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.

76 results found
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Contrast agent pooling sign

The contrast agent pooling sign is a CT sign characterized by dense intravenous contrast agent pooling in veins, and may signal imminent cardiac arrest. Radiographic features The contrast agent pooling sign is characterized by dense intravenous iodinated contrast media pooling and layering in ...
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Flame sign (carotid)

The flame sign refers to a gradual tapering of contrast opacification in the mid-cervical internal carotid artery, sparing the carotid bulb. The sign can be observed on angiography (digital subtraction angiography 1, CT angiography 1, or contrast-enhanced MR angiography 2) in either of two scena...
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Crescent sign (disambiguation)

The characteristic shape of the crescent has been given to many radiological signs over the years. crescent sign (disambiguation) crescent sign (arterial dissection) crescent sign (inguinal hernia) crescent sign (intravenous pyelogram) crescent sign (lung hydatid) crescent sign (osteonecro...
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Contrast level within inferior vena cava

A dependent contrast level within the inferior vena cava is a situation that can be observed in some cases with inferior vena caval contrast reflux. Its presence is usually associated with very poor cardiac output and can be accompanied by dependent layering of venous refluxed contrast within th...
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Inferior vena caval contrast reflux

Reflux of contrast into inferior vena cava can be common findings seen on CT. It is considered a specific but insensitive sign of right-sided heart disease / right heart dysfunction at low contrast injection rates although the usefulness decreases with high injection rates. Conditions associate...
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Egyptian eye sign

"Egyptian eye sign" or "sonographic eye sign" refers to the normal appearance of great saphenous vein on ultrasound, in transverse view 1-2. Ultrasound examination of the great saphenous vein shows echogenic fascia surrounding it, with the saphenous fascia superiorly and the muscular fascia inf...
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Walnut kernel microbleed pattern

The walnut kernel microbleed pattern along with the starfield pattern and corpus callosum diffusion restriction appears to be the most important imaging markers of cerebral fat embolism 1-3. In this pattern, there is a diffuse presence of round microbleeds (punctate focal hypointensities) of si...
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Chinese dragon sign (vascular)

The Chinese dragon sign is a radiological sign on abdominal radiograph and CT describing the radiologic appearance of calcified tortuous splenic artery that resembles a Chinese dragon. The tortuous splenic artery segment on the splenic hilum side represents the dragon head while the other arteri...
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Grey Turner sign

The Grey Turner sign refers to the clinical finding of atraumatic flank ecchymosis, which is occasionally associated with retroperitoneal hemorrhage, classically due to hemorrhagic pancreatitis 2. It is thought to occur when blood extravasates from the posterior pararenal space and crosses throu...
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Billowing phenomenon

Billowing phenomenon refers to the presence of contrast medium on contrast-enhanced CT outside of graft metal struts, due to the specific construction characteristic typical of the AFX® stent-graft (Endologix, Inc., USA), designed to treat abdominal aortic aneurysms. It has a unique internal sca...
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Color bruit artifact

The color bruit or tissue vibration artifact is a type of color Doppler ultrasound artifact which results in color signal overflowing to the perivascular tissues most often caused by stenosis, AV fistulas, or shunts. Thus, this artifact is useful by pinpointing areas of potentially pathological ...
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Spectral broadening (ultrasound)

Spectral broadening is an important artifact in pulsed wave Doppler ultrasound imaging, due to its clinical relevance as a sign of vessel stenosis.  Physics Spectral broadening is caused by turbulence in blood flow as the normally homogeneous velocity of reflective red blood cells becomes more...
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Chen sign

Chen sign on chest radiography is the prominence of the left basal pulmonary vasculature, compared to the right, 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 ...
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Scimitar (disambiguation)

The term scimitar, referring to the characteristic shape of the Middle Eastern sword, may refer to the following: scimitar syndrome (lungs) scimitar sign (cystic adventitial disease) scimitar sacrum (bones)
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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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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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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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Spider web appearance

Spider web appearance is a classic appearance seen on venography in a patient with hepatic venous outflow obstruction. It refers to the dense network of hepatic venous collaterals seen. 
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Trident appearance (disambiguation)

The trident appearance (or sign) can refer to a variety of entities: trident acetabulum trident hand trident sign (osmotic demyelination) trident sign (persistent trigeminal artery) History and etymology The trident is a three-pronged lance employed for spearing fish, and in Classical myth...
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Round belly sign (abdominal compartment syndrome)

Round belly sign is a sign of increased abdominal pressure of greater than 20 mmHg in abdominal compartment syndrome where the abdomen has a rounded appearance of transverse section on CT, rather than its typical oval shape. The sign is positive when the AP to transverse diameter of the abdomen...
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Trident sign (persistent primitive trigeminal artery)

The trident sign of a persistent primitive trigeminal artery refers to the appearance of the intracranial circulation on lateral projection. The internal carotid artery, the abnormal vessel and superior portion of the basilar artery resemble the Greek letter tau (thus tau sign). This configurati...
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Psoas sign (abdominal x-ray)

The psoas sign is a classic non-specific finding on the abdominal radiograph, potentially representing retroperitoneal pathology. Normally on an abdominal radiograph, the lateral margins of both the psoas muscles are clearly visible due to adjacent fat. When the lateral edge of one, or both, ps...
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Pretzel sign (serpentine aneurysm)

The pretzel sign is seen on DSA and is indicative of a serpentine aneurysm 1. The sign refers to the sinusoid configuration of the intra-aneurysmal vascular channel seen in serpentine aneurysms, giving it the appearance of a pretzel.
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Mickey Mouse sign (ultrasound)

The Mickey Mouse sign is said to represent the normal anatomy of the common femoral artery, common femoral vein and great saphenous vein on ultrasound at the level just inferior the inguinal crease.  See also Mickey Mouse appearance
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Temporal tap maneuver

Temporal tap maneuver consists in tapping over the ipsilateral superficial temporal artery while assessing the carotid bifurcation on Doppler ultrasound aiming to produce a reflected flow in the external carotid artery (ECA) and thus helping to distinguish which vessel is being assessed: externa...
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Windsock sign (aortic dissection)

The windsock sign refers to appearances seen in type A thoracic aortic dissections on contrast CT. It results from intimointimal intussusception between the true and false dissected lumens of the thoracic aorta. The altering density of contrast between the dissection lumens which taper distally ...
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Mercedes-Benz sign (aorta)

The Mercedes-Benz sign can be seen in aortic dissection on CT 1.  It is seen as three distinct intimal flaps that have a triradiate configuration similar to the Mercedes-Benz logo (Figure 1). Two of the three lumens outlined by these intimal flaps belong to the false lumen of aortic dissection....
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Thrombus fissuration sign (aortic aneurysm)

Thrombus fissuration is a sign of impending rupture of an aortic aneurysm. It reflects blood dissecting into the intramural thrombus. This sign is observed on contrast-enhanced CT as a linear contrast infiltration from the aneurysm lumen through the intramural thrombus. Thrombus fissurations ext...
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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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Floating viscera sign

The floating viscera sign is an angiographic sign that occurs when there is visualization of branches of the abdominal aorta (e.g. celiac axis, superior mesenteric artery, and renal arteries) during aortography with little or no visualization of the aortic lumen. The floating viscera sign indic...
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Macaroni sign (arteries)

The macaroni sign is a sign seen in Takayasu arteritis on ultrasound. It represents the smooth, homogeneous and moderately echogenic circumferential thickening of the arterial wall that occurs in Takayasu arteritis. The sign is highly specific for Takayasu arteritis, more commonly noted in the ...
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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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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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Westermark sign

Westermark sign is a sign of pulmonary embolus seen on chest radiographs. It is one of several described signs of pulmonary embolus on chest radiographs. Pathology The theory behind the sign is either obstruction of the pulmonary artery or distal vasoconstriction in hypoxic lung 3. In one stu...
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Light bulb sign (pheochromocytoma)

The light bulb sign of an adrenal pheochromocytoma is an MRI feature of this tumor. It refers to marked hyperintensity on T2 weighted sequences, however, this finding is neither sensitive nor specific and pheochromocytomas are more often heterogeneous with intermediate or high T2 signal intensit...
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Teardrop sign (superior mesenteric vein)

The teardrop sign of the superior mesenteric vein is one of the important signs in the local staging of pancreatic adenocarcinoma. Its importance lies in its diagnostic, as well as prognostic, significance. This sign is used in assessing the resectability of pancreatic cancer. Radiographic feat...
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Shmoo sign

Shmoo sign refers to the appearance of a prominent, rounded left ventricle and dilated aorta on a plain PA chest radiograph giving the appearance of Shmoo, a fictional cartoon character in the comic strip Li'l Abner, which first appeared in 1948 5. This sign is indicative of left ventricular enl...
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Tangential calcium sign

A tangential calcium sign is a sign seen with an aortic aneurysm rupture. The calcified intimal rim is discontinuous and is seen to tangentially point away from the aneurysmal lumen. This sign is seen at the point of breach. There is associated retroperitoneal leakage.
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Threads and streaks sign

The threads and streaks sign refers to an angiographic appearance of a vascularized tumor thrombus extending into the ipsilateral renal vein or the inferior vena cava from a renal cell carcinoma. This gives an appearance of linear, thread-like or string-like appearance of the involved vessel.  ...
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Renal arterial cut-off sign

Renal arterial cut-off sign, as the name suggests, is an abrupt termination of the contrast-opacified lumen of the renal artery. It may or may not be associated with contrast extravasation. It is seen in a vascular injury, e.g. segmental or main renal artery thrombosis or occlusion.
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Tulip bulb sign

The tulip bulb sign refers to the characteristic appearance of annuloaortic ectasia as seen on CT angiography. There is symmetric dilatation of the three sinuses of Valsalva, with extension into the ascending aorta and effacement of the sinotubular junction.  It is seen especially in Marfan sy...
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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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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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Signal flare phenomenon

The signal flare phenomenon is a useful sign to identify active bleeding in a liquefied hematoma with hematocrit effect on dynamic CT scan images. When active arterial hemorrhage is present in a liquefied hematoma that has a hematocrit effect, a signal flare phenomenon may be seen as a linear, ...
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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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Sentinel clot sign

The sentinel clot sign is a useful CT finding for the evaluation of probable anatomic sites of hemorrhage. On CT, acute clotted hemorrhage typically has high attenuation (45 to 70 HU), whereas surrounding areas of acute non-clotted hemorrhage or more chronic hemorrhage have either lower attenua...
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String of beads sign (renal artery)

The string of beads sign is the description typically given to the appearance of the renal artery in fibromuscular dysplasia (FMD) but may also be used to describe the appearance of splanchnic arteries in segmental arterial mediolysis (SAM). It refers to the appearance arising from the stenoses ...
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Polo mint sign (venous thrombosis)

The polo mint sign is a description given to a venous thrombosis on contrast-enhanced CT imaging.  When viewed in the axial plane, a thin rim of contrast persists around a central filling defect due to thrombus. This gives an appearance like that of the popular UK mint sweet, the Polo (figure 1)...
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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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Puff of smoke sign

The puff of smoke sign describes the characteristic angiographic appearance of tiny abnormal intracranial collateral vessel networks in moyamoya disease. Progressive narrowing of the supraclinoid internal carotid arteries and circle of Willis vessels results in extensive small collateral arteria...
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Sonographic halo sign

Sonographic halo sign is used in a number of situations. They include: hypoechoic halo sign (also known as target or bull's eye sign) in liver metastases: used in hepatobiliary imaging, is a concerning feature for malignant lesion if the lesion is a hyperechoic liver lesion 1,2 ultrasound halo...
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Yin-yang sign (vascular)

The yin-yang sign, also known as the Pepsi sign, is a radiological sign described in both true and false aneurysms on various imaging modalities. Radiographic features Ultrasound On Doppler ultrasound, the yin-yang sign indicates bidirectional flow due to the swirling of blood within the true...
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Mickey Mouse sign (disambiguation)

In medical imaging, a Mickey Mouse sign or appearance has been given to imaging features that mimic Mickey Mouse when viewed from the front. It has been described in the following: anencephaly 2 progressive supranuclear palsy 1 synonymously with a finger in glove sign the flared shape of the...
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Kissing carotids

The term kissing carotids refers to tortuous and elongated vessels which touch in the midline. They can be found in:  retropharynx 2 intrasphenoid 1 within the pituitary fossa within sphenoid sinuses within sphenoid bones The significance of kissing carotids is two-fold: may mimic intrase...
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Scimitar sign (cystic adventitial disease)

Scimitar sign traditionally referred to a catheter angiographic appearance, although it can also be seen on MRA and CTA. It denotes lateral displacement and stenosis of the popliteal artery in patients with cystic adventitial disease. 
Article

Floating aorta sign

The floating aorta sign refers to the displacement of the abdominal aorta away from the vertebral column. It is a radiographic sign of retroperitoneal masses. Radiographic findings On lateral lumbar spine radiographs, the expected location of the posterior aortic wall is expected to be ≤10 mm...
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High-attenuation crescent sign

The high attenuating crescent sign represents an acute hematoma within either the mural thrombus or the aneurysm wall, especially when detected on unenhanced CT scans. It is a specific sign of impending abdominal aortic aneurysm (AAA) rupture or so-called contained rupture. Pathology The hyper...
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Ivy sign (brain)

The ivy sign refers to the MRI appearance of patients with moyamoya disease or moyamoya syndrome. Prominent leptomeningeal collaterals result in vivid contrast enhancement and high signal on FLAIR due to slow flow. The appearance is reminiscent of the brain having been covered with ivy. Differe...
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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 ...
Article

Capps triad

Capps triad refers to the constellation of clinical and imaging findings in patients with a spontaneous retropharyngeal hematoma, and consists of: tracheal and esophageal compression anterior displacement of the trachea subcutaneous bruising over the neck and anterior chest History and etymo...
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Hair on end sign (mnemonic)

The hair on end sign refers to a radiographic appearance of the diploic space of the skull vault which results from a thickening of trabeculae as the diploic space expands. These trabeculae are perpendicular in orientation, interspersed by radiolucent marrow hyperplasia along with skull vault. ...
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Beak sign (arterial dissection)

The beak sign of arterial dissection is the acute angle formed at the edge of the false lumen in aortic dissection in axial cross-section. It is formed by the borders of the outer aortic wall and the intimal flap, and may be partially thrombosed (blunted beak). It is a reliable characteristic th...
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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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Lyre sign (carotid artery)

The lyre sign refers to the splaying of the internal and external carotid by a carotid body tumor. Classically described on angiography it is also visible on CT angiography.
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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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Reverse figure 3 sign (esophagus)

The reverse figure 3 sign (also known as the E sign) is seen on barium swallows in patients with coarctation of the aorta and is the medial equivalent of the figure 3 sign seen on plain chest radiographs. It is formed by prestenotic dilatation of the ascending aorta, indentation of the coarctati...
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Figure 3 sign (aortic coarctation)

The figure 3 sign is seen in aortic coarctation and is formed by prestenotic dilatation of the aortic arch and left subclavian artery, indentation at the coarctation site (also known as the "tuck"), and post-stenotic dilatation of the descending aorta. On barium studies of the esophagus in pati...
Article

Hyperdense MCA sign (brain)

The hyperdense MCA sign refers to focal hyperdensity of the middle cerebral artery (MCA) on non-contrast brain CT and is the direct visualization of thromboembolic material within the lumen. It is thus the earliest visible sign of MCA infarction as it is seen within 90 minutes after the event 1....
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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 in contrast-enhanced CT, not in unenhanced scans. An equivalent appearance can be noted in the ...
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String sign (disambiguation)

The string sign may refer to: angiographic string sign gastrointestinal string sign string sign of parosteal osteosarcoma myositis ossificans string sign
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String of pearls sign (disambiguation)

String of pearls sign can refer to: string of pearls sign on an abdominal radiograph of fluid-filled dilated small bowel loops string of pearls sign on cerebral MRI in deep border zone infarction string of pearls sign on ultrasound in polycystic ovarian syndrome string of pearls sign for ang...
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Pseudovein sign (bowel)

The pseudovein sign can occur with active gastrointestinal bleeding where contrast extravasation during angiography may have a curvilinear appearance as it pools in the gastric rugae or mucosal folds of bowel, mimicking the appearance of a vein. However, contrast in the “pseudovein” persists bey...
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Hoffman-Rigler sign (heart)

The Hoffman-Rigler sign is a sign of left ventricular enlargement inferred from the distance between the inferior vena cava (IVC) and left ventricle (LV).​ Radiographic features On a lateral chest radiograph, if the distance between the left ventricular border and the posterior border of IVC e...
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Griesinger sign (mastoid)

The Griesinger sign refers to edema of the postauricular soft tissues overlying the mastoid process as a result of thrombosis of the mastoid emissary vein. It is a complication of acute otomastoiditis and may be associated with dural sinus occlusive disease (DSOD). It is said to be a pathognomon...
Article

String sign (artery)

The angiographic string sign, also known as the carotid string sign or slim sign, refers to the thin string of intravascular contrast material distal to a stenotic focus in the internal carotid artery (ICA).  Pathology A thin stripe of flow is caused by decreased pressure and flow distal to th...

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