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.

903 results found
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Bullet-shaped vertebra

Bullet-shaped vertebra refers to the anterior beaking of the vertebral body. It is seen in the following conditions: mucopolysaccharidosis (Morquio disease, Hurler disease) achondroplasia congenital hypothyroidism  See also weapons and munitions inspired signs
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Bunch of grapes sign (disambiguation)

Bunch of grapes sign refers to the ultrasound appearance of multiple cystic spaces or lesions and it has been described in a number of settings: within the uterus as a result of hydropic swelling of trophoblastic villi within a hydatidiform mole in bronchiectasis, where on a chest radiograph, ...
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Bunny waveform sign

Bunny waveform sign refers to the biphasic morphology of the pulsed wave Doppler spectral waveform in the vertebral artery in early (occult/latent or partial) subclavian steal phenomenon (sometimes called a "presteal" state, before it progresses to frank flow reversal). There is a sharp decelera...
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Burst lobe

A burst lobe is an uncommonly used description of traumatic lobar intraparenchymal hemorrhage of the brain that ruptures into the subdural space and communicates with subdural hemorrhage 1. As traumatic hemorrhages are more common in the frontal and temporal lobes, these lobes are the most affe...
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Butterfly glioma

Butterfly gliomas are a high grade astrocytoma, usually a glioblastoma (WHO grade IV), which crosses the midline via the corpus callosum. Other white matter commissures are also occasionally involved. The term butterfly refers to the symmetric wing-like extensions across the midline.  Most freq...
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Butterfly sign (choroid plexus)

The butterfly sign refers to the normal appearance of the choroid plexuses on axial imaging of the fetal brain, commonly observed on the antenatal ultrasound. Its absence may suggest holoprosencephaly 1. In the CNS, the term should not be confused with a butterfly glioma, which is a glioblastom...
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Butterfly vertebra

Butterfly vertebra is a type of vertebral anomaly that results from the failure of fusion of the lateral halves of the vertebral body because of persistent notochordal tissue between them. Pathology Associations an anterior spina bifida, with or without an anterior meningocele can be part of...
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Button sequestrum

A button sequestrum is a small sequestrum of devascularised bone surrounded by lucency. Although classically described in osteomyelitis and eosinophilic granuloma it is also occasionally seen in fibrosarcoma and lymphoma. Differential diagnoses osteoid osteoma tuberculous osteitis radiatio...
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Cecal bar sign (acute appendicitis)

The cecal bar sign is a secondary sign in acute appendicitis. It refers to the appearance of inflammatory soft tissue at the base of the appendix, separating the appendix from the contrast-filled cecum. See also arrowhead sign
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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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Calyceal crescent sign (intravenous pyelogram)

The calyceal crescent sign (Dunbar crescents) refers to the early intravenous pyelogram (IVP) appearance of markedly dilated renal calyces. It is formed by early contrast opacification of the dilated collecting ducts and ducts of Bellini with the characteristic shape as a result of the associate...
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Cannonball metastases (lungs)

Cannonball metastases refer to large, well circumscribed, round pulmonary metastases that appear, well, like cannonballs. The French term "envolée de ballons" which translates to "balloons release" is also used to describe this same appearance. Metastases with such an appearance are classically...
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Capps triad

The Capps triad refers to the constellation of clinical and imaging findings in patients with spontaneous retropharyngeal hematomas, and consists of: tracheal and esophageal compression anterior displacement of the trachea subcutaneous bruising over the neck and anterior chest History and et...
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Caput medusae sign (developmental venous anomaly)

The caput medusae sign refers to developmental venous anomalies of the brain, where a number of veins drain centrally towards a single drain vein. The appearance is reminiscent of Medusa, a gorgon of Greek mythology, who was encountered and defeated by Perseus. The sign is seen on both CT and M...
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Caput medusae sign (disambiguation)

Caput medusae sign can refer to: caput medusae sign (portal hypertension) caput medusae sign (developmental venous anomaly) History and etymology The appearance is reminiscent of Medusa, a gorgon of Greek mythology, who was encountered and defeated by Perseus.
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Caput medusae sign (portal hypertension)

The caput medusae sign is seen in patients with severe portal hypertension. It describes the appearance of distended and engorged paraumbilical veins, which are seen radiating from the umbilicus across the abdomen to join the systemic veins.  History and etymology The appearance is reminiscent...
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Carman meniscus sign

The Carman meniscus sign describes the lenticular shape of barium in cases of large and flat gastric ulcers, in which the inner margin is convex toward the lumen. It usually indicates a malignant ulcerated neoplasm; in cases of benign gastric ulcers, the inner margin is usually concave toward th...
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Cartilage interface sign

Cartilage interface sign, also referred to as double cortex sign, refers to the sonographic presence of a thin markedly hyperechoic line at the interface between the normally hypoechoic hyaline articular cartilage of the humeral head and an abnormally hypoechoic supraspinatus tendon. This arises...
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Caterpillar sign

The caterpillar sign is a radiological sign described in pyloric stenosis. It refers to the appearance of the stomach on an upper gastrointestinal radiographic series or plain abdominal radiograph 1,2. On these imaging modalities in a patient with pyloric stenosis, the stomach appears distended...
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Caton-Deschamps index (knee)

The Caton-Deschamps index is a ratio that is used in everyday practice as well as in research to measure patellar height and allows the diagnosis of patella alta and patella baja. Radiographic features The Caton-Deschamps index is the ratio between the distance between the lower pole of the pa...
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Celery stalk (disambiguation)

Celery stalk appearance can refer to the following: celery stalk anterior cruciate ligament celery stalk metaphysis
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Celery stalk metaphysis

Celery stalk metaphysis refers to a plain film appearance of the metaphyses in a number of conditions characterized by longitudinally aligned linear bands of sclerosis. They are seen in: congenital infections congenital rubella congenital syphilis congenital cytomegalovirus (CMV) osteopathi...
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Celery stalk sign (anterior cruciate ligament)

The celery stalk sign is a term given to the appearance of the anterior cruciate ligament which has undergone mucoid degeneration and has been likened to that of a celery stalk. Its low signal longitudinal fibers are separated from each other by higher signal mucinous material, best appreciated ...
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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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Central vein sign

The central vein sign is a marker for multiple sclerosis (MS) and is the imaging manifestation of the perivenular nature of demyelinating plaques. It is not pathognomonic but can be useful in helping differentiate multiple sclerosis from mimics, such as cerebral small vessel disease, neuromyelit...
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Cerebral paragonimiasis

Cerebral paragonimiasis refers to brain infection with a specific genus of flukes and is a serious manifestation of paragonimiasis which is primarily a lung disease caused by trematodes of the genus Paragonimus. 1 Epidemiology Paragonimiasis is endemic in Asia, West Africa, and Latin America. ...
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Cervicothoracic sign

The cervicothoracic sign, a variation of the silhouette sign, refers to visualization of a lesion above the level of the clavicle, indicating the abnormality is located posteriorly. The anterior mediastinum ends at the level of the clavicles. Thus, the upper border of an anterior mediastinal le...
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Cervix sign of pyloric stenosis

The cervix sign of pyloric stenosis describes indentation of the pylorus into the fluid-filled antrum, seen in pyloric stenosis on ultrasound examination. See also antral nipple sign target sign of pyloric stenosis
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Champagne glass pelvis (achondroplasia)

The champagne glass pelvis is a helpful sign in achondroplasia in which the iliac blades are flattened, giving rise to a pelvic inlet that resembles a champagne glass. The acetabular angles are flattened (horizontal) and the sacrosciatic notch is small.
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Chang sign (pulmonary embolism)

The Chang sign refers to the dilatation and abrupt change in caliber of the main pulmonary artery due to pulmonary embolism 1. It is one of several described signs of pulmonary embolus on chest radiographs. History and etymology It is named after C H Joseph Chang, (July 7 1929 - November 15 20...
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Charcot triad

Charcot triad is the finding of pyrexia, right upper quadrant pain and jaundice, and is a traditional clinical sign of acute cholangitis. A meta-analysis of 4288 patients in 16 studies found that the sensitivity of Charcot triad for acute cholangitis was poor (36.3%) with a much better specific...
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Cheerio sign (disambiguation)

The Cheerio sign has been described in two different scenarios: Cheerio sign (pulmonary nodule) Cheerio sign (shoulder)
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Cheerio sign (pulmonary nodule)

Cheerio sign in thoracic imaging relates to pulmonary nodules with a central lucent cavity supplied by a patent bronchus as seen on CT 3. It is due to proliferation of (malignant or non-malignant) cells around an airway. They are so named because of their resemblance to the breakfast cereal, Che...
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Cheerio sign (shoulder)

The Cheerio sign has been described as a sign seen in a type III superior labral anterior posterior tear (SLAP lesion) of the glenoid labrum. In the cheerio sign, a rounded core of soft tissue is surrounded by a rim of contrast material and gas.  SLAP type III is the bucket handle tear of the s...
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Chen sign

Chen sign on chest radiography is the prominence of left basal pulmonary vasculature compared the right base seen in valvular pulmonary stenosis. It is due to the asymmetric increase in pulmonary blood flow to the left lung due to preferential blood flow into the left pulmonary artery after pass...
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Chilaiditi sign

Chilaiditi sign refers to the interposition of the bowel, usually colon, between the inferior surface of the right hemidiaphragm and the superior surface of the liver. It may be misinterpreted as a true pneumoperitoneum resulting in unnecessary further investigations and/or therapy (so-called ps...
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Chorionic bump

Chorionic bump is a finding that can be uncommonly seen in a first-trimester scan. It may represent a small hematoma bulging into the gestational sac or an anembryonic (failed) second pregnancy that is being resorbed. It is also seen in some patients undergoing infertility treatment. Epidemiolo...
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Cingulate island sign

The cingulate island sign is a highly specific radiological sign described in dementia with Lewy bodies. It refers to the pattern of metabolism seen on FDG-PET in patients with dementia with Lewy bodies 1-3. On FDG-PET, there is occipital hypometabolism with relative sparing of the posterior ci...
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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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Claw sign (mass)

The claw sign is useful in determining that a mass arises from a solid structure rather than is located adjacent to it and distorts the outline. It refers to the sharp angles on either side of the mass, which the surrounding normal parenchyma forms when the mass has arisen from the parenchyma. ...
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Claw sign (MRI)

The claw sign on diffusion weighted imaging refers to a pattern of hyperintensity seen in degenerative changes in the spine. The presence of the claw sign makes spondylodiskitis less likely. Radiographic features MRI DWI the sign appears as well-defined paired regions of restricted diffusion...
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Cloaca (osteomyelitis)

A cloaca (pl. cloacae/cloacas) can be found in chronic osteomyelitis. The cloaca is an opening in an involucrum which allows drainage of purulent and necrotic material out of the dead bone. If the tract extends to the skin surface, the portion extending beyond the involucrum to the skin surface...
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Cloverleaf skull (craniosynostosis)

Cloverleaf skull, also known as kleeblattschädel syndrome or deformity, refers to a type of severe craniosynostosis which gives the skull a cloverleaf shape. It is very rare, with less than 130 case reports globally. It typically results from intrauterine premature closure of the sagittal, coron...
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Cluster of black pearls sign

The "cluster of black pearls" sign refers to a finding on contrast-enhanced CT useful in differentiating sarcoidosis from other causes of lymphadenopathy such as tuberculosis, lymphoma and metastatic adenocarcinoma. The sign is depicted by the presence of multiple tiny round nodules (1-2 mm) di...
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Cluster sign

The cluster sign is a finding on MRI and CT that is associated with pyogenic hepatic abscesses and can help differentiate pyogenic abscesses from other types of liver lesions. Radiographic features The cluster sign is best seen on MRI T2-weighted and postcontrast T1-weighted sequences. Small n...
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Cobblestone appearance (hollow viscera)

Cobblestoning (having a cobblestone appearance) can occur in a number of hollow organs with mucosa, most commonly the bowel, in the setting of Crohn disease.  Longitudinal and circumferential fissures and ulcers separate islands of mucosa, giving it an appearance reminiscent of cobblestones.  ...
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Cobra head sign (ureter)

The cobra head sign, also known as the spring onion sign, refers to dilatation of the distal ureter, surrounded by a thin lucent line, which is seen in patients with an adult-type ureterocoele. The cobra head appearance indicates an uncomplicated ureterocele. During an excretory phase of an int...
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Cobweb sign of arterial dissection

The cobweb sign is seen in cases of arterial dissection (usually aortic dissection) on CT angiogram (CTA) examinations and represents strands or ribbons of media crossing the false lumen, and appearing as thin filiform filling defects. Although it is a specific sign for the false lumen, it is i...
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Coca-Cola bottle sign (thyroid eye disease)

The Coca-Cola bottle sign refers to the appearance of the muscles of the orbit in thyroid eye disease.  The belly of the muscle enlarges with sparing of the tendinous insertion, giving the appearance of the traditional Coca-Cola bottle. The enlargement of the muscles follows the I'M SLOW format...
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Cockade sign (disambiguation)

There are several described cockade signs in radiology: cockade sign (intraosseous lipoma) cockade sign (aorto-left ventricular tunnel) 1 cockade sign (appendicitis) 2 cockade sign (hypertrophic pyloric stenosis) 3 cockade sign (GI tumors) 4
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Cockade sign (intraosseous lipoma)

The cockade sign describes the classic appearance of a calcaneal intraosseous lipoma seen as a well-defined lytic lesion with a central calcification. History and etymology It is named after a cockade, which is a badge, usually in the form of a rosette or knot, generally worn on the hat.
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Codman triangle periosteal reaction

A Codman triangle is a type of periosteal reaction seen with aggressive bone lesions. The periosteum does not have time to ossify with shells of new bone (e.g. as seen in a single layer and multilayered periosteal reaction) in aggressive lesions, so only the edge of the raised periosteum will os...
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Coffee-bean sign (sigmoid colon)

The coffee-bean sign (also known as the kidney bean sign or bent inner tube sign 4) is a sign on an abdominal plain radiograph of a sigmoid volvulus although some authors have also used the term to refer to closed loop small bowel obstructions. Cecal volvulus may be mistaken with sigmoid volvulu...
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Cogwheel sign

The cogwheel sign refers to an imaging appearance in pelvic imaging of thickening loops of the Fallopian tube seen on cross-section. There are infolding projections (sometimes looking like nodules) into the Fallopian tube lumen which is likened to that of a cogwheel. The sign is typically descri...
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Coin lesion (lung)

A coin lesion refers to a round or oval, well-circumscribed solitary pulmonary lesion. It is usually 1-5 cm in diameter and calcification may or may not be present 1,3. Typically but not always the patient is asymptomatic 1.  Differential diagnosis The differential diagnosis for such lesions i...
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Collar sign in diaphragmatic rupture

The collar sign, also called the hourglass sign, is a helpful sign for diagnosis of diaphragmatic rupture on coronal or sagittal CT/ MR images and barium studies. It refers to a waist-like or collar-like appearance of herniated organs at the level of the diaphragm. See also dependent viscera s...
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Colon cut-off sign

The colon cut-off sign describes gaseous distension seen in proximal colon associated with abrupt termination of gas within the colon usually at the level of the splenic flexure and decompression of the more distal part of the colon. Though originally described in abdominal radiographs, this sig...
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Comb sign (mesentery)

The comb sign refers to the hypervascular appearance of the mesentery in active Crohn disease. Fibrofatty proliferation and perivascular inflammatory infiltration outline the distended intestinal arcades. This forms linear densities on the mesenteric side of the affected segments of small bowel,...
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Comet tail (disambiguation)

The distinctive appearance of a comet's tail has been used for several signs: comet tail artifact (ultrasound) color comet tail artifact comet tail sign (chest) comet tail sign (phleboliths)
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Comet tail sign (chest)

The comet tail sign is a finding that can be seen on CT scans of the chest. It consists of a curvilinear opacity that extends from a subpleural "mass" toward the ipsilateral hilum. The comet tail sign is produced by the distortion of vessels and bronchi that lead to an adjacent area of round ate...
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Comet tail sign (phleboliths)

The comet tail sign (in urological imaging) is helpful in distinguishing a ureteric calculus from a phlebolith and strongly favors the latter.  The sign refers to a tail of soft tissue extending from a calcification, representing the collapsed/scarred/thrombosed parent vein. When well seen, it ...
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Concentric ring sign

The concentric ring sign is a pathognomonic sign for a subacute hematoma on MRI. A subacute hematoma may show three characteristic layers of signal intensity: a thin peripheral rim of low signal intensity on all pulse sequences corresponding to hemosiderin an inner peripheral high-signal inten...
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Concentric target sign (cerebral toxoplasmosis)

The concentric target sign is a typical sign for cerebral toxoplasmosis. It is seen on T2 weighted MR imaging as a deep parenchymal lesion showing a series of concentric rings with hyperintense and hypointense/isointense signal alternatingly. Strong perifocal edema is usually visible on T2/FLAIR...
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Cone-shaped cecum (differential)

A cone-shaped cecum refers to a loss of the normal rounded appearance of the cecum, which instead becomes narrow and cone-shaped with the apex pointing towards the base of the appendix. It is encountered in a number of conditions including: inflammatory infective blastomycosis amoebiasis Ye...
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Congenital hallux valgus

Congenital hallux valgus is a very rare finding wherein a fetus or newborn shows lateral deviation of the first toe(s). When found on prenatal imaging, bilateral congenital/foetal hallux valgus is highly suggestive of fibrodysplasia ossificans progressiva 1,2.
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Continuous diaphragm sign

The continuous diaphragm sign is a chest radiograph sign of pneumomediastinum or pneumopericardium if lucency is above the diaphragm, or of pneumoperitoneum if lucency is below the diaphragm.  Normally the central portion of the diaphragm is not discretely visualized on chest radiographs as it ...
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Convoluted cerebriform pattern

A convoluted cerebriform pattern is a term used to denote the appearance of a sinonasal inverted papilloma on MRI. The appearance is seen on both T2 and post contrast T1 images and appears as alternating roughly parallel lines of high and low signal intensity. This sign has been reported as pre...
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Cookie bite skeletal metastases

Cookie bite metastases are characterized by small focal eccentric lytic external cortical destruction in long tubular bones. This type of destruction is typically described for metastases from lung cancer, however, they can also occur with other tumors.
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Copper beaten skull

Copper beaten skull, also known as beaten silver skull or beaten brass skull, refers to the prominence of convolutional markings (gyral impressions on the inner table of the skull) seen throughout the skull vault. Clinical presentation The appearance of a copper beaten skull is associated with...
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Cord sign (dural sinus thrombosis)

The cord sign refers to cordlike hyperattenuation within a dural venous sinus on non-contrast enhanced CT of the brain due to dural venous sinus thrombosis. The sign is most commonly seen in the transverse sinus because along the origin of the tentorium it runs approximately in the axial plane s...
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Corduroy sign (vertebral hemangioma)

The corduroy sign refers to vertically-oriented, thickened trabeculae seen in intraosseous hemangiomas of the spine. It is the sagittal/coronal equivalent of the polka-dot sign seen on axial imaging.  It is caused by the replacement of the normal cancellous bone by thickened vertical trabeculae...
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Corkscrew sign (disambiguation)

Corkscrew sign can refer to: corkscrew sign (midgut volvulus) corkscrew sign (tertiary esophageal contractions) corkscrew sign (corkscrew cochlea)
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Corkscrew sign (midgut volvulus)

The corkscrew sign describes the spiral appearance of the distal duodenum and proximal jejunum seen in midgut volvulus 1. In patients with malrotation and volvulus, the distal duodenum and proximal jejunum do not cross the midline and instead pass in an inferior direction. These loops twist on ...
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Cortical rim sign (kidneys)

The cortical rim sign describes the thin, viable rim of subcapsular cortex seen on contrast-enhanced CT or MRI in major renal vascular compromise including: renal artery obstruction from embolism, thrombosis or dissection renal vein thrombosis acute tubular necrosis acute cortical necrosis ...
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Cortical vein sign

The cortical vein sign refers to the presence of superficial cortical veins seen on MRI and CT (particularly with contrast injection) traversing an enlarged subarachnoid space, differentiating it from the similar radiological appearance of a subdural hygroma. Although initially proposed as a me...
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Costal hook sign (flail chest)

The costal hook sign is a chest x-ray feature seen in some cases of flail chest. It represents the rotation of a fractured rib along its long axis, something that is only possible if a second fracture is present along its length, even if the second fracture is not visible 1. 
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Cottage loaf sign (liver)

The cottage loaf sign occurs as a result of a right-sided diaphragmatic rupture with partial herniation of the liver through the diaphragmatic defect. The herniated component is separated by a waist at the diaphragm from the larger intra-abdominal component. This shape is reminiscent of a cottag...
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Cotton wool appearance (bone)

The cotton wool appearance is a plain film sign of Paget disease and results from thickened, disorganized trabeculae which lead to areas of sclerosis in a previously lucent area of bone, typically the skull. These sclerotic patches are poorly defined and fluffy. See also Other Paget disease re...
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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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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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Coxa profunda

Coxa profunda refers to a deep acetabular socket. On pelvis x-rays it is seen as the acetabular fossa being medial to the ilioischial line. It should be differentiated from protrusio acetabuli, where the femoral head is seen additionally medial to the ilioischial line. Coxa profunda is much more...
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Coxa valga

Coxa valga describes a deformity of the hip where there is an increased angle between the femoral neck and femoral shaft.  Pathology Coxa valga is often associated with shallow acetabular angles and femoral head subluxation.  Etiology bilateral neuromuscular disorders, e.g. cerebral palsy ...
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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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Crazy paving

Crazy paving refers to the appearance of ground-glass opacity with superimposed interlobular septal thickening and intralobular septal thickening, seen on chest HRCT. It is a non-specific finding that can be seen in a number of conditions.  Pathology Etiology Common causes: acute respiratory...
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Crescent in a doughnut sign (intestinal intussusception)

The crescent in a doughnut sign refers to the transverse ultrasound appearance of intestinal intussusception, and is a variation of the target sign (which is also known as the doughnut sign) The doughnut is formed by concentric alternating echogenic and hypoechogenic bands. The echogenic bands ...
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Crescent sign - inverted crescent sign (hydatid disease)

The crescent sign is described in hydatid disease.  When the hydatid cyst erodes the adjacent bronchus or bronchiole, the trapped air between the pericyst and the laminated membrane of the endocyst give a crescent-shaped rim of air around the cyst, thus is termed the crescent sign 1, 2. It can b...
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Crescent sign of arterial dissection

The crescent sign refers to the high signal crescent seen in the wall of a vessel when dissected. This may be seen both on T1 or T2 sequences depending on the age of the blood (see aging blood on MRI). It is classically referred to in internal carotid artery dissection. It should not be confuse...
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Crescent sign of avascular necrosis

The crescent sign of avascular necrosis is seen on conventional radiographs and refers to a linear area of subchondral lucency seen most frequently in the anterolateral aspect of the proximal femoral head (which is optimally depicted on the frog-leg radiographic view). It indicates imminent arti...
Article

Crossing sign (knee)

The crossing sign is seen on true lateral plain radiographs of the knee when the line of the trochlear groove crosses the anterior border of one of the condyle trochlea. It is a predictor of trochlear dysplasia. Trochlear dysplasia has been linked to recurrent patellar dislocation 1,2,4. The cro...
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Crossover sign (femoroacetabular Impingement)

The crossover sign, also known as the 'figure of 8' sign, is a plain film sign that indicates acetabular retroversion 2. Acetabular retroversion is a predisposing factor for pincer-type femoroacetabular impingement and is thought to promote hip osteoarthritis 3.  Radiographic features Plain ra...
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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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CSF cleft sign

The CSF cleft sign in neuroimaging can be used to distinguish an extra-axial lesion from an intra-axial lesion and is typically used in the description of a meningioma. Classically, the cleft was regarded as representing a thin rim of CSF between a tumor and brain parenchyma. However, it often ...
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C sign (talocalcaneal coalition)

The C sign is an important radiological sign which may be seen on a lateral radiograph of the ankle in those with the talocalcaneal subtype of tarsal coalition.  Radiographic appearance A continuous C-shaped arc on a lateral ankle radiograph is formed by the medial outline of the talar dome an...

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