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.

904 results found
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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. It can be seen in both osseous and nonosseous coalition. Radiographic appearance A continuous C-shaped arc on a lateral ankle radiogr...
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CT angiogram sign (lungs)

The CT angiogram sign refers to vessels appearing prominent during a contrast enhanced CT as they traverse an airless low attenuation portion of consolidated lung. Although initially thought to be specific for bronchoalveolar carcinoma, it has now been recognized as a generic appearance provided...
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CT angiographic spot sign (intracerebral hemorrhage)

The CT angiographic (CTA) spot sign is defined as unifocal or multifocal contrast enhancement within an acute primary intracerebral hemorrhage (ICH) visible on CTA source images and discontinuous from adjacent normal or abnormal blood vessels 1. It should not be present on pre-contrast images. I...
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CT comma sign (head)

The CT comma sign is a characteristic sign seen in head trauma. It is the presence of concurrent epidural and subdural hematomas, which gives the characteristic appearance of this sign as a "comma" shape.
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Cupola sign (pneumoperitoneum)

The cupola sign is seen on a supine chest/abdominal radiograph in the presence of pneumoperitoneum.  It refers to non-dependent gas that rises within the abdominal cavity of the supine patient to accumulate underneath the central tendon of the diaphragm in the midline. It is seen as lucency ove...
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Curlicue ureter sign (sciatic hernia)

The curlicue ureter sign1 was described on intravenous pyelogram studies in cases of ureteral herniation into a sciatic hernia, causing a curled appearance of the herniated ureter. Although very rare, this sign is pathognomonic of sciatic hernia. It can also be seen on CT urogram studies.
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Curtain sign (vertebral body mass)

The curtain sign, also known as the draped curtain sign, in neuroimaging refers to the appearance of a vertebral body mass that extends posteriorly towards the anterior epidural space. The posterior longitudinal ligament is strongly attached to the posterior vertebral body cortex in the midline...
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Cyclops lesion (knee)

The cyclops lesion, also known as localized anterior arthrofibrosis, is a painful anterior knee mass that arises as a complication of anterior cruciate ligament (ACL) reconstruction, although has rarely been reported in patients with ACL injuries that have not been reconstructed.  Epidemiology ...
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Cyst with dot sign (neurocysticercosis)

The cyst with dot sign is seen in neurocysticercosis and represents the parasitic cyst with, usually eccentric, scolex. It can be seen on both MRI and CT at: the vesicular stage (CSF density / intensity cyst - denser / hyperintense scolex) and colloidal vesicular stage (enhancement of wall an...
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Dagger sign (spine)

The dagger sign is a radiographic feature seen in ankylosing spondylitis as a single central radiodense line on frontal radiographs related to ossification of the supraspinous and interspinous ligaments secondary to enthesitis.
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Dark bronchus sign

The dark bronchus sign is the appearance of a relatively darker bronchus as compared to adjacent ground glass opacity. If the ground glass opacity progresses to consolidation, air bronchograms will be visualized.  This sign is useful to identify diffuse ground glass opacity on HRCT chest in cas...
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Dawson fingers

Dawson fingers are a radiographic feature of demyelination characterized by periventricular demyelinating plaques distributed along the axis of medullary veins, perpendicular to the body of the lateral ventricles and/or callosal junction. This is thought to reflect perivenular inflammation. They...
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Deep sulcus sign (chest)

The deep sulcus sign on a supine chest radiograph raises suspicion of a pneumothorax. On a supine plain chest film (common in intensive care units or as part of a trauma radiograph series), it may be the only suggestion of a pneumothorax because air collects anteriorly and basally, within the n...
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Deep sulcus sign (disambiguation)

The deep sulcus sign can refer to two different radiographic signs but is best known in the chest: deep sulcus sign (chest): of pneumothorax on supine CXR: deep sulcus sign (knee): better known as the lateral femoral notch sign of ACL injury
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Delayed nephrogram

A delayed nephrogram, commonly described on plain film urography, but also visible on CT urography, is when there is absence or reduction of the normal renal parenchymal enhancement on nephrographic phase images. A delayed nephrogram is characteristically unilateral and is usually distinguished...
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Dense hilum sign

The dense hilum sign suggests a pathological process at the hilum or in the lung anterior or posterior to the hilum. Malignancy, especially lung cancer, should be suspected. Radiographic features On a well-centered chest posteroanterior (PA) radiograph the density of the hilum is comparable on...
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Dense vein sign

The dense vein sign refers to hyperattenuating thrombus within a cortical vein or dural venous sinus due to acute venous thrombosis. When located in the superior sagittal sinus, particularly posteriorly, it is sometimes referred to as the delta, triangle or pseudodelta sign. It is really the sa...
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Dependent viscera sign

The dependent viscera sign is one of the signs of diaphragmatic rupture on axial CT or MR images, where herniated viscera lie against the posterior thoracic wall in a dependent position, as they are no longer supported by the diaphragm. See also  collar sign (or hourglass sign)
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De Winter pattern (electrocardiogram)

An electrocardiographic finding suggestive of impending myocardial infarction, the de Winter's pattern (or "de Winter's T-waves") describes an abnormality thought to be indicative of acute occlusion of the proximal left anterior descending coronary artery (LAD) 2. Timely recognition of this patt...
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Dinner fork deformity (wrist)

A dinner fork deformity, also known as a bayonet deformity, occurs as the result of a malunited distal radial fracture, usually a Colles fracture. The distal fragment is dorsally angulated, displaced and often also impacted. The term is descriptive, as the lateral view of the wrist is similar to...
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Disappearing basal ganglia sign

The disappearing basal ganglia sign is one of the early signs of a middle cerebral artery (MCA) infarction. It is defined as the loss of delineation of the basal ganglia, due to blurring of their grey-white matter interface and hypoattenuation, consequent to cytotoxic edema at the time of an isc...
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Disproportionate posterior horn sign (meniscal tear)

The disproportionate posterior horn sign is a feature described with a meniscal tear having a posteriorly flipped fragment. Pathology Bucket handle tears of meniscus of the knee joint constitute 10% of meniscal tears. They consist of a vertical or longitudinal tear (which includes vertical-obl...
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Dog ear sign (abdomen)

The dog ear sign represents the presence of fluid or blood in the pelvic peritoneal recess on a supine abdominal radiograph. The appearance of the sign comes from a convex soft-tissue density representing fluid or blood in the lateral pelvic peritoneal recess separated from the bladder by a thin...
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Doge cap sign (pneumoperitoneum)

The doge cap sign, also referred to as Morison pouch sign, is a radiographic sign of pneumoperitoneum. It presents as a triangular-shaped gas lucency or can be crescent shaped, or semicircular is usually bound by the 11th rib in the right upper quadrant on abdominal radiographs due to air in the...
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Dog leg sign (popliteal artery)

The "dog leg" sign is a secondary angiographic sign on popliteal angiography, which demonstrates an irregular lumen of the popliteal artery with acute bend in the course of the popliteal artery. It is characteristically seen in popliteal artery aneurysms with mural thrombus. It is an important ...
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Dorsal fat pad sign (wrist)

A positive dorsal fat pad or stripe sign is defined as a convex dorsal displacement of the dorsal fat pad of the wrist. A positive sign may indicate a distal radius fracture. Is it best visualized on the lateral view of the wrist. Anatomy The normal dorsal skin subcutaneous fat pad is a thin c...
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Dot dash pattern (ovarian dermoid cyst)

The dot-dash pattern (dermoid mesh) is one of the characteristic sonographic appearances of an ovarian dermoid cyst. It refers to the short and long echogenic lines which are often seen within a dermoid cyst and are due to the presence of hair.
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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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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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Double artery sign

The double artery sign refers to the appearance of a non-dilated mucus-filled bronchus adjacent to a pulmonary artery producing the appearance of a "double artery" on CT chest. This sign is considered a feature of a central endobronchial lesion such as a mucus plug or neoplasm.
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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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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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Double bleb sign

A double bleb sign is a sonographic feature where there is visualization of a gestational sac containing a yolk sac and amniotic sac giving an appearance of two small bubbles 2. The embryonic disc is located between the two bubbles. It is an important feature of an intrauterine pregnancy and thu...
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Double bubble sign (duodenum)

The double bubble sign is seen in infants and represents dilatation of the proximal duodenum and stomach. It is seen in both radiographs and ultrasound, and can be identified antenatally 2. Pathology Causes include 1,2: congenital obstruction duodenal web duodenal atresia duodenal stenosis...
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Double contour cartilage line

Double contour cartilage line is a sign in ultrasonography of the gout arthropathy which is characterized by an echogenic line on the outer surface of the joint cartilage parallel to the subchondral bone secondary to deposition of monosodium urate crystals on the surface of hyaline articular car...
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Double contour sign (trochlear dysplasia)

The double contour sign is a helpful radiologic sign which is seen on true lateral plain radiographs of trochlear dysplasia.  A double line at the anterior aspect of condyles that seen if medial condyle is hypoplastic. See also crossing sign of trochlear dysplasia
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Double decidual sac sign

The double decidual sac sign (DDSS) is a useful feature on early pregnancy ultrasound to confirm an early intrauterine pregnancy (IUP) when the yolk sac or embryo is still not visualized. It consists of the decidua parietalis (lining the uterine cavity) and decidua capsularis (lining the gestati...
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Double delta sign (meniscal tear)

The double delta sign is a feature that has been described in a bucket handle meniscal tear when the inner meniscal fragment flipped anteriorly adjacent to the anterior horn of the donor site and is referred to as a displaced bucket handle tear. The original location of the posterior horn remain...
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Double density sign (berry aneurysm)

Double density sign of berry aneurysms refers to the angiographic appearance of a small intracranial aneurysm projecting in front or behind a vessel of similar caliber. As such, the border of the aneurysm cannot easily be seen, but the extra contrast within it can be seen as a rounded area of in...
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Double density sign (left atrium)

The double-density sign, also known as the double right heart border, is seen on frontal chest radiographs in the presence of left atrial enlargement, and occurs when the right side of the left atrium pushes behind the right cardiac shadow, indenting the adjacent lung and forming its own distinc...
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Double density sign (osteoid osteoma)

The double density sign, also sometimes clumsily referred to as the hotter spot within hot area sign, is a bone scan sign of an osteoid osteoma. It refers to a central focus of intense uptake (the nidus) within a surrounding lower, but nonetheless increased uptake, rim. See also double densit...
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Double diaphragm sign

The double diaphragm sign is one of several radiological signs seen with a pneumothorax in a supine patient. Supine films are commonly performed in unwell patients, particularly in the ICU. In a supine patient with a pneumothorax, air may outline the anterior portions of the hemidiaphragm and c...
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Double disc sign

Thickening of the insertion of the lateral pterygoid muscle can mimic an anterior displaced temporomandibular disc. When both thickening of the inferior belly insertion and an anteriorly displaced disc are present, as in temporomandibular joint dysfunction, the two structures parallel each other...
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Double duct sign

The double duct sign refers to the presence of simultaneous dilatation of the common bile and pancreatic ducts. Being an anatomical sign it can be seen on all modalities that can visualize the region, including: MRI, CT, ultrasound and endoscopic retrograde cholangiopancreatography (ERCP).  The...
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Double line sign

The double line sign is an MRI finding seen at the periphery of a region of osteonecrosis (avascular necrosis, bone infarct). It is best seen on T2 weighted sequences and consists of an inner bright T2 line representing granulation tissue and surrounding dark zones representing adjacent scleroti...
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Double lung point sign (Ultrasound)

The double lung point sign refers to a sharp boundary found between relatively aerated superior lung fields and coalescent "B‐lines" (representing interstitial edema) in the basal lung fields, with a reported sensitivity of 45.6%-76.7% and a specificity of 94.8%-100% 1,3 in diagnosing transient ...
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Double Oreo cookie sign (glenoid labrum)

The double Oreo cookie sign refers to the presence of two hyperintense lines in the superior glenoid labrum, one of which represents a superior labral tear and the other a physiological sublabral recess 1, 2. This pattern is likened to an Oreo cookie with two layers of (white) cream and three l...
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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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Double PCL sign

The double PCL sign appears on sagittal MRI images of the knee when a bucket-handle meniscal tear (medial meniscus in 80% of cases) flips towards the center of the joint so that it comes to lie anteroinferior to the posterior cruciate ligament (PCL) mimicking a second smaller PCL. A double PCL ...
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Double skull sign (cephalohematoma)

The double skull sign is an eggshell calcification seen on CT in early cases of calcified cephalohematomas.
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Double target sign (hepatic abscess)

The double target sign is a characteristic imaging feature of liver abscess on contrast enhanced CT scans, in which a central, fluid-filled low attenuation lesion is surrounded by a high attenuation inner rim and a low attenuation outer ring 1,2. The inner ring (abscess membrane) demonstrates e...
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Double track sign (pyloric stenosis)

The double track sign is a radiological sign described in pyloric stenosis on various imaging modalities.  Barium study Double streaks of barium passing through the narrow pylorus 1. Ultrasound On fluid aided real-time examination, the pyloric fluid is compressed into smaller tracks as it is...
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Doughnut sign (disambiguation)

The doughnut sign can refer to a variety of different signs: doughnut sign (bone scan) doughnut sign (bowel) crescent in a doughnut sign (bowel) doughnut sign (orbit)
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Doughnut sign on bone scan

The doughnut sign refers to the bone scan pattern whereby there is increased uptake peripherally with a photopenic center. This appearance may be seen in a number of cystic lesions including: aneurysmal bone cyst giant cell tumor simple bone cyst The doughnut sign is a non-specific sign, and...
Article

Draped aorta sign

The draped aorta sign is an important imaging feature that can be seen in contained rupture of an abdominal aortic aneurysm. It is highly indicative of aortic wall deficiency.  This sign is considered present when the posterior wall of an aortic aneurysm drapes or molds to the anterior surface ...
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Dripping candle wax sign (melorheostosis)

Dripping candle wax sign, also known as flowing candle wax appearance, describes the appearance of sclerotic cortical thickening in melorheostosis. The irregular cortical hyperostosis typically occurs on one side of the involved bone and undulates along much like melted wax down a candle. Patho...
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Drooping lily sign (ureter)

The drooping lily sign is a urographic sign in some patients with a duplicated collecting system. It refers to the inferolateral displacement of the opacified lower pole moiety due to an obstructed (and unopacified) upper pole moiety. The similarity to a lily is further strengthened by the smal...
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Drowning (postmortem findings)

Drowning is one of the most prevalent causes of non-natural death. According to the World Health Organization (WHO), an estimated 360,000 annual deaths occur due to drowning. This article concerns itself with postmortem appearances in fatalities from drowning. For non-fatal pulmonary changes pl...
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Dual rim sign (brain abscess)

The dual or double rim sign is seen on MRI in approximately 75% of cerebral abscesses and is helpful in distinguishing an abscess from a glioblastoma.  On both susceptibility weighted imaging (SWI) and T2WI it consists of two concentric rims surrounding the abscess cavity, outer one of which is...
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Duct penetrating sign (pancreas)

The duct penetrating sign is a radiographic sign which 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 li...
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Dumbbell appearance of spinal tumors

The dumbbell appearance of spinal tumors refers to a tumor which has both a component within the canal and a component in the paravertebral space contiguous with each other via a thinner tumor component traversing the neural exit foramen. The appearance can be seen in: spinal nerve sheath tumo...
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Dural tail sign

The dural tail sign occurs as a result of thickening and enhancement of the dura and is most often seen adjacent to a meningioma. Initially, the sign was felt to be pathognomonic of meningiomas, however as radiologist's experience grew, it has become increasingly noted to be present in many oth...
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Ears of the lynx sign (brain)

The ears of the lynx sign refers to abnormal T2/FLAIR cone-shaped hyperintensity at the tip of the frontal horn of the lateral ventricles in the region of forceps minor which resembles the tufts of hair crowning the ears of a lynx. This sign is seen in hereditary spastic paraplegia with thin co...
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Earth-heart sign

The earth-heart sign is a newly recognized 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 obs...
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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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Echogenic fetal bowel

Echogenic fetal bowel is an observation in antenatal ultrasound imaging, in which fetal bowel appears to be brighter than it is supposed to be. It is a soft marker for trisomy 21 and has several other associations. When observed, it needs to be interpreted in the context of other associated abno...
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Egg and banana sign (pulmonary hypertension)

The egg and banana sign is a sign for the diagnosis of pulmonary arterial hypertension (PAH) on axial CT/MR images. It refers to the appearance of the aortic arch (banana) next to a distorted main pulmonary artery (egg). Like an egg, the main pulmonary artery is preferentially dilated in the PA ...
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Egg-on-a-string sign (heart)

Egg-on-a-string sign, also referred to as egg on its side, refers to the cardiomediastinal silhouette seen in transposition of the great arteries (TGA). The heart appears globular due to an abnormal convexity of the right atrial border and left atrial enlargement and therefore appears like an ...
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Eggshell calcification (breast)

Eggshell calcifications in the breast are benign peripheral rim like calcifications Pathology They are typically secondary to fat necrosis or calcification of oil cysts. Radiographic features thin rim-like calcification (<1 mm in thickness) lucent centers small to several centimeters in di...
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Eggshell calcification (lymph nodes)

Eggshell calcification refers to fine calcification seen at the periphery of a mass and usually relates to lamellar lymph node calcification. For similar appearance in the breast see eggshell calcification (breast). In 1967 Jacobsen and Felson published criteria to help "avoid over-reading of t...
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Elbow joint effusion

An elbow joint effusion is a key finding to recognize on an elbow radiograph and should be used as a trigger to search for a fracture.  Finding an effusion  Recognizing an elbow joint effusion on lateral radiographs is an essential radiology skill. While the fluid itself is not discretely seen...
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Empty amnion sign

The empty amnion sign is a sonographic observation where there is the visualization of an amniotic sac without concomitant visualization of an embryo. It is an indicator of pregnancy failure regardless of the mean sac diameter and is considered to have a sufficiently high positive predictive val...
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Empty cyst sign

The empty cyst sign is described in hydatid disease. After rupture of the cyst and complete evacuation of its content, the pericyst becomes empty as an air-filled cyst on x-ray or CT 1,2. With superadded infection, an air-fluid level may appear within the cyst, mimicking a lung abscess 2.
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Empty delta sign (dural venous sinus thrombosis)

The empty delta sign is a CT sign of dural venous sinus thrombosis of the superior sagittal sinus, where contrast outlines a triangular filling defect, which represents thrombus. It is only described with CECT-scan or MRI, not with NECT nor non-contrast MRI. An equivalent appearance can be note...
Article

Empty light bulb sign (brain death)

In brain death, on Tc-99m HMPAO imaging there is absent or reduced flow in the internal carotid arteries and increased flow within the external carotid arteries. This leads to absent uptake in the brain with subsequent increased perfusion in the nasal region. This appearance has been called the ...
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Empty notch sign (anterior cruciate ligament tear)

Empty notch sign is a direct sign of anterior cruciate ligament (ACL) tear/avulsion at its femoral attachment. It denotes a fluid signal at the expected ACL attachment site at the intercondylar notch (fossa) on axial and coronal fluid-sensitive MR images. The proximal ACL is the second most com...
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Empty thecal sac sign

The empty thecal sac sign or empty sac sign is when the thecal sac appears empty on MRI of the lumbar spine, best seen on T2-weighted images. If the empty thecal sac sign is present, a diagnosis of adhesive arachnoiditis can be made.​ Radiographic features MRI There is usually no gadolinium c...
Article

Endosteal scalloping

Endosteal scalloping refers to the focal resorption of the inner layer of the cortex (i.e. the endosteum) of bones, most typically long bones, due to slow-growing medullary lesions. It is important to note that although it is evidence of a slow non-infiltrative lesion, it does not equate to ben...
Article

Ependymal dot-dash sign

The ependymal dot-dash sign has been described as an early MRI imaging feature of multiple sclerosis before other more florid white matter changes (e.g. Dawson's fingers) become evident 1. It has also been suggested as a feature that can be used to distinguish multiple sclerosis from neuromyelit...
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Erased charcoal sign (prostate cancer)

The erased charcoal sign describes the typical appearance of focal prostate cancer in the transition zone characterized as homogeneous hypointensity on T2WI with ill-defined borders, akin to a charcoal pencil drawing smudged with an eraser, often with a lenticular or waterdrop-like shape.
Article

Erlenmeyer flask deformity

Erlenmeyer flask deformity (EFD) (also known as metaphyseal flaring) refers to a radiographic appearance typically on a femoral radiograph demonstrating relative constriction of the diaphysis and flaring of the metaphysis. It has been classically used with reference to the distal ends of the fe...
Article

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 and without diffusion ...
Article

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...
Article

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...
Article

Extracranial brain herniation

Extracranial 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 decompress intracran...
Article

Extrapleural air sign (pneumomediastinum)

The extrapleural air sign is one of the many signs of pneumomediastinum, and was first described by Lillard and Allen in 1965. It is defined as the presence of gas between the parietal pleura and the diaphragm. On a lateral projection, the gas forms a radiolucent pocket of gas posterior to the d...
Article

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...
Article

Extrapleural sign

The extrapleural sign, described by Ben Felson in 1973 1, refers to the appearance of a pulmonary opacity with oblique margins that taper slowly to the chest wall when the lesion is viewed tangentially to the x-ray beam. This appearance suggests that the lesion is pleural or extrapleural in natu...
Article

Eye of the tiger sign (globus pallidus)

The eye of the tiger sign refers to abnormal low T2 signal on MRI (due to abnormal accumulation of iron) in the globus pallidus with a longitudinal stripe of high signal (due to gliosis and spongiosis).  The eye of the tiger sign is most classically associated with pantothenate kinase-associate...
Article

Faceless kidney

A faceless kidney refers to one in which the normal appearance of the renal sinus on cross-sectional imaging is absent. It was initially described as a sign of duplication of the collecting system 1 (a slice obtained between the two collecting systems will not demonstrate the normal components o...
Article

Falciform ligament sign

The falciform ligament sign, also called the Silver sign, is characterized by the falciform ligament being outlined with free abdominal gas in cases of pneumoperitoneum of a large amount.  It is almost never seen in isolation as, if there is enough free gas to outline the falciform ligament, th...
Article

Fallen contrast sign

The fallen contrast sign refers to a trace of concentrated contrast material layering along the dependent left atrial wall during contrast-enhanced cardiac CT, suggestive of a right-to-left shunt. The finding has primarily been described as an indirect sign in sinus venosus atrial septal defect ...
Article

Fallen fragment sign

The fallen fragment sign refers to the presence of a bone fracture fragment resting dependently in a cystic bone lesion. This finding is said to be pathognomonic for a simple (unicameral) bone cyst following a pathological fracture. Although it has occasionally been reported with other cystic le...

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