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.

722 results found
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Thumb sign (chordoma)

The thumb sign or thumbing of the pons is described in chordomas as is meant to be relatively specific. It is seen in midline sagittal projection as a projection of the tumour indenting the pons 1,2. See also thumb sign (disambiguation)
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Thumb sign (disambiguation)

The term thumb sign is used to refer to a number of separate radiological appearances, including:  thumb sign (Marfan's disease) - a clinical sign thumb sign (epiglottitis) thumb sign (chordoma)
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Thumb sign (epiglottitis)

The thumb sign in epiglottitis is a manifestation of an oedematous and enlarged epiglottis which is seen on lateral soft-tissue radiograph of the neck, and it suggests a diagnosis of acute infectious epiglottitis. This is the radiographic corollary of the omega sign 1-3. See also Thumb sign is...
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Thumbprinting

Thumbprinting is a radiographic sign of large bowel wall thickening, usually caused by oedema, related to an infective or inflammatory process (colitis). The normal haustra become thickened at regular intervals appearing like thumbprints projecting into the aerated lumen. Pathology Aetiology ...
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Thurstan Holland fragment

The Thurstan Holland fragment otherwise known as the Thurstan Holland sign is an eponymous radiological sign depicting a triangular portion of the metaphysis remaining with the epiphysis in a physeal fracture. This fragment is one of the tell tale signs of a type 2 Salter-Harris fracture 1.   I...
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Thymic notch sign

The thymic notch sign represents normal thymus in newborn on a frontal chest radiograph. Interruption of the cardiac silhouette forms a notch, which may be seen on either side, but more frequently seen on left side. 
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Thymic sail sign

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

Thyroid inferno refers to the colour Doppler appearance of the thyroid gland in active Graves disease (inclusive of variants such as Marine Lenhart syndrome), and consists of multiple small areas of colour flow seen diffusely throughout the gland representing increased vascularity and arterioven...
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Tiger stripe appearance

The tiger stripe appearance refers to the characteristic distinctive alternating hypo and hyperintense bands on MRI in Lhermitte-Duclos disease. This rare cerebellar tumour appearing like the coat of a tiger. See also tigroid pattern - in brain
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Tip of the iceberg sign (ovarian dermoid cyst)

Tip of the iceberg sign refers to one of the characteristic appearances of an ovarian dermoid cyst. If there are echogenic cyst contents of sebum and hair, they cause marked posterior acoustic attenuation so that only the superficial part of the cyst is seen. Just like an iceberg, you may only b...
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Tombstone iliac wings

Tombstone iliac wings, also referred to as mickey mouse ear pelvis 1, are an imaging descriptor for the iliac wings of individuals with achondroplasia. These are seen to be small and squared and have been likened to the appearance of tombstones or the ears of Mickey Mouse.
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Toothpaste sign

The toothpaste sign in spinal imaging represents an extrusion of an intervertebral disc into the epidural space. It is called after the shape of extruded material relatively to the parent disc in a sagittal plane.
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Tram-track sign (brain)

Tram-track sign in the brain refers to the parallel calcification of the cortex in patients with Sturge-Weber syndrome1.  It should not be confused with other tram-track signs elsewhere in the body. 
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Tram-track sign (chest)

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

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

Tram-track sign refers to the parallel thickening and enhancement around the optic nerve, and is most frequently seen in the setting of optic nerve meningioma. It may however also be seen in 1: orbital pseudotumour perioptic neuritis orbital sarcoidosis oribtal leukemia orbital lymphoma or...
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Tramp-stamp oedema

Tramp-stamp oedema is a colloquial term used by some radiologists to denote posterior lumbar subcutaneous oedema. The term is used to describe oedema in the distribution seen with lower back tattoos, usually in young women, which are known as tramp-stamps.  This oedema is thought to be related ...
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Transient ischaemic dilatation

Transient ischaemic dilatation is a paradoxical phenomenon seen in myocardial perfusion SPECT imaging.   With severe balanced coronary artery disease, myocardial ischaemia may result in apparent enlargement of the left ventricular cavity during stress. The cause of this is not entirely clear, b...
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Transmantle sign (brain)

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

Tree-in-bud sign or pattern describes the CT appearance of multiple areas of centrilobular nodules with a linear branching pattern. Although initially described in patients with endobronchial tuberculosis, it is now recognised in a large number of conditions. Pathology Pathogenesis The tree-i...
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Trethowan sign

The Trethowan sign is used to diagnose slipped capital femoral epiphysis (also called slipped upper femoral epiphysis). In this sign, the line of Klein passes above the femoral head. It is best done on both AP and true lateral projections. On the AP view of a normal hip, the Klein line intersec...
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Triangular cord sign (biliary atresia)

The triangular cord sign is a triangular or tubular echogenic cord of fibrous tissue seen in the porta hepatis at ultrasonography and is relatively specific in the diagnosis of  biliary atresia1,2. This sign is useful in the evaluation of infants with cholestatic jaundice, helping for the diffe...
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Triple bubble sign

The triple bubble sign is the classic radiographic appearance observed in jejunal atresia 1,2. The appearance is due to a proximal obstruction caused by the atretric jejunum. It is equivalent to the double bubble sign, but a third bubble is seen because of proximal jejunal distention.
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Troisier sign

Troisier sign is the clinical finding of a hard and enlarged left supraclavicular node (Virchow node), and is considered a sign of metastatic abdominal malignancy. Terminology It is sometimes referred to as Virchow node, which is the name given by Dr Rudolf Virchow (1821-1902), a German pathol...
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Trough line sign

The trough line sign is a sign of posterior shoulder dislocation on AP films.  In posterior dislocation, the anterior aspect of the humeral head becomes impacted against the posterior glenoid rim. With sufficient force, this causes a compression fracture on the anterior aspect of the humeral he...
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Trumpeted internal acoustic meatus sign

A trumpeted internal acoustic meatus (IAM) is an indirect sign of an acoustic schwannoma and is useful in helping differentiating between one and other cerebellopontine angle entities, especially from a meningioma which typically does not extend into the meatus 1. It is characterized by widenin...
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Tubal ring sign

Tubal ring sign, also referred to as bagel sign or blob sign, one of the ultrasound signs of a tubal ectopic. It comprises of an echogenic ring which surrounds an unruptured ectopic pregnancy. It is said to have a 95% positive predictive value (PPV) for ectopic pregnancy. Differential diagnosis...
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Tuberculous dactylitis

Tuberculous dactylitis, also known as spina ventosa, is a rare skeletal manifestation of tuberculosis where the short tubular bones (i.e. phalanges, metacarpals, metatarsals) are affected. Epidemiology Tuberculous osteitis is one of the commonest bacterial osteitis. Typically the dactylitis fo...
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Tulip bulb sign

Tulip bulb sign refers to characteristic appearance due to dilatation of sinuses of Valsalva slightly extending into the ascending aorta as seen on CT scan of chest.  It is seen especially in Marfan's syndrome. On CT angiography, aneurysm of the aortic root with effacement of sinotubular junct...
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Tullio phenomenon

The Tullio phenomenon describes the precipitation of vertigo and nystagmus by a loud noise. Aetiology The tympanic membrane and ossicular chain must be intact with a mobile footplate. It can be present in may situations congenital syphilis, with a semicircular canal fistula post-fenestratio...
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Turtle back sign

Turtle back sign, also referred as tortoise shell appearance, represents a very characteristic pattern of the schistosomiasis cirrhotic liver in which calcified fibrotic septa are seen aligned perpendicular to the liver capsule resembling the turtle's carapace. 
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Twin-peak sign (twin pregancy)

The twin peak sign (also known as the lambda (λ) sign) is a triangular appearance of the chorion insinuating between the layers of the inter twin membrane and strongly suggests a dichorionic twin pregnancy. It is best seen in the first trimester (between 10-14 weeks). 5 While the presence of a t...
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Two-slice-touch rule (knee MRI)

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

The U sign denotes the characteristic "U" shaped appearance of the subcentral gyrus which surrounds the inferolateral end of the central sulcus and abuts the lateral (Sylvian) fissure. It has been found, at least in one study, to be the most reliable anatomical feature to identify the central su...
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Unfolded aorta

The term unfolded aorta refers to the widened and 'opened up' appearance of the aortic arch on a frontal chest radiograph. It is one of the more common causes for apparent mediastinal widening and is seen with increasing age. It occurs due to the discrepancy in the growth of the ascending aorta...
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Upper lobe pulmonary venous diversion

Upper lobe pulmonary venous diversion (cephalisation) reflects elevation of left atrial pressure and can occur with pulmonary oedema. It produces Stag-antler's sign on frontal chest x-ray. The normal left atrial pressure is 5-10 mmHg. An elevation of left atrial pressure to 10-15 mmHg will resu...
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Upper T sign

The upper T sign is one of the features useful in identifying the central sulcus on cross-sectional imaging. It relies on identifying the superior frontal sulcus which intersects the precentral sulcus in a "T" junction, thus defining the precentral gyrus. The central sulcus is the next posterio...
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Vacuum phenomenon in shoulder

Vacuum phenomenon in the shoulder refers to the presence of intra-articular gas in the shoulder joint. It is a very common occurrence, particularly in external rotation. This can cause circular or linear areas of low signal intensity on GRE MR images of the shoulder obtained with external rotati...
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Vegetable and plant inspired signs

There are many signs in radiology which are vegetable and plant inspired, they include Unprocessed produce celery stalk metaphysis: osteopathia striata and congenital rubella infection celery stalk anterior cruciate ligament: ACL mucoid degeneration Christmas tree intestinal atresia coffee ...
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Venous distension sign

The venous distension sign is a finding that may be identified on sagittal imaging of the dural venous sinuses which is said to have a diagnostic sensitivity and specificity of 94% for intracranial hypotension. The sign is positive when there is a convex inferior margin of the midportion of the ...
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Venus necklace

A venus necklace is a term almost never used, but for the sake of completeness is included here. It is used by some authors 1 to describe a series of T2 hyperintense lesions on the inferior surface of the corpus callosum in the midline (callososeptal interface), most frequently seen in multiple ...
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Vertebra plana

Vertebra plana or pancake vertebra is the term given when a vertebral body has lost almost its entire height anteriorly and posteriorly, representing a very advanced crush fracture. It can occur with a variety of settings, including: trauma osteoporosis Langerhans cell histiocytosis (LCH) mo...
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Vertebral body squaring (differential)

Vertebral body squaring refers to the loss of normal concavity of the anterior border. It is seen in a variety of conditions including:  Differential diagnosis Ankylosing spondylitis Ankylosing spondylitis is the most common cause of vertebral body squaring. It usually involves multiple level...
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Vertebral scalloping

Vertebral scalloping is a concavity to the posterior (or less commonly anterior) aspect of the vertebral body when viewed in a lateral projection. A small amount of concavity is normal, as is concavity of the anterior vertebral body (see vertebral body squaring). Posterior scalloping Causes of...
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Viking helmet appearance

The viking helmet appearance refers to the lateral ventricles in coronal projection in patients with dysgenesis of the corpus callosum. The cingulate gyrus is everted into narrowed and elongated frontal horns.  An alternative name is moose head appearance. 
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Waldenström sign (hip)

Waldenström sign is the increased distance between the pelvic tear drop and the femoral head. It is a non-specific sign of hip joint effusion. Radiographic features Radiograph >11 mm total distance or >2 mm difference compared to contralateral hip 1, 2 measured between the lateral aspect of ...
Article

Walking man sign (chest x-ray)

The walking man sign is seen on a lateral chest radiograph and is a sign of left atrial enlargement. It results from posterior displacement of the left main bronchus such that it no longer overlaps the right bronchus. The left and right bronchus thus appear as an inverted 'V', mimicking the legs...
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Wasp-waist sign (spine)

The wasp-waist sign is a radiographic appearance seen in patients with Klippel Feil syndrome. It results from fusion of the vertebral bodies such that the anteroposterior diameter at the level of the affected discovertebral joint is smaller than the diameter at the superior and inferior limits o...
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Water bottle sign (heart)

The water bottle sign or configuration refers to the shape of the cardiac silhouette on erect frontal chest x-rays in patients who have a very large pericardial effusion. Typically the effusion has accumulated over many weeks to months (e.g. in patients with malignancy) and the pericardium has g...
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Water-lily sign (liver)

The water-lily sign is seen in hydatid infections when there is detachment of the endocyst membrane which results in floating membranes within the pericyst that mimic the appearance of a water lily. It is classically described on plain radiographs (mainly chest X-ray) when the collapsed membran...
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Wave sign

The wave sign refers to the indentation of the normal thymus in young children by the ribs, resulting in a wavy border.
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Weapon and munition inspired signs

Weapon and munition inspired signs include the following with their corresponding pathologic conditions: bayonet deformity Turner syndrome chondrodysplasia bullet-shaped vertebra ​mucopolysaccharidosis achondroplasia cannonball metastases ​metastases from renal cell carcinoma dagger sig...
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Westermark sign (lungs)

Westermark sign is a sign of pulmonary embolus (PE) seen on chest radiographs. Along with Fleishner sign and Hampton hump, it makes one of the three described signs of pulmonary embolus on chest radiographs. Pathology In one study (PIOPED) this sign was present on ~10% of chest x-rays of pati...
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Wheels within wheels sign

This sign is seen in USG of patient with the hepatic candidiasis and described as central hypoechoic area (necrosis containing fungi) surrounded by an echogenic zone (inflammatory cells). Differs from bull’s-eye sign for reverse echogeniticity, as it consists a central echogenic nidus surrounde...
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Whirlpool sign

The whirlpool sign, also known as the whirl sign, is seen when a structure twists upon itself. It is most commonly described in the abdomen where bowel rotates around its mesentery, with mesenteric vessels creating the whirls. It can also be seen in ovarian torsion. Whirlpool sign: mesenteric ...
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White cerebellum sign

White cerebellum sign, also called reversal sign or dense cerebellum sign, is encountered when there is a diffuse decrease in density of the supratentorial brain parenchyma, with relatively increased attenuation of the thalami, brainstem and cerebellum. This sign indicates irreversible brain dam...
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White matter buckling sign

The white matter buckling sign is helpful in distinguishing an extra-axial mass from an intra-axial one, and represents the white matter projecting into gyri being compressed and displaced by the mass, even in the presence of oedema (which would usually expand gyri, if the mass were intra-axial)...
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White pyramid sign (kidney)

The white pyramid sign refers to the CT appearance of the medullary pyramids of the kidney which can be seen normally on unenhanced CT scans as high-attenuation triangular structures.  Bilateral high-attenuation renal pyramids are an occasional incidental normal finding.  In contrast, unilatera...
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Widened intercondylar notch

A widened intercondylar notch on knee radiographs is a sign associated with: haemophilic arthropathy (most commonly bilateral) juvenile rheumatoid arthritis (most commonly bilateral) tuberculosis arthropathy (usually unilateral) (3)
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Widow's peak hair anomaly

Widow's peak hair anomaly refers to a frontal hairline projection. Clinical features Prominent V shaped hairline projection. Ocular hypertelorism might be noted. On examination a bony prominence may be present. Pathology It is purported that the periorbital fields of hairless region or hairg...
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Wimberger ring sign

Wimberger ring sign refers to a circular calcification surrounding the osteoporotic epiphyseal center of ossification in scurvy, which may result from bleeding. It must not be confused with Wimberger sign, pathognomonic of congenital syphilis.
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Wimberger sign

The Wimberger sign, also called Wimberger corner sign, refers to localised bilateral metaphyseal destruction of the medial proximal tibias. It is a pathognomonic sign for congenital syphilis. It must not be confused with Wimberger ring sign seen in scurvy, which is sometimes also referred to as...
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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 intimo-intimal 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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Windsock sign (duodenal web)

The windsock sign is a typical appearance of a duodenal web (intraluminal duodenal diverticulum) on upper gastrointestinal contrast series which consists of an intraduodenal barium-contrast filled sac that is surrounded by a narrow lucent line (web or intraluminal mucosal diaphragm) which is wel...
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Winking owl sign (spine)

The (absent) pedicle sign, also called the winking owl sign, occurs on plain film when a pedicle is absent. The term, winking owl sign, where the missing pedicle corresponds to the closed eye, the contralateral pedicle to the other open eye, and the spinous process to the beak of the animal on ...
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X-marks-the-spot sign (large bowel volvulus)

The X-marks-the-spot is a sign of complete bowel volvulus and refers to the crossing loops of the bowel at the site of the transition. It has been reported to improve diagnostic confidence in detecting caecal and sigmoid volvulus. This is in contrast to the split-wall sign which indicates partia...
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Y sign (epidural lipomatosis)

The Y sign refers to a common appearance in lumbar epidural lipomatosis where excess fat in the extradural space compresses the dural sac into the shape of the letter "Y". 
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Yin-yang sign

The yin-yang sign is a radiological sign described in both true and false aneurysms on various imaging modalities.  Radiographic features Doppler sonography The yin-yang sign indicates bidirectional flow due to swirling of blood within the (true or false) aneurysm. Contrast-enhanced CT The ...
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Zebra sign (cerebellum)

The zebra sign has been termed to describe the finding of layering of blood in amongst the folia of the cerebellum, particularly in the setting of remote cerebellar haemorrhage.1 This type of haemorrhage is characterised by a streaky pattern, like a zebra's stripes, due to blood spreading in th...
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Zebra spleen

Zebra spleen, also referred to as psychedelic spleen or more correctly inhomogeneous splenic enhancement refers to the transient heterogeneous parenchymal enhancement of the spleen during the arterial or early portal venous phases of contrast enhancement in CT, MRI, or ultrasound imaging. It is...
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Zebra stripe sign (bones)

The zebra stripe sign occurs where children with osteogenesis imperfecta have been treated with cyclical bisphosphonate therapy, e.g. pamidronate. When the drug is delivered in cycles, dense bone is formed while treatment is being given. This results in dense stripes across the metaphyses of bon...

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