Forensic  imaging provides graphic documentation of an  autopsy , which manual autopsy does not. CT scanning provides quick whole-body imaging of skeletal and  parenchymal  alterations, whereas MR imaging gives better representation of soft tissue  pathology . [ 146 ]  All that being said, MRI is more expensive, and more time-consuming to utilize. [ 146 ]  Moreover, the quality of MR imaging deteriorates below 10 °C. [ 147 ]


In 1971 at  Stony Brook University ,  Paul Lauterbur  applied magnetic field gradients in all three dimensions and a back-projection technique to create NMR images. He published the first images of two tubes of water in 1973 in the journal  Nature , [ 148 ]  followed by the picture of a living animal, a clam, and in 1974 by the image of the thoracic cavity of a mouse. Lauterbur called his imaging method zeugmatography, a term which was replaced by (N)MR imaging. [ 1 ]  In the late 1970s, physicists  Peter Mansfield  and  Paul Lauterbur  developed MRI-related techniques, like the  echo-planar imaging  (EPI) technique. [ 149 ]


Raymond Damadian 's work into  nuclear magnetic resonance  (NMR) has been incorporated into MRI, having built one of the first scanners. [ 150 ]


Advances in  semiconductor  technology were crucial to the development of practical MRI, which requires a large amount of  computational power . This was made possible by the rapidly increasing number of  transistors  on a single  integrated circuit  chip. [ 151 ]  Mansfield and Lauterbur were awarded the 2003  Nobel Prize in Physiology or Medicine  for their "discoveries concerning magnetic resonance imaging". [ 152 ]


Marie Curie, une femme sur le front  (English: Marie Curie, a woman on the front) is a Franco-Belgian drama historical television film directed by  Alain Brunard  [ fr ]  and starring  Dominique Reymond . [ 2 ] [ 3 ]  It was broadcast on April 25, 2014 on  RTBF [ 4 ]  and November 11, 2014 on  France 2 . [ 5 ]


The fictional scenes are interspersed with many sequences from filmed archives including, at the end of the movie, several sequences where Marie Curie herself appears. [ 2 ]


Marie Curie ,  Nobel laureate in physics  and  chemistry , directs the  Radium Institute  when  World War I  breaks out in 1914. She equips a first van with  X-ray  equipment and goes to the site of the  Battle of the Marne . The  field hospital  she takes care of becomes notable for the few deaths recorded. In addition to the help of Doctor  Claudius Regaud , one of her collaborators who works on the treatment of cancer by radiotherapy, Marie Curie receives that of her 17-year-old daughter,  Irène . She quickly equips other vehicles, nicknamed by the soldiers “the  Little Curies  [ fr ] ”. Following the different fronts, her work becomes recognised and  radiography , which until then was mainly an amusement for the public, became a precious aid for medicine.


The movie participated to the  Luchon TV Festival  [ fr ] [ 6 ] [ 7 ]  and was awarded the Audience Award for Best TV Movie, while Dominique Reymond obtained the Best Actress Award. [ 8 ]


In  mammography ,  mean glandular dose  ( MGD ) is a quantity used to describe the  absorbed dose  of  radiation  to the  breast . It is based on a measurement of  air kerma  and conversion factors. MGD can be calculated from measurements made with  poly(methyl methacrylate)  (PMMA) blocks. It is often used to compare typical doses to patients between different centres or internationally, and is the preferred measure of the potential risk from mammography. [ 1 ] [ 2 ] [ 3 ]


MGD can be calculated from a measured incident air kerma at the top of the breast,

 K

 {\displaystyle K}

 , as follows: [ 4 ]


D
 =
 K
 g
 c
 s

 {\displaystyle D=Kgcs}


g

 {\displaystyle g}

  converts from incident air kerma to MGD, with a glandularity of 50%, based on breast thickness and  HVL .

 c

 {\displaystyle c}

  corrects for glandularity other than 50%, depending on the breast thickness and HVL, with two versions for ages 50–64 and 40–49.

 s

 {\displaystyle s}

  corrects for the x-ray  spectra  in use with a table of target/ filter  combinations. [ 4 ] [ 5 ]


MGD is typically used to define limits on mammography exposures by national and international organisations such as the  European Union  and  International Atomic Energy Agency , at <2.5  milligray  (mGy) per exposure to a standard breast (4.5 cm PMMA). [ 6 ]


In routine quality assurance testing of mammographic equipment, MGD measurements for a range of effective breast thicknesses with PMMA, and from real patient exposures, is widely recommended. [ 2 ]


Neuroimaging  is the use of quantitative (computational) techniques to study the  structure  and function of the  central nervous system , developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Increasingly it is also being used for quantitative research studies of brain disease and psychiatric illness.  Neuroimaging is highly multidisciplinary involving neuroscience, computer science, psychology and statistics, and is not a medical specialty.  Neuroimaging is sometimes confused with neuroradiology.


Neuroradiology  is a medical specialty that uses non-statistical brain imaging in a clinical setting, practiced by radiologists who are medical practitioners. Neuroradiology primarily focuses on recognizing brain lesions, such as vascular diseases, strokes, tumors, and inflammatory diseases. In contrast to neuroimaging, neuroradiology is qualitative (based on subjective impressions and extensive clinical training) but sometimes uses basic quantitative methods.  Functional brain imaging techniques, such as functional magnetic resonance imaging ( fMRI ), are common in neuroimaging but rarely used in neuroradiology.  Neuroimaging falls into two broad categories:


The first chapter of the history of neuroimaging traces back to the Italian neuroscientist  Angelo Mosso  who invented the 'human circulation balance', which could non-invasively measure the redistribution of  blood  during emotional and intellectual activity. [ 1 ]


In 1918, the American neurosurgeon  Walter Dandy  introduced the technique of ventriculography.  X-ray  images of the  ventricular system  within the brain were obtained by injection of filtered air directly into one or both lateral ventricles of the brain. Dandy also observed that air introduced into the subarachnoid space via lumbar spinal puncture could enter the cerebral ventricles and also demonstrate the cerebrospinal fluid compartments around the base of the brain and over its surface.  This technique was called  pneumoencephalography . [ citation needed ]


In 1927,  Egas Moniz  introduced  cerebral angiography , whereby both normal and abnormal blood vessels in and around the brain could be visualized with great precision.


In the early 1970s,  Allan McLeod Cormack  and  Godfrey Newbold Hounsfield  introduced  computerized axial tomography  (CAT or CT scanning), and ever more detailed anatomic images of the brain became available for diagnostic and research purposes. Cormack and Hounsfield won the 1979  Nobel Prize for Physiology or Medicine  for their work. Soon after the introduction of CAT in the early 1980s, the development of  radioligands  allowed  single-photon emission computed tomography  (SPECT) and  positron emission tomography  (PET) of the brain.


More or less concurrently,  magnetic resonance imaging  (MRI or MR scanning) was developed by researchers including  Peter Mansfield  and  Paul Lauterbur , who were awarded the  Nobel Prize for Physiology or Medicine  in 2003. In the early 1980s MRI was introduced clinically, and during the 1980s a veritable explosion of technical refinements and diagnostic MR applications took place. Scientists soon learned that the large blood flow changes measured by PET could also be imaged by the correct type of MRI.  Functional magnetic resonance imaging  (fMRI) was born, and
since the 1990s, fMRI has come to dominate the brain mapping field due to its low invasiveness, lack of radiation exposure, and relatively wide availability.


In the early 2000s, the field of neuroimaging reached the stage where limited practical applications of functional brain imaging have become feasible. The main application area is crude forms of  brain–computer interface .


The world record for the spatial resolution of a whole-brain MRI image was a 100-micrometer volume (image) achieved in 2019. The sample acquisition took about 100 hours. [ 2 ]  The spatial world record of a whole human brain of any method was an
X-ray tomography scan performing at the ESRF (European synchrotron radiation facility), which had a resolution of about 25 microns and requiring about 22 hours. This scan was part of the human organ atlas which has X-ray tomography scans of other organs in the human body with the same resolution. [ 3 ] [ 4 ]


A crucial idea for magnetic resonance imaging is that the net magnetization vector can be moved by exposing the spin system to energy of a frequency equal to the energy difference between the spin states (e.g., by a radio frequency pulse). If enough energy is delivered to the system, it is possible to make the net magnetization vector orthogonal to that of the external magnetic field.


Neuroradiology often follows a  neurological examination  in which a physician has found cause to more deeply investigate a patient who has or may have a  neurological disorder .


Common clinical indications for neuroimaging include head trauma, stroke like symptoms e.g.: sudden weakness/numbness in one half of body, difficulty talking or walking; seizures, sudden onset severe headache, sudden change in level of consciousness for unclear reasons.


Another indication for neuroradiology is CT-, MRI- and PET- guided   stereotactic surgery  or  radiosurgery  for treatment of intracranial tumors, arteriovenous malformations and other surgically treatable conditions. [ 5 ] [ 6 ] [ 7 ]


One of the more common neurological problems which a person may experience is simple  syncope . [ 8 ] [ 9 ]  In cases of simple  syncope  in which the patient's history does not suggest other neurological symptoms, the diagnosis includes a  neurological examination  but routine neurological imaging is not indicated because the likelihood of finding a cause in the central nervous system is extremely low and the patient is unlikely to benefit from the procedure. [ 9 ]


Neuroradiology is not indicated for patients with stable headaches which are diagnosed as migraine. [ 10 ]  Studies indicate that presence of migraine does not increase a patient's risk for intracranial disease. [ 10 ]  A diagnosis of migraine which notes the absence of other problems, such as  papilledema , would not indicate a need for radiological investigations. [ 10 ]  In the course of conducting a careful diagnosis, the physician should consider whether the headache has a cause other than the migraine and might require radiological investigations. [ 10 ] [ 11 ]


Computed tomography  (CT) or  Computed Axial Tomography  (CAT) scanning uses a series of  x-rays  of the head taken from many different directions. Typically used for quickly viewing  brain injuries , CT scanning uses a computer program that performs a numerical integral calculation (the inverse  Radon transform ) on the measured x-ray series to estimate how much of an x-ray beam is absorbed in a small volume of the brain. Typically the information is presented as cross-sections of the brain. [ 12 ]


Magnetic resonance imaging  (MRI) uses magnetic fields and radio waves to produce high quality two- or three-dimensional images of brain structures without the use of ionizing radiation (X-rays) or radioactive tracers.


The record for the highest spatial resolution of a whole intact brain (postmortem) is 100 microns, from Massachusetts General Hospital. The data was published in  Scientific Data  on 30 October 2019. [ 13 ]


Positron emission tomography  (PET) and  brain positron emission tomography , measure emissions from radioactively labeled metabolically active chemicals that have been injected into the bloodstream. The emission data are computer-processed to produce 2- or 3-dimensional images of the distribution of the chemicals throughout the brain. [ 14 ] : 57   The  positron  emitting  radioisotopes  used are produced by a  cyclotron , and chemicals are labeled with these radioactive atoms. The labeled compound, called a  radiotracer , is injected into the bloodstream and eventually makes its way to the brain.  Sensors in the PET scanner detect the radioactivity as the compound accumulates in various regions of the brain.  A computer uses the data gathered by the sensors to create multicolored 2- or 3-dimensional images that show where the compound acts in the brain. Especially useful are a wide array of  ligands  used to map different aspects of neurotransmitter activity, with by far the most commonly used PET tracer being a labeled form of glucose (see  Fludeoxyglucose (18F)  (FDG)).


The greatest benefit of PET scanning is that different compounds can show blood flow and oxygen and  glucose   metabolism  in the tissues of the working brain.  These measurements reflect the amount of brain activity in the various regions of the brain and allow to learn more about how the brain works.  PET scans were superior to all other metabolic imaging methods in terms of resolution and speed of completion (as little as 30 seconds) when they first became available.  The improved resolution permitted better study to be made as to the area of the brain activated by a particular task. The biggest drawback of PET scanning is that because the radioactivity decays rapidly, it is limited to monitoring short tasks. [ 14 ] : 60    Before fMRI technology came online, PET scanning was the preferred method of functional (as opposed to structural) brain imaging, and it continues to make large contributions to  neuroscience .


PET scanning is also used for diagnosis of brain disease, most notably brain tumors, epilepsy, and neuron-damaging diseases which cause dementia (such as Alzheimer's disease) all cause great changes in brain metabolism, which in turn causes easily detectable changes in PET scans. PET is probably most useful in early cases of certain dementias (with classic examples being  Alzheimer's disease  and  Pick's disease ) where the early damage is too diffuse and makes too little difference in brain volume and gross structure to change CT and standard MRI images enough to be able to reliably differentiate it from the "normal" range of cortical atrophy which occurs with aging (in many but not all) persons, and which does  not  cause clinical dementia.


FDG-PET scanning is also often used in assessment of patients with epilepsy who continue to have seizures despite adequate medical treatment. In focal epilepsy, where seizures begin in a small part of the brain before spreading elsewhere, it is one of the many modalities used to identify the region of brain responsible for seizure onset. Typically, the area of brain where seizures begin is dysfunctional even when patient is not having a seizure and uptakes less glucose, hence less FDG compared to healthy brain regions. [ 15 ]  This information can help plan for epilepsy surgery as a treatment for drug resistant epilepsy.


Other radiotracers have also been used to identify areas of seizure onset though they are not available commercially for clinical use. These include  11 C-flumazenil, 1 1 C-alpha-methyl-L-tryptophan,  11 C-methionine,  11 C-cerfentanil. [ 15 ]


Single-photon emission computed tomography  (SPECT) is similar to PET and uses  gamma ray -emitting  radioisotopes  and a  gamma camera  to record data that a computer uses to construct two- or three-dimensional images of active brain regions. [ 16 ]  SPECT relies on an injection of radioactive tracer, or "SPECT agent," which is rapidly taken up by the brain but does not redistribute. Uptake of SPECT agent is nearly 100% complete within 30 to 60 seconds, reflecting  cerebral blood flow  (CBF) at the time of injection. These properties of SPECT make it particularly well-suited for epilepsy imaging, which is usually made difficult by problems with patient movement and variable seizure types. SPECT provides a "snapshot" of cerebral blood flow since scans can be acquired after seizure termination (so long as the radioactive tracer was injected at the time of the seizure). A significant limitation of SPECT is its poor resolution (about 1 cm) compared to that of MRI. Today, SPECT machines with Dual Detector Heads are commonly used, although Triple Detector Head machines are available in the marketplace.  Tomographic reconstruction , (mainly used for functional "snapshots" of the brain) requires multiple projections from Detector Heads which rotate around the human skull, so some researchers have developed 6 and 11 Detector Head SPECT machines to cut imaging time and give higher resolution. [ 17 ] [ 18 ]


Like PET, SPECT also can be used to differentiate different kinds of disease processes which produce dementia, and it is increasingly used for this purpose. SPECT scan using Isoflupane labeled with I-123 (also called DaT scan) is useful in differentiating Parkinson's disease from other causes of tremor. [ 19 ]


SPECT scan is also used in evaluation of drug resistant epilepsy. This uses Tc 99  labeled hexamethyl-propylene amine oxime (Tc 99 HMPAO) or ethyl cysteinate dimer ( Tc 99  ECD) as the tracers. The radiotracer is injected into the patient's vein as soon as the start of a seizure is detected and scanning is done within few hours after the seizure is over. This technique is called ictal SPECT and relies on the increased CBF in areas of seizure onset during the seizure. Interictal SPECT is a scan done using the same tracers but during a time when the patient is not having a seizure. In between seizures, a reduction in CBF is seen in areas of seizure onset and is not as pronounced as the blood flow increase during the seizure. [ 20 ]


Cranial ultrasound  is usually only used in babies, whose open  fontanelles  provide acoustic windows allowing ultrasound imaging of the brain.  Advantages include the absence of  ionising radiation  and the possibility of bedside scanning, but the lack of soft-tissue detail means  MRI  is preferred for some conditions.


Functional magnetic resonance imaging  (fMRI) and  arterial spin labeling  (ASL) relies on the paramagnetic properties of oxygenated and deoxygenated  hemoglobin  to see images of changing blood flow in the brain associated with neural activity. This allows images to be generated that reflect which brain structures are activated (and how) during the performance of different tasks or at resting state. According to the oxygenation hypothesis, changes in oxygen usage in regional cerebral blood flow during cognitive or behavioral activity can be associated with the regional neurons as being directly related to the cognitive or behavioral tasks being attended.


Most fMRI scanners allow subjects to be presented with different visual images, sounds and touch stimuli, and to make different actions such as pressing a button or moving a joystick. Consequently, fMRI can be used to reveal brain structures and processes associated with perception, thought and action. The resolution of fMRI is about 2-3 millimeters at present, limited by the spatial spread of the hemodynamic response to neural activity. It has largely superseded PET for the study of brain activation patterns. PET, however, retains the significant advantage of being able to identify specific brain  receptors  (or  transporters ) associated with particular  neurotransmitters  through its ability to image radiolabeled receptor "ligands" (receptor ligands are any chemicals that stick to receptors). There is also significant concern regarding the validity of some of the statistics used in fMRI analyses; hence, the validity of conclusions drawn from many fMRI studies. [ 22 ]


With between 72% and 90% accuracy where chance would achieve 0.8%, [ 23 ]  fMRI techniques can decide which of a set of known images the subject is viewing. [ 24 ]


Recent studies on machine learning in psychiatry have used fMRI to build machine learning models that can discriminate between individuals with or without suicidal behaviour. Imaging studies in conjunction with machine learning algorithms may help identify new markers in neuroimaging that could allow stratification based on patients' suicide risk and help develop the best therapies and treatments for individual patients. [ 25 ]


Diffuse optical imaging  (DOI) or diffuse optical tomography (DOT) is a  medical imaging  modality which uses near  infrared  light to generate images of the body. The technique measures the  optical absorption  of  haemoglobin , and relies on the  absorption spectrum  of haemoglobin varying with its oxygenation status.  High-density diffuse optical tomography (HD-DOT) has been compared directly to fMRI using response to visual stimulation in subjects studied with both techniques, with reassuringly similar results. [ 26 ]  HD-DOT has also been compared to fMRI in terms of language tasks and resting state functional connectivity. [ 27 ]


Event-related optical signal  (EROS) is a brain-scanning technique which uses infrared light through optical fibers to measure changes in optical properties of active areas of the cerebral cortex. Whereas techniques such as  diffuse optical imaging  (DOT) and near-infrared spectroscopy (NIRS) measure optical absorption of haemoglobin, and thus are based on blood flow, EROS takes advantage of the scattering properties of the neurons themselves and thus provides a much more direct measure of cellular activity. EROS can pinpoint activity in the brain within millimeters (spatially) and within milliseconds (temporally). Its biggest downside is the inability to detect activity more than a few centimeters deep. EROS is a new, relatively inexpensive technique that is non-invasive to the test subject. It was developed at the University of Illinois at Urbana-Champaign where it is now used in the Cognitive Neuroimaging Laboratory of Dr. Gabriele Gratton and Dr. Monica Fabiani.


Magnetoencephalography  (MEG) is an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via extremely sensitive devices such as  superconducting quantum interference devices  (SQUIDs) or  spin exchange relaxation-free [ 28 ]  (SERF) magnetometers. MEG offers a very direct measurement of neural electrical activity (compared to fMRI for example) with very high temporal resolution but relatively low spatial resolution. The advantage of measuring the magnetic fields produced by neural activity is that they are likely to be less distorted by surrounding tissue (particularly the skull and scalp) compared to the electric fields measured by  electroencephalography  (EEG).  Specifically, it can be shown that magnetic fields produced by electrical activity are not affected by the surrounding head tissue, when the head is modeled as a set of concentric spherical shells, each being an isotropic homogeneous conductor. Real heads are non-spherical and have largely anisotropic conductivities (particularly white matter and skull). While skull anisotropy has a negligible effect on MEG (unlike EEG), white matter anisotropy strongly affects MEG measurements for radial and deep sources. [ 29 ]  Note, however, that the skull was assumed to be uniformly anisotropic in this study, which is not true for a real head: the absolute and relative thicknesses of  diploë  and tables layers vary among and within the skull bones. This makes it likely that MEG is also affected by the skull anisotropy, [ 30 ]  although probably not to the same degree as EEG.


There are many uses for MEG, including assisting surgeons in localizing a pathology, assisting researchers in determining the function of various parts of the brain, neurofeedback, and others.


Functional ultrasound imaging  (fUS) is a medical ultrasound imaging technique of detecting or measuring changes in neural activities or metabolism, for example, the loci of brain activity, typically through measuring blood flow or hemodynamic changes. Functional ultrasound relies on Ultrasensitive Doppler and ultrafast ultrasound imaging which allows high sensitivity blood flow imaging.


In June 2021, researchers reported the development of the first modular quantum brain scanner which uses magnetic imaging and could become a novel whole-brain scanning approach. [ 31 ] [ 32 ]


fMRI is commonly classified as a minimally-to-moderate risk due to its non-invasiveness compared to other imaging methods. fMRI uses blood oxygenation level dependent (BOLD)-contrast in order to produce its form of imaging. BOLD-contrast is a naturally occurring process in the body so fMRI is often preferred over imaging methods that require radioactive markers to produce similar imaging. [ 33 ]  A concern in the use of fMRI is its use in individuals with medical implants or devices and metallic items in the body. The magnetic resonance (MR) emitted from the equipment can cause failure of medical devices and attract metallic objects in the body if not properly screened for. Currently, the FDA classifies medical implants and devices into three categories, depending on MR-compatibility: MR-safe (safe in all MR environments), MR-unsafe (unsafe in any MR environment), and MR-conditional (MR-compatible in certain environments, requiring further information). [ 34 ]


The CT scan was introduced in the 1970s and quickly became one of the most widely used methods of imaging. A CT scan can be performed in under a second and produce rapid results for clinicians, with its ease of use leading to an increase in CT scans performed in the United States from 3 million in 1980 to 62 million in 2007. Clinicians oftentimes take multiple scans, with 30% of individuals undergoing at least 3 scans in one study of CT scan usage. [ 36 ]  CT scans can expose patients to levels of radiation 100-500 times higher than traditional x-rays, with higher radiation doses producing better resolution imaging. [ 37 ]  While easy to use, increases in CT scan use, especially in asymptomatic patients, is a topic of concern since patients are exposed to significantly high levels of radiation. [ 36 ]


In PET scans, imaging does not rely on intrinsic biological processes, but relies on a foreign substance injected into the bloodstream traveling to the brain. Patients are injected with radioisotopes that are metabolized in the brain and emit positrons to produce a visualization of brain activity. [ 33 ]  The amount of radiation a patient is exposed to in a PET scan is relatively small, comparable to the amount of environmental radiation an individual is exposed to across a year. PET radioisotopes have limited exposure time in the body as they commonly have very short half-lives (~2 hours) and decay rapidly. [ 38 ]  Currently, fMRI is a preferred method of imaging brain activity compared to PET, since it does not involve radiation, has a higher temporal resolution than PET, and is more readily available in most medical settings. [ 33 ]


The high temporal resolution of MEG and EEG allow these methods to measure brain activity down to the millisecond. Both MEG and EEG do not require exposure of the patient to radiation to function. EEG electrodes detect electrical signals produced by neurons to measure brain activity and MEG uses oscillations in the magnetic field produced by these electrical currents to measure activity. A barrier in the widespread usage of MEG is due to pricing, as MEG systems can cost millions of dollars. EEG is a much more widely used method to achieve such temporal resolution as EEG systems cost much less than MEG systems. A disadvantage of EEG and MEG is that both methods have poor spatial resolution when compared to fMRI. [ 33 ]


Owl's eye appearance , also known as  owl's eye sign , is a pattern used in the medical field to describe cells (or cell attributes) that resemble the shape of an actual owl's eye. Using the techniques of  histology  and  radiology , microscopes and other  medical imaging  are used to locate this pattern of "owl's eye" shaped cells. The term may be applied to the appearance of the cells themselves, or to aspects of their  morphology , such as reference to an "owl eye  nucleus ". The presence of "owl's eye" cells has been linked to a variety of conditions, such as in the  pathology  of  Hodgkin's lymphoma , a form of cancer. In particular, owl's eye appearance has been used to indicate the presence of  cytomegalovirus (CMV) , a  genus  of virus found in humans and other primates.


The description "owl's eye" may refer to:


The owl's eye appearance has a relationship with  Reed–Sternberg cells  in regard to  cytomegalovirus infection . [ 3 ]  Owl's eye appearance was used as an indication of the presence of the  cytomegalovirus  for the following case studies.


In 1982, a textbook wrote a chapter on cytomegalovirus and elaborated on its further relevance to owl's eye appearances. [ 4 ]  It was stated that the owl's eye had a characteristic of a clear halo that extended towards the cell membrane's nucleus. The cellular structure was found to be relevant to pneumonia which was caused by cytomegalovirus.


In a 1986 case study, a journal wrote that an owl's eye appearance was found in a total of 10 out of 10 patients. [ 5 ]  This was apparently due to the cytomegalovirus found in the patients that were also found to be diagnosed with AIDS. [ 5 ]  This case study involved  CT scans  that were used as a proposal as a way to detect the cytomegalovirus; however, the case study found that the cytomegalovirus had little relevance to the ability of CT scans. [ 5 ]


In 1987, a 33-year-old man diagnosed with AIDS was discovered with the cytomegalovirus in his eyes. [ 6 ]  The presence of an owl's eye appearance indicated the hospital that this patient was infected with the cytomegalovirus.


In 1990, a case study journal found that the owl's eye appearance correlated with the appearance of  HIV infection . [ 7 ]  This was where the case study involved the study of hospital cases and concluding that HIV plays a role in certain symptoms such as diarrhea. [ 7 ]  In another case study journal, the owl's eye appearances were found within the four patients that were observed. [ 8 ]  These patients were diagnosed with AIDS, and the presence of the owl's eye appearances proved the presence of cytomegalovirus. The confirmation of this virus was by the use of  immunohistochemistry . [ 8 ]


In a 2000 case study, it was discovered that the owl's eye appearance as a cell body was key for the  histopathological  understanding of the cytomegalovirus. [ 2 ]  The study found a strong relationship with a positive CMV PCR (p < 0.001). [ 2 ]  The discovery led to a result that owl's eye appearances were a strong sign for finding cytomegalovirus inside organs. [ 2 ]


In 2006, a case study journal wrote that owls' eye signs were found in patients with compromised  immune system . [ 9 ]  The purpose of this case study was to identify the features of the cytomegalovirus itself and the appearance of owl's eyes in relevance.


In 2009, a case study journal found a 44-year-old male patient to be infected with the cytomegalovirus. [ 10 ]  The presence of an eye's owl appearance found within the infected area, gave the necessary clues to confirm cytomegalovirus infection. [ 10 ]  A different case study found the appearance of an owl's eye in eighteen patients who were induced with drugs with a syndrome. [ 11 ]  The case study concluded that the cytomegalovirus disease was present, as the syndrome caused these patients to compromise their immune system. The case also found that the significant decrease of  white blood cells  was a factor in the preliminary stage of cytomegalovirus infection.


In 2011, a second edition textbook found that an owl's eye appearance was found inside a dead  retina . [ 12 ]  It was found due to the cause of the cytomegalovirus [ 12 ]  that had been residing inside an eye causing it to transition from healthy to dead.


In 2012, a journal was written on patients with cytomegalovirus infection and was used in mapping out the owl's eye cells using their microscopic technology. [ 13 ]  The patients were two elderly men at ages 75 and 77 years old. The image of the owl's eye appearance was created using the microscope via lasers, and two-dimensional images were created using computer software. The conclusion made by the journal was that the owl's eye had relevance to cytomegalovirus infection.


In 2019, a four-year-old boy was found with  acute flaccid paralysis  and was found to have an owl's eye appearance. [ 14 ]  The case also spoke on the presence of  enterovirus . [ 14 ]  The boy was also found to have a compromised immune system, which the enterovirus came through in infection. This case is unique due to the owl's eye appearance in relevance to the enterovirus.


Owl's eye appearances were also found within  tissues  and  organs  and are tied with  histopathological  cases. Most of these cases are also relevant to the pathology cases. However, these cases focused more on the specifics of a singular organ or tissue where the owl's eye appeared. These cases also have moderate relevance to the  cytomegalovirus .


In 1983, a journal wrote on a case study that found owl's eye appearance within the human eyes with the presence of potential cytomegalovirus with a deficient immune system. [ 15 ]  This was from the symptoms of  inflammation  that gave the diagnosis of an immune system to be deficient.


In 1985, a journal wrote that the appearance of owl's eye signs was due to the presence of  inflammatory bowel disease . [ 16 ]  This finding created a suspicion that the patient, in this case, was, infected with the  cytomegalovirus infection . However, further investigations showed that the patient was leading to a weak immune system. The patient was also identified as an 80-year-old man with a short-term case of diarrhea of blood and mucus, [ 16 ]  which was not contained and resulted in his death. The autopsy found the presence of cytomegalovirus this way.


In 2002, a rare case study journal wrote that a range of cytomegalovirus could infect patients diagnosed with AIDS and compromised immune systems. However, it was rare to involve the patient's skin. [ 17 ]  The skin at the cellular level was found to have owl's eye appearance and was concluded after several tests to be the cytomegalovirus infection.


In 2007, a journal wrote about the presence of owls' eye appearance as cells found in a transplant to a patient. [ 18 ]  The owl's eye appearance was considered rare for cytomegalovirus infection in the transplant, but was considered concerning. [ 18 ]  The cytomegalovirus infection was found of relevance towards compromised immune patients, as previous cases show that immune problems for patients have a similar case of cytomegalovirus infection.


In 2015, a review journal wrote on  herpes infection . It made a finding that owl's eye appearance was found in most organs [ 19 ]  through the investigation of a liver transplant. This provides evidence that the appearance of an owl's eye allowed the doctors to diagnose that cytomegalovirus infection from the liver transplant can be detected through detection tools.


In 2019, a case study was conducted on a series of patients that were infected with cytomegalovirus, [ 20 ]  and found the presence of the owl's eye appearance due to the presence of the virus. These owl's eye appearances were able to conclude that high-risk patients had a higher risk of cytomegalovirus.


Another particular case in 1957 found that an owl's eye appearance was found by two cells mirroring each other, producing the pattern inside the  histological  case study of  tumors . [ 21 ]  This is essentially what an owl's eye appearance is, however, the symptom did not occur from the presence of  cytomegalovirus  but from a unique case.


In another particular case in 1999, a case study was conducted by investigating a series of babies and found a baby with the presence of an owl's sign which was also found to be known as an  eye mask . This had to do with the presence of a rash, not the reality of cytomegalovirus. [ 22 ]


In a particular case in 2011, the owl's eye appearance was found within the cellular structure of the  spinal ganglia . [ 23 ]


Owl's eye appearance is also found within  radiology  images from  X-rays  and  CT scans . [ 24 ]  They appear as an indication of a clue to be used for analyzing the problem. These scans so far do not indicate that the owl's eye appearance found within radiology has any relevance towards the  cytomegalovirus infection  within patients. [ 25 ]  An example of the appearance of an owl's eye appearing within an image is of a skeleton within the bone structure, especially in the  spinal cord .


In 2009, a journal wrote on the presence of an owl's eye appearance that was found within the  skeletal structure  from the  magnetic resonance imaging  (MRI) scan in regards to compression of the  spinal cord . [ 26 ]  The owl's eye sign indicated that the spinal issues may be similar to other spinal cord cases and can be used to identify future cases.


In 2012, a case study journal article was written on a 10-year-old boy and discovered the owl's eye appeared inside the brain from an MRI scan. [ 27 ]  In the findings, it was found that the owl eye's sign was seen when doing  neuroradiology  images. The owl's eye sign was also detected from the spinal cord in spine MRI scans conducted post-treatment for the boy.


In 2015, a case study on owl's eye sign was found in a  neuroimaging  via MRI, which was rare due to the patient's diagnosis. [ 28 ]  The patient was found with  Flailing Arm Syndrome .


In June 2016, a journal article was written on a  central pontine myelinolysis  presence. [ 29 ]  And from doing radiology scans within the brain, they were able to find observations of owl's eye signs that also resembled similar to  monkey signs . [ 29 ]  The owl's eye appearance was also used as a sign in the MRI scans conducted in the scanning of the brain to show its relevance to the patient's diagnosed profile. In September 2016, a journal article examined MRI scans relevant to spinal cord conditions. [ 30 ]  These tests found owls' eye appearance as they were relevant to spinal cords in past cases. The journal concluded that the owl's eyes were not a main characteristic of tissue death.


A textbook has stated that within radiology, the appearance of an owl's eye can be seen from the  cells  and  neurological disorders . [ 31 ]  This textbook is a clinical review textbook and has provided relevance between owl's eye signs and  neurological imaging .


It was found that a 1986 case study found that  CT scans [ 5 ]  were of little effect when trying to find  cytomegalovirus  in the presence of owl's eye appearance.


Paediatric radiology  (or  pediatric radiology ) is a  subspecialty  of  radiology  involving the imaging of fetuses, infants, children, adolescents and young adults. Many paediatric radiologists practice at  children's hospitals .


Although some diseases seen in  paediatrics  are the same as that in adults, there are many conditions which are seen only in infants. The specialty has to take in account the dynamics of a growing body, from  preterm infants  to large  adolescents , where the organs follow growth patterns and phases. These require specialised imaging and treatment which is carried out in a children's hospital, which has all the facilities necessary to treat children and their specific pathologies.


To successfully diagnose a  paediatric condition , high-quality images are needed to give a diagnosis. To achieve this requires creating an environment where a child is comfortable. This is one of the most essential elements to paediatric radiology. For imaging departments which specialise in paediatric radiology, rooms can be tailored to suit a child's needs. For example, bright wall designs, visual stimulation and toys. These can be permanent fixtures as the department wouldn't need to cater to any other age range. For departments which only see children occasionally, creating a child-friendly environment is more difficult. It is usually achieved by creating one room as a child-friendly room where murals / stencils can be painted on the wall. Modern children's hospitals are now designed with much glass to allow as much natural light in as possible, the  Evelina Children's Hospital  being one of these.


Paediatric radiology comes with many challenges. Unlike adults, children cannot always understand / comprehend a change of environment. Therefore, staff are usually required to wear colourful uniforms, usually  scrubs , as opposed to a normal hospital uniform. It is also important to recognise that when a child is unwell, they follow their instincts, which is usually to cry and stay close to their parents. This presents a huge challenge for the radiographer, who must try to gain the child's trust and gain their co-operation. Once co-operation has been achieved there is another big challenge of keeping the child still for their imaging test. This can be very difficult for children in a lot of pain. Coercion and support from parents is usually enough to achieve this, however, in some extreme cases (such as  MRI  and  CT ), it may be necessary to sedate the child.


Another challenge faced is the radiation difference between an adult and child.


Medical Use of Radiation : Medicine has used ionising radiation for decades to help diagnose or treat children (and adults). There is no doubt that this imaging has saved lives. Medical imaging use has grown exponentially in the past few years, particularly the use of CAT Scans (also called CT scans). There are approximately 65 million CT scans done in the United States annually with an estimated 8 million in children. However, there is a much higher radiation dose from CT scans than from the traditional radiographs and fluoroscopy tests that radiologists perform and interpret. CT scans provide in general more information about the anatomy and diseases in the body but could be replaced for some orthopedic indications by other low-dose imaging modalities like  EOS . [ 1 ]  To do this, though, they may expose a person to 100 to 250 times the radiation dose compared to a chest x-ray. [ 2 ]


Radiation Safety Issues : There are risks from ionising radiation that are comprehensively studied in the survivors of the atomic bomb in Hiroshima in 1945. Longitudinal studies led by the National Academy of Sciences in the United States have shown increased cancer rates in this population that are dose dependent. From these data, modelling research suggests that even at the lower doses used in medical imaging, there may be an added risk of cancer. [ 3 ]  Last year, two medical physicists suggested that the increasing use of CAT Scans in the United States may increase cancer incidence in the future. [ 4 ]


Paediatric Radiation Protection Issues : Children are more radiosensitive than adults. They also have a longer life expectancy over which they may develop cancer from exposures to ionising radiation. The paediatric radiology and medical community has long had an awareness of this issue and has developed radiation protection policies and practices that reflect this. With the increased use of imaging and in particular, CT scanning, there is increasing attention to this issue by the entire medical and radiology communities. An educational resource for health care providers as well as patients and parents is the Image Gently web site started in 2008. [1]  There is collaboration by several radiology, medical physics, paediatrics, and governmental organisations to increase awareness of radiation safety issues in children and to provide education to all stakeholders caring for children on ways to decrease the ionising radiation exposure in children  [2] . For parents, basic information brochures that can be printed or downloaded that describe what an X ray is, what are its risks and benefits, and what can be done to decrease these risks  [3] . A call to action has been published advocating a reduction of ionising radiation exposure to children by delivering the right imaging exam, the right way with the right dose. [ 5 ]


Equipment adapted for use in paediatric radiology includes:


An example of positioning equipment for X ray scans on infants is the Pigg-O-Stat baby tube. [ 6 ]


Most equipment is the same used for adult imaging, but using lower dose and exposure setting adapted for children.


In many countries, paediatric radiology does not officially require a specific training. Where there is, paediatric radiologists have usually completed a  diagnostic radiology   residency , then complete one or two more years of subspecialty fellowship training before they are eligible to take the board examination for official subspecialty certification (e.g. Canada, UK, Switzerland). This then qualifies them in the specialised area of paediatric radiology.


Paleoradiology  (ancient radiology) is the study of  archaeological  remains through the use of  radiographic  techniques, such as  X-ray ,  CT  (computer tomography) and  micro-CT  scans. [ 1 ]  It is predominately used by archaeologists and  anthropologists  to examine  mummified  remains due to its non-invasive nature. [ 2 ]  Paleoradiologists can discover post-mortem damage to the body, or any artefacts buried with them, while still keeping the remains intact. Radiological images can also contribute evidence about the person's life, such as their age and cause of death. The first recorded use of paleoradiology (although not by that name) was in 1896, just a year after the Rōntgen radiograph was first produced. [ 3 ]  Although this method of viewing ancient remains is advantageous due to its non-invasive manner, many radiologists lack expertise in archeology and very few radiologists can identify ancient diseases which may be present. [ 4 ]


CT scans are most commonly used in paleoradiological studies because they can create images of soft tissue, organs and body cavities of mummified remains without performing an invasive and damaging autopsy. [ 5 ]  This enables archaeologists and anthropologists to digitally unwrap the remains and reveal what they contain. CT scanners create these images by taking multiple radiographic planes (or cuts) of the body at different angles which records the layers of different structures in the remains. This differs from typical  radiographic scans  (X-rays) where all the structural layers are documented in one image, which can create shadows and therefore limit their accuracy. [ 6 ] [ 7 ]


There are several main viewing techniques used in CT imaging. [ 8 ]


After these different views of the remains have been obtained, it is possible to create a three-dimensional reconstruction of the body. This brings into focus details which may have been missed on the axial imagining.  Algorithm  manipulation is used to create the rotational 3D images. [ 6 ] [ 5 ]  In paleoradiology, the 3D images provide a greater understanding of the remains themselves. For example, in 2002, a study of nine Egyptian mummies found that by using the 3D reconstructions they could see the preservation of soft tissues, such as the penis on one male body and braided hair on female remains. The 3D modelling also illustrated discrepancies between the remains, as some had their internal organs removed while others had not. [ 5 ]


Due to their ability to take multiple planes of the remains, CT scans are able to virtually 'fly through' the body to assess internal composition and cavities. [ 2 ]  These techniques are commonly used for diagnostic scans such as  colonoscopy  and  bronchoscopy , and the same method is applied to ancient remains. [ 5 ]  This enables researchers to digitally look through the remains from the top down, as though they were watching a short video of footage from the interior of the body. The technique presents observable data from the hollow cavities in the chest and abdomen regions. It can demonstrate whether there are internal organs present or if, in the case of Egyptian mummies, linen has been packed to maintain the body shape of the remains. [ 5 ]


Micro-CT is a specialised form of CT scan used to create images with pixels in micrometres. These images are frequently used for bone density examinations and produce greater detail for images of bony structures. This radiology technique is often used to examine the teeth from mummified remains. [ 6 ] [ 9 ]


Radiographs, or X-rays, have been used to study and observe ancient remains since their invention by  Wilhelm Röntgen  in 1895. This early form of X-ray, sometimes known as Röntgenograms, was immediately used by physicists, anthropologists, anatomists and archaeologists as shown below. [ 3 ] [ 6 ]


CT scans are the most common radiological technique used in modern archaeology due to their ability to provide more detailed information about ancient remains (such as soft tissue and blood vessels) and to produce 3D images by taking layers of different angled pictures. Archaeologists are able to collect data such as age, sex, the cause of death, socioeconomic status, mummification and burial practices by analysing the CT images. The images can also reveal whether the remains were subject to ancient diseases or post-mortem damage. [ 9 ]  Although paleoradiology practices are used on preserved remains such as European  bog bodies  and frozen bodies from the High Andes, they are more frequently documented in the analysis of Egyptian mummified remains. [ 4 ]


CT scans are used in  Egyptology  to gain insight into mummified bodies without risking damage to the integrity of the remains. Hoffman's recent study of nine Egyptian remains discovered new information regarding the mummification practices of Egyptians. The typical process of  mummification , as written by  Herodotus , involves the removal of the four major internal organs (liver, intestines, lungs and stomach) and placement of them in four  canopic jars . The heart is removed, embalmed and placed back into the body as it is an important feature in the journey to the  Egyptian afterlife . However, Hoffman discovered that this was not the case in all mummies. Through analysis of CT-produced 3D images, the "fly-through" technique and a combination of axial and coronal images, it was discovered that four of the remains had not had their internal organs removed and in another four the heart could not be identified. [ 5 ]  Hoffman suggests this may be due to socioeconomic differences between the mummies during the time they were alive. CT scans were further used in Hoffman's study to potentially identify one of the remains as  Ramesses I , a Pharaoh during  New Kingdom Egypt . It was found that the mummification practices of this particular body were in conjunction with those typically used during the New Kingdom period, as images showed rolled linen placed inside the body in order to preserve its shape. The mummy's arms were also found to be placed across the chest as a symbol of nobility. [ 5 ]


Imaging done by Rethy Chhem, in 2004, was able to correct a diagnosis of Ramesses II from X-rays done in 1976. The incorrect diagnosis had been of  ankylosing spondylitis , a form of arthritis. However, Chhem perceived that the pharaoh actually had  diffuse idiopathic skeletal hyperostosis , a calcification of the joints causing ligaments to attach to the spine. [ 6 ]  The CT images provided a clearer and more detailed image of the spine when compared with the early X-rays. This enabled the researchers to provide a greater insight into diseases found in ancient remains and achieve a more accurate diagnosis.


A recent CT scan of Tutankhamun in 2006 was able to provide evidence against the 'homicide theory'. [ 2 ] [ 6 ]  A depression fracture noted on the skull from X-rays taken 30 years previously was found to be a post-mortem injury rather than a cause of death. [ 6 ]  The hole in the head had been created in order to continue the embalming process of mummification. [ 10 ]  This CT investigation was also able to confirm Tutankhamun's age of death as nineteen and disprove the idea that the young pharaoh had suffered from  scoliosis ; rather the bend in his spine was from additional post-mortem damage to the body. [ 10 ]


Although the information and evidence gathered by radiological imaging of ancient remains have been largely beneficial to the fields of archaeology and anthropology, not all of the information can be considered accurate due to the lack of radiologists who specialise in  paleopathology . Instead, to obtain the most information from CT or X-ray images a team must meet to discuss the findings (e.g. for a skeletal study of the remains, an orthopaedic surgeon, bone pathologist and musculoskeletal radiologist would meet). [ 2 ] [ 4 ]  Another disadvantage to this technique is the low contrast resolution. The researcher may be unable to determine a difference between soft tissue and artefacts left from the embalming process. Due to the decomposed state of some of the mummified remains, it can also be difficult to distinguish internal organs due to shrinkage and a lack of preservation. Post-mortem injuries and damage to the body can also hinder the ability of radiological scans to provide accurate information for researchers. For example, in frozen remains, there can difficulty when differentiating whether a CT suggests the body has air-inflated lung tissue or if there is frozen fluid in the lungs. [ 4 ]


Paleoradiology is informative in its ability to assist in determining the age of death of the remains, however, this is not always completely accurate or available information. In a sample of bog bodies, 35% were not able to be identified with any age group and 30% could not be sex determined. A radiological study of an iceman was only able to produce an estimate of 40–50 years at age of death. In order to achieve a more accurate time frame, the body would have to be subject to an autopsy or similar physical assessment which would cause irreversible damage to the remains. [ 4 ]


Another disadvantage of paleoradiology is the difficulty in transporting the equipment or the artefact/remains to spaces where the images can be taken. [ 1 ] [ 11 ]  For example, in 2005 the mummy of Tutankhamun was imaged using a CT-scanner which had to be brought from the  Cairo Museum  to  tomb KV62  in the  Valley of the Kings . [ 10 ]  This was due to the fragile state of the remains which were unable to be removed from the climate-controlled tomb. In this study, funding came from  a five-year grant from the  Supreme Council of Antiquities , which was aided by the donation of a Siemens CT-scanner by the  National Geographic Society , [ 10 ]  however typically funding for research can be problematic as equipment is costly and there may not be sufficient interest to prompt donations.


Peak kilovoltage  ( kVp ) refers to the maximum  high voltage  applied across an  X-ray tube  to produce the X-rays. During X-ray generation, surface electrons are released from a heated cathode by  thermionic emission . The applied voltage (kV) accelerates these electrons toward an  anode  target, ultimately producing X-rays when the  electrons are stopped  in the anode. Thus, the kVp corresponds to the highest  kinetic energy  of the  electrons  striking the target, and is proportional to the maximum  photon energy  of the resulting  X-ray emission spectrum . [ 1 ]  In early and basic X-ray equipment, the applied voltage varies cyclically, with one, two, or more pulses per  mains AC power cycle . One standard way to measure  pulsating DC  is its  peak amplitude , hence kVp. Most modern X-ray generators apply a constant potential across the X-ray tube; in such systems, the kVp and the steady-state kV are identical.


kVp controls the property called "radiographic contrast" of an X-ray image (the ratio of transmitted radiation through regions of different thickness or density). Each body part contains a certain type of cellular composition which requires an X-ray beam with a certain kVp to penetrate it. The body part is said to have "subject contrast" (that is, different cellular make up: some dense, some not so dense tissues all within a specific body part). For example: bone to muscle to air ratios in the abdomen differ from those of the chest area. So the subject contrast is said to be higher in the chest than in the abdomen. In order to image the body so that the maximum information will result, higher subject contrast areas require a higher kVp so as to result in a low radiographic contrast image, and vice versa.


Although the product of tube current and exposure time, measured in  milliampere-seconds  (mA·s), is the primary controlling factor of radiographic density, kVp also affects the radiographic density indirectly. As the energy (which is proportional to the peak voltage) of the stream of electrons in the X-ray tube increases, the X-ray photons created from those electrons are more likely to penetrate the cells of the body and reach the image receptor (film or plate), resulting in increased film density (compared to lower energy beams that may be absorbed in the body on their way to the  image receptor ). However, scattered X-rays also contribute to increased film density: the higher the kVp of the beam, the more scatter will be produced. Scatter adds unwanted density (that is, density that does not bring pertinent information to the image receptor). This is why kVp is not primarily used to control  film  density – as the density resulting from increasing kVp exceeds what is needed to penetrate a body part, it only adds useless photons to the image.


Increasing mAs causes more photons (radiation) of the particular kVp energy to be produced. This is helpful when larger body parts are imaged, because they require more photons. The more photons that pass through a particular tissue type (whose kVp is interacting at the cellular level), the more photons reach the image receptor. The more photons that pass through a part and reach the image receptor with pertinent information, the more useful the film density on the resulting image. Conversely, lower mAs creates fewer photons, which will decrease film density, but is helpful when imaging smaller parts. The measurement of kVp is done by kV meter. The quality of X-ray tube depends upon the kV applied across the filament at the target. A slight change in kV affects the image significantly. Therefore, it is necessary to measure kV applied to tube accurately.


PI-RADS  is an  acronym  for Prostate Imaging Reporting and Data System, defining standards of high-quality clinical service for multi-parametric  magnetic resonance imaging  (mpMRI), including image creation and reporting.


In 2007, the AdMeTech Foundation's International Prostate MRI Working Group  [ 1 ]  convened the key global experts, including members of the  European Society of Urogenital Radiology  (ESUR) and the  American College of Radiology  (ACR). In March 2009 in Vienna an ESUR Prostate MRI Committee was formed, with the aim to produce minimal and maximal standards for acquisition and reporting of prostate MRI. This standardization was endorsed by the results of a consensus meeting in London in December 2009 [ 2 ]


Dr. Jelle Barentsz published with the ESUR Prostate MRI Committee the first PI-RADS (v.1) version in December 2011. [ 3 ]  Following this initiative the ACR, ESUR, and the AdMeTech Foundation formed a Joint Steering Committee, and by 2016 published a second version of PI-RADS (v.2) in European Urology. [ 4 ]  This paper enabled acceptance of the urologists of prostate MRI and was awarded “Best clinical scientific paper of 2016 in European Urology”.  In 2019 the PI-RADS Steering Committee published an updated version: PI-RADS v2.1. [ 5 ]


The aim of prostate MRI using PI-RADS is to assess the risk of clinically significant prostate cancer being present. Furthermore, the PI-RADS v2 system is designed to standardize prostate MRI.


Various studies have compared the predictive performance of PI-RADS v1 for detecting significant prostate cancer against either image-guided biopsy results (definitive  pathology ) and/or prostatectomy specimens ( histopathology ). In a 2015 articles in the Journal of Urology, Thompson reported multi-parametric MRI detection of significant prostate cancer had sensitivity of 96%, specificity of 36%, negative predictive value and positive predictive values of 92% and 52%; when PI-RADS was incorporated into a multivariate analysis (PSA, digital rectal exam, prostate volume, patient age) the area under the curve (AUC) improved from 0.776 to 0.879, p<0.001. [ 6 ]   A similar paper in European Radiology found that when correlated with histopathology, PI-RADS v2 correctly identified 94-95% of prostate cancer foci ≥0.5 mL, but was limited for the assessment of GS ≥4+3 (significant) tumors ≤0.5 mL; in their series, DCE-MRI offered limited added value to T2WI+DW-MRI. [ 7 ]   Other applications for which PI-RADS may be useful include prediction of termination of Active Surveillance due to  tumor  progression/aggressiveness, [ 8 ]  detection of extraprostatic extension of prostate cancer, [ 9 ]  and supplemental information when considering whether to re-biopsy patients with a history of previous negative biopsy. [ 10 ]


PI-RADS v2 is designed to improve detection, characterization and risk stratification in patients suspected of prostate cancer with a goal of better treatment decisions, improved outcomes and simplified reporting. However, multi-center validation trials are needed and expected to lead to modifications in the scoring system. [ 11 ]


Calculators designed to assist with PI-RADS criteria application have been developed to streamline the evaluation of prostate MRI. These tools, while not officially endorsed by the ACR, are becoming more popular among radiologists for their ability to reduce variability and improve diagnostic efficiency. Examples include PI-RADS v. 2.1 calculators available on independent online platforms, [ 12 ]  which helps in systematically applying the PI-RADS scoring system. These tools are increasingly recognized for their potential to enhance clinical workflow and reporting accuracy.


Plesiotherapy  is a  radiation therapy  modality in which a source of ionizing radiation is placed in contact with the exterior surface of the body. [ 1 ]


This is as distinguished from  teletherapy  in which radiation is projected by the source from a distance, from  brachytherapy  in which one or more sealed sources of radiation are placed inside the body, and from  radiopharmaceutical  therapy in which a source is introduced into the body, but that source is unsealed. [ citation needed ]


In contrast with teletherapy, where the distance between the source and the patient is exploited to produce a shallow fall-off of beam intensity with depth; in plesiotherapy, the source geometry is exploited to produce a dose fall-off that is steep, for treating superficial areas. [ 2 ] [ 3 ] [ 4 ]


One example of plesiotherapy is use of the  90 Sr  eye applicator in the treatment of  pterygium . [ 5 ]


This  medical treatment –related article is a  stub . You can help Wikipedia by  expanding it .


A  radioactive tracer ,  radiotracer , or  radioactive label  is a  synthetic  derivative of a  natural compound  in which one or more atoms have been replaced by a  radionuclide  (a radioactive atom). By virtue of its  radioactive decay , it can be used to explore the mechanism of chemical reactions by tracing the path that the radioisotope follows from reactants to products.  Radiolabeling  or  radiotracing  is thus the radioactive form of  isotopic labeling . In biological contexts, experiments that use radioisotope tracers are sometimes called  radioisotope feeding  experiments.


Radioisotopes of  hydrogen ,  carbon ,  phosphorus ,  sulfur , and  iodine  have been used extensively to trace the path of  biochemical reactions . A radioactive tracer can also be used to track the distribution of a substance within a natural system such as a  cell  or  tissue , [ 1 ]  or as a  flow tracer  to track  fluid flow . Radioactive tracers are also used to determine the location of fractures created by  hydraulic fracturing  in natural gas production. [ 2 ]  Radioactive tracers form the basis of a variety of imaging systems, such as,  PET scans ,  SPECT scans  and  technetium scans .  Radiocarbon dating  uses the naturally occurring  carbon-14  isotope as an  isotopic label .


Isotopes  of a  chemical element  differ only in the mass number. For example, the isotopes of  hydrogen  can be written as  1 H ,  2 H  and  3 H , with the mass number superscripted to the left. When the  atomic nucleus  of an isotope is unstable, compounds containing this isotope are  radioactive .  Tritium  is an example of a radioactive isotope.


The principle behind the use of radioactive tracers is that an  atom  in a  chemical compound  is replaced by another atom, of the same chemical element. The substituting atom, however, is a radioactive isotope. This process is often called radioactive labeling. The power of the technique is due to the fact that radioactive decay is much more energetic than chemical reactions. Therefore, the radioactive isotope can be present in low concentration and its presence detected by sensitive  radiation detectors  such as  Geiger counters  and  scintillation counters .  George de Hevesy  won the 1943  Nobel Prize for Chemistry  "for his work on the use of isotopes as tracers in the study of chemical processes".


There are two main ways in which radioactive tracers are used


The commonly used radioisotopes have short  half lives  and so do not occur in nature in large amounts. They are produced by  nuclear reactions . One of the most important processes is absorption of a  neutron by an atomic nucleus, in which the mass number of the element concerned increases by 1 for each neutron absorbed. For example,


In this case the atomic mass increases, but the element is unchanged. In other cases the product nucleus is unstable and decays, typically emitting protons, electrons ( beta particle ) or  alpha particles . When a nucleus loses a proton the  atomic number  decreases by 1. For example,


Neutron irradiation is performed in a  nuclear reactor . The other main method used to synthesize radioisotopes is proton bombardment. The proton are accelerated to high energy either in a  cyclotron  or a  linear accelerator . [ 3 ]


Tritium  (hydrogen-3) is produced by neutron irradiation of  6 Li :


Tritium has a  half-life   4500 ± 8  days (approximately 12.32 years) [ 4 ]  and it decays by  beta decay . The  electrons  produced have an average energy of 5.7 keV. Because the emitted electrons have relatively low energy, the detection efficiency by scintillation counting is rather low. However, hydrogen atoms are present in all organic compounds, so tritium is frequently used as a tracer in  biochemical  studies.


11 C  decays by  positron emission  with a half-life of ca. 20 min.  11 C is one of the isotopes often used in  positron emission tomography . [ 3 ]


14 C  decays by  beta decay , with a half-life of 5730 years. It is continuously produced in the upper atmosphere of the earth, so it occurs at a trace level in the environment. However, it is not practical to use naturally-occurring  14 C for tracer studies. Instead it is made by neutron irradiation of the isotope  13 C  which occurs naturally in carbon at about the 1.1% level.  14 C has been used extensively to trace the progress of organic molecules through metabolic pathways. [ 5 ]


13 N  decays by  positron emission  with a half-life of 9.97 min. It is produced by the nuclear reaction


13 N  is used in  positron emission tomography  (PET scan).


15 O  decays by positron emission with a half-life of 122 seconds. It is used in positron emission tomography.


18 F  decays predominantly by β emission, with a half-life of 109.8 min. It is made by proton bombardment of  18 O  in a cyclotron or  linear particle accelerator . It is an important isotope in the  radiopharmaceutical  industry. For example, it is used to make labeled  fluorodeoxyglucose  (FDG) for application in PET scans. [ 3 ]


32 P  is made by neutron bombardment of  32 S


It decays by beta decay with a half-life of 14.29 days. It is commonly used to study protein phosphorylation by  kinases  in biochemistry.


33 P  is made in relatively low yield by neutron bombardment of  31 P . It is also a beta-emitter, with a half-life of 25.4 days. Though more expensive than  32 P , the emitted electrons are less energetic, permitting better resolution in, for example, DNA sequencing.


Both isotopes are useful for labeling  nucleotides  and other species that contain a  phosphate  group.


35 S  is made by neutron bombardment of  35 Cl


It decays by beta-decay with a half-life of 87.51 days. It is used to label the sulfur-containing  amino-acids   methionine  and  cysteine . When a sulfur atom replaces an oxygen atom in a  phosphate  group on a  nucleotide  a  thiophosphate  is produced, so  35 S can also be used to trace a phosphate group.


99m Tc  is a very versatile radioisotope, and is the most commonly used radioisotope tracer in medicine. It is easy to produce in a  technetium-99m generator , by decay of  99 Mo .


The molybdenum isotope has a half-life of approximately 66 hours (2.75 days), so the generator has a useful life of about two weeks. Most commercial  99m Tc generators use  column chromatography , in which  99 Mo in the form of molybdate, MoO 4 2−  is adsorbed onto acid alumina (Al 2 O 3 ). When the  99 Mo decays it forms  pertechnetate  TcO 4 − , which because of its single charge is less tightly bound to the alumina. Pulling normal saline solution through the column of immobilized  99 Mo elutes the soluble  99m Tc, resulting in a saline solution containing the  99m Tc as the dissolved sodium salt of the pertechnetate. The pertechnetate is treated with a  reducing agent  such as  Sn 2+  and a  ligand . Different ligands form  coordination complexes  which give the technetium enhanced affinity for particular sites in the human body.


99m Tc decays by gamma emission, with a half-life: 6.01 hours. The short half-life ensures that the body-concentration of the radioisotope falls effectively to zero in a few days.


123 I  is produced by proton irradiation of  124 Xe . The  caesium  isotope produced is unstable and decays to  123 I. The isotope is usually supplied as the iodide and hypoiodate in dilute sodium hydroxide solution, at high isotopic purity. [ 6 ]   123 I has also been produced at Oak Ridge National Laboratories by proton bombardment of  123 Te . [ 7 ]


123 I decays by  electron capture  with a half-life of 13.22 hours. The emitted 159  keV   gamma ray  is used in  single-photon emission computed tomography  (SPECT). A 127 keV gamma ray is also emitted.


125 I  is frequently used in  radioimmunoassays  because of its relatively long half-life (59 days) and ability to be detected with high sensitivity by gamma counters. [ 8 ]


129 I  is present in the environment as a result of the testing of  nuclear weapons  in the atmosphere. It was also produced in the  Chernobyl  and  Fukushima  disasters.  129 I decays with a  half-life  of 15.7 million years, with low-energy  beta  and  gamma  emissions. It is not used as a tracer, though its presence in living organisms, including human beings, can be characterized by measurement of the gamma rays.


Many other isotopes have been used in specialized radiopharmacological studies. The most widely used is  67 Ga  for  gallium scans .  67 Ga is used because, like  99m Tc, it is a gamma-ray emitter and various ligands can be attached to the Ga 3+  ion, forming a  coordination complex  which may have selective affinity for particular sites in the human body.


An extensive list of radioactive tracers used in hydraulic fracturing can be found below.


In  metabolism  research, tritium and  14 C -labeled glucose are commonly used in  glucose clamps  to measure rates of  glucose uptake ,  fatty acid synthesis , and other metabolic processes. [ 9 ]   While radioactive tracers are sometimes still used in human studies,  stable isotope  tracers such as  13 C  are more commonly used in current human clamp studies. Radioactive tracers are also used to study  lipoprotein  metabolism in humans and experimental animals. [ 10 ]


In  medicine , tracers are applied in a number of tests, such as  99m Tc in  autoradiography  and  nuclear medicine , including  single-photon emission computed tomography  (SPECT), positron emission tomography (PET) and  scintigraphy . The  urea breath test  for  helicobacter pylori  commonly used a dose of  14 C labeled urea to detect h. pylori infection. If the labeled urea was metabolized by h. pylori in the stomach, the patient's breath would contain labeled carbon dioxide. In recent years, the use of substances enriched in the non-radioactive isotope  13 C  has become the preferred method, avoiding patient exposure to radioactivity. [ 11 ]


In  hydraulic fracturing , radioactive tracer isotopes are injected with hydraulic fracturing fluid to determine the injection profile and location of created fractures. [ 2 ]   Tracers with different half-lives are used for each stage of hydraulic fracturing. In the United States amounts per injection of radionuclide are listed in the US  Nuclear Regulatory Commission  (NRC) guidelines. [ 12 ]   According to the NRC, some of the most commonly used tracers include  antimony-124 ,  bromine-82 ,  iodine-125 ,  iodine-131 ,  iridium-192 , and  scandium-46 . [ 12 ]  A 2003 publication by the  International Atomic Energy Agency  confirms the frequent use of most of the tracers above, and says that  manganese-56 ,  sodium-24 ,  technetium-99m ,  silver-110m ,  argon-41 , and  xenon-133  are also used extensively because they are easily identified and measured. [ 13 ]


Radiodensity  (or  radiopacity ) is  opacity  to the  radio wave  and  X-ray  portion of the  electromagnetic spectrum : that is, the relative inability of those kinds of  electromagnetic radiation  to pass through a particular material.  Radiolucency  or  hypodensity  indicates greater passage (greater  transradiancy ) to X-ray  photons [ 1 ]  and is the analogue of  transparency and translucency  with  visible light . Materials that inhibit the passage of electromagnetic radiation are called  radiodense  or  radiopaque , while those that allow radiation to pass more freely are referred to as  radiolucent . Radiopaque volumes of material have white appearance on  radiographs , compared with the relatively darker appearance of radiolucent volumes. For example, on typical radiographs, bones look white or light gray (radiopaque), whereas muscle and skin look black or dark gray, being mostly invisible (radiolucent).


Though the term radiodensity is more commonly used in the context of  qualitative  comparison, radiodensity can also be quantified according to the  Hounsfield scale , a principle which is central to  X-ray computed tomography  (CT scan) applications. On the Hounsfield scale,  distilled water  has a value of 0 Hounsfield units (HU), while air is specified as -1000 HU.


In modern medicine, radiodense substances are those that will not allow X-rays or similar radiation to pass.  Radiographic imaging  has been revolutionized by radiodense  contrast media , which can be passed through the bloodstream, the  gastrointestinal tract , or into the cerebral spinal fluid and utilized to highlight CT scan or X-ray images. Radiopacity is one of the key considerations in the design of various devices such as guidewires or  stents  that are used during  radiological  intervention. The radiopacity of a given endovascular device is important since it allows the device to be tracked during the interventional procedure.
The two main factors contributing to a material's radiopacity are density and atomic number. Two common radiodense elements used in medical imagery are  barium  and  iodine .


Medical devices often contain a radiopacifier to enhance visualization during implantation for temporary implantation devices, such as catheters or guidewires, or for monitoring the position of permanently implanted medical devices, such as stents, hip and knee implants, and screws. Metal implants usually have sufficient radiocontrast that additional radiopacifier is not necessary. Polymer-based devices, however, usually incorporate materials with high electron density contrast compared to the surrounding tissue. Examples of radiocontrast materials include titanium, tungsten, barium sulfate, [ 2 ]  bismuth oxide [ 3 ]  and zirconium oxide. Some solutions involve direct binding of heavy elements, for instance iodine, to polymeric chains in order to obtain a more homogeneous material which has lower interface criticalities. [ 4 ]  When testing a new medical device for regulatory submission, device manufacturers will usually evaluate the radiocontrast according to  ASTM F640 "Standard Test Methods for Determining Radiopacity for Medical Use."


The term  radiogenomics  is used in two contexts: either to refer to the study of genetic variation associated with response to radiation (radiation genomics) or to refer to the correlation between cancer imaging features and gene expression (imaging genomics).


In radiation genomics, radiogenomics is used to refer to the study of  genetic variation  associated with response to  radiation therapy . Genetic variation, such as  single nucleotide polymorphisms , is studied in relation to a cancer patient's risk of developing toxicity following  radiation therapy . [ 1 ] [ 2 ] [ 3 ]     It is also used in the context of studying the  genomics  of tumor response to  radiation therapy . [ 4 ] [ 5 ]


The term radiogenomics was coined in 2002 by Andreassen et al. (2002) [ 6 ]   as an analogy to  pharmacogenomics , which studies the genetic variation associated with drug responses. See also West et al. (2005) [ 7 ]   and Bentzen (2006). [ 8 ]


In 2009, [ 9 ] [ 10 ]  a Radiogenomics Consortium (RGC) was established to facilitate and promote multi-centre collaboration of researchers linking genetic variants with response to radiation therapy. The Radiogenomics Consortium ( http://epi.grants.cancer.gov/radiogenomics/ ) is a Cancer Epidemiology Consortium supported by the Epidemiology and Genetics Research Program of the National Cancer Institute of the National Institutes of Health. [ 11 ]  RGC researchers have completed numerous clinical studies that identified genetic variants associated with radiation toxicities in patients with prostate, breast, lung, head and neck, and other cancers.


Radiological images are used to diagnose disease on a large scale: tissue imaging correlates with tissue  pathology .  The addition of genomic data including  DNA microarrays ,  miRNA ,  RNA-Seq  allows new correlations to be made between cellular genomics and tissue-scale imaging.


Radiographers , also known as  radiologic technologists ,  diagnostic radiographers  and  medical radiation technologists [ 1 ]  are  healthcare professionals  who specialise in the  imaging  of  human anatomy  for the  diagnosis  and  treatment  of  pathology . Radiographers are infrequently, and almost always erroneously, known as  x-ray technicians.  In countries that use the title  radiologic technologist  they are often informally referred to as  techs  in the clinical environment; this phrase has emerged in popular culture such as television programmes. [ 2 ]  The term  radiographer  can also refer to a  therapeutic radiographer , also known as a  radiation therapist .


Radiographers are  allied health professionals  who work in both  public healthcare  and private healthcare and can be physically located in any setting where appropriate diagnostic equipment is located, most frequently in  hospitals . The practice varies from country to country and can even vary between hospitals in the same country. [ 3 ]


Radiographers are represented by a variety of organizations worldwide, including the  International Society of Radiographers and Radiological Technologists  which aims to give direction to the profession as a whole through collaboration with national representative bodies. [ 4 ]


For the first three decades of  medical imaging 's existence (1897 to the 1930s), there was no standardized differentiation between the roles that we now differentiate as radiologic technologist (a technician in an  allied health profession  who obtains the images) versus  radiologist  (a  physician  who interprets them). By the 1930s and 1940s, as it became increasingly apparent that proper interpretation of the images required not only a physician but also one who was specifically trained and experienced in doing so, the differentiation between the roles was formalized. Simultaneously, it also became increasingly true that just as a radiologic technologist cannot do the radiologist's job, the radiologist also cannot do the radiologic technologist's job, as it requires some knowledge, skills, experience, and  certifications  that are specific to it.


Radiography's origins and  fluoroscopy's origins  can both be traced to 8 November 1895, when German physics professor  Wilhelm Röntgen  discovered the X-ray and noted that, while it could pass through human tissue, it could not pass through bone or metal. [ 5 ]  Röntgen referred to the radiation as "X", to indicate that it was an unknown type of radiation. He received the first  Nobel Prize in Physics  for his discovery. [ 6 ]


There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a likely reconstruction by his biographers: [ 7 ] [ 8 ]  Röntgen was investigating  cathode rays  using a  fluorescent  screen painted with barium  platinocyanide  and a  Crookes tube  which he had wrapped in black cardboard to shield its fluorescent glow. He noticed a faint green glow from the screen, about 1 metre away. Röntgen realized some invisible rays coming from the tube were passing through the cardboard to make the screen glow: they were passing through an opaque object to affect the film behind it. [ 9 ]


Röntgen discovered X-rays' medical use when he made a picture of his wife's hand on a photographic plate formed due to X-rays. The photograph of his wife's hand was the first ever photograph of a human body part using X-rays. When she saw the picture, she said, "I have seen my death." [ 9 ]


The first use of X-rays under clinical conditions was by  John Hall-Edwards  in  Birmingham, England  on 11 January 1896, when he radiographed a needle stuck in the hand of an associate. [ 10 ] [ self-published source? ]  On 14 February 1896, Hall-Edwards also became the first to use X-rays in a surgical operation. [ 11 ]


The United States saw its first medical X-ray obtained using a  discharge tube  of  Ivan Pulyui 's design. In January 1896, on reading of Röntgen's discovery, Frank Austin of  Dartmouth College  tested all of the discharge tubes in the physics laboratory and found that only the Pulyui tube produced X-rays. This was a result of Pulyui's inclusion of an oblique "target" of  mica , used for holding samples of  fluorescent  material, within the tube. On 3 February 1896 Gilman Frost, professor of medicine at the college, and his brother Edwin Frost, professor of physics, exposed the wrist of Eddie McCarthy, whom Gilman had treated some weeks earlier for a fracture, to the X-rays and collected the resulting image of the broken bone on  gelatin photographic plates  obtained from Howard Langill, a local photographer also interested in Röntgen's work. [ 12 ]


X-rays were put to diagnostic use very early; for example,  Alan Archibald Campbell-Swinton  opened a radiographic laboratory in the United Kingdom in 1896, before the dangers of ionizing radiation were discovered. Indeed,  Marie Curie  pushed for radiography to be used to treat wounded soldiers in World War I. Initially, many kinds of staff conducted radiography in hospitals, including physicists, photographers, physicians, nurses, and engineers. The medical speciality of radiology grew up over many years around the new technology. When new diagnostic tests were developed, it was natural for the radiographers to be trained in and to adopt this new technology. Radiographers now perform  fluoroscopy ,  computed tomography ,  mammography ,  ultrasound ,  nuclear medicine  and  magnetic resonance imaging  as well. Although a nonspecialist dictionary might define radiography quite narrowly as "taking X-ray images", this has long been only part of the work of "X-ray Departments", Radiographers, and Radiologists. Initially, radiographs were known as roentgenograms, [ 13 ]  while  Skiagrapher  (from the  Ancient Greek  words for "shadow" and "writer") was used until about 1918 to mean  Radiographer . [ 14 ]


The history of  magnetic resonance imaging  includes many researchers who have discovered  NMR  and described  its underlying physics , but it is regarded to be invented by  Paul C. Lauterbur  in September 1971; he published the theory behind it in March 1973. [ 15 ] [ 16 ]  The factors leading to image contrast (differences in tissue relaxation time values) had been described nearly 20 years earlier by Erik Odeblad (doctor and scientist) and Gunnar Lindström. [ 17 ] [ 18 ] [ 19 ] [ 20 ]


In 1950,  spin echoes  and  free induction decay  were first detected by  Erwin Hahn [ 21 ] [ 22 ]  and in 1952,  Herman Carr  produced a one-dimensional NMR spectrum as reported in his Harvard PhD thesis. [ 23 ] [ 24 ] [ 25 ]  In the  Soviet Union ,  Vladislav Ivanov  filed (in 1960) a document with the USSR State Committee for Inventions and Discovery at Leningrad for a Magnetic Resonance Imaging device, [ 26 ] [ 27 ] [ 28 ]  although this was not approved until the 1970s. [ 29 ]


By 1959, Jay Singer had studied blood flow by NMR relaxation time measurements of blood in living humans. [ 30 ] [ 31 ]  Such measurements were not introduced into common medical practice until the mid-1980s, although a patent for a whole-body NMR machine to measure blood flow in the human body was already filed by Alexander Ganssen in early 1967. [ 19 ] [ 31 ] [ 32 ] [ 33 ] [ 34 ]


In the 1960s and 1970s the results of a very large amount of work on relaxation, diffusion, and chemical exchange of water in cells and tissues of various types appeared in the scientific literature. [ 19 ]  In 1967, Ligon reported the measurement of NMR relaxation of water in the arms of living human subjects. [ 19 ]  In 1968, Jackson and Langham published the first NMR signals from a living animal. [ 19 ] [ 35 ]


A radiographer uses their expertise and knowledge of  patient care ,  physics ,  human anatomy ,  physiology ,  pathology  and  radiology  to assess patients, develop optimum radiological techniques and evaluate the resulting radiographic media. [ 36 ]


This branch of healthcare is extremely varied, especially between different countries, and as a result radiographers in one country often have a completely different role to that of radiographers in another. However, the base responsibilities of the radiographer are summarised below: [ 37 ]


On a basic level, radiographers do not generally interpret diagnostic media, rather they evaluate media and make a decision about its diagnostic effectiveness. In order to make this evaluation radiographers must have a comprehensive but not necessarily exhaustive knowledge of pathology and radiographic appearances; it is for this reason that radiographers often do not interpret or diagnose without further training. Notwithstanding, it is now becoming more common that radiographers have an extended and expanded clinical role, this includes a role in initial radiological diagnosis, diagnosis consultation and what subsequent investigations to conduct. [ 38 ]  It is not uncommon for radiographers to now conduct procedures which would have previously been undertaken by a cardiologist, urologist, radiologist or oncologist autonomously. [ 39 ]


Contrary to what could be inferred, radiographers conduct and contribute to investigations which are not necessarily radiological in nature, e.g.  sonography  and  magnetic resonance imaging .


Radiographers often have opportunities to enter military service due to their role in healthcare. As with most other occupations in the medical field many radiographers have rotating shifts that include night duties.


Radiography is a deeply diverse profession with many different modalities and specialities. It is not uncommon for radiographers to be specialised in more than one modality and even have expertise of interventional procedures themselves; however this depends on the country in which they operate. As a result of this the typical career pathway for a radiographer is hard to summarise. Upon qualifying it is common for radiographers to focus solely on plain film radiography before specialising in any one chosen modality. After a number of years in the profession, non-imaging based roles often become open and radiographers may then move into these positions. [ 3 ]


Generally, imaging modalities are all diagnostic, all have the potential to be used therapeutically in order to deliver an intervention. Modalities (or specialities) include but are not limited to:


Non-imaging modalities vary, and are often undertaken in addition to imaging modalities. They commonly include:


Education varies worldwide due to legal limitations on scope of practice.


The profession of diagnostic radiographer is called "medical imaging technologist", it is a regulated healthcare profession. A diploma of a specific professional Bachelor is a requirement for registration and recognition. [ 41 ]


Since 2 December 2014, everyone who works at a Medical Imaging department, is obliged to be in possession of the recognition and the visa issued by the Ministry of Health (a professional identity card that is considered a license) [ 42 ]


To practice a health care profession with a foreign diploma from within the EEA or equivalent in the EEA, it is necessary to request the recognition for the profession from Government of Flanders (Agency of Care and Health). [ 43 ]


It is possible to request the recognition if:


In Germany radiographers must complete a 3-year apprenticeship before they qualify as a 'Medizinisch-technischer Radiologieassistent'. Only after qualifying do radiographers in Germany fulfil the requirements to practise as a fully qualified MTRA.


Similar to other countries, they work within the areas of radiography diagnostics ( CT scans ,  magnetic resonance imaging ,  radiography ,  digital subtraction angiography ),  radiation therapy ,  radiation dosimeters  and  nuclear medicine . [ 44 ]


Radiographers  in the  Republic of Ireland  (ROI) must be registered with  CORU  before they can practice in the Republic of Ireland. Student radiographers training in the ROI will typically study for 4 years on an approved bachelor's degree program; currently degree programs only exist at  University College Dublin . [ 45 ] [ 46 ]


Applicants must have either an approved qualification, a schedule 3 qualification, an appropriate letter of recommendation/accreditation or another qualification which is deemed 'suitably relevant' by registration board in order to successfully fulfil the vocational education requirements to become a Radiographer in the ROI. Applications for registration with qualifications outside of this are considered on an individual basis; typically this includes most international applicants. [ 47 ]


The professional body representing Radiographers in the ROI is the  Irish Institute of Radiography and Radiation Therapy (IIRRT) . [ 48 ]


To practice as a Radiographer or Radiation Therapist in Ireland, one must register with CORU as of 31 October 2015. [ 49 ]  CORU is Ireland's multi-profession health regulator. Set up under the Health and Social Care Professionals Act 2005, CORU is used to protect the public by promoting high standards of professional conduct, education, training and competence through statutory registration of health and social care professionals. [ 50 ]  If a radiographer commences clinical practice without registration then they may be prosecuted with a fine or an imprisonment of up to six months. [ 49 ]


Radiography is a regulated profession in Malta and anyone wanting to practice Diagnostic or Therapeutic Radiography would need to obtain state registration in order to be licensed as a Radiographer, obtained from the Council for Professions Complementary to Medicine (CPCM). [ 51 ]


In Malta, in order for an individual to become a Radiographer he/she first has to follow a course offered by the University of Malta. The course is BSc (Hons) Radiography and its duration is of four years. On completion of the course, the graduate will have the conditions to be eligible for registration with the council for professions complementary to Medicine [ 52 ]


A foreign radiographer can work in Malta should the necessary documentation and competencies have been obtained and presented. Radiographers working on Malta should abide by the rules of the host country and title of radiographer will be used. [ 53 ]


An application form has to be filled along with the necessary authenticated copies of several documents. The application form includes the insertion of personal details of the individual along with the description of qualifications and the university which granted the qualifications. The individual has to declare whether he or she is registered with another Health Care Profession Register in Malta. [ 53 ]


Below is a list of the documents needed for a professional to register with the council:


In cases where the professional qualification acquired was not obtained from an Accredited Institution in Malta, a letter is to be submitted, issued from the Malta Qualifications Recognition Information Centre ( MQRIC ), certifying that the Institution from where the qualification was obtained is equivalently accredited and indicate the level of qualification in accordance to the Malta Qualifications Framework. [ 53 ]


For applicants from the  European Economic Area  countries, once the application is submitted, it will follow the regulations established on the  Directive 2005/36/EC  on the recognition of qualifications between member states. [ 54 ]  In these cases, the professional document and theoretical and practical training are required to be equivalent to the requirements of Malta, i.e. An EQF Level 6 Bachelor's Degree with an equivalent syllabus to that of the University of Malta and their course is no more than one year shorter. Should the radiographer have a substantial difference between their professional qualifications and those required by CPCM, the radiographer has the right to provide further evidence of competence (including professional experience or CPD), otherwise, the CPCM board should offer the applicant the possibility to do an aptitude test or adaptation period (as chosen by the applicant). A  Flow chart  explaining this procedure for EEA applicants can be found on the government's website. [ 55 ]


As a developing country, the health care sector in  Federal Democratic Republic of Nepal  has very limited resources meaning radiological services are rather limited.
Nepal is still struggling to improve and manage conventional radiological examinations. Radiological Services in Nepal commenced in 1923 at Military Hospital by Dr. Rana and Dr Asta Bahadur Shrestha. The first health related training program began in 1933 at the Nepal Rajkiya Ayurved School; the Civil Medical School was later established in 1934. Radiological education in Nepal started in 1923 in a 64 bedded Military Hospital, Tri-ChandraElectro-Medical Institute. The post graduate (MSc) program in physics at TU began in 1965 with only Nuclear Physics specialization. In 1972, the Institute of Medicine (IOM) which is affiliated with TU started the Proficiency Certificate Level (PCL) Radiography course however this has since stopped.


Radiotherapy was first introduced at Maternity Hospital in 1976 utilising radium needle treatment. CT and Nuclear Medicine was introduced in 1988 at Bir Hospital. The Radiotherapy unit with Tele Cobalt-60 machine was established at Bir Hospital in 1991.


Nepal became a member of IAEA in 2008. Since 2008 onwards diploma level radiography courses have been conducted across the country by the Council for Technical Education and Vocational Training (CTEVT) and other affiliated institutions.


In Nepal there are 125 vocational health training institutes however only 15 are conducting radiological technological education. Bachelor level radiography education is taught in two universities & one college whereas master level radiography course is taught
in one where another university is in pipeline. Until recently, therapeutic radiography courses have not been taught in Nepal;
radiation therapists are predominantly trained abroad.


The Nepal Health Professional Council (NHPC) is the legislative body for registering, accrediting, developing & enforcing quality assurance of Health Professionals, including Radiographers, in Nepal.  [ citation needed ]


Until 1997, radiographers were required to register the Evidence of Competence at the Chief of Medical Inspections. This was mandatory under the Law on Paramedic professions. After innovate the law of Individual Health Care Professions (BIG), the registration requirements for radiographers were cancelled. A voluntary register has been set up in consultation with the Health Care Inspectorate: the Paramedics Quality Register. [ citation needed ]


The Paramedics Quality Register comes from the BIG. The purpose of the Paramedics Quality Register is to guarantee the quality of professional practice. Through the registration and re-registration (once in five years) it becomes visible for patients, health insurers etc. that the registered radiographer professional is and remains competent in the field of professional practice. Despite the fact that the quality register is not compulsory according to the law, many hospitals are obliged to do it. The hospitals are obliged to provide good quality care. Health insurers also attach great value to the Paramedics Quality Register because they are also required to provide good care.


Radiographers who are in possession of a valid Certificate of Competence, diploma of certificate and endorse the code of professional conduct of the professional association, can be enroll in the Paramedics historical register.