Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

14,938 results found
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Adrenal vein sampling

Adrenal vein sampling (AVS) is a procedure where blood is collected from the adrenal veins via catheter to confirm autonomous hormone production, if it is unilateral or bilateral, and to guide further treatment. Indication Adrenal vein sampling is commonly performed in primary aldosteronism, b...
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Adrenal washout

Adrenal washout can be calculated using the density value of an adrenal mass on non-enhanced, portal venous phase and 15 minutes delayed CT scans (density measured in Hounsfield units (HU)). It is primarily used to diagnose adrenal adenoma. absolute washout [(HUportal venous phase) - (HUdelaye...
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Adrenocorticotropin independent macronodular adrenocortical hyperplasia

Adrenocorticotropin independent macronodular adrenocortical hyperplasia (AIMAH) is considered a rare form of macronodular adrenal hyperplasia. It is an uncommon cause of primary adrenal hypercortisolism. Clinical presentation Patients with AIMAH tend to present 10 years earlier on average than...
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Adrenomyeloneuropathy

Adrenomyeloneuropathy is a form of X-linked adrenoleukodystrophy characterized by pronounced involvement of the spinal cord with only minor involvement of the cerebral white matter.  Clinical presentation Clinical presentation depends on whether or not there is also cerebral involvement.  In ...
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Adult acquired flatfoot disease

Adult acquired flatfoot disease is a common condition that results in foot pain and disability.  Epidemiology Most commonly affects middle-aged and elderly females 1. Pathology Adult acquired flatfoot disease is a combination of: flattened medial arch (pes planus) peritalar subluxation ex...
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Adult cervical lymphadenopathy (differential)

Cervical lymphadenopathy in an adult can result from a vast number of conditions. They include: malignancy metastases  from head and neck tumors lymphoma other neoplastic lesions Castleman disease Kaposi sarcoma infection bacterial infection viral infection Epstein-Barr virus herpes ...
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Adult chest radiograph common exam pathology

Adult chest radiograph common exam pathology is essential to consider in the build up to radiology exams. The list of potential diagnoses is apparently endless, but there are some favorites that seem to appear with more frequency. When dealing with the adult chest radiograph in the exam setting...
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Adult chest radiograph in the exam setting

A chest radiograph in the exam setting may contain a vast variety of pathology. However, consider the history and correlate the likely diagnoses that may be demonstrated on film. Furthermore, check your review areas to ensure that the abnormality isn't at the corner of the film. Locating pathol...
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Adult chest radiograph pathology checklist

The adult chest radiograph pathology checklist is just a pathology checklist of things not to miss when reviewing a chest radiograph, especially in the exam setting. standard review areas apices retrocardiac area hilar regions below the diaphragm right descending pulmonary artery (like a l...
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Adult chest radiograph set-pieces

There are a number of adult chest radiograph set-pieces. These are based on common patterns of disease that are seen on chest radiographs. Make sure that you have relevant differentials for these appearances and a quick oral set-piece for them when they come up. Pulmonary parenchyma lobar coll...
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Adult cystic renal disease

Adult cystic renal disease comprises multiple distinct hereditary and non-hereditary disease processes.  Pathology Etiology Hereditary adult polycystic kidney disease (APCKD), a.k.a. autosomal dominant polycystic kidney disease (ADPCKD) medullary cystic kidney disease von Hippel-Lindau dis...
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Adult elbow radiograph (an approach)

Systematic review Whenever you look at an adult elbow x-ray, review: alignment fat pads bone cortex Alignment Check the anterior humeral line: drawn down the anterior surface of the humerus should intersect the middle 1/3 of the capitellum if it doesn't, think distal humeral fracture C...
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Adult fibrosarcoma

Adult fibrosarcomas are rare, malignant and highly aggressive fibroblastic soft tissue tumors. They constitute a diagnosis of exclusion. Epidemiology Adult fibrosarcomas by more recent definition are rare and make up for around 1% of soft tissue sarcomas. They are mostly seen in the middle-age...
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Adult granulosa cell tumor of the ovary

Adult granulosa cell tumor of the ovary is a type of ovarian sex cord / stromal tumor. They are by far the most frequent subtype of granulosa cell tumors of the ovary (95%) and are commoner than the juvenile granulosa tumor of the ovary. Epidemiology Approximately two-thirds of this subtype ar...
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Adult hypophosphatasia

Adult hypophosphatasia is generally considered a milder form of hypophosphatasia. It is usually classified as hypophosphatasia occurring after 18 years of age and typically diagnosed after middle age 2. It is normally not associated with low bone mass in general but can be have considerable het...
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Adult leukodystrophies

Adult-onset leukodystrophies are uncommon compared to those that present in childhood and in most instances are a delayed and atypical presentation of conditions more common in childhood. They are important differential considerations when assessing adults with white matter diseases.  Terminolo...
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Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), also known as hereditary diffuse leukoencephalopathy with spheroids (HDLS) and pigmentary orthochromatic leukodystrophy (POLD), refers to a rare inherited autosomal dominant disease characterized by an adult-onset l...
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Adult-onset Still disease

Adult-onset Still disease is a rare multisystem inflammatory disorder, and was originally thought to be a variant of Still disease, a pediatric arthropathy. Epidemiology Still disease in adults is rare affecting around 1.5 per 100,000 people, it occurs in a bimodal distribution with one peak a...
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Advanced multiple beam equalization radiography

The advanced multiple beam equalization radiography (AMBER) system is used to control the distribution of local exposure to the film. An array of independently functioning detectors is used to send feedback signals to the modulators kept in front of the x-ray tube to modulate the exposure levels.
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Adventitial bursae

Adventitial bursae are those bursae that develop later in life in response to pressures developed as a result of acquired bony prominences or deformities 1.  These bursa can become inflamed resulting in adventitious bursitis.
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Adventitious bursitis

Adventitious or adventitial bursitis refers to inflammation associated with adventitious bursae. Adventitious bursae are not permanent native bursae. They can develop in adulthood at sites where subcutaneous tissue becomes exposed to high pressure and friction. Clinical presentation When pres...
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Adynamic ileus

Adynamic ileus is the failure of passage of enteric contents through the small bowel and colon that are not mechanically obstructed. Essentially it represents the paralysis of intestinal motility. Clinical presentation Patients may be asymptomatic or present with symptoms similar to mechanical...
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Adynamic ileus (mnemonic)

A mnemonic for the common causes of adynamic ileus is: 5 Ps Mnemonic The classic "5 Ps" are: P: postoperative P: peritonitis P: potassium: low (also disturbances of other electrolytes) P: pelvic and spinal fractures P: parturition However, there are a few further Ps that can be included...
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Aerophagia

Pathologic aerophagia is a rare condition caused by excessive and inconvenient air swallowing. It is a self-limiting condition affecting mainly children exposed to high grades of stress but can be a persistent problem in children with psychiatric or neurological disorders. Clinical presentation...
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Afferent loop syndrome

Afferent loop syndrome is an intermittent partial or complete mechanical obstruction of the afferent limb of a gastrojejunostomy. The syndrome classically refers to obstruction of the upstream limb of a side-to-side gastrojejunostomy but has also been used to refer to the biliopancreatic limb o...
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Afibrinogenemia

Afibrinogenemia, also called congenital afibrinogenemia, is a rare autosomal recessive inherited blood disorder due to deficiency of the clotting protein fibrinogen. The disorder is associated with increased risk of spontaneous hemorrhage1. Epidemiology Afibrinogenemia has an estimated prevale...
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Aflatoxins

Aflatoxins are naturally-occurring mycotoxins that are produced by Aspergillus species, especially Aspergillus flavus. They are acutely toxic and carcinogenic. Acute exposure High-level aflatoxin exposure can result in acute aflatoxicosis with acute hepatic necrosis, leading to cirrhosis, and ...
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Agatston score

Agatston score is a semi-automated tool to calculate a score based on the extent of coronary artery calcification detected by an unenhanced low-dose CT scan, which is routinely performed in patients undergoing cardiac CT. Due to an extensive body of research, it allows for early risk stratificat...
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Aging blood on MRI (mnemonic)

Aging blood on MRI is dependent on the varying MRI signal characteristics of hemorrhagic collections with time and can be very useful in correlating the imaging findings with the clinical picture. However, as it can be complicated to recall the MRI features of aging blood through the five stages...
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Agenesis (general)

The biological/medical term agenesis (plural: ageneses) refers to failure of an organ to grow or develop during the embryological period. Examples include: appendiceal agenesis cerebellar agenesis corpus callosum agenesis dental agenesis (anodontia) diaphragmatic agenesis dorsal pancreati...
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Agenesis of the appendix

Agenesis of the appendix is extremely rare, with an incidence at surgery of approximately 1 in 100,000 laparotomies 1. It is most commonly due to a sporadic etiology. However in the rare genetic condition, familial apple peel jejunal atresia, absence of the appendix is a recognized feature. Also...
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Agenesis of the diaphragm

Agenesis of the diaphragm is a congenital diaphragmatic developmental anomaly where all or part of diaphragm fails to form. It can sometimes be thought of as an extreme form congenital diaphragmatic herniation 1. Pathology The agenesis can either be unilateral or bilateral. Herniation of abdom...
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Agenesis of the left hepatic lobe

Agenesis of the left hepatic lobe is a rare variation in liver anatomy. It is clinically asymptomatic and discovered during imaging or surgery. Radiographic features absence of the left hepatic lobe (left of the falciform ligament, Couinaud segments 2 and 3) absence of left hepatic artery, le...
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Agenesis of the right hepatic lobe

Agenesis of the right hepatic lobe is a rare variation in liver anatomy. Radiographic features absence of the right hepatic lobe absence of right hepatic artery, right portal vein, and right hepatic biliary system compensatory hypertrophy of the left hepatic lobe and caudate lobe possible r...
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Agger nasi cells

Agger nasi air cells are the most anterior ethmoidal air cells lying anterolateral and inferior to the frontal recess and anterior and above the attachment of the middle turbinate. They are located within the lacrimal bone and therefore have as lateral relations the orbit, the lacrimal sac and t...
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Aggressive angiomyxoma

Aggressive angiomyxomas are rare tumors that arise in the pelvis and typically cross the levator ani muscles. Despite its name, it is essentially a benign tumor and the term "aggressive" is due to a predilection for local recurrence. Only rarely does it metastasize. Epidemiology It is seen pre...
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Aggressive fibromatosis

Aggressive fibromatosis is a type of musculoskeletal fibromatosis. While it is a non-metastasizing fibrous lesion, it is thought to be a true neoplasm that arises from the fascial and musculoaponeurotic coverings, sometimes at the site of a traumatic or post-surgical scar. Terminology The term...
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Aggressive granulomatosis post hip replacement

Aggressive granulomatosis post hip replacement (also known as particle disease) is a potential complication of a hip joint replacement. Pathology Aggressive granulomas consist of well organized connective tissue containing histiocytic-monocytic and fibroblastic reactive zones. They can be high...
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Aggressive vertebral hemangioma

Aggressive vertebral hemangiomata are a rare form of vertebral hemangiomata where significant vertebral expansion, extra-osseous component with epidural extension, disturbance of blood flow, and occasionally compression fractures can be present causing spinal cord and/or nerve root compression 1...
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Agnosia

Agnosia is a neurological disorder characterized by an inability to identify an object despite both having knowledge of that object and functional sensory input. For example, a patient with posterior cortical atrophy who characteristically has visual agnosia, will be unable to identify a hammer,...
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Agranulocytosis

Agranulocytosis refers to a situation where the absolute neutrophil count (ANC) falls to less than 100 neutrophils per microliter of blood. It predisposes to a very high risk of severe infection. Pathology It can be hereditary or acquired.  hereditary: usually due to genetic mutations in the ...
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Agraphia

Agraphia represents acquired impairments of writing ability secondary to damage or dysfunction of the central nervous system. Impairments caused solely by motor dysfunction (e.g. hand paresis or tremor) are not considered to be forms of agraphia 1. Clinical presentation Agraphia is rarely an i...
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Ahlbäck classification of knee osteoarthritis

The Ahlbäck classification is one of many ways to grade knee osteoarthritis. Classification grade 1: joint space narrowing (less than 3 mm) grade 2: joint space obliteration grade 3: minor bone attrition (0-5 mm) grade 4: moderate bone attrition (5-10 mm) grade 5: severe bone attrition (mo...
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AICA-PICA dominance

AICA-PICA dominance refers to the principle that the cerebellar vascular territory supplied by the anterior inferior cerebellar artery and posterior inferior cerebellar artery have a reciprocal arrangement. That is the size of the AICA and the subsequent territory it supplies is inversely propor...
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Aicardi-Goutières syndrome

Aicardi-Goutières syndrome is a rare hereditary neurodegenerative disease which usually presents in early infancy with systemic and central nervous system inflammatory syndrome characterized by hepatosplenomegaly, vasculopathy and encephalopathy. Many of the features are similar to congenital TO...
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Aicardi syndrome

Aicardi syndrome is a rare severe developmental disorder. It results from an X-linked genetic defect that is fatal in males and therefore only manifests in females (except for rare 47, XXY cases). Note: Aicardi syndrome is distinct from Aicardi-Goutieres syndrome although both are named after J...
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AIDS cholangiopathy

AIDS cholangiopathy refers to an acalculous, secondary opportunistic cholangitis that occurs in AIDS patients as a result of immunosuppression.  Pathology Characterized by multiple irregular strictures essentially indistinguishable from primary sclerosing cholangitis (PSC). There are four path...
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AIDS-defining illness

AIDS-defining illnesses are conditions that in the setting of a HIV infection confirm the diagnosis of AIDS and do not commonly occur in immunocompetent individuals 2. According to the CDC surveillance case definition 1, they are: Infectious bacterial infections: multiple or recurrent candidi...
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AIDS embryopathy

Acquired immunodeficiency syndrome (AIDS) embryopathy is characterized by a group of dysmorphic features, which manifests either before or after birth in offsprings of women who are infected by HIV virus. The diagnosis, however, is in disfavour according to some authors 2. Pathology Transplace...
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AIDS-related diffuse large B-cell lymphoma

AIDS-related diffuse large B-cell lymphomas are one of the immunodeficiency-associated CNS lymphomas, and in western countries represented a dramatic increase in primary CNS lymphoma during the HIV/AIDS epidemic of the 1980s, although the incidence is likely lower in patients treated with HAART ...
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AIDS-related pulmonary lymphoma

AIDS-related pulmonary lymphoma (ARPL) is classified as a distinct form of pulmonary lymphoma. Pulmonary involvement is a common extranodal site in AIDS-related NHL. Pathology ARPL is typically a high-grade B-cell non-Hodgkin's lymphoma and the majority of patients have advanced HIV infection,...
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Ainhum

Ainhum, also known as dactylolysis spontanea, is a rare cutaneous condition in which a hyperkeratotic band partially or totally encircles a digit. The constriction thins the underlying bone, which is then prone to fracture. Some cases result in autoamputation. Epidemiology Some have suggested ...
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Air bronchogram

Air bronchogram refers to the phenomenon of air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white). It is almost always caused by a pathologic airspace/alveolar process, in which something other than air fills the alveoli. Air bronchograms will not ...
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Air-bronchogram (summary)

This is a basic article for medical students and other non-radiologists Air-bronchograms are gas-filled bronchi surrounded by alveoli filled with fluid, pus or other material 1. It is a very useful sign because it is highly sensitive and specific for the presence of lung consolidation rather th...
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Air bubble artifact

The air bubble artifact on CT is due to the presence of abnormal gas in the oil coolant which surrounds the x-ray tube. The artifact manifests as subtle low density, which has only been described on brain scans. Cause The x-ray tube in a CT scanner is prevented from overheating by a heat excha...
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Air bubble sign (pulmonary hydatid)

The air bubble sign is seen in CT of complicated (ruptured or infected) pulmonary hydatid cyst and refers to small bubbles of gas within the periphery of pulmonary mass and is helpful, particularly in endemic areas, in suggesting the diagnosis over other masses (e.g. metastases or primary lung t...
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Air bubble sign (tension pneumocephalus)

The air bubble sign is seen on CT of the brain and represents multiple small foci of air within the subarachnoid space, especially the Sylvian fissure.1 Although described as a sign of tension pneumocephalus it is also seen in pneumocephalus without elevated pressures.2 It should not be confus...
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Air crescent sign (lung)

An air crescent sign describes the crescent of air that can be seen in invasive aspergillosis, semi-invasive aspergillosis, or other processes that cause pulmonary necrosis. It usually heralds recovery and is the result of increased granulocyte activity. Terminology It should not be confused w...
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Air gap technique

The air gap technique is a radiographic technique that improves image contrast resolution through reducing the amount of scattered radiation that reaches the image detector. In select situations, this technique can be used instead of an antiscatter grid as the primary scatter reduction method in...
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Air gap technique (general radiography)

The utilization of the air gap technique in general radiography is limited due to the need for equipment facilitation to create the air gap when it is not inherent in the standard technique. Horizontal-beam lateral hip There are many different methods of performing the horizontal beam lateral ...
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Air gap technique (mammography)

The air gap technique is utilized for the magnification mammography view. Magnification mammography is a high dose imaging technique which is generally utilized as a follow-up to a standard mammogram image series when a focal area needs to be more clearly examined 1. The air gap technique is ut...
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Air space nodule

An air space nodule is a small (few millimeters to 1 cm), ill-defined, nodular opacity that is often centrilobular in location and is non-specific, seen in many conditions. Commonly it represents a focal area of consolidation or peribronchiolar inflammation, and can indicate endobronchial spread...
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Airspace nodules

Airspace nodules are irregularly marginated nodular opacities with air bronchograms that tend to measure 8 mm in diameter. They are quite separate from pulmonary nodules that range in size, are homogeneous and well-defined (being surrounded by normal lung).
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Air space opacification

Air space opacification is a descriptive term that refers to filling of the pulmonary tree with material that attenuates x-rays more than the surrounding lung parenchyma. It is one of the many patterns of lung opacification and is equivalent to the pathological diagnosis of pulmonary consolidati...
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Air-space opacification (summary)

This is a basic article for medical students and other non-radiologists Air-space opacification is a descriptive term that refers to filling of the lung parenchyma with material that attenuates x-rays more than the unaffected surrounding lung tissue. It is the radiological correlate of the path...
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Air space opacities

The differential for air space opacities is extensive, and needs to be interpreted in context of chronicity (previous imaging) and clinical context. It is therefore useful to divide airspace opacities as follows: acute airspace opacities with lymph node enlargement acute airspace opacities: un...
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Air trapping

Air trapping in chest imaging refers to retention of excess gas (“air”) in all or part of the lung, especially during expiration, either as a result of complete or partial airway obstruction or as a result of local abnormalities in pulmonary compliance. It may also sometimes be observed in norma...
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Airway centered interstitial fibrosis

Airway centered interstitial fibrosis is a rare subtype of pulmonary fibrosis with variable outcomes. Pathology It is characterized by fibrosis of the respiratory bronchioles and the peribronchiolar interstitium. It may be triggered by exogenous agents or endogenous autoimmune conditions such ...
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Airway foreign bodies in adults

Adults may inadvertently or intentionally ingest foreign bodies into the airway.  
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Airway foreign bodies in children

Airway foreign bodies in children are potentially fatal, which is why immediate recognition is important. Unfortunately, delayed diagnosis is common. Epidemiology Children under the age of four years are at increased risk of foreign body (FB) aspiration, with a slight male predominance 1.  Cl...
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Airway invasive aspergillosis

Airway invasive aspergillosis, also known as Aspergillus bronchopneumonia or bronchopneumonic aspergillosis, refers to a form of invasive aspergillosis that affects the airways as the major or only feature. Epidemiology It usually occurs in immunocompromised neutropenic patients, particularly ...
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Airway pressure release ventilation

Airway pressure release ventilation (APRV) is an alternative mode for mechanical ventilation. It can be adopted as a method of alternative method for difficult-to-oxygenate patients with acute lung injury / acute respiratory distress syndrome (ALI/ARDS). Its is usually not recommended in patien...
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Alagille syndrome

Alagille syndrome (also known as arteriohepatic dysplasia) is a congenital genetic multisystem disorder. Clinical presentation Infants typically present with symptoms relating to the liver where it is one of the most common causes of hereditary cholestasis. Genetics Alagille syndrome is inhe...
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Alanine peak

Alanine is one of the compounds examined in MR spectroscopy. It resonates at 1.48 ppm chemical shift. It is elevated in meningiomas.
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Alar fascia

The alar fascia is a thin fibroareolar membrane separating the (anterior) true retropharyngeal space from the (posterior) danger space. It is the ventral component of the deep layer of the deep cervical fascia. Notably, in the well patient, the alar fascia is not usually visible on cross-sectio...
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Alar ligament

The alar ligaments join the lateral margins of the sloping upper posterior margin of the dens of C2 to the lateral margins of the foramen magnum (adjacent to the occipital condyles) and lie on either side of the apical ligament. They may be oblique or vertical and are thickest at the occipital a...
Article

Alar ligament calcification

Alar ligament calcification​ is rare. The alar ligaments arise bilaterally from the upper portion of the odontoid process and run obliquely cephalad and laterally to insert on the medial surface of the occipital condyles. They stabilize the head during rotatory movements.  Epidemiology Focal c...
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Alar thoracic artery

The alar thoracic artery is a rare variant arterial glandular branch of the axillary artery (usually the second part) that supplies the axillary fat, lymph nodes and skin of the axilla.
Article

Alban Köhler

Alban Köhler (1874-1947) was a German radiologist best known for both his work in describing avascular necrosis of the navicular (now known as Köhler disease) and the publication of ‘Roentgenology - The Borderlands of the Normal and Early Pathological in the Skiagram’ a textbook exploring anatom...
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Alberta stroke program early CT score (ASPECTS)

The Alberta stroke programme early CT score (ASPECTS) 1 is a 10-point quantitative topographic CT scan score used in patients with middle cerebral artery (MCA) stroke. It has also been adapted for the posterior circulation (see below).  Scoring system Segmental assessment of the middle cerebra...
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Albert Salomon

Albert Salomon (1883-1976), a German surgeon, was the first physician to study x-rays of breast tissue. Early life To be completed. Development of mammography Salomon worked at the Royal Surgical University Clinic in Berlin and from about 1913 x-rayed 3000 breast specimens obtained from the...
Article

Albert Soiland

Albert Soiland (1873-1946), was a key figure in the establishment of radiology as an independent medical specialty in the United States. He is most famously remembered for his crucial role in the founding of the American College of Radiology. He was also a pioneering radiotherapist. Early life ...
Article

Albright hereditary osteodystrophy

Albright hereditary osteodystrophy (AHO) is a form of osteodystrophy and is also classified as a phenotype of pseudohypoparathyroidism (i.e. type 1a).  Typical clinical spectrum includes short, stocky build round facies with a low, flat nasal bridge short neck ectopic ossifications brachym...
Article

Alcoholic cerebellar degeneration

Alcoholic cerebellar degeneration is a common type of acquired cerebellar ataxia characterized by chronic vermian atrophy 1. It is a sequela of chronic alcohol abuse or malnutrition and has also been described in the literature as alcohol-related cerebellar degeneration, alcohol-induced cerebell...
Article

Alexander disease

Alexander disease, also known as fibrinoid leukodystrophy, is a rare fatal leukodystrophy, which usually becomes clinically evident in the infantile period, although neonatal, juvenile and even adult variants are recognized. As with many other diseases with variable age of presentation, the earl...
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Alexia

Alexia (or acquired dyslexia) is a neurological term refers to an acquired impairment of reading resulting from damage of critical brain areas. Clinical presentation Alexia can manifest itself as an impairment of oral reading and reading comprehension alike and can occur in combination with va...
Article

Aliasing artifact (CT)

Aliasing artifact, otherwise known as undersampling, in CT refers to an error in the accuracy proponent of analog to digital converter (ADC) during image digitization.  Image digitization has three distinct steps: scanning, sampling, and quantization.  When sampling, the brightness of each pix...
Article

Aliasing in MRI

Aliasing in MRI, also known as wrap-around, is a frequently encountered MRI artifact that occurs when the field of view (FOV) is smaller than the body part being imaged. The part of the body that lies beyond the edge of the FOV is projected onto the other side of the image. This can be correcte...
Article

Aliasing phenomenon (ultrasound)

Aliasing is a phenomenon inherent to Doppler modalities which utilize intermittent sampling in which an insufficient sampling rate results in an inability to record direction and velocity accurately.  Physics Unlike continuous wave Doppler, pulsed wave and color flow Doppler modalities alterna...
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Alien limb syndrome

Alien limb syndrome is a rare neurological phenomenon in which a patient has the impression that their limb does not belong to them and is controlled by some external force 1.  It can occur in a number of neurodegenerative diseases, typically those with cortical involvement, including: cortico...
Article

A-line (ultrasound)

An a-line is an ultrasonographic artifact appreciated during the insonation of an aerated lung. 1 The term may be applied to the horizontal, echogenic long path reverberation artifacts that occur beneath the pleural line at multiples of the distance between the ultrasound probe and the visceral...
Article

Allan Macleod Cormack

Allan M Cormack (1924-1998) was a South African-American physicist who was instrumental in the development of CT 1,3. Early life Allan Macleod Cormack was born on 23 February 1924 in Johannesburg, South Africa. His parents - teacher Amelia MacLeod and engineer George Cormack - had both emigrat...
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Allantoic cyst

Allantoic cysts are a type of true cyst of the umbilical cord. Pathology The allantois forms from the part of the fetal yolk sac that eventually becomes the primitive hindgut (the cloaca). The cloaca divides into the hindgut posteriorly and the urogenital sinus anteriorly. The allantois remain...

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