Radiation and Environmental Biophysics  is a quarterly  peer-reviewed   scientific journal  covering research in  biophysics  and  radiation biology . It is published by  Springer Science+Business Media  and the  editors-in-chief  are Anna A. Friedl ( Ludwig-Maximilian University ), Werner Rühm ( Helmholtz Zentrum München ), and Andrzej Wojcik ( Stockholm University ).


It was established in 1974, by continuing in part the former title  Biophysik .


According to the  Journal Citation Reports , the journal has a 2020  impact factor  of 1.925. [ 5 ]


This article about a  biophysics  journal is a  stub . You can help Wikipedia by  expanding it .


Radiation Protection Dosimetry  is a monthly  peer-reviewed   scientific journal  covering  radiobiology , especially  dosimetry  and  radiation monitoring  for both  ionizing  and  non-ionizing radiation . The  editor-in-chief  is J. Hans Zoetelief ( Delft University of Technology ).


According to the  Journal Citation Reports , the journal had a 2019  impact factor  of 0.773. [ 1 ]


Radiography  is a  peer-reviewed   medical journal  covering  diagnostic  and therapeutic  radiography . The journal is published by  Elsevier  and was established in 1995. The founding  editor-in-chief  was H. Brian Bentley from 1995 until 2003. [ 1 ]  The current editor-in-chief is Julie Nightingale ( University of Salford ). The journal was preceded by an insert in the  British Journal of Radiology  starting in 1927. [ 2 ]  In 1935, the current journal's predecessor, which was also known as  Radiography  was first published. [ 3 ]  It is the official journal of the  Society and College of Radiographers  and the  European Federation of Radiographer Societies . [ 4 ]  Besides regular issues, the journal occasionally publishes special issues. [ 5 ]


Radiology  is a monthly,  peer reviewed ,  medical journal , owned and published by the  Radiological Society of North America . The editor is Linda Moy, MD. The focus of  Radiology  is imaging research articles in radiology and medical imaging. [ 2 ] [ 3 ] [ 4 ]


Publishing formats are  original research  articles (3000 words), research letters (600 words),  technical developments (2000), invited perspectives (2500)   review articles  (4500), special report, invited  editorial , statements and guidelines (3000), Images in Radiology, Radiology Diagnosis Please, and  letter to the editor . [ 5 ]


According to the  Journal Citation Reports ,  Radiology  has a 2021  impact factor  of 29.146. In addition, the journal is indexed in the following databases: [ 2 ] [ 6 ] [ 7 ] [ 8 ]


Skeletal Radiology  is a  peer-reviewed   medical journal  published by  Springer Science+Business Media , covering disorders of the  musculoskeletal system , including the  spine . It is the official journal of  The International Skeletal Society . [ 1 ]


The journal is abstracted and indexed in  Current Contents /Clinical Medicine,  EMBASE ,  PASCAL ,  PubMed / Medline ,  Science Citation Index , and  Scopus . [ 2 ]  According to the  Journal Citation Reports , the journal has a 2016  impact factor  of 1.737. [ 3 ]


Ultrasound in Medicine and Biology  is a monthly  peer-reviewed   medical journal  published by  Elsevier  on behalf of the  World Federation for Ultrasound in Medicine and Biology . It covers  ultrasound technology  in  clinical   diagnostic ,  interventional  and  therapeutic  applications, including the  physics ,  engineering , and  technology  of  ultrasound  in  medicine  and  biology . It was established in 1973. The  editor-in-chief  is   Paul S. Sidhu  ( King's College Hospital ) since 2021. The founding editor was Denis N. White, who served from 1973 to 1992 and was succeeded by  Peter N. T. Wells .


According to the  Journal Citation Reports , the journal has a 2023  impact factor  of 2.4. [ 5 ]


Journal of Ultrasound in Medicine  is a  medical journal  that covers aspects of medical ultrasound, mainly its direct application to patient care but also relevant basic science, and biological effects etc. The journal is published by  Wiley . [ 1 ]


According to the  Journal Citation Reports , the journal has a 2021  impact factor  of 2.754. [ 2 ]


Ultrasound Quarterly  is a quarterly  peer-reviewed   medical journal  covering research on  medical ultrasound . It was established in 1988 and is published by  Lippincott Williams & Wilkins  on behalf of the  Society of Radiologists in Ultrasound , of which it is the official journal. The  editor-in-chief  is Theodore J. Dubinsky. According to the  Journal Citation Reports , the journal has a 2017  impact factor  of 1.021, ranking it 108th out of 126 journals in the category "Radiology, Nuclear Medicine, and Medical Imaging". [ 1 ]


The  absent bowtie sign  is a  radiologic sign  indicative of a  meniscal tear  in the knee joint. On sagittal  magnetic resonance  (MR) images, the body of the meniscus normally looks like a bow tie, with two distinct segments. The  absent bowtie sign  is present when there is a lack of two segments seen on consecutive sagittal MR images. [ 1 ]  This sign can be used to diagnose "bucket-handle" tears of the mensici, which are longitudinal tears with displaced fragment(s). The "handle" is created when the inner meniscal fragment is displaced into the intercondylar notch. [ 2 ]


The  anteater nose sign  is a  radiologic sign  characterized by a tubular extension of the anterior process of the  calcaneus  bone that either extends towards or overlaps the  navicular  bone. This sign indicates the presence of a calcaneonavicular  tarsal coalition , which is an inherited  congenital  malformation of the foot. In this condition, there are abnormal bony, cartilaginous, or fibrous connections between the bones of the hindfoot, midfoot, or both regions. [ 1 ]


The  aortic nipple sign  is a  radiologic sign  that describes the appearance of the left  superior intercostal vein  on  chest radiography.  The left superior intercostal vein is located next to the  aortic arch , appearing on radiographs as a small mass (or "nipple") projecting from the arch. [ 1 ]  This sign is seen in a small number of individuals and may be mistaken for  lymphadenopathy  or a  neoplasm . [ 2 ]  The  aortic nipple sign  may be helpful in identifying certain thoracic pathologies, such as  pneumomediastinum , [ 2 ]  as it may change in size due to changes in intrathoracic pressure. [ 1 ]  Its appearance is also affected by changes in posture and vascular flow. [ 1 ]


The  bear paw sign  is a  radiologic sign  that describes the appearance of xanthogranulomatous pyelonephritis on computer tomography (CT) scans. Xanthogranulomatous pyelonephritis is a rare type of chronic  pyelonephritis  where the damaged areas of the kidneys are replaced by  foam cells . On CT, multiloculated hypoattenuating masses with bright rim enhancement may be seen in the renal parenchyma, resembling the toe pads of a bear's paw. These masses are indicative of dilated renal  calyces  and  xanthomas . [ 1 ]


The Royal College of Radiologists (RCR)  is the professional body responsible for the specialties of clinical  oncology  and  clinical radiology  throughout the  United Kingdom . Its role is to advance the science and practice of radiology and oncology, further public education, and set appropriate professional standards of practice. The college sets and monitors the educational curriculum for those training to enter the profession and administers the Fellowship of the Royal College of Radiologists exams. It is a  registered charity  in the United Kingdom (no. 211540). [ 1 ]


The RCR has 2 faculties, representing Clinical Oncology and Clinical Radiology. It publishes two academic journals,  Clinical Oncology  and  Clinical Radiology .


The RCR has been based at 63 Lincoln's Inn Fields in London since July 2013.


A series of bodies has represented practitioners of radiological medicine in the UK, starting in 1897 with the foundation of the  Roentgen Society  (named for the  physicist   Wilhelm Conrad Röntgen ). Subsequently, the British Association of Radiologists was founded in 1934. In 1935, The Society of Radiotherapists of Great Britain and Ireland was set up for doctors specializing in the treatment of cancers using X-rays and radium. The latter two bodies amalgamated in 1939 to form the Faculty of Radiologists, which was granted a Royal Charter in 1953. In 1975, a Supplemental Charter was granted, and the faculty became the Royal College of Radiologists. [ citation needed ]


In 1950, the first issue of the  Clinical Radiology Journal  was published by the Faculty of Radiologists. The first issue of  Clinical Oncology  was published in September 1989. [ citation needed ]


In May 2021, the RCR launched the first national radiotherapy consent forms to help standardize and strengthen the informed consent process for adult cancer patients undergoing radiotherapy. Standardized consent forms with tailored information regarding radiotherapy for different tumor sites were released, and digital versions developed in collaboration with digital consent company Concentric Health. [ 2 ]  Welsh language versions of the consent forms were published in June 2022. [ citation needed ]


Candidates are examined against the Specialty Training Curriculum for Clinical Radiology. The specialty trainees are expected to complete their First FRCR examination before progressing to ST2. During their ST3 training year they are expected to pass the Final FRCR Part A examination and must complete this before progressing to ST4. During ST4, trainees are expected to pass the Final FRCR Part B examination. [ 3 ]


The fellowship examinations start at the beginning of the Specialty Training Year 1 (ST1). The First FRCR examination expects candidates to have gained a knowledge of the physical principles that underpin diagnostic medical imaging and of the anatomy needed to perform and interpret radiological studies. [ 4 ] [ 5 ]  The First FRCR examination comprises two modules: Physics and Anatomy. The anatomy modules is a 90-minute exam comprising 100 images, where each image has several annotations, each of which in turn has a single related question. [ 6 ]  The physics module is a 120-minute multiple choice question paper comprising 40 questions, each with five true or false answers. [ 6 ]


The Final FRCR Part A examination comprises the single best of answers, split into two separate papers for the purposes of delivery. Each paper contains 120 questions and examining candidates on all aspects of clinical radiology and the basic sciences of physics, anatomy and techniques. [ 7 ]


The main areas examined are:


1. Cardiothoracic and Vascular


2. Musculoskeletal and Trauma


3. Gastro-intestinal


4. Genito-urinary, Adrenal, Obstetrics & Gynecology and Breast


5. Pediatric


6. Central Nervous and Head & Neck


During the ST4 training, the specialty trainees are expected to complete the Final FRCR Part B. The Final FRCR (Part B) examination consists of a reporting session, a rapid reporting session and an oral examination. [ 8 ]


The extensive examination provided by the RCR ensures the high quality and standard of radiology consultants. It has been deemed as one of the hardest examinations in the medical profession, along with the  FRCA  and  FRCPath . [ citation needed ]


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Radiology  ( / ˌ r eɪ d ɪ ˈ ɒ l ə dʒ i /   rey-dee-ol-uh-jee ) is the medical specialty that uses  medical imaging  to diagnose  diseases  and guide treatment within the bodies of humans and other animals. It began with  radiography  (which is why its name has a root referring to  radiation ), but today it includes all imaging modalities. This includes technologies that use no ionizing electromagnetic radiation, such as  ultrasonography  and  magnetic resonance imaging ), as well as others that do use radiation, such as  computed tomography  (CT),  fluoroscopy , and  nuclear medicine  including  positron emission tomography  (PET).  Interventional radiology  is the performance of usually  minimally invasive  medical procedures with the guidance of imaging technologies such as those mentioned above.


The modern practice of radiology involves a team of several different healthcare professionals. A radiologist, who is a medical doctor with specialized post-graduate training, interprets medical images, communicates these findings to other physicians through reports or verbal communication, and uses imaging to perform minimally invasive medical procedures [ 1 ] [ 2 ]  The  nurse  is involved in the care of patients before and after imaging or procedures, including administration of medications, monitoring of vital signs and monitoring of sedated patients. [ 3 ]  The  radiographer , also known as a "radiologic technologist" in some countries such as the  United States  and  Canada , is a specially trained healthcare professional that uses sophisticated technology and positioning techniques to produce medical images for the radiologist to interpret. Depending on the individual's training and country of practice, the radiographer may specialize in one of the above-mentioned imaging modalities or have expanded roles in image reporting. [ 4 ]


Radiographs  (originally called roentgenographs, named after the discoverer of  X-rays ,  Wilhelm Conrad Röntgen ) are produced by transmitting X-rays through a patient. The X-rays are projected through the body onto a detector; an image is formed based on which rays pass through (and are detected) versus those that are absorbed or scattered in the patient (and thus are not detected). Röntgen discovered X-rays on November 8, 1895, and received the first  Nobel Prize in Physics  for his discovery in 1901. [ citation needed ]


In film-screen radiography, an X-ray tube generates a beam of X-rays, which is aimed at the patient. The X-rays that pass through the patient are filtered through a device called a grid or  X-ray filter , to reduce scatter, and strike an undeveloped film, which is held tightly to a screen of light-emitting phosphors in a light-tight cassette. The film is then developed chemically and an image appears on the film. Film-screen radiography is being replaced by  phosphor plate radiography  but more recently by  digital radiography  (DR) and the  EOS imaging . [ 5 ]  In the two latest systems, the X-rays strike sensors that converts the signals generated into digital information, which is transmitted and converted into an image displayed on a computer screen. In  digital radiography  the sensors shape a plate, but in the EOS system, which is a slot-scanning system, a linear sensor vertically scans the patient. [ citation needed ]


Plain radiography was the only imaging modality available during the first 50 years of radiology. Due to its availability, speed, and lower costs compared to other modalities, radiography is often the first-line test of choice in radiologic diagnosis. Also despite the large amount of data in CT scans, MR scans and other digital-based imaging, there are many disease entities in which the classic diagnosis is obtained by plain radiographs. Examples include various types of arthritis and pneumonia, bone tumors (especially benign bone tumors), fractures, congenital skeletal anomalies, and certain kidney stones. [ citation needed ]


Mammography  and  DXA  are two applications of low energy projectional radiography, used for the evaluation for  breast cancer  and  osteoporosis , respectively. [ citation needed ]


Fluoroscopy and  angiography  are special applications of  X-ray  imaging, in which a fluorescent screen and image intensifier tube is connected to a closed-circuit television system. [ 6 ] : 26   This allows real-time imaging of structures in motion or augmented with a  radiocontrast  agent. Radio contrast agents  are usually administered by swallowing or injecting into the body of the patient to delineate anatomy and functioning of the blood vessels, the  genitourinary system , or the  gastrointestinal tract  (GI tract). Two radiocontrast agents are presently in common use. Barium sulfate (BaSO 4 ) is given orally or rectally for evaluation of the GI tract. Iodine, in multiple proprietary forms, is given by oral, rectal, vaginal, intra-arterial or intravenous routes. These radiocontrast agents strongly absorb or scatter X-rays, and in conjunction with the real-time imaging, allow demonstration of dynamic processes, such as  peristalsis  in the digestive tract or blood flow in arteries and veins. Iodine contrast may also be concentrated in abnormal areas more or less than in normal tissues and make abnormalities ( tumors ,  cysts ,  inflammation ) more conspicuous. Additionally, in specific circumstances, air can be used as a contrast agent for the gastrointestinal system and carbon dioxide can be used as a contrast agent in the venous system; in these cases, the contrast agent attenuates the X-ray radiation less than the surrounding tissues. [ citation needed ]


CT imaging uses X-rays in conjunction with computing  algorithms  to image the body. [ 7 ]
In CT, an X-ray tube opposite an X-ray detector (or detectors) in a ring-shaped apparatus rotate around a patient, producing a computer-generated cross-sectional image (tomogram). [ 8 ]  CT is acquired in the  axial  plane, with coronal and sagittal images produced by computer reconstruction. Radiocontrast agents are often used with CT for enhanced delineation of anatomy. Although radiographs provide higher spatial resolution, CT can detect more subtle variations in attenuation of X-rays (higher contrast resolution). CT exposes the patient to significantly more ionizing radiation than a radiograph. [ citation needed ]


Spiral multidetector CT uses 16, 64, 254 or more detectors during continuous motion of the patient through the radiation beam to obtain fine detail images in a short exam time. With rapid administration of intravenous contrast during the CT scan, these fine detail images can be reconstructed into three-dimensional (3D) images of carotid, cerebral, coronary or other arteries. [ citation needed ]


The introduction of computed tomography in the early 1970s revolutionized diagnostic radiology by providing front-line clinicians with detailed images of anatomic structures in three dimensions. CT scanning has become the test of choice in diagnosing some urgent and emergent conditions, such as cerebral hemorrhage,  pulmonary embolism  (clots in the arteries of the lungs),  aortic dissection  (tearing of the aortic wall),  appendicitis ,  diverticulitis , and obstructing kidney stones. Before the development of CT imaging, risky and painful  exploratory surgery  was often the only way to obtain a definitive diagnosis of the cause of severe abdominal pain which could not be otherwise ascertained from external observation. [ 9 ]  Continuing improvements in CT technology, including faster scanning times and improved resolution, have dramatically increased the accuracy and usefulness of CT scanning, which may partially account for increased use in medical diagnosis. [ citation needed ]


Medical ultrasonography uses ultrasound (high-frequency sound waves) to visualize soft tissue structures in the body in real time. No  ionizing radiation  is involved, but the quality of the images obtained using ultrasound is highly dependent on the skill of the person (ultrasonographer) performing the exam and the patient's body size. Examinations of larger,  overweight  patients may have a decrease in image quality as their  subcutaneous fat  absorbs more of the sound waves. This results in fewer sound waves penetrating to organs and reflecting back to the transducer, resulting in loss of information and a poorer quality image. Ultrasound is also limited by its inability to image through air pockets (lungs, bowel loops) or bone. Its use in medical imaging has developed mostly within the last 30 years. The first ultrasound images were static and two-dimensional (2D), but with modern ultrasonography, 3D reconstructions can be observed in real time, effectively becoming "4D". [ citation needed ]


Because ultrasound imaging techniques do not employ ionizing radiation to generate images (unlike radiography, and CT scans), they are generally considered safer and are therefore more common in  obstetrical imaging . The progression of pregnancies can be thoroughly evaluated with less concern about damage from the techniques employed, allowing early detection and diagnosis of many fetal anomalies. Growth can be assessed over time, important in patients with chronic disease or pregnancy-induced disease, and in multiple pregnancies (twins, triplets, etc.). Color-flow Doppler ultrasound measures the severity of  peripheral vascular disease  and is used by cardiologists for dynamic evaluation of the heart, heart valves and major vessels.  Stenosis , for example, of the  carotid arteries  may be a warning sign for an impending  stroke . A  clot , embedded deep in one of the inner veins of the legs, can be found via ultrasound before it dislodges and travels to the lungs, resulting in a potentially fatal  pulmonary embolism . Ultrasound is useful as a guide to performing  biopsies  to minimize damage to surrounding tissues and in drainages such as  thoracentesis . Small, portable ultrasound devices now replace  peritoneal lavage  in  trauma  wards by non-invasively assessing for the presence of internal  bleeding  and any internal organ damage. Extensive internal bleeding or injury to the major organs may require surgery and repair.


MRI uses strong magnetic fields to align  atomic nuclei  (usually  hydrogen   protons ) within body tissues, then uses a radio signal to disturb the axis of rotation of these nuclei and observes the  radio frequency  signal generated as the nuclei return to their baseline states. [ 10 ]   The radio signals are collected by small antennae, called coils, placed near the area of interest. An advantage of MRI is its ability to produce images in  axial ,  coronal ,  sagittal  and multiple oblique planes with equal ease. MRI scans give the best soft tissue contrast of all the imaging modalities. With advances in scanning speed and spatial resolution, and improvements in computer 3D algorithms and hardware, MRI has become an important tool in musculoskeletal radiology and neuroradiology. [ citation needed ]


One disadvantage is the patient has to hold still for long periods of time in a noisy, cramped space while the imaging is performed. Claustrophobia (fear of closed spaces) severe enough to terminate the MRI exam is reported in up to 5% of patients. Recent improvements in magnet design including stronger magnetic fields (3  teslas ), shortening exam times, wider, shorter magnet bores and more open magnet designs, have brought some relief for claustrophobic patients. However, for magnets with equivalent field strengths, there is often a trade-off between image quality and open design. MRI has great benefit in imaging the brain, spine, and musculoskeletal system. The use of MRI is currently contraindicated for patients with pacemakers, cochlear implants, some indwelling medication pumps, certain types of cerebral aneurysm clips, metal fragments in the eyes, some metallic hardware due to the powerful magnetic fields, and strong fluctuating radio signals to which the body is exposed. Areas of potential advancement include functional imaging, cardiovascular MRI, and MRI-guided therapy.


Nuclear medicine imaging involves the administration into the patient of radiopharmaceuticals consisting of substances with affinity for certain body tissues labeled with radioactive tracer. The most commonly used tracers are technetium-99m, iodine-123, iodine-131, gallium-67, indium-111, thallium-201 and  fludeoxyglucose ( 18 F)  ( 18 F-FDG). The  heart ,  lungs ,  thyroid ,  liver ,  brain ,  gallbladder , and bones are commonly evaluated for particular conditions using these techniques. While  anatomical  detail is limited in these studies, nuclear medicine is useful in displaying  physiological  function. The excretory function of the kidneys, iodine-concentrating ability of the thyroid, blood flow to heart muscle, etc. can be measured. The principal imaging devices are the  gamma camera  and the PET Scanner, which detect the radiation emitted by the tracer in the body and display it as an image. With computer processing, the information can be displayed as axial, coronal and sagittal images (single-photon emission computed tomography - SPECT or Positron-emission tomography - PET). In the most modern devices, nuclear medicine images can be fused with a CT scan taken quasisimultaneously, so the  physiological  information can be overlaid or coregistered with the anatomical structures to improve diagnostic accuracy. [ citation needed ]


Positron emission tomography  (PET) scanning deals with positrons instead of gamma rays detected by  gamma cameras . The positrons annihilate to produce two opposite traveling gamma rays to be detected coincidentally, thus improving resolution. In PET scanning, a radioactive, biologically active substance, most often  18 F-FDG, is injected into a patient and the radiation emitted by the patient is detected to produce multiplanar images of the body. Metabolically more active tissues, such as cancer, concentrate the active substance more than normal tissues. PET images can be combined (or "fused") with anatomic (CT) imaging, to more accurately localize PET findings and thereby improve diagnostic accuracy. [ citation needed ]


The fusion technology has gone further to combine PET and MRI similar to PET and CT.  PET/MRI  fusion, largely practiced in academic and research settings, could potentially play a crucial role in fine detail of brain imaging, breast cancer screening, and small joint imaging of the foot. The technology recently blossomed after passing the technical hurdle of altered positron movement in strong magnetic field thus affecting the resolution of PET images and attenuation correction. [ citation needed ]


Interventional radiology (IR or sometimes VIR for vascular and interventional radiology) is a subspecialty of radiology in which minimally invasive procedures are performed using image guidance. Some of these procedures are done for purely diagnostic purposes (e.g.,  angiogram ), while others are done for treatment purposes (e.g.,  angioplasty ). [ citation needed ]


The basic concept behind interventional radiology is to diagnose or treat  pathologies , with the most minimally invasive technique possible. Minimally invasive procedures are currently performed more than ever before. These procedures are often performed with the patient fully awake, with little or no sedation required. Interventional radiologists and interventional radiographers [ 11 ]  diagnose and treat several disorders, including  peripheral vascular disease ,  renal artery stenosis ,  inferior vena cava  filter placement,  gastrostomy  tube placements,  biliary   stents  and  hepatic  interventions. Radiographic images, fluoroscopy, and ultrasound modalities are used for guidance, and the primary instruments used during the procedure are specialized needles and  catheters . The images provide maps that allow the clinician to guide these instruments through the body to the areas containing disease. By minimizing the physical trauma to the patient, peripheral interventions can reduce infection rates and recovery times, as well as hospital stays. To be a trained interventionalist in the United States, an individual completes a five-year residency in radiology and a one- or two-year fellowship in IR. [ 12 ]


The basic technique is optical density evaluation (i.e. histogram analysis). It is then described that a region has a different optical density, e.g. a cancer metastasis to bone can cause radiolucency. The development of this is the digital radiological subtraction. It consists in overlapping two radiographs of the same examined region and subtracting the optical densities  Comparison of changes in dental and bone radiographic densities in the presence of different soft-tissue simulators using pixel intensity and digital subtraction analyses . The resultant image only contains the time-dependent differences between the two examined radiographs. The advantage of this technique is the precise determination of the dynamics of density changes and the place of their occurrence. However, beforehand the geometrical adjustment and general alignment of optical density should be done  Noise in subtraction images made from pairs of intraoral radiographs: a comparison between four methods of geometric alignment .
Another possibility of radiographic image analysis is to study second order features, e.g. digital texture analysis  Basic research Textural entropy as a potential feature for quantitative assessment of jaw bone healing process   Comparative Analysis of Three Bone Substitute Materials Based on Co-Occurrence Matrix  or fractal dimension  Using fractal dimension to evaluate alveolar bone defects treated with various bone substitute materials . On this basis, it is possible to assess the places where bio-materials are implanted into the bone for the purpose of guided bone regeneration. They take an intact bone image sample (region of interest, ROI, reference site) and a sample of the implantation site (second ROI, test site) can be assessed numerically/objectively to what extent the implantation site imitates a healthy bone and how advanced is the process of bone regeneration  Fast-Versus Slow-Resorbable Calcium Phosphate Bone Substitute Materials—Texture Analysis after 12 Months of Observation   New Oral Surgery Materials for Bone Reconstruction—A Comparison of Five Bone Substitute Materials for Dentoalveolar Augmentation . It is also possible to check whether the bone healing process is influenced by some systemic factors  Influence of General Mineral Condition on Collagen-Guided Alveolar Crest Augmentation .


Teleradiology is the transmission of radiographic images from one location to another for interpretation by an appropriately trained professional, usually a radiologist or reporting radiographer. It is most often used to allow rapid interpretation of emergency room, ICU and other emergent examinations after hours of usual operation, at night and on weekends. In these cases, the images can be sent across time zones (e.g. to Spain, Australia, India) with the receiving Clinician working his normal daylight hours. However, at present, large private teleradiology companies in the U.S. currently provide most after-hours coverage employing night-working radiologists in the U.S. Teleradiology can also be used to obtain consultation with an expert or subspecialist about a complicated or puzzling case. In the U.S., many hospitals outsource their radiology departments to radiologists in India due to the lowered cost and availability of high speed internet access. [ citation needed ]


Teleradiology requires a sending station, a high-speed internet connection, and a high-quality receiving station. At the transmission station, plain  radiographs  are passed through a digitizing machine before transmission, while CT, MRI, ultrasound and nuclear medicine scans can be sent directly, as they are already digital data. The computer at the receiving end will need to have a high-quality display screen that has been tested and cleared for clinical purposes. Reports are then transmitted to the requesting clinician.


The major advantage of teleradiology is the ability to use different time zones to provide real-time emergency radiology services around-the-clock. The disadvantages include higher costs, limited contact between the referrer and the reporting Clinician, and the inability to cover for procedures requiring an onsite reporting Clinician. Laws and regulations concerning the use of teleradiology vary among the states, with some requiring a license to practice medicine in the state sending the radiologic exam. In the U.S., some states require the teleradiology report to be preliminary with the official report issued by a hospital staff radiologist. Lastly, a benefit of teleradiology is that it might be automated with modern  machine learning  techniques. [ 13 ] [ 14 ] [ 15 ]


Some radiologists, like teleradiologists, have no interaction with patients. Other radiologists, like interventional radiologists, primarily interact with patients and spend less time analyzing images.  Diagnostic radiologists tend to spend the majority of their time analyzing images and a minority of their time interacting with patients. Compared to the healthcare provider who sends the patient to have images interpreted by a diagnostic radiologist, the radiologist usually does not know as much about the patient's clinical status or have as much influence on what action should be taken based on the images. Thus, the diagnostic radiologist reports image findings directly to that healthcare provider and often provides recommendations, who then takes the appropriate next steps for recommendations about medical management. Because radiologists undergo training regarding risks associated with different types of imaging tests and image-guided procedures, [ 16 ]  radiologists are the healthcare providers who generally educate patients about those risks to enable informed consent, not the healthcare provider requesting the test or procedure. [ 17 ]


Radiology is a field in medicine that has expanded rapidly after 2000 due to advances in computer technology, which is closely linked to modern imaging techniques. Applying for residency positions in radiology has become highly competitive. Applicants are often near the top of their medical school classes, with high  USMLE  (board) examination scores. [ 18 ]  Diagnostic radiologists must complete prerequisite undergraduate education, four years of medical school to earn a medical degree ( D.O.  or  M.D. ), one year of internship, and four years of residency training. [ 19 ]  After residency, most radiologists pursue one or two years of additional specialty fellowship training.


The  American Board of Radiology  (ABR) administers professional certification in Diagnostic Radiology, Radiation Oncology and Medical Physics as well as subspecialty certification in neuroradiology, nuclear radiology, pediatric radiology and vascular and interventional radiology. "Board Certification" in diagnostic radiology requires successful completion of two examinations. The Core Exam is given after 36 months of residency. Although previously taken  in Chicago or Tucson, Arizona, beginning in February 2021, the computer test transitioned permanently to a remote format. It encompasses 18 categories. A passing score is 350 or above. A fail on one to five categories was previously a Conditioned exam, however beginning in June 2021, the conditioned category will no longer exist and the test will be graded as a whole. The Certification Exam, can be taken 15 months after completion of the Radiology residency. This computer-based examination consists of five modules and graded pass-fail. It is given twice a year in Chicago and Tucson. Recertification examinations are taken every 10 years, with additional required continuing medical education as outlined in the Maintenance of Certification document. [ citation needed ]


Certification may also be obtained from the  American Osteopathic Board of Radiology  (AOBR) and the American Board of Physician Specialties. [ citation needed ]


Following completion of residency training, radiologists may either begin practicing as a general diagnostic radiologist or enter into subspecialty training programs known as fellowships. Examples of subspeciality training in radiology include abdominal imaging, thoracic imaging, cross-sectional/ultrasound,  MRI ,  musculoskeletal  imaging,  interventional radiology ,  neuroradiology ,  interventional neuroradiology ,  paediatric radiology , nuclear medicine, emergency radiology, breast imaging and women's imaging. Fellowship training programs in radiology are usually one or two years in length. [ 20 ]


Some medical schools in the US have started to incorporate a basic radiology introduction into their core MD training.  New York Medical College , the  Wayne State University School of Medicine ,  Weill Cornell Medicine , the Uniformed Services University, and the University of South Carolina School of Medicine offer an introduction to radiology during their respective MD programs. [ 21 ] [ 22 ] [ 23 ]   Campbell University School of Osteopathic Medicine  also integrates imaging material into their curriculum early in the first year. [ citation needed ]


Radiographic exams are usually performed by  radiographers . Qualifications for radiographers vary by country, but many radiographers now are required to hold a degree. [ citation needed ]


Veterinary radiologists are veterinarians who specialize in the use of X-rays, ultrasound, MRI and nuclear medicine for diagnostic imaging or treatment of disease in animals. They are certified in either diagnostic radiology or radiation oncology by the American College of Veterinary Radiology. [ citation needed ]


Radiology is an extremely competitive speciality in the UK, attracting applicants from a broad range of backgrounds. Applicants are welcomed directly from the  Foundation Programme , as well as those who have completed higher training. Recruitment and selection into training post in clinical radiology posts in England, Scotland and Wales is done by an annual nationally coordinated process lasting from November to March. In this process, all applicants are required to pass a Specialty Recruitment Assessment (SRA) test. [ 24 ]  Those with a test score above a certain threshold are offered a single interview at the London and the South East Recruitment Office. [ 25 ]  At a later stage, applicants declare what programs they prefer, but may in some cases be placed in a neighbouring region. [ 25 ]


The training programme lasts for a total of five years. During this time, doctors rotate into different subspecialities, such as paediatrics, musculoskeletal or neuroradiology, and breast imaging. During the first year of training, radiology trainees are expected to pass the first part of the Fellowship of the  Royal College of Radiologists  (FRCR) exam. This comprises a medical physics and anatomy examination. Following completion of their part 1 exam, they are then required to pass six written exams (part 2A), which cover all the subspecialities. Successful completion of these allows them to complete the FRCR by completing part 2B, which includes rapid reporting, and a long case discussion.


After achieving a  certificate of completion of training  (CCT), many fellowship posts exist in specialities such as neurointervention and vascular intervention, which would allow the doctor to work as an Interventional radiologist. In some cases, the CCT date can be deferred by a year to include these fellowship programmes.


UK radiology registrars are represented by the Society of Radiologists in Training (SRT), which was founded in 1993 under the auspices of the Royal College of Radiologists. [ 26 ]  The society is a nonprofit organisation, run by radiology registrars specifically to promote radiology training and education in the UK. Annual meetings are held by which trainees across the country are encouraged to attend.


Currently, a shortage of radiologists in the UK has created opportunities in all specialities, and with the increased reliance on imaging, demand is expected to increase in the future.  Radiographers , and less frequently  Nurses , are often trained to undertake many of these opportunities in order to help meet demand. Radiographers often may control a "list" of a particular set of procedures after being approved locally and signed off by a consultant radiologist. Similarly, radiographers may simply operate a list for a radiologist or other physician on their behalf. Most often if a radiographer operates a list autonomously then they are acting as the operator and practitioner under the Ionising Radiation (Medical Exposures) Regulations 2000. Radiographers are represented by a variety of bodies; most often this is the  Society and College of Radiographers . Collaboration with nurses is also common, where a list may be jointly organised between the nurse and radiographer.


After obtaining medical licensure, German radiologists complete a five-year residency, culminating with a board examination (known as  Facharztprüfung ).


Italian radiologists complete a four-year residency program, after completing the six-year MD program.


Dutch radiologists complete a five-year residency program, after completing the six-year MD program.


In India, one must obtain a bachelor's degree which requires 4.5 years of training, along with 1 year internship, followed by NEET PG examination which is one of the hardest examinations in India. Previous rank data shows only top rankers take radiology which means if the score is less, one might get accepted into other branches, but not radiology. The radiology program is a post graduate 3-year program (MD/DNB Radiology) or a 2-year diploma (DMRD). [ 27 ]


Radiologists in Singapore complete a five-year undergraduate MD program, followed by a one-year  internship , and then a five-year residency program. Some radiologists may elect to complete a one or two-year fellowship for further sub-specialization in fields such as  interventional radiology .


Slovenia


After finishing a six-year study of medicine and passing the emergency medicine internship, MDs can apply for radiology residency. Radiology is a five-year post-graduate program that involves all fields of radiology with a final board exam.


France


To become a radiologist, after having validated the common core of medical studies, one must obtain a DES (Specialized Studies Diploma) in radiology and medical imaging (specialized studies in 5 years), or a DES in advanced interventional radiology (specialized studies in 6 years). At the end of his DES, once validated, the future doctor will have to defend his “practice thesis” in order to validate his DE (State Diploma) as a doctor of medicine (common to all doctors of medicine therefore) and to be able to practice in France.


Training for interventional radiology occurs in the residency portion of  medical education , and has gone through developments.


In 2000, the  Society of Interventional Radiology  (SIR) created a program named "Clinical Pathway in IR", which modified the "Holman Pathway" that was already accepted by the American Board of Radiology to including training in IR; this was accepted by ABR but was not widely adopted. In 2005 SIR proposed and ABR accepted another pathway called "DIRECT (Diagnostic and Interventional Radiology Enhanced Clinical Training) Pathway" to help trainees coming from other specialities learn IR; this too was not widely adopted.  In 2006 SIR proposed a pathway resulting in certification in IR as a speciality; this was eventually accepted by the ABR in 2007 and was presented to the  American Board of Medical Specialities  (ABMS) in 2009, which rejected it because it did not include enough  diagnostic radiology  (DR) training. The proposal was reworked, at the same time that overall DR training was being revamped, and a new proposal that would lead to a dual DR/IR specialization was presented to the ABMS and was accepted in 2012 and eventually was implemented in 2014. [ 28 ] [ 29 ] [ 30 ]  By 2016 the field had determined that the old IR fellowships would be terminated by 2020. [ 30 ]


A handful of programs have offered interventional radiology  fellowships  that focus on training in the treatment of children. [ 31 ]


In Europe the field followed its own pathway; for example in Germany the parallel interventional society began to break free of the DR society in 2008. [ 32 ]  In the UK, interventional radiology was approved as a sub-specialty of clinical radiology in 2010. [ 33 ] [ 34 ]  While many countries have an interventional radiology society, there is also the European-wide  Cardiovascular and Interventional Radiological Society of Europe , whose aim is to support teaching, science, research and clinical practice in the field by hosting meetings, educational workshops and promoting patient safety initiatives. Furthermore, the Society provides an examination, the European Board of Interventional Radiology (EBIR), which is a highly valuable qualification in interventional radiology based on the European Curriculum and Syllabus for IR.


Four-dimensional computed tomography  ( 4DCT ) is a type of  CT scanning  which records multiple images over time. It allows playback of the scan as a video, so that  physiological  processes can be observed and internal movement can be tracked. The name is derived from the addition of time (as the  fourth dimension ) to traditional  3D  computed  tomography . Alternatively, the phase of a particular process, such as  respiration , may be considered the fourth dimension. [ 1 ]


Fluoroscopy  is a similar technique to 4DCT, however it refers to the introduction of a time element to  2D   planar radiography , rather than to 3D CT. [ 2 ] [ 3 ] [ 4 ] [ 5 ]


4DCT is used in  radiation therapy  planning to reduce doses to healthy organs such as the heart or lungs. Most radiation therapy is  planned  using the results of a 3D CT scan. A 3D scan largely presents a snapshot of the body at a particular point in time, however due to the time of the acquisition, in which the patient is likely to have moved in some way (even if only breathing), there will be an element of blurring or averaging in the 3D scan. [ 6 ]  When it comes to treatment planning, this motion can mean there is less accuracy in the positioning of treatment beams, and reduce the likelihood of a repeatable set-up on the  linear accelerator  when it comes to treatment. [ 7 ]


To minimise physical movements of the patient, some sort of immobilisation is typically used. To overcome physiological motion, such as breathing, 4DCT acquires images at a range of times and positions, allowing the extent of motion to be visualised (e.g. from maximum inspiration to maximum exhalation). The treatment plan can then be designed with a knowledge of the full range of possible positions of important organs, and the tumour (target) itself. [ 8 ]


4DCT will usually involve a  gating  technique, such as breathing tracking, so that image acquisition is automatically triggered at set points. [ 9 ]  This gating can also be applied at treatment, where the radiotherapy beam is only switched on at certain points in the breathing cycle (as in the  deep inspiration breath-hold  technique). [ 10 ]


4DCT has started to be used for  diagnostic radiology  procedures, for example looking at  joint  problems, the  cardiac cycle  and parathyroid washout of  contrast . Downsides of 4DCT for diagnostic purposes include large and complex datasets, and increased  radiation dose  to the patient. [ 11 ]


4DCT aims to visualise the temporal dynamics of a 3D sample with a sufficiently high  temporal  and  spatial resolution . Successive time frames are typically obtained by sequential scanning, followed by independent reconstruction of each 3D dataset. Such an approach requires a large number of projections for each scan to obtain images with sufficient quality (in terms of artefacts and  SNR ). Hence, there is a clear trade-off
between the rotation speed of the gantry (i.e. time resolution) and the quality of the reconstructed images.
Motion vector based  Iterative  Techniques are available which reconstruct a particular time frame by including the projections of neighbouring time frames as well. Such a strategy allows to improve the trade-off between the rotation speed and the SNR.
 [ 12 ]


For  fluid dynamics , specialized reconstruction algorithms have been developed that model the attenuation course throughout time. [ 13 ]  An example of such fluid dynamics is  perfusion CT  in which the propagation of  contrast agent  is modelled and simultaneously estimated with the CT images.
 [ 14 ]


Acute radiation syndrome  ( ARS ), also known as  radiation sickness  or  radiation poisoning , is a collection of health effects that are caused by being exposed to high  amounts  of  ionizing radiation  in a short period of time. [ 1 ]  Symptoms can start within an hour of exposure, and can last for several months. [ 1 ] [ 3 ] [ 5 ]  Early symptoms are usually nausea, vomiting and loss of appetite. [ 1 ]  In the following hours or weeks, initial symptoms may appear to improve, before the development of additional symptoms, after which either recovery or death follow. [ 1 ]


ARS involves a total dose of greater than 0.7  Gy  (70  rad ), that generally occurs from a source outside the body, delivered within a few minutes. [ 1 ]  Sources of such radiation can occur accidentally or intentionally. [ 6 ]  They may involve  nuclear reactors ,  cyclotrons , certain devices used in  cancer therapy ,  nuclear weapons , or  radiological weapons . [ 4 ]  It is generally divided into three types: bone marrow, gastrointestinal, and neurovascular syndrome, with bone marrow syndrome occurring at 0.7 to 10 Gy, and neurovascular syndrome occurring at doses that exceed 50 Gy. [ 1 ] [ 3 ]  The  cells  that are most affected are generally those that are rapidly dividing. [ 3 ]  At high doses, this causes DNA damage that may be irreparable. [ 4 ]  Diagnosis is based on a history of exposure and symptoms. [ 4 ]  Repeated  complete blood counts  (CBCs) can indicate the severity of exposure. [ 1 ]


Treatment of ARS is generally  supportive care . This may include  blood transfusions ,  antibiotics ,  colony-stimulating factors , or  stem cell transplant . [ 3 ]  Radioactive material remaining on the skin or in the stomach should be removed. If  radioiodine  was inhaled or ingested,  potassium iodide  is recommended. Complications such as  leukemia  and other  cancers  among those who survive are managed as usual. Short-term outcomes depend on the dose exposure. [ 4 ]


ARS is generally rare. [ 3 ]  A single event can affect a large number of people, [ 7 ]  as happened in the  atomic bombings of Hiroshima and Nagasaki  and the  Chernobyl nuclear power plant disaster . [ 1 ]  ARS differs from  chronic radiation syndrome , which occurs following prolonged exposures to relatively low doses of radiation. [ 8 ] [ 9 ]


Classically, ARS is divided into three main presentations:  hematopoietic ,  gastrointestinal , and  neuro vascular . These syndromes may be preceded by a  prodrome . [ 3 ]  The speed of symptom onset is related to radiation exposure, with greater doses resulting in a shorter delay in symptom onset. [ 3 ]  These presentations presume whole-body exposure, and many of them are markers that are invalid if the entire body has not been exposed. Each syndrome requires that the tissue showing the syndrome itself be exposed (e.g., gastrointestinal syndrome is not seen if the stomach and intestines are not exposed to radiation). Some areas affected are:


Early symptoms of ARS typically include nausea, vomiting, headaches, fatigue,  fever , and a short period of  skin reddening . [ 3 ]  These symptoms may occur at radiation doses as low as 0.35 grays (35 rad). These symptoms are common to many illnesses, and may not, by themselves, indicate acute radiation sickness. [ 3 ]


A similar table and description of symptoms (given in  rems , where 100 rem = 1  Sv ), derived from data from the effects on humans subjected to the  atomic bombings of Hiroshima and Nagasaki , the indigenous peoples of the  Marshall Islands  subjected to the  Castle Bravo  thermonuclear bomb, animal studies and lab experiment accidents, have been compiled by the  U.S. Department of Defense . [ 12 ]


A person who was less than 1 mile (1.6 km) from the atomic bomb  Little Boy 's   hypocenter  at Hiroshima, Japan, was found to have absorbed about 9.46 grays (Gy) of ionizing radiation. [ 13 ] [ 14 ] [ 15 ] [ 16 ]  The doses at the hypocenters of the Hiroshima and Nagasaki atomic bombings were 240 and 290 Gy, respectively. [ 17 ]


Cutaneous radiation syndrome  (CRS) refers to the skin symptoms of radiation exposure. [ 1 ]  Within a few hours after irradiation, a transient and inconsistent  redness  (associated with  itching ) can occur. Then, a latent phase may occur and last from a few days up to several weeks, when intense reddening,  blistering , and  ulceration  of the irradiated site is visible. In most cases, healing occurs by regenerative means; however, very large skin doses can cause permanent hair loss, damaged  sebaceous  and  sweat glands ,  atrophy ,  fibrosis  (mostly  keloids ), decreased or increased skin pigmentation, and ulceration or  necrosis  of the exposed tissue. [ 1 ]


As seen at  Chernobyl , when skin is irradiated with high energy  beta particles , moist  desquamation  (peeling of skin) and similar early effects can heal, only to be followed by the collapse of the dermal vascular system after two months, resulting in the loss of the full thickness of the exposed skin. [ 20 ]  Another example of skin loss caused by high-level exposure of radiation is during the  1999 Tokaimura nuclear accident , where technician Hisashi Ouchi had lost a majority of his skin due to the high amounts of radiation he absorbed during the irradiation. This effect had been demonstrated previously with pig skin using high energy beta sources at the Churchill Hospital Research Institute, in  Oxford . [ 21 ]


ARS is caused by exposure to a large dose of ionizing radiation (> ~0.1 Gy) over a short period of time (> ~0.1 Gy/h). Alpha and beta radiation have low penetrating power and are unlikely to affect vital internal organs from outside the body. Any type of ionizing radiation can cause burns, but alpha and beta radiation can only do so if  radioactive contamination  or  nuclear fallout  is deposited on the individual's skin or clothing.


Gamma and neutron radiation can travel much greater distances and penetrate the body easily, so whole-body irradiation generally causes ARS before skin effects are evident. Local gamma irradiation can cause skin effects without any sickness. In the early twentieth century, radiographers would commonly calibrate their machines by irradiating their own hands and measuring the time to onset of  erythema . [ 26 ]


Accidental exposure may be the result of a  criticality  or  radiotherapy  accident. There have been  numerous  criticality accidents dating back to  atomic testing  during World War II, while computer-controlled radiation therapy machines such as  Therac-25  played a major part in radiotherapy accidents. The latter of the two is caused by the failure of equipment software used to monitor the radiational dose given. Human error has played a large part in accidental exposure incidents, including some of the criticality accidents, and larger scale events such as the  Chernobyl disaster . Other events have to do with  orphan sources , in which radioactive material is unknowingly kept, sold, or stolen. The  Goiânia accident  is an example, where a forgotten radioactive source was taken from a hospital, resulting in the deaths of 4 people from ARS. [ 27 ]   Theft and attempted theft  of radioactive material by clueless thieves has also led to lethal exposure in at least one incident. [ 28 ]


Exposure may also come from routine spaceflight and  solar flares  that result in radiation effects on earth in the form of  solar storms . During spaceflight, astronauts are exposed to both  galactic cosmic radiation  (GCR) and  solar particle event  (SPE) radiation. The exposure particularly occurs during flights beyond  low Earth orbit  (LEO). Evidence indicates past SPE radiation levels that would have been lethal for unprotected astronauts. [ 29 ]  GCR levels that might lead to acute radiation poisoning are less well understood. [ 30 ]  The latter cause is rarer, with an event possibly occurring during the  solar storm of 1859 .


Intentional exposure is controversial as it involves the use of  nuclear weapons ,  human experiments , or is given to a victim in an act of murder. The intentional atomic bombings of Hiroshima and Nagasaki resulted in tens of thousands of casualties; the survivors of these bombings are known today as  hibakusha . Nuclear weapons emit large amounts of  thermal radiation  as visible, infrared, and ultraviolet light, to which the atmosphere is largely transparent. This event is also known as "flash", where radiant heat and light  are bombarded  into any given victim's exposed skin, causing radiation burns. [ 31 ]  Death is highly likely, and radiation poisoning is almost certain if one is caught in the open with no terrain or building masking-effects within a radius of 0–3 km from a 1 megaton airburst. The  50% chance of death  from the blast extends out to ~8 km from a 1 megaton atmospheric explosion. [ 32 ]


Scientific testing on humans within the United States occurred extensively throughout the atomic age. Experiments took place on a range of subjects including, but not limited to; the disabled, children, soldiers, and incarcerated persons, with the level of understanding and consent given by subjects varying from complete to none. Since 1997 there have been requirements for patients to give informed consent, and to be notified if experiments were classified. [ 33 ]  Across the world, the  Soviet nuclear program  involved human experiments on a large scale, which is still [ as of? ]  kept secret by the Russian government and the  Rosatom  agency. [ 34 ] [ 35 ]  The human experiments that fall under intentional ARS exclude those that involved  long term exposure . Criminal activity has involved murder and attempted murder carried out through abrupt victim contact with a radioactive substance such as  polonium  or  plutonium .


The most commonly used predictor of ARS is the whole-body  absorbed dose . Several related quantities, such as the  equivalent dose ,  effective dose , and  committed dose , are used to gauge long-term stochastic biological effects such as cancer incidence, but they are not designed to evaluate ARS. [ 36 ]  To help avoid confusion between these quantities, absorbed dose is measured in units of  grays  (in  SI , unit symbol  Gy ) or  rad  (in  CGS ), while the others are measured in  sieverts  (in SI, unit symbol  Sv ) or  rem  (in CGS). 1 rad = 0.01 Gy and 1 rem = 0.01 Sv. [ 37 ]


In most of the acute exposure scenarios that lead to radiation sickness, the bulk of the radiation is external whole-body gamma, in which case the absorbed, equivalent, and effective doses are all equal. There are exceptions, such as the Therac-25 accidents and the 1958  Cecil Kelley criticality accident , where the absorbed doses in Gy or rad are the only useful quantities, because of the targeted nature of the exposure to the body.


Radiotherapy  treatments are typically prescribed in terms of the local absorbed dose, which might be 60 Gy or higher. The dose is fractionated to about 2 Gy per day for  curative  treatment, which allows normal tissues to undergo  repair , allowing them to tolerate a higher dose than would otherwise be expected. The dose to the targeted tissue mass must be averaged over the entire body mass, most of which receives negligible radiation, to arrive at a whole-body absorbed dose that can be compared to the table above. [ citation needed ]


Exposure to high doses of radiation causes  DNA  damage, later creating serious and even lethal  chromosomal aberrations  if left unrepaired. Ionizing radiation can produce  reactive oxygen species , and does directly damage cells by causing localized ionization events. The former is very damaging to DNA, while the latter events create clusters of DNA damage. [ 38 ] [ 39 ]  This damage includes loss of  nucleobases  and breakage of the sugar-phosphate backbone that binds to the nucleobases. The DNA organization at the level of  histones ,  nucleosomes , and  chromatin  also affects its susceptibility to  radiation damage . [ 40 ]  Clustered damage, defined as at least two lesions within a helical turn, is especially harmful. [ 39 ]  While DNA damage happens frequently and naturally in the cell from endogenous sources, clustered damage is a unique effect of radiation exposure. [ 41 ]  Clustered damage takes longer to repair than isolated breakages, and is less likely to be repaired at all. [ 42 ]  Larger radiation doses are more prone to cause tighter clustering of damage, and closely localized damage is increasingly less likely to be repaired. [ 39 ]


Somatic mutations cannot be passed down from parent to offspring, but these mutations can propagate in cell lines within an organism. Radiation damage can also cause chromosome and  chromatid  aberrations, and their effects depend on in which stage of the mitotic cycle the cell is when the irradiation occurs. If the cell is in  interphase , while it is still a single strand of chromatin, the damage will be replicated during the S1 phase of the  cell cycle , and there will be a break on both chromosome arms; the damage then will be apparent in both  daughter cells . If the irradiation occurs after replication, only one arm will bear the damage; this damage will be apparent in only one daughter cell. A damaged chromosome may cyclize, binding to another chromosome, or to itself. [ 43 ]


Diagnosis is typically made based on a history of significant radiation exposure and suitable clinical findings. [ 3 ]  An  absolute lymphocyte count  can give a rough estimate of radiation exposure. [ 3 ]  Time from exposure to vomiting can also give estimates of exposure levels if they are less than 10 Gy (1000 rad). [ 3 ]


A guiding principle of radiation safety is  as low as reasonably achievable  (ALARA). [ 44 ]  This means try to avoid exposure as much as possible and includes the three components of time, distance, and shielding. [ 44 ]


The longer that humans are subjected to radiation the larger the dose will be. The advice in the  nuclear war  manual entitled  Nuclear War Survival Skills  published by  Cresson Kearny  in the  U.S.  was that if one needed to leave the shelter then this should be done as rapidly as possible to minimize exposure. [ 45 ]


In chapter 12, he states that "[q]uickly putting or dumping wastes outside is not hazardous once fallout is no longer being deposited. For example, assume the shelter is in an area of heavy fallout and the dose rate outside is 400  roentgen (R)  per hour, enough to give a potentially fatal dose in about an hour to a person exposed in the open. If a person needs to be exposed for only 10 seconds to dump a bucket, in this 1/360 of an hour he will receive a dose of only about 1 R. Under war conditions, an additional 1-R dose is of little concern." In peacetime, radiation workers are taught to work as quickly as possible when performing a task that exposes them to radiation. For instance, the recovery of a radioactive source should be done as quickly as possible.


Usually, matter attenuates radiation, so placing any mass (e.g., lead, dirt, sandbags, vehicles, water, even air) between humans and the source will reduce the radiation dose. This is not always the case, however; care should be taken when constructing shielding for a specific purpose. For example, although high atomic number materials are very effective in shielding  photons , using them to shield  beta particles  may cause higher radiation exposure due to the production of  bremsstrahlung  x-rays, and hence low atomic number materials are recommended. Also, using material with a high  neutron activation   cross section  to shield neutrons will result in the shielding material itself becoming radioactive and hence more dangerous than if it were not present. [ citation needed ]


There are many types of shielding strategies that can be used to reduce the effects of radiation exposure. Internal contamination protective equipment such as respirators are used to prevent internal deposition as a result of inhalation and ingestion of radioactive material. Dermal protective equipment, which protects against external contamination, provides shielding to prevent radioactive material from being deposited on external structures. [ 46 ]  While these protective measures do provide a barrier from radioactive material deposition, they do not shield from externally penetrating gamma radiation. This leaves anyone exposed to penetrating gamma rays at high risk of ARS.


Naturally, shielding the entire body from high energy gamma radiation is optimal, but the required mass to provide adequate attenuation makes functional movement nearly impossible. In the event of a radiation catastrophe, medical and security personnel need  mobile protection equipment  in order to safely assist in containment, evacuation, and many other necessary public safety objectives.


Research has been done exploring the feasibility of partial body shielding, a radiation protection strategy that provides adequate attenuation to only the most radio-sensitive organs and tissues inside the body. Irreversible stem cell damage in the bone marrow is the first life-threatening effect of intense radiation exposure and therefore one of the most important bodily elements to protect. Due to the regenerative property of  hematopoietic stem cells , it is only necessary to protect enough bone marrow to repopulate the exposed areas of the body with the shielded supply. [ 47 ]  This concept allows for the development of lightweight mobile radiation protection equipment, which provides adequate protection, deferring the onset of ARS to much higher exposure doses. One example of such equipment is the  360 gamma , a radiation protection belt that applies selective shielding to protect the bone marrow stored in the pelvic area as well as other radio sensitive organs in the abdominal region without hindering functional mobility.


Where radioactive contamination is present, an  elastomeric respirator ,  dust mask , or good hygiene practices may offer protection, depending on the nature of the contaminant.  Potassium iodide  (KI) tablets can reduce the risk of cancer in some situations due to slower uptake of ambient radioiodine. Although this does not protect any organ other than the thyroid gland, their effectiveness is still highly dependent on the time of ingestion, which would protect the gland for the duration of a twenty-four-hour period. They do not prevent ARS as they provide no shielding from other environmental radionuclides. [ 48 ]


If an intentional dose is broken up into a number of smaller doses, with time allowed for recovery between irradiations, the same total dose causes less  cell death . Even without interruptions, a reduction in dose rate below 0.1 Gy/h also tends to reduce cell death. [ 36 ]  This technique is routinely used in radiotherapy. [ citation needed ]


The human body contains many types of  cells  and a human can be killed by the loss of a single type of cells in a vital organ. For many short term radiation deaths (3–30 days), the loss of two important types of cells that are constantly being regenerated causes death. The loss of cells forming  blood cells  ( bone marrow ) and the cells in the digestive system ( microvilli , which form part of the wall of the  intestines ) is fatal. [ citation needed ]


Treatment usually involves supportive care with possible symptomatic measures employed. The former involves the possible use of  antibiotics ,  blood products ,  colony stimulating factors , and  stem cell transplant . [ 3 ]


There is a direct relationship between the degree of the  neutropenia  that emerges after exposure to radiation and the increased risk of developing infection. Since there are no controlled studies of therapeutic intervention in humans, most of the current recommendations are based on animal research. [ citation needed ]


The  treatment  of established or suspected infection following exposure to radiation (characterized by neutropenia and fever) is similar to the one used for other febrile neutropenic patients. However, important differences between the two conditions exist. Individuals that develop neutropenia after exposure to radiation are also susceptible to irradiation damage in other tissues, such as the gastrointestinal tract, lungs and central nervous system. These patients may require therapeutic interventions not needed in other types of neutropenic patients. The response of irradiated animals to antimicrobial therapy can be unpredictable, as was evident in experimental studies where  metronidazole [ 49 ]  and  pefloxacin [ 50 ]  therapies were detrimental.


Antimicrobials that reduce the number of the strict  anaerobic  component of the gut flora (i.e., metronidazole) generally should not be given because they may enhance systemic infection by aerobic or  facultative bacteria , thus facilitating mortality after irradiation. [ 51 ]


An empirical regimen of antimicrobials should be chosen based on the pattern of bacterial susceptibility and  nosocomial infections  in the affected area and medical center and the degree of neutropenia. Broad-spectrum empirical therapy (see below for choices) with high doses of one or more antibiotics should be initiated at the onset of fever. These antimicrobials should be directed at the eradication of Gram-negative aerobic bacilli (i.e.,  Enterobacteriaceae ,  Pseudomonas ) that account for more than three quarters of the isolates causing sepsis. Because aerobic and facultative Gram-positive bacteria (mostly  alpha-hemolytic streptococci ) cause  sepsis  in about a quarter of the victims, coverage for these organisms may also be needed. [ 52 ]


A standardized management plan for people with neutropenia and fever should be devised. Empirical regimens contain antibiotics broadly active against Gram-negative aerobic bacteria ( quinolones : i.e.,  ciprofloxacin ,  levofloxacin , a third- or fourth-generation cephalosporin with pseudomonal coverage: e.g.,  cefepime ,  ceftazidime , or an aminoglycoside: i.e.  gentamicin ,  amikacin ). [ 53 ]


The prognosis for ARS is dependent on the exposure dose, with anything above 8 Gy being almost always lethal, even with medical care. [ 4 ] [ 54 ]   Radiation burns  from lower-level exposures usually manifest after 2 months, while reactions from the burns occur months to years after radiation treatment. [ 55 ] [ 56 ]  Complications from ARS include an increased risk of developing radiation-induced cancer later in life. According to the controversial but commonly applied  linear no-threshold model , any exposure to ionizing radiation, even at doses too low to produce any symptoms of radiation sickness, can induce cancer due to cellular and genetic damage. The probability of developing cancer is a linear function with respect to the  effective radiation dose . Radiation cancer may occur after ionizing radiation exposure following a latent period averaging 20 to 40 years. [ 57 ] [ 55 ]


Acute effects of ionizing radiation were first observed when  Wilhelm Röntgen  intentionally subjected his fingers to X-rays in 1895. He published his observations concerning the burns that developed that eventually healed, and misattributed them to ozone. Röntgen believed the  free radical  produced in air by X-rays from the ozone was the cause, but other free radicals produced within the body are now understood to be more important. David Walsh first established the symptoms of radiation sickness in 1897. [ 58 ]


Ingestion of radioactive materials caused many  radiation-induced cancers  in the 1930s, but no one was exposed to high enough doses at high enough rates to bring on ARS.


The  atomic bombings of Hiroshima and Nagasaki  resulted in high acute doses of radiation to a large number of Japanese people, allowing for greater insight into its symptoms and dangers. Red Cross Hospital Surgeon  Terufumi Sasaki  led intensive research into the syndrome in the weeks and months following the Hiroshima and Nagasaki bombings. Sasaki and his team were able to monitor the effects of radiation in patients of varying proximities to the blast itself, leading to the establishment of three recorded stages of the syndrome. Within 25–30 days of the explosion, Sasaki noticed a sharp drop in white blood cell count and established this drop, along with symptoms of fever, as prognostic standards for ARS. [ 59 ]   Actress  Midori Naka , who was present during the atomic bombing of Hiroshima, was the first incident of radiation poisoning to be extensively studied. Her death on 24 August 1945 was the first death ever to be officially certified as a result of ARS (or "Atomic bomb disease").


There are two major databases that track radiation accidents: The American  ORISE  REAC/TS and the European  IRSN  ACCIRAD. REAC/TS shows 417 accidents occurring between 1944 and 2000, causing about 3000 cases of ARS, of which 127 were fatal. [ 60 ]  ACCIRAD lists 580 accidents with 180 ARS fatalities for an almost identical period. [ 61 ]  The two deliberate bombings are not included in either database, nor are any possible radiation-induced cancers from low doses. The detailed accounting is difficult because of confounding factors. ARS may be accompanied by conventional injuries such as steam burns, or may occur in someone with a pre-existing condition undergoing radiotherapy. There may be multiple causes for death, and the contribution from radiation may be unclear. Some documents may incorrectly refer to radiation-induced cancers as radiation poisoning, or may count all overexposed individuals as survivors without mentioning if they had any symptoms of ARS.


The following table includes only those known for their attempted survival with ARS. These cases exclude chronic radiation syndrome such as  Albert Stevens , in which radiation is exposed to a given subject over a long duration. The table also necessarily excludes cases where the individual was exposed to so much radiation that death occurred before medical assistance or dose estimations could be made, such as an attempted cobalt-60 thief who reportedly died 30 minutes after exposure. [ 62 ]  The result column represents the time of exposure to the time of death attributed to the short and long term effects attributed to initial exposure. As ARS is measured by a whole-body  absorbed dose , the exposure column only includes units of gray (Gy).


Thousands of scientific experiments have been performed to study ARS in animals. [ citation needed ]  There is a simple guide for predicting survival and death in mammals, including humans, following the acute effects of inhaling radioactive particles. [ 69 ]


Aidoc Medical  is an Israeli technology company that develops  computer-aided simple triage  and notification systems. Aidoc has obtained  FDA  and  CE mark  approval for its stroke,  pulmonary embolism ,  cervical fracture , intracranial hemorrhage,  intra-abdominal free gas , and  incidental pulmonary embolism  algorithms. [ 2 ] [ 3 ]


Aidoc algorithms are in use in more than 900 hospitals and imaging centers, including  Montefiore Nyack Hospital ,  LifeBridge Health , LucidHealth,  Yale New Haven Hospital , Cedars-Sinai Medical Center,  University of Rochester Medical Center , and  Sheba Medical Center . [ 4 ]


Aidoc was founded in 2016 by Elad Walach as the CEO, [ 5 ]  Michael Braginsky as the CTO and Guy Reiner as the VP. In April 2017, the company raised $7M, led by TLV Partners, [ 6 ]  and in April 2019, the company raised another $27M, led by Square Peg capital. [ 7 ]


In August 2018, Aidoc gained FDA clearance for its  intracranial hemorrhage  system, [ 8 ]  and in May 2019 it received clearance for the  pulmonary embolism  system. [ 9 ] [ 10 ]


In January 2020, the system for detecting large- vessel occlusions  (LVOs) in head CTA examinations obtained FDA clearance. [ 11 ] [ 12 ] [ 13 ]


Aidoc has developed a suite of artificial intelligence products that flag both time-sensitive and time-consuming (for the radiologist) abnormalities across the body. The algorithms are developed with large quantities of data to provide diagnostic aid for a broad set of pathologies. The company offers an array of algorithms that span across the body, including for intracranial hemorrhage, spine fractures (C, T & L), free air in the abdomen, pulmonary embolism, and more. It developed "Always-on AI", a term coined by Elad Walach that refers to a type of artificial intelligence that is "Always-on—constantly running in the background and automatically analyzing medical imaging data, identifying urgent findings, and sparing radiologists from "drowning" in vast amounts of irrelevant data. [ 14 ] [ 15 ]


Aidoc's solutions cover medical conditions prevalent in all settings ( ED / inpatient / outpatient ), including  level 1 trauma centers , outpatient imaging centers,  teleradiology  groups and, are set up in over 200 medical centers worldwide. Notable customers include the  University of Rochester Medical Center [ 16 ]  and Global Diagnostics Australia. [ 17 ]


A clinical study on Aidoc’ accuracy of deep  convolutional neural networks  for the detection of pulmonary embolism (PE) on CT pulmonary angiograms (CTPAs) was performed by the University Hospital of Basel and presented at the European Congress of Radiology, showing that the Aidoc algorithm reached 93% sensitivity and 95% specificity. [ 18 ] [ 19 ] [ 20 ]  Clinical research has also been performed to test the diagnostic performance of Aidoc's deep learning-based triage system for the flagging of acute findings in abdominal computed tomography (CT) examinations. Overall, the algorithm achieved 93% sensitivity (91/98, 7 false negatives) and 97% specificity (93/96, 3 false-positive) in the detection of acute abdominal findings. [ 21 ] [ 22 ]


Additional clinical research on Aidoc's Intracranial hemorrhage algorithm accuracy was presented at the European Congress of Radiology by Antwerp University Hospital, evaluating the use of its deep learning algorithm for the detection of intracranial hemorrhage on non-contrast enhanced  CT  of the  brain . [ 23 ]  The University of Washington completed a study on the accuracy of Aidoc's intracranial hemorrhage algorithm. [ 24 ]


In  medical imaging , an  anti-scatter grid  (also known as a  Bucky-Potter grid ) is a device for limiting the amount of scattered  radiation  reaching the detector, [ 1 ] [ 2 ]  thereby improving the quality of diagnostic  medical x-ray  images.  The grid is positioned on the opposite side of the patient from the  x-ray  source, and between the patient and the  X-ray detector  or film.  Reducing the amount of scattered x-rays increases the image's contrast resolution, and consequently the visibility of  soft tissues .


The device was first invented by German  radiologist   Gustav Peter Bucky , who showed in 1913 that a grid can be used to 'reject' scattered x-rays before they reach the detector.  It was later improved by American radiologist Hollis E. Potter by introducing moving grid. The Bucky-Potter grid facilitated the transition from small glass photographic plates to film in a variety of sizes. [ 3 ]


Scattered x-rays do not travel in parallel to rays that pass directly through the patient. The quantity of scattering depends on several factors including: x-ray beam area, x-ray photon energies (determined by tube voltage setting), thickness of the tissue, and the composition of the tissue. [ 4 ]  By 'rejecting' scattered x-rays before they reach the detector, the Bucky-Potter grid improves recorded contrast.


The grid is constructed of a series of alternating parallel strips of  lead  and a  radiolucent  substance such as a  plastic ,  carbon fibre ,  aluminium , even paper.  The grid is placed between the  patient  and the detector during the exposure. Radiation which has travelled straight through the patient from the x-ray source moves directly through the radiolucent portions of the grid and strikes the detector.  Radiation which has been scattered while travelling through the patient strikes the lead strips at an angle, and is either attenuated or further scattered.  As a result, only radiation which has travelled directly through the patient is imaged on the detector, increasing contrast.


The single most important parameter that influences the performance of an anti-scatter grid is the grid ratio. [ 5 ]  The grid ratio is the ratio of the height to the width of the interspaces (not the grid bars) in the grid. Grid ratios of 8:1, 10:1, and 12:1 are most. A 5:1 grid is most common for  mammography . [ 5 ]  The grid is essentially a one-dimensional  Collimator  and increasing the grid ratio increases the degree of collimation. Higher grid ratios provide better scatter cleanup, but they also result in greater radiation doses to the patient. [ 5 ]  In addition, though higher ratios are possible, they require greater radiation intensity increases when used, require more precise positioning, and are more expensive to produce. [ 6 ]


Grids are used particularly in examinations where a large quantity of scatter is created, i.e., those involving a large volume of tissue being irradiated and those requiring low energy i.e.  voltage . The scatter would otherwise degrade the image by reducing the  contrast  and  resolution . Use of a grid, however, requires a greater radiation exposure to the patient as a good deal of primary beam is also attenuated by the lead slats, and for this reason grids are not used for all examinations, particularly in pediatric practice.


One drawback of a fixed radiographic grid is that it creates grid lines on the image. Hollis Potter (1880-1964) showed in 1920 that these grid lines could be eliminated by moving the grid at right angles to the grid lines during the exposure. If the range and speed of motion is sufficient, the grid lines will be blurred out. The motion may be oscillating, vibrating, or reciprocating and must be continuous and smooth. The motion must also begin before exposure and continue until after exposure.


Aortopulmonary window (APW)  is a faulty connection between the  aorta  and the main  pulmonary artery  that results in a significant  left-to-right shunt . [ 2 ]  The aortopulmonary window is the rarest of  septal defects , accounting for 0.15-0.6% of all congenital heart malformations. [ 4 ]  An aortopulmonary window can develop alone or in up to 50% of cases alongside other cardiac defects such as  interrupted aortic arch ,  coarctation of the aorta ,  transposition of great vessels , and  tetralogy of Fallot . [ 3 ]


A  left-to-right shunt  can cause  heart failure , with symptoms such as  tachypnea , poor eating, and  diaphoresis .  Dyspnea  and indications of laborious breathing can be caused by low lung compliance and increased  airway resistance . Infants may have  failure to thrive  as well as recurrent  pneumonia . [ 2 ]


Findings among individuals with an isolated aortopulmonary window vary based on the size of the defect and the  pulmonary vascular resistance . Cardiac examination typically indicates a parasternal lift resulting from  right ventricular  overload, a loud single second  heart sound  induced by  pulmonary hypertension , and increased peripheral pulses. [ 2 ]


When the defect is larger,  pulmonary vascular resistance  may continue to be elevated in the initial weeks or months of life, and there is a modest amount of pulmonary overcirculation. A rather faint  basal systolic ejection murmur  without a diastolic element and a loud single second heart sound develop due to mild overcirculation. As the  pulmonary vascular resistance  decreases throughout the first few months, the left-to-right shunting of blood into the lungs increases, and the  systolic murmur  becomes more intense and longer, eventually extending into diastole and becoming a continuous murmur. [ 2 ]


Because there is a pressure gradient from the  aorta  to the  pulmonary artery  throughout systole and diastole, a small aortopulmonary defect may produce a  murmur  similar to a  patent ductus arteriosus . [ 2 ]


When a large defect is left unrepaired,  Eisenmenger syndrome   will develop with reversal of the shunt. [ 2 ]


Untreated cases with major malformations have a poor prognosis, with 40% dying within their first year of life. [ 4 ]


Physical examination findings,  ECG , and imaging are used to diagnose aortopulmonary window. An electrocardiogram reveals  right ventricular hypertrophy  or biventricular hypertrophy.  Cardiomegaly , a big main  pulmonary artery  segment, and enhanced  pulmonary vascular  marking are all visible on a  chest x-ray . [ 2 ]


The appearance of aortopulmonary window has similarities to that of  truncus arteriosus ,  ventricular septal defect , and large  patent ductus arteriosus . A two-dimensional  echocardiogram  can detect and distinguish between these problems. [ 3 ]


Corrective heart surgery, which is normally performed in the first year of life, is the definitive intervention for an aortopulmonary window. If the patient's symptoms don't allow for corrective surgery, medical therapy of  congestive heart failure  is the second choice.  Permanent alterations in the pulmonary vasculature can be prevented with early intervention. [ 2 ]


Bone age  is the degree of a person's  skeletal  development. In children, bone age serves as a measure of physiological maturity and aids in the diagnosis of growth abnormalities, endocrine disorders, and other medical conditions. [ 1 ] [ 2 ] [ 3 ]  As a person grows from  fetal  life through childhood,  puberty , and finishes growth as a young adult, the bones of the  skeleton  change in size and shape. These changes can be seen by  x-ray  and other imaging techniques. A comparison between the appearance of a patient's bones to a standard set of bone images known to be representative of the average bone shape and size for a given age can be used to assign a "bone age" to the patient.


Bone age is distinct from an individual's biological or chronological age, which is the amount of time that has elapsed since  birth . Discrepancies between bone age and biological age can be seen in people with stunted growth, where bone age may be less than biological age. Similarly, a bone age that is older than a person's chronological age may be detected in a child growing faster than normal. A delay or advance in bone age is most commonly associated with normal variability in growth, but significant deviations between bone age and biological age may indicate an underlying medical condition that requires treatment. A child's current height and bone age can be used to predict adult height. [ 4 ]  Other uses of bone age measurements include assisting in the diagnosis of medical conditions affecting children, such as  constitutional growth delay ,  precocious puberty ,  thyroid dysfunction ,  growth hormone deficiency , and other causes of abnormally short or tall stature.


In the United States, the most common technique for estimating a person's bone age is to compare an x-ray of the patient's left hand and wrist to a reference atlas containing x-ray images of the left hands of children considered to be representative of how the skeletal structure of the hand appears for the average person at a given age. [ 2 ]  A  paediatric radiologist  specially trained in estimating bone age assesses the patient's x-ray for growth, shape, size, and other bone features. The image in the reference atlas that most closely resembles the patient's x-ray is then used to assign a bone age to the patient. [ 5 ]  Other techniques for estimating bone age exist, including x-ray comparisons of the bones of the knee or elbow to a reference atlas and  magnetic resonance imaging  approaches. [ 1 ] [ 6 ]


Estimating the bone age of a living child is typically performed by comparing images of their bones to images of models of the average skeleton for a given age and sex acquired from healthy children and compiled in an atlas. [ 7 ] [ 8 ]  Features of bone development assessed in determining bone age include the presence of bones (have certain bones  ossified  yet), the size and shape of bones, the amount of mineralization (also called  ossification ), and the degree of fusion between the  epiphyses  and  metaphyses . [ 5 ] [ 9 ]  The first atlas published in 1898 by John Poland consisted of x-ray images of the left hand and wrist. [ 10 ] [ 11 ]  Since then, updated atlases of the left hand and wrist have appeared, [ 12 ] [ 5 ]  along with atlases of the foot and ankle, [ 13 ]  knee, [ 14 ]  and elbow. [ 15 ]  An alternative approach to the atlas method just described is the so-called "single-bone method" where maturity scales are assigned to individual bones. [ 7 ] [ 8 ]  Here, a selection of bones are given a score based on their perceived development, a sum is totaled based on the individual bone scores, and the sum is correlated to a final bone age. [ 7 ] [ 8 ] [ 16 ]


The two most common techniques for estimating bone age are based on a posterior-anterior x-ray of a patient's left hand, fingers, and  wrist . [ 5 ] [ 17 ]  The reason for imaging only the left hand and wrist are that a hand is easily x-rayed with minimal radiation [ 18 ]  and shows many bones in a single view. [ 19 ]  Further, most people are right-hand dominant and the left hand is therefore less likely to be deformed due to trauma. [ 17 ] [ 20 ]  Finally, only the wrist and hand are imaged out of a desire to minimize the amount of potentially harmful ionizing radiation delivered to a child. [ 2 ]


In the United States, bone age is usually determined by comparing an x-ray of the patient's left hand and wrist to a set of reference images contained in the Greulich and Pyle atlas. [ 5 ] [ 2 ] [ 3 ] [ 1 ]  Drs. William Walter Greulich and Sarah Idell Pyle published the first edition of their standard reference atlas of x-ray images of the left hands and wrists of boys and girls in 1950. [ 12 ]  The Greulich and Pyle atlas contains x-ray images of the left hands and wrists of different children deemed to be good models of the average appearance of the bones of the hand at a given age. The atlas has a set of images arranged in chronological order by age for males ranging from 3 months to 19 years and for females ranging from 3 months to 18 years in varying intervals of 3 months to 1 year. [ 3 ] [ 21 ]


Images in the Greulich and Pyle atlas came from healthy white boys and girls enrolled in the Brush Foundation Study for Human Growth and Development between the years 1931 and 1942. [ 2 ] [ 5 ]


To assign a bone age to the patient under review, a radiologist compares the patient's hand and wrist x-ray to images in the Greulich and Pyle atlas. Assessment of the carpals, metacarpals, and phalanges are used to find the closest match in the atlas; the chronological age of the patient in the atlas becomes the bone age assigned to the patient under review. [ 3 ]  If a patient's x-ray is found to be very close in appearance to two contiguous images in the atlas, then an average of the chronological ages in the atlas may be used as the patient's bone age, although some evaluators choose to interpolate the closest age while others report a range of possible bone ages. [ 11 ]


A drawback associated with the Greulich and Pyle method of assessing bone age is that it relies on x-ray imaging and therefore requires exposing the patient to ionizing radiation. Further, there can be moderate levels of variability in the bone ages assigned to the same patient by different assessors. [ 21 ]  Other downsides are that the atlas has not been updated since 1959 and the images in the atlas were acquired from healthy white children living in Cleveland, Ohio in the 1930s and 1940s and therefore may not yield accurate bone age assignments when applied to non-white patients or unhealthy children. [ 1 ] [ 2 ] [ 21 ]


The Tanner-Whitehouse (TW) technique of estimating bone is a "single-bone method" based on an x-ray image of a patient's left hand and wrist. There have been two updates since the first publication of the TW method in 1962: the TW2 method in 1975 and the TW3 method in 2001. [ 16 ] [ 22 ]  The TW methods consist of evaluating individual bones and assigning a letter grade to each bone based on its degree of maturation. Next, the scores for all evaluated bones are compiled into a sum, and that sum is correlated to bone age through a lookup table for males or females depending on the sex of the patient. [ 16 ]


The bones considered in the TW3 method include the distal radius and ulna, the metacarpals and phalanges of the 1st, 3rd, and 5th fingers, and all of the carpal bones except the pisiform. [ 8 ] [ 16 ]


An atlas based on knee maturation has also been compiled. [ 1 ] [ 14 ] [ 23 ]


The bones in the hand a wrist in a newborn do not change much in the first year of life. [ 3 ]  However, most pediatric radiologists still use the Greulich and Pyle technique for estimating bone age in infancy. [ 11 ] [ 7 ]  Alternative techniques for estimating bone age in infancy include tallying the number of ossification centers present in the left half of the infant's body requiring a hemiskeleton x-ray. [ 11 ] [ 7 ]  One common method based on x-rays of the hemiskeleton is the Sontag method. [ 24 ]  This technique was created to avoid errors in estimating bone age thought to arise from focusing on only one area of the body. [ 24 ]  The Sontag method uses x-rays of all the bones and joints of the upper and lower limbs on the left side of the body. [ 24 ]  Then, a radiologist counts the number of ossification centers present and uses a chart to convert the sum of ossification centers to a bone age. There is a chart for males and another for females with possible bone ages ranging from 1 month to 5 years. [ 24 ]  Since most of the ossification centers counted using this technique appear early in life, this method is only valid for measuring bone age up to around 5 years of age. [ 24 ]


Lamparski (1972) [ 25 ]  used the cervical vertebrae and found them to be as reliable and valid as the hand-wrist area for assessing skeletal age. He developed a series of standards for the assessment of skeletal age for both males and females. This method has the advantage of eliminating the need for additional radiographic exposure in cases where the vertebrae have already been recorded on a lateral cephalometric radiographic. [ 26 ]  This method is called the  Cervical vertebral maturation method


Hassel & Farman (1995) [ 27 ]  developed an index based on the second, third, and fourth cervical vertebrae (C2, C3, C4) and proved that atlas maturation was highly correlated with skeletal maturation of the hand-wrist.  Several smartphone applications have been developed to facilitate the use of vertebral methods such as  Easy Age .


Assessment of a patient's bone age is used in pediatric medicine to help determine if a child is growing normally. [ 3 ]  Large differences between a person's bone age and their chronological age may indicate a growth disorder. [ 5 ]  For example, a patient's bone age may be less than their chronological age suggesting a delay in growth as may be caused by a growth hormone deficiency. In the case of too much growth hormone, a child may have a bone age that is older than their chronological age suggesting that they are growing abnormally fast. Since bone age measurements are inherently approximations, they are conventionally reported with a standard deviation which serves as an estimate of the associated error. For a child's bone age to be considered abnormal, the chronological age must differ from the assigned bone age by more than 2  standard deviations . [ 1 ] [ 2 ]


Bone age acts as a surrogate for physiological development because growth and maturation of the skeletal system depend on the presence of hormones like growth hormone, sex steroids (e.g., estrogen and testosterone), and thyroxine. [ 2 ] [ 5 ]  Studies of bone age in children allow physicians to correlate a child's current height and bone age to their predicted future maximum height in adulthood. [ 3 ] [ 5 ]


Not only can bone age help in diagnosing a child with a growth abnormality, but it can also play a role in treatment. [ 3 ]  In certain instances, abnormal growth conditions may be treated with supplemental hormone therapy. The best time to start and stop such therapies can be determined based on a patient's bone age.


Statistics have been compiled to indicate the percentage of height growth remaining at a given bone age. By simple arithmetic, a predicted adult height can be computed from a child's height and bone age. Separate tables are used for boys and girls because of the sex difference in timing of puberty, and slightly different percentages are used for children with unusually advanced or delayed bone maturation. These tables, the Bayley-Pinneau tables, are included as an appendix in the Greulich and Pyle atlas.


In several conditions involving atypical growth, bone age height predictions are less accurate. For example, in children born small for gestational age who remain short after birth, bone age is a poor predictor of adult height. [ 28 ]


For the average person with average puberty, the bone age would match the person's chronological age. In terms of height growth and height growth related to bone age, average females stop growing taller two years earlier than average males. Peak height velocity (PHV) occurs at the average age of 11 years for girls and at the average age of 13 years for boys. [ 29 ]  While there is no exact age for the culmination of bone maturity, modern research suggests a range of between 15-17 years for bone maturity in boys and 14-16 years for girls. [ 30 ] [ 31 ] [ 32 ] [ 33 ] [ 34 ] [ 35 ] [ 36 ]


There are exceptions with people who have an  advanced  bone age (bone age is older than chronological age) due to being an early bloomer (someone starting puberty and hitting PHV earlier than average), being an early bloomer with precocious puberty, or having another condition. There are also exceptions with people who have a  delayed  bone age (bone age is younger than chronological age) due to being a late bloomer (someone starting puberty and hitting PHV later than average), being a late bloomer with  delayed puberty , or having another condition. [ 37 ]


An  advanced  bone age is common when a child has had prolonged elevation of  sex steroid  levels, as in  precocious puberty  or  congenital adrenal hyperplasia . The bone age is often marginally advanced with premature  adrenarche , when a child is overweight from a young age or when a child has lipodystrophy. Those with an advanced bone age typically hit a growth spurt early on but stop growing at an earlier age. Bone age may be significantly advanced in genetic overgrowth syndromes, such as  Sotos syndrome ,  Beckwith-Wiedemann syndrome  and  Marshall-Smith syndrome . [ 38 ]


Bone maturation is  delayed  with the variation of normal development termed  constitutional  delay of growth and puberty, but delay also accompanies growth failure due to  growth hormone deficiency  and  hypothyroidism . [ 39 ] [ 40 ]