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.

44 results found
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Dagger sign

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

Dark bronchus sign is the appearance of relatively darker bronchus to the adjacent ground glass opacity. If the ground glass opacity progress to consolidation, air bronchograms will be visualised.  This sign is useful to identify diffuse ground glass opacity on HRCT in cases of Pneumocystis jir...
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Dawson fingers

Dawson fingers are a radiographic feature depicting demyelinating plaques through the corpus callosum, arranged at right angles along medullary veins (callososeptal location). They are a relatively specific sign for multiple sclerosis (MS), which presents as T2 hyperintensities. History and ety...
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Deep sulcus sign

The deep sulcus sign on a supine chest radiograph is an indication of a pneumothorax. In a supine film (common in the ICU), it may be the only indication of a pneumothorax because air collects anteriorly and basally, within the nondependent portions of the pleural space, as opposed to the apex ...
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Dense hilum sign

The dense hilum sign suggests a pathological process at the hilum - hilar malignancy or bronchogenic carcinoma should be suspected. On a well-centred chest PA radiograph the density of the hilum is comparable on both sides. In absence of calcification or adenopathy, the hila should appear of eq...
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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 lies against the posterior thoracic wall in a dependent position, as it is no longer supported by the diaphragm. See also  collar sign (or hour glass sign)
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Dinner fork deformity

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 an 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 oedema at the time of an ischaemic event. It is be...
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Disc herniation

Disc herniation refers to displacement of intervertebral disc material beyond the normal confines of the disc, but involving less than 25% of the circumference (to distinguish it from a disc bulge. A herniation may contain nucleus pulposus, vertebral endplate cartilage, apophyseal bone/osteophyt...
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Disproportionate posterior horn sign

The disproportionate posterior horn sign is a feature described with a mensical 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 tears ( which includes vertical-o...
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Distal intersection syndrome

The distal intersection syndrome relates to tenosynovitis of the extensor pollicis longus (EPL) tendon, where it crosses the extensor carpi radialis longus (ECRL) and brevis (ECRB) tendons1. It is distinct from intersection syndrome which occurs more proximally in the forearm at the intersection...
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Dog leg sign

The "dog leg" sign is a secondary angiographic sign on popliteal angiography, which demonstrates an irregular lumen of popliteal artery with acute bend in the course of popliteal artery. It is characteristically seen in popliteal artery aneurysms with mural thrombus. It is important s...
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Doge cap sign

Doge cap sign a radiographic sign of pneumoperitoneum. It is due to air in Morrison pouch, which presents as a triangular gas density.
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Dot dash pattern

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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Double axillary pouch sign

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 anter...
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Double barrel sign

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 oesophagus: oesophageal dissection
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Double bleb sign

A double bleb sign is a sonographic feature where there is visualisation of a gestational sac containing a yolk sac and amniotic sac giving an appearence 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

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 characterised 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 of 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 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). It consists of the decidua parietalis (lining the uterine cavity) and decidua capsularis (lining the gestational sac) and is seen as two concentric rings surrou...
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Double delta sign

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 so refers as displaced bucket handle tear. The original location of the posterior horn remains empty giv...
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Double density sign of berry aneurysms

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 calibre. 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 of left atrial enlargement

Double-density sign is seen on frontal chest radiograph 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 distinct silhouette 1-3.  If large enough, the left atriu...
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Double density sign of 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 TMJ disc. When both thickening of the inferior belly insertion and an anteriorly displaced disc are present, the two structures parallel each other; the so called "double disc" sign.
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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 visualise the region, including: MRI, CT, ultrasound and endoscopic retrograde cholangiopancreatography (ERCP).  The...
Article

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 an outer dark line representing sclerotic bone. This ...
Article

Double panda sign

The double panda sign refers to combination of 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 nuclei an...
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Double PCL sign

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

Double rim sign

Double rim sign is best described on T2WI MRI, in the early capsule stage of brain abscess. It consists two concentric rims surrounding the abscess cavity, one of which is hypointense (outer rim), and the other relatively more hyperintense (inner rim). It is described in more than 75% of cases.
Article

Double target sign of hepatic abscess

The double target sign is a characteristic imaging feature of liver abscess demonstrated 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 ring1-2 . The inner ring (abscess membrane) d...
Article

Double track sign of 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, Pyloric fluid compressed into smaller tracks as it is impinge...
Article

Double wall sign

The double wall sign is another name for the Rigler sign. It is a sign of pneumoperitoneum with air outlining both sides of the bowel wall. It is seen when large amount of free air, > 1000 ml, is present. It should be distinguished from the false double-wall sign which refers to two dilated ...
Article

Doughnut sign on bone scan

The doughnut sign refers to bone scan pattern which demonstrate increased uptake peripherally with a photopenic center. This appearance may be seen in a number of cystic lesions include: aneurysmal bone cyst giant cell tumour simple bone cyst The doughnut sign is a nonspecific sign, and also...
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 moulds to the anterior surface...
Article

Dripping candle wax sign

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

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 moeity. The similarity to a lily is further strengthened by the smal...
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Dual rim sign

The dual rim sign is seen on susceptibility weighted imaging (SWI) in cerebral abscesses and is helpful in distinguishing an abscess from a gliblastoma (GBM).  Pathology It has been postulated that granulation tissue lines the inner part of fibrocollagenous abscess capsule and together they fo...
Article

Duct penetrating sign

The duct-penetrating sign is a radiographic sign which can be useful in differentiating between focal pancreatitis (inflammatory pancreatic mass ) from pancreatic carcinoma. Best description of positive sign is visualisation of a mass penetrated by an unobstructed pancreatic duct makes focal pa...
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Dumbbell appearance of spinal tumours

Dumbbell appearance of spinal tumours refers to a tumour which has both a component within the canal and a component in the paravertebral space linked by tumour traversing the neural exit foramen. The appearance can be seen in: spinal nerve sheath tumours spinal schwannoma (90%) 1 spinal neu...
Article

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 experience grew, it has become increasingly noted to be present in many other conditions, ...

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