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.

33 results found
Article

Raccoon sign

Raccoon sign is periorbital ecchymosis and is indicative of skull base fracture of anterior cranial fossa.
Article

Rachitic rosary

Rachitic rosary refers to expansion of the anterior rib ends at the costochondral junctions and is most frequently seen in rickets as nodularity at the costochondral junctions. Differential diagnosis Other causes of this appearance include:  scurvy:  the costochondral junction is more angula...
Article

Racing car sign

The racing car sign refers to widely spaced lateral ventricles due to agenesis of the corpus callosum with intervening Probst bundles. Appearances on axial MRI or CT are reminiscent of a formula one car seen from above, with the tires represented by the widely spaced frontal horns, and the dilat...
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Radial bands sign

The radial bands sign refers to linear bands seen on MRI, radiating from the periventricular white matter to the subcortical region, thought to be specific for tuberous sclerosis 1-2. Pathology The exact pathogenesis of radial bands is uncertain, but they are thought to relate to dysfuction or...
Article

Radiocapitellar line

The radiocapitellar line is one of the key lines used to assess alignment on the elbow radiograph. It is particularly useful in the paediatric setting. The rule A line drawn down the neck of the radius should intersect the capitellum. It is important to ensure that you draw the line down the r...
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Radiological signs: gastrointestinal tract

Radiological signs are described across the disciplines of imaging, including the gastrointestinal tract. Fruit-inspired, nature-related, and more feature in the list of signs described for a wide array of pathology. How fascinating are the minds of radiologists work in describing pathology?
Article

Raindrop skull

The appearance of multiple, well-defined lytic lesions (punched out lesions) of various size scattered throughout the skull constitutes the raindrop skull appearance of multiple myeloma. This term is applied as an analogy to rain hitting a surface and splashing, where it leaves a random pattern ...
Article

Ranke complex

Ranke complex is seen in 'healed' primary pulmonary tuberculosis comprised of two parts: Ghon lesion: calcified parenchymal tuberculoma ipsilateral calcified hilar node
Article

Rat-tail sign

The rat-tail sign is used to refer to the tapering of the inferior oesophagus in achalasia. The same appearance (although it is difficult to see the similarity) is also referred to as the bird-beak sign. 
Article

Renal arterial cut-off sign

Renal arterial cut-off sign  as the name suggests is an abrupt termination of the vascular contrast opacified renal arterial lumen. It may be associated with or without any contrast extravasation It is seen in a vascular injury like segmental or main renal artery thrombosis or occlusion.
Article

Reverse bat wing pulmonary opacities

Reverse bat wing pulmonary opacities refer to peripheral opacities of the lungs, sparing the perihilar region. It is a relatively unusual appearance with a relatively narrow differential. chronic eosinophilic pneumonia cryptogenic organising pneumonia, formerly bronchiolitis obliterans with or...
Article

Reverse figure 3 sign

The reverse figure 3 sign (also known as the E sign) is seen on barium swallows in patients with a coarctation of the aorta and is the medial equivalent of the figure 3 sign seen on CXR. It is formed by prestenotic dilatation of the ascending aorta, indentation of the coarctation site (or "...
Article

Reverse target sign: cirrhotic nodules

A reverse target sign is a potential ultrasound marker for cirrhotic nodules on ultrasound.It represents central iso-hyperechogenecity with surrounding hyperechoic rim .This sign is useful to differentiate metastases from cirrhotic nodules where target sign is seen in liver metastases.
Article

Reversed halo sign

Reversed halo sign (RHS), also known as the atoll sign, is defined as central ground-glass opacity (GGO) surrounded by denser consolidation of crescentic (forming more than three fourths of a circle) or ring (forming a complete circle) shape of at least 2 mm in thickness. It was initially descri...
Article

Ribbon ribs deformity

Ribbon-ribs deformity refers to the presence of thinned ribs on image studies. Such findings could be present in patients with neurofibromatosis type 1 (NF1) due the presence of multiple neurofibromas of intercostal nerves.  This deformity is also described in osteogenesis imperfecta 1 Edward...
Article

Rice grain calcification

Rice grain calcification is characteristic of infection with Taenia solium (cysticercosis); when the inflammatory response of the host kills the larval cysts (cysticerci), they undergo granulomatous change and become calcified. Radiographic features Ovoid flecks of calcification resembling gra...
Article

Rigler notch sign

The Rigler notch sign refers to an indentation in the border of a solid lung mass, which is thought to represents a feeding vessel, thus suggesting the presence of a bronchial carcinoma1. However, this sign is also observed in other conditions, including granulomatous infections, and its differe...
Article

Rigler sign

The Rigler sign, also known as the double wall sign, is seen on a radiograph of the abdomen when the air is present on both sides of the intestine, i.e. when there is air on both the luminal and peritoneal side of the bowel wall. Pneumoperitoneum may be a result of perforation or, from recent i...
Article

Rigler triad

Rigler triad consists of three findings seen in gallstone ileus: pneumobilia small bowel obstruction gallstone, usually in the right iliac fossa Rigler triad should not be confused with Rigler sign or the Hoffman-Rigler sign. History and etymology It is named after Leo George Rigler, Ameri...
Article

Rim sign in chronic hydronephrosis

The rim sign can be seen in association with chronic hydronephrosis.  In patient's with chronic hydronephrosis, in all forms of contrast-enhanced imaging of the obstructed kidney, enhancement may occur in the residual, but markedly atrophic, renal parenchyma, surrounding the dilated calices and...
Article

Rim sign in renal vascular compromise

Rim sign in renal vascular compromise is seen in major renal vascular compromise. It can be seen in: renal artery obstruction from embolism, thrombosis or dissection renal vein thrombosis acute tubular necrosis Radiographic features At contrast enhanced CT or MR imaging, a thin (1-3 mm) ri...
Article

Rim sign of avascular necrosis

The rim sign comprises a high T2 or intermediate T1 signal line sandwiched between two low signal lines, and represents fluid between sclerotic borders of an osteochondral fragment, and implies instability (stage III). The rim sign should not be confused with the double line sign of osteonecros...
Article

Rind sign

The rind sign indicates a lesion surrounded by a layer of thick, sclerotic reactive bone (rind) and is suggestive of fibrous dysplasia. The classic rind is most commonly seen in the proximal femur.
Article

Ring of fire sign

The ring of fire sign also known as ring of vascularity signifies a hypervascular lesion with peripheral vascularity on colour or pulsed doppler examination of the adnexa due to low impedance high diastolic flow 1. This sign can be seen in corpus luteum cyst (more commonly) ectopic pregnancy
Article

Ring shadow (disambiguation)

Ring shadows are radiographic signs seen on either chest x-rays or on upper gastrointestinal fluoroscopy: ring shadow (chest) ring shadow (abdomen)
Article

Rings and arcs calcification

Rings and arcs calcification is characteristic of chondroid lesions, such as enchondromas and chondrosarcomas. It is due to endochondral mineralisation of multiple hyaline cartilage nodules and is similar to popcorn calcification, which has rings and arcs on the background of more amorphous calc...
Article

Robert sign

Robert sign refers to the presence of a gas shadow within the heart or the greater vessels, in cases of fetal death in utero. It is a rare sign caused by postmortem blood degeneration, usually seen 1-2 days after death; and may be seen as early as 12 hours. Related articles fetal death in utero
Article

Rokitansky nodule

A Rokitansky nodule or dermoid plug refers to a solid protuberence projecting from an ovarian cyst in the context of a mature cystic teratoma. It often contains calcific, dental, adipose, hair and/or sebaceous components 1. 
Article

Rolling stone sign

The rolling stone sign refers to the presence of gallstones within the gallbladder that are mobile when the patient moves. Small gallstones can sometimes be difficult to diagnose due to the absence of posterior shadow artefact but the presence of a rolling stone sign increases the confidence of...
Article

Romana sign

Romana sign, also known as chagoma, refers to periorbital swelling, palpebral oedema and conjunctivitis seen 1-2 weeks following infection with Trypanosoma cruzi (causative agent in the Chagas disease).  Romana sign is associated with ipsilateral regional lymphadenopathy.  History and etymolog...
Article

Romanus lesion

The Romanus lesion represents an early finding in inflammatory spondyloarthropathies, such as ankylosing spondylitis and enteropathic arthritis, and appears as irregularity and erosion involving the anterior and posterior edges of the vertebral endplates 1. Healing response to these inflammatory...
Article

Rosary sign

The rosary sign is a CT finding in adenomyomatosis of the gallbladder. It is formed by the enhanced proliferative mucosal epithelium, with the intramural diverticula surrounded by the unenhanced hypertrophied muscle coat of the gallbladder. The rosary sign is similar to the pearl necklace sign.
Article

Rugger-jersey spine

Rugger-jersey spine describes the prominent subendplate densities at multiple contiguous levels to produce an alternating sclerotic-lucent-sclerotic appearance. This simulates the transverse bands of a rugby jersey. This term and pattern is distinctive for hyperparathyroidism. Pathology The e...

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