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.

58 results found
Article

T1 black holes

T1 black holes are hypointense lesions commonly seen on T1WI in patients with multiple sclerosis, and indicates the chronic stage with white matter destruction, axonal loss and irreversible clinical outcome. There is a correlation between the number of black holes and patient positive outcome3.
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T2 dark spot sign

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

The talar beak sign is seen in cases of tarsal coalition, and refers to a superior projection of the distal aspect of the talus. It is most frequently encountered in talocalcaneal coalition. It is thought to result from abnormal biomechanic stresses at the talonavicular joint.  Differential dia...
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Tam o' shanter sign (skull)

The "tam o' shanter" is a Scottish hat, named after the character in Robert Burns' 1 poem of the same name. The appearances of advanced Paget disease of the skull are similar in appearance to the hat.  Paget involvement of the skull, with widening of the diploic space and an overall enlargement...
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Target sign (choledocholithiasis)

The target sign of choledocholithiasis is a finding seen on contrast-enhanced CT and comprises: central density within the bile duct: stone surrounding low density: bile or mucosa
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Target sign (disambiguation)

There are many bull's eye signs, also referred to as target signs: red bone marrow located in the shaft of long bone with central yellow marrow on MRI peripheral plexiform neurofibromas on MRI intussusception: see target sign of intussusception choledocholithiasis: see target sign of choledo...
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Target sign (intussusception)

The target sign of intestinal intussusception, also known as the doughnut sign or bull's eye sign. The appearance is generated by concentric alternating echogenic and hypoechogenic bands. The echogenic bands are formed by mucosa and muscularis whereas the submucosa is responsible fo the hypoec...
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Target sign (pyloric stenosis)

The target sign of pyloric stenosis is a sign seen due to hypertrophied hypoechoic muscle surrounding echogenic mucosa, seen in pyloric stenosis. This is likened to that of a target. See also antral nipple sign cervix sign of pyloric stenosis shoulder sign of pyloric stenosis
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Target sign (tuberculosis)

The target sign of tuberculosis refers to the bull's-eye appearance of some parenchymal tuberculomas involving the brain (see: CNS tuberculosis) and solid abdominal organs (see: hepatic and splenic tuberculosis) on cross-sectional imaging.  Radiographic features Ultrasound hypoechoic nodules ...
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Tattoo sign (mammogram)

The tattoo sign is a feature given to describe dermal calcifications seen on mammography 1. The basis of this sign is that dermal calcifications maintain fixed relationships to one another which are reproducible with similar projections at different times. This is in contrast to intramammary cal...
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Tau sign

The tau sign represents the appearance of a persistent trigeminal artery on the sagittal plane of an angiogram or on sagittal MRI images. It resembles the greek letter 'tau'. Persistent trigeminal artery arising from the junction between the petrous and cavernous ICA and runs posterolaterally al...
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Tear drop sign of the superior mesenteric vein

Tear drop sign of the superior mesenteric vein (SMV) is one of the important signs in the staging of pancreatic adenocarcinoma. Its importance lies in its diagnosis as well as prognostic significance. This sign is used in assessing the resectability of pancreatic cancer. Radiographic features ...
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Tectal beaking (midbrain)

Tectal beaking refers to fusion of midbrain colliculi into a single beak pointing posteriorly and invaginating into the cerebellum. It is seen with a Chiari type II malformation. Terminology The term bird's beak sign is used in a number of other contexts: see bird beak sign (disambiguation). 
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Temporal tap manoeuvre

Temporal tap manoeuvre consists in tapping over the ipsilateral 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: external vs. inter...
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Tensile gallbladder fundus sign

The tensile gallbladder fundus sign is positive when the gallbladder fundus is seen to bulge into, and distort, the anterior abdominal wall and is a feature of acute cholecystitis. It is particularly useful as an early sign of the condition on CT as it has around a 75% sensitivity and 95% speci...
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Tent sign (breast)

The tent sign is a term referred to a characteristic of the posterior edge of the breast parenchyma when a mass (usually an infiltrating lesion) causes its retraction and forms an inverted "V" that resembles the tip of a circus tent. The detection of a "tent-sign" is facilitated by the systemat...
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Terry Thomas sign

The Terry Thomas sign refers to an increase in the scapholunate space on an AP radiograph of the wrist (or coronal CT). The increased distance indicates scapholunate dissociation (often with rotary subluxation of the scaphoid) due to ligamentous injury. There is no consensus as to what measureme...
Article

Third mogul sign

The third mogul sign can be seen on frontal chest radiograph in the presence of left atrial enlargement. It refers to an extra mogul or bump along the upper left cardiac silhouette just below the left main bronchus. The third mogul sign commonly represents the enlarged left atrial appendage, pa...
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Thoracic spine sign (ultrasound)

The thoracic spine sign on lung ultrasound is an indirect indicator of the presence of a pleural effusion or haemothorax. It represents the visualisation of the vertebral bodies in the thoracic cavity above the diaphragm which are usually not seen unless there is a fluid collection.  Radiograph...
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Thoracoabdominal sign

Thoracoabdominal sign, a variation of the silhouette sign, is a frontal chest radiograph sign which helps to localize a thoracic lesion. Since the posterior costophrenic sulcus is more caudal than the anterior lung, a thoracic lesion must be posterior if its caudal end is visible below the dome...
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Threads and streaks sign

The threads and streaks sign refers to an angiographic appearance of a vascularised tumour 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.  ...
Article

Three line sign (common bile duct)

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

Throckmorton sign (pelvis)

Throckmorton sign, also known as John Thomas sign, refers to when the penis points in the direction of unilateral disease, typically of the pelvis or hip.  Throckmorton sign is a slang term used jokingly by medical students and residents. History and etymology It is named after Tom Bentley Th...
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Thrombus fissuration

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 linear contrast infiltrations from the aneurysm lumen through the intramural thrombus. Thrombus fissurations exte...
Article

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 ...
Article

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...
Article

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...
Article

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...
Article

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...
Article

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.
Article

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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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 ...
Article

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...
Article

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...
Article

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...
Article

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 ...
Article

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...
Article

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...
Article

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...
Article

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.
Article

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...
Article

Trough line sign

The trough line sign is a sign of posterior shoulder dislocation on AP films.  In a 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 ...
Article

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...
Article

T sign (obstetrics)

The "T sign" is really the absence of a twin-peak sign (or lambda sign) and is used in ultrasound assessment of a mulifetal pregnancy. It refers to the lack of chorion extending between the layers of the intertwin membrane, denoting a monochorionic pregnancy. The intertwin membrane comes to an ...
Article

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...
Article

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...
Article

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...
Article

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...
Article

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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