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.

1,098 results found
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Double panda sign

The double panda sign refers to the combination of the face of the giant panda and face of the miniature panda (cub of the giant panda) seen on T2 weighted images of midbrain and pons respectively in Wilson disease. The midbrain face of the giant panda sign consists of normal intensity of red n...
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Simultanagnosia

Simultanagnosia, also known as simultagnosia, is an individual's inability to perceive more than one object at a time. It is a characteristic symptom of Bálint syndrome and can also be seen with posterior cortical atrophy (PCA).
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Bayonet deformity (wrist)

Bayonet deformity is a term used to describe the shape of the wrist after the infamous weapon. It occurs secondary to a prominent distal ulna as a result of dorsal subluxation. This deformity is found in the following conditions: Madelung deformity hereditary multiple exostoses with pseudo-Ma...
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Thymic sail sign

The thymic sail sign represents a triangular-shaped inferior margin of the normal thymus seen on a neonatal frontal chest radiograph. It is more commonly seen on the right side, but can also be bilateral. It is seen in 3-15% of all cases. This sign should not be confused with the spinnaker sail ...
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Thymic notch sign

The thymic notch sign represents the normal thymus in a newborn on a frontal chest radiograph. Interruption of the cardiac silhouette forms a notch, which may be seen on either side, but more frequently is seen on the left side.   See also thymic sail sign thymic wave sign  
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Stag's antler sign (lungs)

The stag's antler sign, also known as the hands-up or inverted moustache sign, refers to upper lobe pulmonary venous diversion in pulmonary venous hypertension or pulmonary edema as seen on an erect frontal chest radiograph. The prominence of upper lobe pulmonary veins resembles a stag's antler...
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Knuckle sign (pulmonary embolism)

The knuckle sign refers to the abrupt tapering or cutoff of a pulmonary artery secondary to a pulmonary embolus (PE). It is better visualized on CT pulmonary angiography (CTPA) than chest x-ray. This is an important ancillary finding in pulmonary embolism, and often associated with the Fleischne...
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Earth-heart sign

The earth-heart sign is a sign of cardiac compromise that may be seen on chest radiographs of patients with tension pneumomediastinum. The substantial pressure exerted on the heart by the gas trapped in the mediastinum with subsequent impairment of central venous return and obstruction of diast...
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Pulmonary plethora

Pulmonary plethora is a term used to describe the appearances of increased pulmonary perfusion on chest radiographs. It is commonly used in pediatric radiology.  Pathology Usually a left-to-right shunt of 2:1 is required for pulmonary plethora to occur 2,3. Increased pulmonary perfusion occurs...
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Frimann-Dahl sign

The Frimann-Dahl sign is a diagnostic sign demonstrated when three dense lines, representing the sigmoid walls, are seen converging to the site of obstruction in sigmoid volvulus and associated with empty rectal gas 1. History and etymology Johan Frimann-Dahl (1902-1982) was a Norwegian Profes...
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Courvoisier sign (hepatobiliary)

Courvoisier sign or Courvoisier-Terrier sign states that in a patient with painless jaundice and an enlarged gallbladder (or right upper quadrant mass), the cause is unlikely to be gallstones and therefore presumes the cause to be an obstructing pancreatic or biliary neoplasm until proven otherw...
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Reverse target sign (cirrhotic nodules)

A reverse target sign is a potential ultrasound marker for cirrhotic nodules on ultrasound. It represents central iso-hyperechogenicity with surrounding hyperechoic rim. This sign is useful to differentiate metastases from cirrhotic nodules, conversely the target sign is seen with liver metastas...
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T2 dark spot sign (endometrioma)

T2 dark spot sign is an MRI appearance of endometriomas seen as a result of chronic hemorrhage. The sign is useful in differentiating a solitary endometrioma from a functional hemorrhagic ovarian cyst, as both might show high T1 signal with T2 shading.  The T2 dark spot, described in the sign, ...
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Atoll sign (disambiguation)

The atoll sign in radiology can refer to: reverse halo sign: atoll sign in thoracic CT atoll sign in liver MRI: suggestive of an inflammatory hepatic adenoma
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Atoll sign (liver MRI)

The atoll sign in hepatic imaging has been described when a liver lesion shows a peripheral rim of high T2 signal intensity with the center of the lesion appearing isointense to the background of non-cirrhotic liver on T2WI mimicking an atoll. The peripheral rim shows hyperenhancement in the por...
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Parrot beak meniscal tear

Parrot beak meniscal tear is a type of radial meniscal tear with a more oblique course, which on axial images gives the characteristic appearance of a curved V, similar to a parrot's beak. As it is obliquely oriented in relation to the coronal and sagittal plane, it results in a marching cleft s...
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Pneumothorax (ultrasound)

Pneumothorax is a serious potential consequence of blunt thoracic trauma and, if misdiagnosed, it may quickly become life-threatening. For a discussion on epidemiology, clinical presentation, pathology, and treatment and prognosis please see the main pneumothorax article.  Radiographic feature...
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Positive PCL line sign

The positive PCL line sign is an indirect sign of anterior cruciate ligament (ACL) tear based on secondary changes of the posterior cruciate ligament (PCL) on MRI images. A line tangent to the upper border of the PCL should normally intersect the medullary cavity of the distal femur, if it does ...
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Coxa magna

Coxa magna is the asymmetrical, circumferential enlargement and deformation of the femoral head and neck. Definitions in the literature vary but enlargement with asymmetry >10% in size is a reasonable cut-off for diagnosis 1.  Pathology Etiology Legg-Calve-Perthes disease transient synovitis...
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Posterior pituitary bright spot

The posterior pituitary bright spot is the normal hyperintensity of the neurohypophysis on non-contrast T1 weighted MR images.  Epidemiology Most studies have found posterior pituitary bright spots in 90-100% of normal patients 2,3,6,8,9. One notable exception found it in only 52% of patients ...
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Swiss cheese sign (lungs)

The Swiss cheese sign has been used for the appearance on CT of fluid-containing pneumatoceles, that typically occurs following pulmonary lacerations 1. They have also been described on CT appearances where there is pulmonary infection superimposed on emphysema 2. The pneumatocoeles appear as '...
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Snowman sign (pituitary macroadenoma)

Snowman sign in neuroimaging refers to the configuration of many pituitary macroadenomas. As they are soft tumors they are indented by the diaphragma sellae giving them a snowman configuration (or "figure 8" or "dumbbell" configuration). This feature helps in differentiating these tumors from me...
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Snowman sign (disambiguation)

Snowman sign, also sometimes referred to as a figure of 8 sign or dumbell sign, is a radiologic sign related to conditions that have a shape which resembles a snowman. This include:  snowman sign (total anomalous pulmonary venous return) 1 snowman sign (pituitary macroadenoma) 2,3
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Hanging noose sign

Hanging noose sign in obstetric imaging is a rarely described but classical finding of a true umbilical cord knot. It demonstrates a transverse section of the umbilical cord surrounded by a loop of umbilical cord and changes in the pressure of the knot can be demonstrated with the fetal movement...
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Bronchial cut-off sign

The bronchial cut-off sign refers to the abrupt truncation of a bronchus from obstruction, which may be due to cancer, mucus plugging, trauma or foreign bodies. Typically, there is associated distal lobar collapse. 
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Hyoid elevation

Hyoid elevation on a modified barium swallow study indicates that the pharyngeal muscles are contracting appropriately. Radiographic features Modified barium swallow With real time fluoroscopy (or videofluoroscopy) during the act of swallowing, the larynx moves upward and forward when there i...
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Powers ratio

The Powers ratio is a measurement of the relationship of the foramen magnum to the atlas, used in the diagnosis of atlanto-occipital dissociation injuries. The ratio, AB/CD, is measured as the ratio of the distance in the median (midsagittal) plane between the: basion (A) and the posterior spi...
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Geyser sign (shoulder)

The geyser sign is the flow of arthrographic contrast or joint fluid from the glenohumeral joint across the acromioclavicular joint (ACJ) to form a supraclavicular collection. It is seen in some cases of long-standing rotator cuff tear and advanced degenerative change of the shoulder.  Clinical...
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Pseudo-omphalocele

Pseudo-omphalocele is a spurious sonographic appearance giving an impression of an anterior abdominal wall defect. Radiographic features Antenatal ultrasound Pseudo-omphalocele may be seen in: scanning errors where there is a deformation of the fetal abdomen by transducer pressure and the im...
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Snowstorm sign (complete hydatiform mole)

Snowstorm sign in obstetric imaging is classically seen in complete hydatiform mole. It is characterized by the presence of many hydropic villi which gives the ultrasonographic appearance of a central heterogeneous mass having a solid, hyperechoic area and interspersed with a multitude of cystic...
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Widened intercondylar notch

A widened intercondylar notch on knee radiographs is a sign associated with: haemophilic arthropathy (most commonly bilateral) juvenile rheumatoid arthritis (most commonly bilateral) tuberculous arthropathy (usually unilateral) 3
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Transmantle sign (brain)

The transmantle sign is an MRI feature of focal cortical dysplasia (FCD), almost exclusively seen in type II focal cortical dysplasia (Taylor dysplasia - also known as transmantle cortical dysplasia for this reason). However, it is not always present, seen in ~45% (range 21-72%) of patients with...
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Callosal angle

The callosal angle has been proposed as a useful marker of patients with idiopathic normal pressure hydrocephalus (iNPH), helpful in distinguishing these patients from those with ex-vacuo ventriculomegaly (see hydrocephalus versus atrophy).  It should be noted that there is nothing magical abou...
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Cingulate sulcus sign

The cingulate sulcus sign has been proposed as being useful as an MRI feature of idiopathic normal pressure hydrocephalus (NPH). It denotes the posterior part of the cingulate sulcus being narrower than the anterior part. The divider between the anterior and posterior parts of the sulcus being a...
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Focal hepatic hot spot sign

The focal hepatic hot spot sign, also known as the hot quadrate sign can be seen on technetium 99m sulfur colloid scans of the liver and spleen, as well as CT studies. Radiographic features It occurs as a focal area of increased radiopharmaceutical uptake, or iodinated contrast accumulation, i...
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Orbital emphysema

Orbital emphysema is the presence of gas within the orbital soft tissues. It is usually due to orbital fractures communicating with the paranasal sinuses but can be caused by penetrating trauma and infection. It is a common finding also after orbital or ocular surgery.  Location preseptal ...
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Genu recurvatum

Genu recurvatum describes the malalignment or deformity of the knee joint with extension beyond neutral (i.e. hyperextension).  Pathology Genu recurvatum can be associated with subluxation or dislocation of the knee joint.  Etiology congenital arthrogryposis multiplex congenita congenital ...
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Double barrel sign (disambiguation)

Double barrel sign is an imaging appearance of two lumens adjacent to each other. It can be seen in: dilated bile duct adjacent to portal vein double barrel aorta: aortic dissection double barrel esophagus: esophageal dissection
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Unfolded aorta

The term unfolded aorta refers to the widened and decreased curvature of the aortic arch on a frontal chest radiograph giving an ‘opened up’ appearance. It is one of the more common causes of apparent mediastinal widening and is seen with increasing age, usually associated with aortic calcificat...
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Sulcal effacement

Sulcal effacement is a local secondary sign of mass effect in the cranium. Any lesion exerting mass effect on brain parenchyma can push adjacent gyri together, thereby displacing the CSF from the sulci. It is greatest at the site where the cause of the mass effect is located (e.g. tumor, hemorr...
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Pistol grip deformity (hip)

The pistol grip deformity is considered a typical radiographic sign of cam-type femoroacetabular impingement. The shape of the proximal femur is reminiscent of a flintlock pistol known from old pirate movies. History and etymology It was first described by American orthopedic surgeon S David S...
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Kirklin sign

The Kirklin sign refers to a deformity of the normal gastric bubble on an upright chest radiograph due to a mass lesion of the gastric cardia or fundus. The Kirklin sign is different from the Kirklin complex, a gastric finding on upper GI fluoroscopy. History and etymology Byrl Raymond Kirkli...
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White matter buckling sign

The white matter buckling sign is helpful in distinguishing an extra-axial intracranial mass from an intra-axial one and represents the white matter projecting into gyri being compressed and displaced by the mass, even in the presence of edema (which would usually expand gyri, if the mass were i...
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Fetal maceration

Fetal maceration is one of the signs of fetal death. It is a destructive process caused by enzymatic autolysis of cells that begins immediately following fetal death. It results in epidermal desquamation and edema. It is visible on ultrasound between 12 to 24 hours after fetal death. It may not ...
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Putaminal rim sign

The putaminal rim sign, also known as the putaminal slit sign, is said to be a relatively specific sign of multiple system atrophy - parkinsonism (MSA-P), and refers to a linear region of high signal surrounding the lateral aspect of the putamen at 1.5 T MRI on T2 weighted images or ADC map. Un...
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Extrapleural fat sign

The extrapleural fat sign is an imaging feature which can be seen on CT under certain circumstances. It occurs from the inward displacement of extrapleural fat by an extrapleural fluid collection, extrapleural hematoma or extrapleural mass. The presence of the extrapleural fat sign is indicative...
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Fallen lung sign

The fallen lung sign (also known as CT fallen lung sign) describes the appearance of collapsed lung away from the mediastinum encountered with tracheobronchial injury (in particular those >2 cm away from the carina). It is helpful to look for this rare but specific sign, in cases of unexplained ...
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Hole within a hole sign

The hole within a hole sign or bevelled edge sign describes one classic appearance of lytic skull lesions in patients with eosinophilic granuloma. The bevelled edge of the defects indicates asymmetrical destruction of both inner and outer tables of the skull, giving the appearance of two overlap...
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Extracranial brain herniation

Extracranial or transcalvarial brain herniation refers to herniation of brain tissue external to the calvaria through a skull bone defect, which may be post-traumatic or post-surgical. Unlike encephaloceles, brain herniation is not surrounded by the meninges.  Craniectomy may be performed to de...
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Perinephric stranding

Perinephric stranding refers to the appearance of edema within the fat of the perirenal space on CT or MRI. While a degree of symmetric bilateral perinephric stranding is common, particularly in the elderly, asymmetric or unilateral perinephric stranding is an important sign of renal inflammatio...
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Expanded amnion sign

The expanded amnion sign has been described as a poor prognostic sign in early pregnancy, suspicious though not diagnostic of failed early pregnancy. Any visible embryo that is surrounded by an amnion (visible on transvaginal ultrasound) should also have a heartbeat, regardless of crown-rump len...
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Sunburst sign (meningioma)

The sunburst sign refers to the characteristic vascular supply seen in some meningiomas when seen from the side (tangential to the dural attachment). It is the result of the same phenomenon which results in the spoke wheel pattern of vessels (viewed in cross-section, parallel to the dural attach...
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Tiger stripe appearance

The tiger stripe appearance refers to the characteristic alternating hypo and hyperintense bands on MRI in Lhermitte-Duclos disease. This rare cerebellar tumor appears like the coat of a tiger. See also tigroid pattern - in brain
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Romanus lesion (vertebral bodies)

The Romanus lesion represents an early finding in inflammatory spondyloarthropathies, such as ankylosing spondylitis and enteropathic arthritis, and appears as irregularity and erosion involving the anterior and posterior edges of the vertebral endplates 1. Healing response to these inflammatory...
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T1 black holes

T1 black holes are hypointense lesions commonly seen on T1WI in patients with multiple sclerosis and indicates the chronic stage with white matter destruction, axonal loss and irreversible clinical outcome. Treatment and prognosis There is a correlation between the number of black holes and pa...
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Locked facet joint

Locked facet joint is a type of facet joint dislocation that results from jumping of the inferior articular process over the superior articular process of the vertebra below and becomes locked in the position. It can be unilateral or bilateral. Radiographic features Plain radiograph The tip ...
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État lacunaire

État lacunaire is a term describing the presence of multiple lacunar infarcts, which are ischemic strokes due to occlusion of penetrating cerebral arterioles, especially in the basal ganglia. The term has been strongly described as a pathological substrate for a multi-infarct vascular dementia 4...
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État criblé

État criblé, also known as status cribrosum, is a term that describes the diffusely widened perivascular spaces (Virchow-Robin spaces) in the basal ganglia, especially in the corpus striatum on MRI. It is usually symmetrical, with the perivascular spaces showing CSF signal on all sequences and w...
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Seatbelt sign (abdomen)

The seatbelt sign is both a clinical and radiological sign. It is simply the presence of ecchymosis and/or abraded skin in the distribution of a seatbelt (i.e. horizontal and/or diagonal) extending across the abdomen evident after a motor vehicle accident. Epidemiology A positive abdominal sea...
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Haystack sign (pneumomediastinum)

The haystack sign on chest radiographs in pediatric patients is indicative of pneumomediastinum. The pediatric heart is surrounded above and below with gas, giving it an appearance of a haystack from Monet's paintings. 
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Craniotabes

Craniotabes is defined as a softening of the skull bones that may be normally present in newborns.
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Northern exposure sign (sigmoid volvulus)

The northern exposure sign has been described as a high specificity sign in sigmoid volvulus. On a supine abdominal radiograph, the apex of the sigmoid volvulus is seen above (cranial to) the transverse colon.
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Centipede sign (mesentery)

The centipede sign is seen as engorged mesenteric vessels in cases of acute sigmoid diverticulitis which gives an appearance similar to a centipede 1.
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Duct penetrating sign (pancreas)

Duct penetrating sign is a radiographic sign that can be useful in differentiating between focal pancreatitis (inflammatory pancreatic mass) from pancreatic carcinoma. A positive sign is when a mass is penetrated by an unobstructed pancreatic duct; this makes focal pancreatitis the most likely ...
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Eccentric target sign (cerebral toxoplasmosis)

The eccentric target sign is considered pathognomonic for cerebral toxoplasmosis. It is seen on postcontrast MRI/CT as a ring enhancing lesion with an eccentrically located enhancing mural nodule. It is believed that this mural nodule is an extension from the abscess wall itself with inflamed ve...
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Ace-of-spades sign (heart)

Ace-of-spades sign refers to the pathognomonic configuration of the left ventricle as seen in apical hypertrophic cardiomyopathy 1-3. It consists of marked ventricular wall thickening at the apex resulting in cavity narrowing at the apex with a relatively normal appearance of the mid-ventricula...
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Cloaca (osteomyelitis)

A cloaca (pl. cloacae or cloacas) is a gap in the cortex of a bone affected by chronic osteomyelitis that allows the drainage of pus or other material from the bone into the adjacent tissues. Terminology The use of the term cloaca should be reserved for cortical breaches that are the result of...
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Double axillary pouch sign (shoulder)

The double axillary pouch sign is a collection of fluid between a torn anteroinferior glenoid labrum and the glenoid rim, giving the appearance of a second axillary pouch. The sign is seen best with MR arthrography on the coronal view, and is considered by some, a very specific sign for an ante...
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Ghost meniscus

A ghost meniscus, also known as the empty meniscus sign, refers to either a complete radial tear that has transected the meniscus, a displaced root avulsion or, alternatively, be due to a previous meniscectomy. Terminology Defined by the presence of a meniscus which disappears then reappears l...
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Ivory phalanx

Ivory phalanx is a finding of increased radiodensity of an entire phalanx as a result of periosteal and endosteal bone formation. This sign is a unique and specific radiographic manifestation of psoriatic arthritis, yet it is uncommon and thus of low sensitivity. Nevertheless, it is of particul...
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Ghost sign (cervical spine)

The ghost sign is a feature that has been described in a clay shoveler fracture as seen on the AP projection of a cervical spine radiograph. It is caused by the appearance of a "double spinous process" on C6 or C7 resulting from caudal displacement of the avulsed spinous process fragment, giving...
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Lentiform fork sign (basal ganglia)

The lentiform fork sign has been described on MRI and is seen as bilateral symmetrical hyperintensities in the basal ganglia surrounded by a hyperintense rim delineating the lentiform nucleus. It has been postulated to result from metabolic acidosis due to any cause 1, e.g. end stage renal dise...
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Two-slice-touch rule (knee MRI)

The two-slice-touch rule is a sign on MRI of the knee used to increase the sensitivity of diagnosing meniscal tears. This rule states a meniscal tear is present if abnormal findings are present on two or more images - these do not have to be contiguous, e.g. can occur on sagittal and coronal sl...
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Widow's peak hair anomaly

Widow's peak hair anomaly refers to a frontal hairline projection. Epidemiology Associations Aarskog syndrome Opitz syndrome Waardenburg syndrome frontonasal dysplasia craniofrontonasal dysplasia Clinical presentation Prominent V-shaped hairline projection. Ocular hypertelorism might be...
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Tram-track sign (disambiguation)

Tram-track sign may refer to a variety of appearances characterized by near-parallel lines in a number of contexts and regions including: tram-track sign (brain): cortical calcification in Sturge-Weber syndrome tram-track sign (orbit): e.g. optic nerve meningioma tram-track sign (chest): thic...
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Tram-track sign (chest)

Tram-track sign may be used in chest radiography or CT to denote the thickened non-tapering (parallel) walls of cylindrical bronchiectasis. It should not be confused with other tram-track signs elsewhere in the body. 
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Three line sign (common bile duct)

The three line sign refers to an MRI term that describes the appearance of roundworm Ascaris lumbricoides within the CBD lumen which appears as two hypointense lines representing the worm walls and hyperintense center which represents the worm gut. See also biliary ascariasis
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Lateral crescent sign (inguinal hernia)

The lateral crescent sign is a useful diagnostic sign of a direct inguinal hernia on CT scan, the hernia causing compression and lateral displacement of the inguinal canal contents (ductus deferens, testicular vessels, fat, etc.) to form a semicircle of tissue that resembles a moon crescent seen...
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Ribbon ribs deformity

Ribbon ribs deformity refers to the presence of thinned ribs on image studies. Such findings could be present in patients with neurofibromatosis type 1 due to the presence of multiple neurofibromas of intercostal nerves.  This deformity is also described in osteogenesis imperfecta 1 Edwards s...
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Transient ischemic dilatation

Transient ischemic dilatation (TID) is a paradoxical phenomenon seen in myocardial perfusion SPECT imaging.   With severe balanced coronary artery disease, myocardial ischemia may result in apparent enlargement of the left ventricular cavity during stress. The cause of this is not entirely clea...
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Septal bounce

Septal bounce is a sign of ventricular interdependence on echocardiography, cardiac CT, and cardiac MRI, manifested by paradoxical interventricular septal movement during early diastole (i.e. initial septal movement towards and then away from the left ventricle) seen mainly in constrictive peric...
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Porcelain left atrium

Porcelain left atrium, also known as coconut left atrium, is a term used when a large part of or the entire left atrial wall becomes calcified. It can occur as a rare consequence of endocarditis (with underlying rheumatic heart disease). It has also been described in the setting of end-stage ren...
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Ghost vertebra

Ghost vertebra is a sign, that is generally used synonymously with bone-within-a-bone vertebra, and as such, the causes form a subset of those causing bone within a bone appearance 2: Thorotrast administration: bone within a bone appearance due to temporary growth arrest 1 stress line rickets...
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Dot in a circle sign

Dot in a circle sign is an MRI sign for maduromycosis or mycetoma. It is described as a classic appearance on T2 weighted images which show a small rounded hyperintensity (representing granulation tissue), surrounded by a low signal intensity rim (representing fibrous septa) with a hypointense ...
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Crow feet sign (round atelectasis)

Crow feet sign is a characteristic, but uncommon, feature seen in round atelectasis. On CT, this is seen as linear bands radiating from a mass into adjacent lung tissue resembling the feet of a crow. This sign should not be confused with fibrotic changes occurring in the lung.
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Swallow tail sign (substantia nigra)

The swallow tail sign describes the normal axial imaging appearance of a hyperintensity within the substantia nigra on high-resolution T2*/SWI weighted MRI. It was previously thought that this sign was caused by nigrosome-1, but this has not been found to be correct in more recent studies, and t...
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Scalpel sign (spinal cord)

The scalpel sign has been recently described in dorsal thoracic arachnoid web on sagittal MRI spine studies. It relates to focal distortion of the thoracic cord, appearing anteriorly displaced. The enlarged dorsal CSF space mimics the profile of a surgical scalpel. It is helpful in distinguishi...
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Shred sign (lungs)

The shred sign, also known as the fractal sign, is a static sonographic sign of lung consolidation. Consolidated lung tissue appears as a subpleural hypoechoic region that has an irregular (shredded) deep border (fractal line) abutting normally aerated lung, which has echogenic artifacts. This ...
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Sinusoid sign (ultrasound)

The sinusoid sign is a dynamic sonographic sign, present when respiratory variation decreases the distance between the parietal and visceral pleura, when separated by a pleural effusion. Classically demonstrated in M-mode, the appearance of which the moniker is derived, it is specific for the id...
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Quad sign

The quad sign is a static sonographic sign observed in pleural effusion. It consists of four lines representing the pleura, rib, fluid, and lung. Similar to the sinusoid sign, this sign has a high sensitivity and specificity for pleural effusion, which - when simple - is itself anechoic.
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Fluid color sign

The fluid color sign is a diagnostic sign to differentiate a pleural effusion from pleural thickening by means of color Doppler ultrasound. In the case of pleural effusion a color signal is seen in the pleural fluid during respiratory and cardiac movement, whereas this color signal is not seen i...
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Waldenström sign (hip)

Waldenström sign is the increased distance between the pelvic teardrop and the femoral head. It is a highly specific sign of a hip joint effusion. Radiographic features Plain radiograph >11 mm total distance or >2 mm difference compared to contralateral hip 1,2 measured between the lateral a...
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Dot in box appearance

A "dot in box" appearance is a pattern that has been described with pulmonary lymphangitis carcinomatosis.  The interlobular septal thickening from lymphangitis forms polygonal arcades accounting for the box while the prominence of the centrilobular bronchovascular bundle is thought to represent...

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