla, will cause any level of dislodging to occur to the IVC filter. [ citation needed ]


Studies of MR examination of both animals and humans, with implanted IVC filters, have not reported complications or symptomatic filter displacement. [ 34 ] [ 35 ] [ 36 ] [ 37 ] [ 38 ] [ 39 ]


Several animal studies have even used "real-time" MR for the placement of IVC filters to check for rotation, sheering, and other artifacts. [ 40 ] [ 41 ]


As part of the 'routing' survey for MRI studies, patients who have IVC filters will often need verification from the doctor, or medical records, to state that the IVC is safe for the MRI.  Most patients with weakly or non-safe ferromagnetic implants will be given a card, which they keep on their person at all time, that can help isolate if it is safe to do an MRI.


For patients who have been denied MRI scans for safety reasons, doctors usually recommend the CT scan with contrast as an alternative.


Most IVC filters that have been tested have been labeled as “MRi safe”; the remainder of IVC filters that have been tested are “MR conditional.” Patients who have been treated with nonferromagnetic IVC filters can undergo MR examination any time after filter implantation. In patients who have been treated with a weakly ferromagnetic IVC filter (Gianturco bird nest IVC filter [Cook], stainless steel Greenfield vena cava filter [Boston Scientific]), it is advised that the patient wait at least six weeks before undergoing an MR examination (because these older devices initially may not be anchored as firmly in place as other devices discussed in the present context), unless there is a strong clinical indication to perform the MR examination sooner after implantation, and as long as there is no reason to suspect that the device is not positioned properly or that it is not firmly in place. Most studies of IVC filters have generally been conducted at 1.5 tesla or less, although many IVC filters have now been evaluated at 3 tesla and deemed acceptable for MR examination. [ 42 ] [ 43 ]


IVC filters are placed endovascularly, meaning that they are inserted via the blood vessels.  Historically, IVC filters were placed surgically, but with modern filters that can be compressed into much thinner  catheters , access to the venous system can be obtained via the  femoral vein  (the large vein in the groin), the  internal jugular vein  (the large vein in the neck) or the arm veins with one design.  Choice of route depends mainly on the number and location of any  blood clot  within the venous system.  To place the filter, a catheter is guided into the IVC using fluoroscopic guidance, then the filter is pushed through the catheter and deployed into the desired location, usually just below the junction of the IVC and the lowest  renal vein . [ 44 ]


Review of prior cross-sectional imaging or a venogram of the IVC is performed before deploying the filter to assess for potential anatomic variations, thrombi within the IVC, or areas of stenoses, as well as to estimate the diameter of the IVC.  Rarely, ultrasound-guided placement is preferred in the setting of contrast allergy,  chronic kidney disease , and when patient immobility is desired.  The size of the IVC may affect which filter is deployed, as some (such as the Birds Nest) are approved to accommodate larger cavae.  There are situations where the filter is placed above the renal veins (e.g. pregnant patients or women of childbearing age, renal or gonadal vein thromboses, etc.).  Also, if there is duplication of the IVC, the filter is placed above the confluence of the two IVCs  [ 45 ]  or a filter can be placed within each IVC. [ 46 ]


The concept of a removable IVC filter was first conceived in 1967. [ 47 ]   In 2003 and 2004 that the United States Food and Drug Administration first approved retrievable filters. [ 48 ]   In 2005 that the Society of Interventional Radiology (SIR) convened a multidisciplinary conference to address the clinical application of nonpermanent vena cava filters. [ citation needed ]


Retrievable filters are fitted with a device (varying from model to model) that allows them to be easily  snared  and pulled back into a catheter and removed from the body, often through the  jugular vein . Prior to 2004, filters that had been in the IVC for less than three weeks were considered suitable to attempt retrieval, as filters that have been in place longer might have been overgrown by cells from the IVC wall and there was an increased risk of IVC injury if the filter is dislodged. Newer designs, and developments in techniques mean that some filters can now be left in for prolonged periods and retrievals after a year are now being reported. [ 49 ]  This would include the ALN, Bard G2 and G2x, Option, Tulip and Celect filters. [ citation needed ]


It is important to note that the clinical exam prior to the removal of the filter is vital in understanding both the risk and pathophysiological effects removing the filter will have on the patient.  Doctors and medical professionals must consider several key factors (see  Indications for removing IVC filters ). [ citation needed ]


Irreversible electroporation  or  IRE  is a soft tissue  ablation  technique using short but strong  electrical fields  to create permanent and hence lethal nanopores in the  cell membrane , to disrupt cellular  homeostasis . The resulting cell death results from induced  apoptosis  or  necrosis  induced by either membrane disruption or secondary breakdown of the membrane due to transmembrane transfer of electrolytes and  adenosine triphosphate . [ 1 ] [ 2 ] [ 3 ] [ 4 ]  The main use of IRE lies in tumor ablation in regions where precision and conservation of the  extracellular matrix , blood flow and nerves are of importance. The first generation of IRE for clinical use, in the form of the NanoKnife System, became commercially available for research purposes in 2009, solely for the surgical ablation of soft tissue tumors. [ 5 ]  Cancerous tissue ablation via IRE appears to show significant cancer specific immunological responses which are currently being evaluated alone and in combination with  cancer immunotherapy . [ 6 ] [ 7 ] [ 8 ] [ 9 ]


First observations of IRE effects go back to 1754. Nollet reported the first systematic observations of the appearance of red spots on animal and human skin that was exposed to electric sparks. [ 10 ]  However, its use for modern medicine began in 1982 with the seminal work of Neumann and colleagues. [ 11 ]  Pulsed electric fields were used to temporarily permeabilize cell membranes to deliver foreign DNA into cells. In the following decade, the combination of high-voltage pulsed electric fields with the chemotherapeutic drug bleomycin and with DNA yielded novel clinical applications:  electrochemotherapy  and  gene electrotransfer , respectively. [ 12 ] [ 13 ] [ 14 ] [ 15 ] [ 16 ]  The use of irreversible electroporation for therapeutic applications was first suggested by Davalos, Mir, and Rubinsky. [ 17 ]


Utilizing ultra short pulsed but very strong electrical fields, micropores and nanopores are induced in the  phospholipid bilayers  which form the outer cell membranes. [ citation needed ]  Two kinds of damage can occur:


It should be stated that even though the ablation method is generally accepted to be apoptosis, some findings seem to contradict a pure apoptotic cell death, making the exact process by which IRE causes cell death unclear. [ 18 ] [ 4 ]  In any case, all studies agree that the cell death is an induced one with the cells dying over a varying time period of hours to days and does not rely on local extreme heating and melting of tissue via high energy deposition like most ablation technologies  (see  radiofrequency ablation ,  microwave ablation ,  High-intensity focused ultrasound ). [ citation needed ]


When an electrical field of more than 0.5 V/nm [ 19 ]  is applied to the resting trans-membrane potential, it is proposed that water enters the cell during this dielectric breakdown. Hydrophilic pores are formed. [ 20 ] [ 21 ]  A molecular dynamics simulation by Tarek [ 22 ]  illustrates this proposed pore formation in two steps: [ 23 ]


It is proposed that as the applied electrical field increases, the greater is the perturbation of the phospholipid head groups, which in turn increases the number of water filled pores. [ 24 ]  This entire process can occur within a few nanoseconds. [ 22 ]  Average sizes of nanopores are likely cell-type specific. In swine livers, they average around 340-360 nm, as found using  SEM . [ 23 ]


A secondary described mode of cell death was described to be from a breakdown of the membrane due to transmembrane transfer of electrolytes and adenosine triphosphate. [ 3 ]  Other effects like heat [ 25 ]  or electrolysis [ 26 ] [ 27 ]  were also shown to play a role in the currently clinically applied IRE pulse protocols.


A number of electrodes, in the form of long needles, are placed around the target volume. The point of penetration for the electrodes is chosen according to anatomical conditions. Imaging is essential to the placement and can be achieved by ultrasound, magnetic resonance imaging or tomography. The needles are then connected to the IRE-generator, which then proceeds to sequentially build up a potential difference between two electrodes. The geometry of the IRE-treatment field is calculated in real time and can be influenced by the user. Depending on the treatment-field and number of electrodes used, the ablation takes between 1 and 10 minutes. In general muscle relaxants are administered, since even under general anesthetics, strong muscle contractions are induced by excitation of the motor end-plate. [ citation needed ]


Typical parameters (1st generation IRE system): [ citation needed ]


The shortly pulsed, strong electrical fields are induced through thin, sterile, disposable electrodes. The potential differences are calculated and applied by a computer system between these electrodes in accordance to a previously planned treatment field. [ 39 ]


One specific device for the IRE procedure is the  NanoKnife  system manufactured by AngioDynamics, which received FDA 510k clearance on October 24, 2011. [ 40 ]  The NanoKnife system has also received an Investigational Device Exemption (IDE) from the FDA that allows AngioDynamics to conduct clinical trials using this device. [ 40 ]  The Nanoknife system transmits a low-energy direct current from a generator to electrode probes placed in the target tissues for the surgical ablation of soft tissue. In 2011, AngioDynamics received an FDA warning letter for promoting the device for indications for which it had not received approval. [ 41 ]


In 2013, the UK National Institute for Health and Clinical Excellence issued a guidance that the safety and efficacy of the use of irreversible electroporation of the treatment of various types of cancer has not yet been established. [ 42 ]


Newer generations of Electroporation-based ablation systems are being developed specifically to address the shortcomings of the first generation of IRE but, as of June 2020, none of the technologies are available as a medical device. [ 27 ] [ 43 ] [ 44 ]


Potential organ systems, where IRE might have a significant impact due to its properties include the pancreas, liver, prostate and the kidneys, which were the main focus of the studies listed in Table 1-3 (state: June 2020).


None of the potential organ systems, which may be treated for various conditions and tumors, are covered by randomized multicenter trials or long-term follow-ups (state. June 2020).


2016 [ 47 ]


3.0 cm


laparoscopic
(n = 20)


2013 [ 48 ]


CRLM (n = 20),
Other (n = 10);
2.5 cm


(n = 28), open
(n = 14), laparoscopic
(n = 2)


2017 [ 49 ]


CRLM (n = 23),
other (n = 7); 2.4 cm


(n = 30)


(at 6 months)


2014 [ 50 ]


2.7 cm


(n = 28)


2012 [ 51 ]


CRLM (n = 21),
other (n = 5);
1.0 cm


(n = 6), open
(n = 22)


2014 [ 52 ]


CRLM (n = 20),
CCC (n = 5);
2.7 cm


(n = 67)


2015 [ 53 ]


CRLM (n = 16),
CCC (n = 6),
other (n = 4); 1.7 cm


(n = 25)


2016 [ 54 ]


CRLM (n = 22),
CCC (n = 5),
other (n = 5); 2.4 cm


(n = 34)


2017 [ 55 ]


CRLM (n = 16),
CCC (n = 6), other
(n = 4); 2.3 cm


(n = 71)


2013 [ 56 ]


CRLM (n = 23),
CCC (n = 2),
other (n = 22);
3.8 cm


(NS) open
(NS)


2014 [ 57 ]


2.4 cm


2011 [ 58 ]


CRLM (n = 15), other
(n = 31); 2.5 cm


Hepatic IRE appears to be safe, even when performed near vessels and bile ducts [ 59 ] [ 60 ]  with an overall complication rate of 16%, with most complications being needle related (pneumothorax and hemorrhage).The COLDFIRE-2 trial with 50 patients showed 76% local tumor progression-free survival after 1 year. [ 61 ]  Whilst there are no studies comparing IRE to other ablative therapies yet, thermal ablations have shown a higher efficacy in that matter with around 96% progression free survival. Therefor Bart et al. [ 36 ]  concluded that IRE should currently only be performed for only truly unresectable and non-ablatable tumors.


Patients


and Median
Largest Tumor Diameter


Follow-up


(mo)


Overall
Survival (mo)


Recurrence
(%)


Downstaging
Caused by IRE


2017 [ 62 ]


2019 [ 63 ]


(88% after chemotherapy or radiation
therapy)


(n = 32), open (n = 1)


10.7 (IRE)


2016 [ 64 ]


2016 [ 65 ]


percutaneous (n = 2)


2018 [ 66 ]


chemotherapy)


2016 [ 67 ]


7.0 (IRE)


2019 [ 68 ]


2015 [ 69 ]


chemo- or radiation
therapy)


18 (IRE)


et al., 2016 [ 70 ]


(after chemo- or radiation therapy)


14.2 (IRE)


2015 [ 71 ]


6.4 (IRE)


2019 [ 72 ]


and local recurrence (n = 10), 4.0 cm (68% after chemotherapy)


9.6 (IRE)


2017 [ 73 ]


(52% after chemotherapy)


11.0 (IRE)


2018 [ 74 ]


percutaneous, NS


2017 [ 75 ]


2016 [ 76 ]


2017 [ 77 ]


Animal studies have shown the safety and efficacy of IRE on pancreatic tissue. [ 78 ]  The overall survival rates in studies on the use of IRE for pancreatic cancer provide an encouraging nonvariable endpoint and show an additive beneficial effect of IRE compared with standard-of care chemotherapeutic treatment with FOLFIRINOX (a combination of 5-fluorouracil, leucovorin, irinotecan, and oxaliplatin) (median OS, 12–14months). [ 79 ] [ 80 ]  However, IRE appears to be more effective in conjunction with systemic therapy and is not suggested as first-line treatment. [ 68 ]  Despite that IRE makes adjuvant tumor mass reduction therapy for  LAPC  possible, IRE remains, in its current state, a high risk procedure requiring additional safety data before it can be used widely. [ 81 ]


Concurrent Treatment


(% of patients)


(no. of patients)


(2010) [ 82 ]


3+4: n = 6


4+4: n = 3


urinary incontinence 0% erectile dysfunction 0%


out-of-field occurrence, n = 1


(2016) [ 83 ]


4+3: n = 3


4+4: n = 2


4 weeks after IRE


complete fibrosis or necrosis of ablation zone


(2018) [ 84 ]


3+4: n = 38


4+3: n = 16


Grade 2: 11%


Grade 3–5: 0%


urinary incontinence 0%;


erectile dysfunction 23%


out-of-field recurrence, n = 4


(2019) [ 85 ]


n = 225


4+4: n = 68


5+3/3+5: n = 3


>4+4 = 42


prostatectomy (n = 21),


radiation therapy (n = 28),


TURP (n = 17),


HIFU (n = 8)


ADT (n = 29)


erectile dysfunction 3%


local recurrence, n = 20;


out-of-field recurrence, n = 27


(2014) [ 86 ]


3+4: n = 19


4+3: n = 5


4+4: n = 1


incontinence 0%;


erectile dysfunction 5%


only one histologic verification. Out-of-field
recurrence, NS


(2016) [ 87 ]


3+4: n = 15


4+3: n = 8


4+4: n = 0


Grade 2: 29%


erectile dysfunction, unknown


out-of-fieldrecurrence, n = 5 (with histologic verification)


3+4: n = 37


4+3: n = 6


Grade 2: 9


erectile dysfunction 6%


out-of-field recurrence, NS


Focal ablation using IRE for PCa in the distal apex appears safe and feasible.


The concept of treating prostate cancer with IRE was first proposed by Gary Onik and Boris Rubinsky in 2007. [ 89 ]  Prostate carcinomas are frequently located near sensitive structures which might be permanently damaged by thermal treatments or radiation therapy. The applicability of surgical methods is often limited by accessibility and precision. Surgery is also associated with a long healing time and high rate of side effects. [ 90 ]  Using IRE, the urethra, bladder, rectum and neurovascular bundle and lower urinary sphincter  can potentially be included in the treatment field without creating (permanent) damage. [ citation needed ]


IRE has been in use against prostate cancer since 2011, partly in form of clinical trials, compassionate care or individualized treatment approach. As for all other ablation technologies and also most conventional methods, no studies employed a randomized multi-center approach or targeted  cancer-specific mortality  as endpoint.  Cancer-specific mortality  or  overall survival  are notoriously hard to assess for prostate cancer, as the trials require more than a decade and usually several treatment types are performed during the years making treatment-specific survival advantages difficult to quantify. Therefore, the results of ablation-based treatments and focal treatments in general usually use local recurrences and functional outcome (quality of life) as endpoint. In that regard, the clinical results collected so far and listed in Table 3 shown encouraging results and uniformly state IRE as a safe and effective treatment (at least for focal ablation) but all warrant further studies. The largest cohort presented by Guenther et al. [ 85 ]  with up to 6-year follow-up is limited as a heterogeneous retrospective analysis and no prospective clinical trial. Therefore, despite that several hospitals in Europe have been employing the method for many years with one private clinic even listing more than one thousand treatments as of June 2020, [ 91 ]  IRE for prostate cancer is currently not recommended in treatment guidelines.


While nephron-sparing surgery is the gold standard treatment for small, malignant renal masses, ablative therapies are considered a viable option in patients who are poor surgical candidates. Radiofrequency ablation (RFA) and cryoablation have been used since the 1990s; however, in lesions larger than 3 cm, their efficacy is limited. The newer ablation modalities, such as IRE, microwave ablation (MWA), and high-intensity focused ultrasound, may help overcome the challenges in tumor size. [ 92 ]


The first human studies have proven the safety of IRE for the ablation of renal masses; however, the effectiveness of IRE through histopathological examination of an ablated renal tumor in humans is yet to be known. Wagstaff et al. have set out to investigate the safety and effectiveness of IRE ablation of renal masses and to evaluate the efficacy of ablation using MRI and contrast-enhanced ultrasound imaging. In accordance with the prospective protocol designed by the authors, the treated patients will subsequently undergo radical nephrectomy to assess IRE ablation success. [ 93 ]


Later phase 2 prospective trials showed good results in terms of safety and feasibility   [ 94 ] [ 95 ]  for small renal masses but the cohort was limited in numbers (7 and 10 patients respectively), hence efficacy is not yet sufficiently determined. IRE appears safe for small renal masses up to 4 cm. However, the consensus is that current evidence is still inadequate in quality and quantity. [ 36 ]


In a prospective, single-arm, multi-center, phase II clinical trial, the safety and efficacy of IRE on lung cancers were evaluated. The trial included patients with primary and secondary lung malignancies and preserved lung function. The expected effectiveness was not met at interim analysis and the trial was stopped prematurely. Complications included pneumothoraces (11 of 23 patients), alveolar hemorrhage not resulting in significant hemoptysis, and needle tract seeding was found in 3 cases (13%). Disease progression was seen in 14 of 23 patients (61%). Stable disease was found in 1 (4%), partial remission in 1 (4%) and complete remission in 7 (30%) patients. The authors concluded that IRE is not effective for the treatment of lung malignancies. [ 96 ]  Similarly poor treatment outcomes have been observed in other studies. [ 97 ] [ 98 ]


A major obstacle of IRE in the lung is the difficulty in positioning the electrodes; placing the probes in parallel alignment is made challenging by the interposition of ribs. Additionally, the planned and actual ablation zones in the lung are dramatically different due to the differences in conductivity between tumor, lung parenchyma, and air. [ 99 ]


Maor et el have demonstrated the safety and efficiency of IRE as an ablation modality for smooth muscle cells in the walls of large vessels in rat model. [ 100 ]  Therefore, IRE has been suggested as preventive treatment for coronary artery re-stenosis after  percutaneous coronary intervention . [ citation needed ]


Numerous studies in animals have demonstrated the safety and efficiency of IRE as a non-thermal ablation modality for pulmonary veins in the context of  atrial fibrillation  treatment. [ 101 ]  In 2023, irreversible electroporation is being widely used and evaluated in humans, as  cardiac ablation therapy  to kill very small areas of heart muscle. This is done to treat  irregularities of heart rhythm . A  cardiac catheter  delivers trains of high-voltage ultra-rapid electrical pulses that form irreversible pores in cell membranes, resulting in cell death. It is thought to allow better selectivity than the previous techniques, which used heat or cold to kill larger volumes of muscle. [ 102 ]


IRE has also been investigated in ex-vivo human eye models for treatment of uveal melanoma [ 103 ]  and in thyroid cancer. [ 104 ]


Successful ablations in animal tumor models have been conducted for lung, [ 105 ] [ 106 ]  brain, [ 107 ] [ 108 ]  heart, [ 109 ]  skin, [ 110 ] [ 111 ]  bone, [ 112 ] [ 113 ]  head and neck cancer, [ 114 ]  and blood vessels. [ 115 ]


Microwave ablation  is a form of thermal ablation used in  interventional radiology  to treat  cancer . MWA uses  electromagnetic waves  in the microwave energy spectrum (300 MHz to 300 GHz) to produce tissue-heating effects. The oscillation of polar molecules produces frictional heating, ultimately generating  tissue necrosis  within solid tumors. It is generally used for the treatment and/or  palliation  of solid tumors in patients who are nonsurgical candidate.


For isolated, nonmetastatic  lung tumors , surgical resection remains the reference standard for treatment. However, many patients are precluded from surgery due to poor  cardiopulmonary function , advanced age, or extensive disease burden. For these patients, minimally invasive therapeutic options such as  radiofrequency ablation , microwave ablation, and  cryoablation  have emerged as possible alternatives.


Tumor ablation of thoracic malignancies should be considered a viable treatment option for patients with early stage, primary or secondary lung cancers who are not surgical candidates or for patients in whom  palliation  of tumor related symptoms is the intent. MWA is regarded as a particularly efficient option for the treatment of lung tumors since unlike RFA it does not rely on impedance to generate heat, rather electromagnetic microwave waves heat matter by agitating water molecules in the surrounding tissue, producing friction and heat.


Another common use for microwave ablation is the treatment of  liver tumors . For nonsurgical patients, local thermal ablation techniques have enabled local control of tumors without resection. In particular, this therapy has grown in use for patients with  hepatocellular carcinoma , since many patients present with advanced disease or compromised liver function.


Clinical applications of MWA have also included treatment of renal, adrenal, and bone malignancies. The goals of ablation of thoracic malignancies include:
1. Ablating the entire tumor and a margin of normal parenchyma surrounding it
2. Avoiding injury to critical structures
3. Creating a large ablation area quickly.


The most common adverse effects of MWA for lung tumors include pain, fever,  pneumothorax , and  pleural effusions . [6-12]  Rib fractures, following thermal ablation, particularly MWA, have been newly noted in the literature. [13]


One of the limitations of thermal-based ablation therapies, including MWA, is the risk of marginal recurrences and/or residual disease. Residual or recurrent tumor is particularly likely in areas adjacent to heat sinks, such as larger blood vessels or airways. Theoretically, the greater heat intensity generated in MWA compared to other thermal modalities should allow for more complete ablations in larger tumors and thus decreased incidence of residual disease or recurrence at the tumor margins. [3]


MWA allows for flexible treatment approaches, including  percutaneous ,  laparoscopic , and open surgical access. Therapy is generally performed with the patient under  conscious sedation ; however, in cases where intra-procedural pain is problematic a  general anesthetic  may be used. Ablations can be performed using a single MW antenna or a cluster of three to achieve a greater ablation volume. [4]  Tumor temperatures during ablation can be measured with a separate thermal couple; tumors are treated to over 60 °C to achieve coagulation necrosis.


Currently, there are six MWA systems commercially available in the United States. The systems use either a  915 MHz  generator (Evident, Covidien, Mansfield, MA; MicrothermX, BSD Medical, Salt Lake City, UT; Avecure, Medwaves, San Diego, CA) or a  2450 MHz  generator (Certus 140, Neuwave, Madison, WI; Amica, Hospital Service, Rome, Italy; Acculis MTA, AngioDynamics, Latham, NY). The MW antennas used are straight applicators with active tips ranging in lengths from 0.6 to 4.0 cm. Five of the six available systems require that the antennas are internally cooled with either room-temperature fluid or carbon dioxide to reduce conductive heating and to prevent possible skin damage. [5]


The technique for thermal ablation in the lung by using  radiofrequency ablation  was first described in 1995 for use in animal lung tumor models and then in 2000 in humans. [1-2]  Microwave ablation has emerged as a newer ablation modality and an addition to the arsenal of minimally invasive cancer care.


The purported benefits of microwave ablation over other heat-based modalities such as radiofrequency ablation and laser include a larger and faster volume of tissue heating with a given application. Unlike radiofrequency ablation, MWA does not rely on an electrical circuit allowing for multiple applicators to be used simultaneously. [3]


Devi Elizabeth Nampiaparampil  (also known as  Doctor Devi ; born May 13, 1977) is an American  physician  and researcher who specializes in preventing and treating  chronic pain . She performs X-ray-guided invasive spinal procedures for pain, teaches medical students and trainees, comments on medical issues for various platforms, and appears on news and talk shows. She has appeared on the daytime soap opera  General Hospital . Dr. Nampiaparampil also ran as for New York City Public Advocate in the November 2021 general election.


Doctor Devi was born at  NYU Medical Center  (where she now teaches [ 1 ] ) to Mary and Joseph Nampiaparampil,  Catholic  Indians who had immigrated to the U.S. from  Kerala , India. She was educated at  Ardsley High School  in New York. Between 1995 and 2002, Nampiaparampil attended the seven-year combined B.A./M.D. program at  Northwestern University , where she double-majored in economics and biology. She completed her specialty and subspecialty medical training at  Harvard Medical School . [ 2 ]  Doctor Devi is board-certified in four specialties including Pain Medicine, Sports Medicine, Physical Medicine and Rehabilitation and Hospice and Palliative Medicine


In 2015, she became an associate professor of  Rehabilitation Medicine at NYU School of Medicine , WNYW-Fox 5 NY's on-air medical contributor, and opened her own private practice,  Metropolis Pain Medicine , in downtown Manhattan. Dr. Devi has also served as a medical legal consultant to Fortune 500 companies.


Doctor Devi began working for the  U.S. Department of Veterans Affairs  in 2008 and started the Brain Injury Clinic at the VA Central California in Fresno. She moved to New York City in 2009 to direct and develop the Pain Management program at the VA Hudson Valley. [ 3 ]  She served as the head of the regional Pain Management program for the New York/New Jersey region but stepped down to further develop the VA's Interventional Pain Management program in  New York City . She established the Veterans' Hospital in Manhattan (the VA New York Harbor) as a referral center for invasive pain procedures. [ 4 ]  She was an assistant professor in the Department of Rehabilitation Medicine at  NYU School of Medicine  from 2009 to 2015 and then was promoted to associate professor. [ 5 ]  In 2015, she was elected to the board of the American Society of Interventional Pain Physicians. [ 6 ]  She is also an editor for Pain Physician, an academic journal for pain management specialists. [ 7 ]


The  U.S. Department of Veterans Affairs  recognized Doctor Devi for "outstanding service" during the wars in Iraq and Afghanistan wars and  NYU Langone Medical Center  honored her for her achievements in research and education. The Department of Physical Medicine & Rehabilitation (PM&R) at  Harvard Medical School  honored her for her efforts "to further the field of PM&R." Doctor Devi has won research awards from institutions and organizations such as  Massachusetts General Hospital , Harvard Medical School, the  Massachusetts Medical Society , the  American Pain Society , the  American Medical Association  and the  American Society for Regional Anesthesia and Pain Medicine  for her work on pain and the  opioid crisis . [ 8 ]  Dr. Devi has also been named one of  Caste Connolly's Top Doctors  since 2015. Doctor Devi has also been awarded the Lifetime Achievement Award from the  New York State Senate  for her services and sacrifice during COVID pandemic.


Doctor Devi has over 50 peer-reviewed academic publications including  20 publications  in the Journal of the American Medical Association ( JAMA ).


Doctor Devi has appeared as a physician on the daytime  soap opera ,  General Hospital , before becoming a physician in her real life. She intermittently appeared on the show between 2002 and 2005. She made her debut as a medical expert on television on  The Dr. Oz Show  when she demonstrated  botox  injections for chronic migraine pain in front of a live audience.  Mehmet Oz  nicknamed her Doctor Devi when she appeared on his show.


In 2015, She worked on a short documentary, entitled, "A Life For A Life: Trading Organs For One More Today," [ 15 ]  which won a Jury Award at the  Directors Guild of America  Student Film Awards. She published a related article in  Newsweek  entitled "How a Death Row Inmate's Request to Give His Organs Kept Him Alive". [ 16 ]


In 2016, Doctor Devi became an  on-air medical contributor  for  Fox 5 , analyzing medical developments for  Good Day NY , Fox 5 News at 5, News at 6, and News at 10. She has appeared in over 350 national news segments for  Fox News Channel ,  MSNBC , and  CNN  among other networks. [ 17 ] [ 18 ]  She also has a master's degree in journalism from the  Columbia University Graduate School of Journalism .


Doctor Devi ran for New York York City  Public Advocate  in the   2021 election . She won the republican primary, losing in the general election to incumbent democrat  Jumaane Williams . [ 19 ]


A  nephrostomy  or  percutaneous nephrostomy  is an artificial opening created between the  kidney  and the  skin  which allows for the  urinary diversion  directly from the upper part of the urinary system ( renal pelvis ). [ 2 ]  It is an  interventional radiology / surgical procedure  in which the  renal pelvis  is punctured whilst using imaging as guidance. Images are obtained once an antegrade  pyelogram  (an injection of contrast), with a fine needle, has been performed. A nephrostomy tube may then be placed to allow drainage. [ 3 ]


An  urostomy  is a related procedure performed more distally along the urinary system to provide urinary diversion.


A nephrostomy is performed whenever a blockage keeps urine from passing from the kidneys, through the  ureter  and into the  urinary bladder . Without another way for urine to drain, pressure would rise within the urinary system and the kidneys would be damaged. [ 4 ]


The most common cause of blockage necessitating a nephrostomy is  cancer , especially  ovarian cancer  and  colon cancer . Nephrostomies may also be required to treat  pyonephrosis ,  hydronephrosis  and  kidney stones . [ 5 ]


Percutaneous nephrostomy is used in Whitaker test to differentiate recurrent obstruction or permanent dilatation after an operative surgery that corrects the cause of obstruction. This procedure is also used for  antegrade pyelography  to visualize the upper urinary tract system. [ 6 ]


Percutaneous nephrostomy is also used to treat  hydronephrosis  caused by kidney stones, pregnancy, stricture of the urinary tract, urinary tract/cervical/prostate tumours. Besides, infections such as urosepsis and  pyonephrosis  can also be drained by nephrostomy tube insertion. [ 6 ]  Percutaneous nephrostomy is also useful in divert urine away from diseased site to enhance healing. Examples of conditions that can be treated with such method are malignant/traumatic/inflammatory  fistula , and  haemorrhagic cystitis . [ 6 ]


Percutaneous nephrostomy is also used to provide access for chemotherapy/antibiotic/antifungal therapy, antegrade urethral stent placement, stone retrieval, and endopyelotomy (endoscopic surgery for the enlargement of the junction of renal pelvis and ureter). [ 6 ]


Nephrostomies are created either by  surgeons  or  interventional radiologists .


Under interventional radiology, the subject either lies down on the side or in a prone position. An area is selected below the 12th rib, bounded laterally by the posterior axillary line and the muscles of the spine and from below by the pelvic bone. The exact area is then located by ultrasound. Local anesthetic infiltration is used to numb the area. Then a needle would pass through to make the puncture on the kidney. Then, urine from the kidney is aspirated and check for its contents. If the urine is clear, dye will be injected to delineate the  renal pelvis  and  renal calyx . If the urine is turbid, it means the urine is infected. Dye injection is avoided in case of turbid urine to prevent the spread of infection to other parts of the urinary system. [ 6 ]  Then, a guidewire is inserted into the through the needle and parked within the upper renal calyx or within the  ureter  under  fluoroscopy  guidance. Then the puncture tract is dilated using a dilator. [ 6 ]  Various types of catheters such as pigtail catheter [ 7 ]  or Malecot catheter (a catheter that has a special mechanism for preventing blockage in case of thick pus in  pyonephrosis  and not easily dislodged when compared to pigtail catheter) can be used. [ 6 ]  The catheter is inserted through the guidewire and is secured in place by suturing it to the skin. The other end of the catheter is attached to a urine bag for drainage of urine from the kidney. [ 6 ]


Percutaneous nephrostomy is overall a very safe procedure. [ 8 ]  Risks and complications include: [ 8 ]


Although pneumothorax and colonic injury are more common on subcostal needle insertion, these are rare complications. [ 6 ]


Blood in urine usually clears up after 48 to 72 hours. Bleeding longer than this period may signifies more serious bleeding complication. About 2–4% of percutaneous nephrostomy cases require blood transfusion. [ 9 ]  Arteriovenous fistula is a rare complication. [ 10 ]


The  BMJ  has published original research of this condition and its treatment,


In  interventional radiology ,  Onyx  is a trade name for a copolymer used for  embolisation therapy , [ 1 ]  which involves the occlusion of  blood vessels . It is a  liquid embolic agent . Onyx is produced and sold by Medtronic (previously Covidien, which acquired ev3 Inc., the original developer of Onyx, in 2010).


Onyx consists of  Ethylene Vinyl Alcohol Copolymer , soluted in  Dimethyl-Sulfoxide  (DMSO). Depending on the desired character of the liquid, the concentration can be varied: For example, 6% EVOH (trade name Onyx 18) or 8% EVOH (trade name Onyx 34). Micronized tantalum powder is added in order to maintain  Radiopacity . [ 2 ]


Onyx was approved as 'Humanitarian Use Device (HUD)' for the treatment of  saccular aneurysms  that are not surgically removable by the  Food and Drug Administration (FDA)  in the United States on April 11, 2007. [ 3 ] [ 4 ]


Paracentesis  (from  Greek  κεντάω, "to pierce") is a form of  body fluid sampling  procedure, generally referring to  peritoneocentesis  (also called  laparocentesis  or  abdominal paracentesis ) in which the  peritoneal cavity  is punctured by a needle to sample  peritoneal fluid . [ 1 ] [ 2 ]


The procedure is used to remove fluid from the peritoneal cavity, particularly if this cannot be achieved with medication. The most common indication is  ascites  that has developed in people with  cirrhosis .


It is used for a number of reasons: [ 3 ]


The procedure is often performed in a doctor's office or an outpatient clinic. In an expert's hands, it is usually very safe, [ 4 ]  although there is a small risk of infection, excessive bleeding or perforating a loop of bowel. These last two risks can be minimized greatly with the use of ultrasound guidance. [ 4 ] [ 5 ]


The use of  ultrasound  has become the standard of care when preparing a patient for paracentesis. Confirmation of an ascitic effusion reduces the risks associated with a dry or blind tap of the abdomen. Anatomic landmarks, such as the midline  linea alba  approach, were traditionally used as reference points for needle insertion. Phased array or curvilinear ultrasound transducers are typically used in the hospital and outpatient setting to identify ascites in the abdominal cavity. Fluid within the abdominal cavity appears hypoechoic or anechoic (black) on ultrasound.  Morison's pouch  (hepatorenal recess) is a common starting location in concordance with ultrasound FAST ( focused assessment with sonography for trauma ) exam. Fluid collection can occur in a number of different locations and may be difficult to find, especially if the patient only exhibits a small volume of ascites. Measurement of the amount of fluid within the abdominal cavity is not necessary or very successful. Identification of sufficient fluid within the abdominal cavity for fluid analysis or to achieve a therapeutic benefit is all that is required to proceed to paracentesis. Ultrasound guidance of the paracentesis can also be used as an additional safety measure to ensure the needle stays within the ascitic fluid and avoidance of important vessels within the abdominal cavity. [ 5 ]


The patient is requested to urinate before the procedure; alternately, a  Foley catheter  is used to empty the bladder. The patient is positioned in the bed with the head elevated at 45–60 degrees to allow fluid to accumulate in lower abdomen. After cleaning the side of the abdomen with an antiseptic solution, the physician numbs a small area of skin and inserts a large-bore needle with a plastic sheath 2 to 5 cm (1 to 2 in) in length to reach the peritoneal (ascitic) fluid. The needle is removed, leaving the plastic sheath to allow drainage of the fluid. The fluid is drained by gravity, a syringe, or by connection to a vacuum bottle. Several litres of fluid may be drained during the procedure; however, if more than two litres are to be drained, it will usually be done over the course of several treatments. [ 6 ]  After the desired level of drainage is complete, the plastic sheath is removed and the puncture site bandaged. [ 6 ]  The plastic sheath can be left in place with a flow control valve and protective dressing if further treatments are expected to be necessary. [ 6 ]


If fluid drainage in  cirrhotic  ascites is more than 5 litres, patients may receive  intravenous   serum albumin  (25% albumin, 8 g/L) to prevent  hypotension  (low blood pressure). [ 7 ]  There has been debate as to whether albumin administration confers benefit, but a recent 2016  meta-analysis  concluded that it can reduce mortality after large-volume paracentesis significantly. [ 8 ]  However, for every end-point investigated, while albumin was favorable as compared to other agents (e.g., plasma expanders, vasoconstrictors), these were not statistically significant and the meta-analysis was limited by the quality of the studies—two of which that were in fact unsuitable—included in it. [ 8 ]


The procedure generally is not painful and does not require  sedation . The patient is usually discharged within several hours following post-procedure observation provided that blood pressure is otherwise normal and the patient experiences no dizziness. [ 1 ] [ 9 ] [ 10 ]


Paracentesis is known to be a safe procedure when ascitic fluid is readily visible, so complications are typically rare. Possible complications following or during the procedure involve infection, bleeding, the leakage ascitic of fluid, or  bowel perforation . [ 7 ] [ 5 ]  Of these, the most concerning in the immediate setting is bleeding within the peritoneal cavity. [ 11 ]


The z-tracking technique has held particular importance in performing paracentesis. A z-track is a technique that allows for decreased ascitic fluid leak following the paracentesis by displacing the needle tracks with respect to the  epidermis  and the  peritoneum . [ 6 ]


The  serum-ascites albumin gradient  can help determine the cause of the ascites. [ 7 ]


The color of the ascitic fluid can also be useful in analysis. Blood fluid can indicate trauma or  malignancy . A milky appearance of the fluid can indicate  lymphoma  or malignant peritoneal ascites. Cloudy or turbid fluid can indicate possible infection or inflammation within the peritoneal cavity. Straw or light yellow colored fluid indicates more plasma-like and benign causes of peritoneal ascites. [ 3 ]


The ascitic white blood cell count can help determine if the ascites is infected. A count of 250 neutrophils per ml or higher is considered diagnostic for spontaneous bacterial peritonitis. Cultures of the fluid can be taken, but the yield is approximately 40% (72–90% if  blood culture  bottles are used). Empiric antibiotics are typically started when  spontaneous bacterial peritonitis  is highly suspected. A third-generation cephalosporin is typically started in these cases to cover the most common organisms,  E. coli  and  Klebsiella , in SBP. [ 7 ]


Mild hematologic abnormalities do not increase the risk of bleeding. [ 12 ] [ 7 ]  The risk of bleeding may be increased if: [ 13 ]


Absolute contraindication is the acute abdomen that requires surgery.


Relative contraindications are: [ 6 ]


Percutaneous intentional extraluminal revascularization   is a percutaneous technique used in  interventional radiology  for limb salvage in patients with  lower limb ischemia  due to long  superficial femoral artery  occlusions. This method is intended for those patients who make poor candidates for infrainguinal arterial   bypass  surgery. [ 1 ]   A  guide wire [ 2 ]  is intentionally introduced in the  subintimal space , after which balloon dilatation is performed to create a new  lumen  for the blood to flow through. [ 3 ]  The technique is not without complications but may serve as a "temporary bypass" to provide wound healing and limb salvage. [ 4 ]


Percutaneous intentional extraluminal revascularization, or PIER, is an  endovascular  approach to  revascularization  of peripheral occlusions that may serve as an alternative to  transluminal  angioplasty. It is a minimally invasive procedure requiring only local anesthetic, which proves to be a major advantage over invasive surgical bypass procedures. [ 5 ]  Endovascular approaches, both extraluminal and transluminal, are usually indicated in patients who cannot tolerate the gold-standard treatment of surgical bypass, usually due to comorbid medical conditions that make them unsuitable for surgery. [ 6 ]


Typically, PIER is considered an indication when the transluminal approach is unable to be achieved due to anatomical complexity of the occluding lesion. Research has shown comparable outcomes between extraluminal and transluminal approaches when the extraluminal technique is used in more complex cases, however, the current literature is lacking in data when comparing these two techniques in clinically comparable lesions. [ 6 ]


Risks of the PIER procedure include those associated with all endovascular procedures, with the overall complication rate ranging between 8-17%. [ 7 ]  Some common complications are listed below:


Although variations of the procedure exist depending on physician preference and patient anatomy, a common technique for PIER of the  superficial femoral artery  is briefly outlined below.


Entry is made in an antegrade fashion into the common femoral artery near the mid-femoral head using a 5-French rigid catheter with an angulated tip. The catheter is advanced to the proximal portion of the SFA, proximal to the occlusion. The catheter tip is then advanced into the extraluminal, or subintimal, space. Adequate positioning is confirmed with injections of contrast. [ 8 ]


Once the catheter is in the extraluminal space, a guidewire is advanced in a loop configuration which allows for a more rigid structure that can be used to traverse the subintimal dissection plane when compared to the free end of a straight guidewire. The looped guidewire is further advanced towards the patent portion of the artery distal to the occlusion, where re-entry into the true lumen can now be achieved. To avoid bleeding complications in the event of arterial perforation, heparin is only administered once re-entry into the true lumen is confirmed. The false lumen created in the subintimal space is then dilated with a balloon catheter. [ 8 ]


A systematic review of 23 studies investigating subintimal angioplasty performed for occlusions in the femoral, femoropopliteal, and crural arteries found that the extraluminal technique achieves clinically similar outcomes as the transluminal approach. [ 7 ]