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.

29 results found
Article

Macaroni sign

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

Magic angle effect - MRI artifact

The magic angle is an MRI artifact which occurs on sequences with a short TE (less than 32ms; T1W sequences, PD sequences and gradient echo sequences).  It is confined to regions of tightly bound collagen at 54.74° from the main magnetic field (B0), and appears hyperintense, thus potentially be...
Article

Maiden waist deformity

Maiden waist deformity is the appearance of the deviation of bilateral ureters. This typically occurs in retroperitoneal fibrosis. In this condition, there is medial drawing of the ureter due to deposition of fibrous tissue in the lumbosacral junction. Due to involvement of both ureters, the cou...
Article

Mallory Weiss tear

Mallory Weiss tears occur due to violent projection of gastric contents against the lower oesophagus, which results in mucosal and submucosal tear with involvement of the venous plexus.  Clinical presentation Patients present with massive painless haematemesis. Pathology Tears most commonly ...
Article

Mamillopontine distance

Mamillopontine distance is defined as the distance between the inferior aspect of the mammillary bodies to superior aspect of the pons. In normal subjects, it should be >5.5 mm. It is decreased in conditions such as intracranial hypotension: it is one of the helpful quantitative signs helpf...
Article

Manta ray sign

The manta ray sign is a radiographic appearance in bladder exstrophy. It describes wide midline separation of the pubic bones simulating the appearance of a manta ray swimming towards you 1. Differential diagnosis On a plain radiograph consider: open book pelvic injuries: the smooth arc of th...
Article

Marcus Gunn pupil

Marcus Gunn pupil, also known as afferent pupillary defect, is a nonspecific finding that indicates partial optic nerve dysfunction. It is mainly due to unilateral optic neuropathy, or rarely optic chiasm or optic tract lesions. In response to light input to the affected eye, both eyes do not c...
Article

MCA dot sign

The middle cerebral artery (MCA) dot sign is seen on CT of the head and represents the cross-sectional M2 equivalent of the hyperdense MCA sign. Rather than imaging a length of middle cerebral artery (typically the M1 segment), the dot sign represents a thromboembolus within a segmental branch o...
Article

Medial stripe sign

Medial stripe sign refers to an area of increased lucency at the interface of the medial lung and the mediastinum in case of medial pneumothorax. A small volume of pneumothorax generally accumulates anteriorly or medially which can be difficult to detect hence this sign holds a certain significa...
Article

Melting sign

The melting ice cube sign describes the resolution of pulmonary haemorrhage following pulmonary embolism (PE).  When there is pulmonary haemorrhage without infarction following PE, the typical wedge-shaped, pleural-based opacification (Hampton's hump) resolves within a week while preserving its...
Article

Mercedes-Benz sign

The Mercedes-Benz sign describes a star-shaped pattern of gas-fissuring within gallstones initially described on an abdominal radiograph 2. Fissures, usually fluid-filled, are present in close to 50% of gallstones. Less than half of these fissured gallstones contain some amount of gas 1. The ra...
Article

Metaphyseal flaring

Metaphyseal flaring is a radiological sign seen in long bones referring to narrowing of the diaphysis and widening of the metaphysis. It is also known as metaphyseal cupping and Erlenmeyer flask deformity. It can be seen in various disorders such as: rickets achondroplasia craniometaphyseal ...
Article

Meth mouth

Meth mouth is the name given to the overt dental disease that is one of the signs of methamphetamine use. Clinical presentation Clinical examination often reveals blackened, stained, rotting or crumbling teeth. Serial studies only a few years apart may show a striking deterioration in the pati...
Article

Mickey mouse appearance

In medical imaging literature, a mickey mouse appearance has been given to imaging features that depict that of a Mickey mouse when viewed from the front. It has been described with: anencephaly 2 progressive supranuclear palsy 1 synonymously with a finger in glove sign the flared shape of t...
Article

Middle cerebellar peduncle sign

The middle cerebellar peduncle (MCP) sign is a feature of a number of conditions, particularly neurodegenerative diseases, and most commonly associated with fragile X-associated tremor/ataxia syndrome (FXTAS) although many other conditions are recognised.  It represents high T2 signal in the mi...
Article

Molar tooth sign - abdominal

Abdominal molar tooth sign refers to the appearance of contrast media spillled out of the urinary bladder on CT cystography after extraperitoneal bladder rupture. Contrast flows out of the ruptured bladder, occupying preperitoneal cavum Retzii and surrounds the bladder in the shape of a molar t...
Article

Molar tooth sign - CNS

The molar tooth sign refers to the appearance of the midbrain in axial section which the elongated superior cerebellar peduncles give the midbrain an appearance reminiscent of a molar or wisdom tooth. It was initially described in Joubert syndrome and related disorders (JSRD) 2, but is now reco...
Article

Mondor sign

Mondor sign refers when there is a haematoma that is formed and extending distally along the sole of the foot. It is considered pathognomonic for calcaneal fracture. It is detected on CT. See also Calcaneal fracture Lover fracture Mondor disease
Article

Monod sign

Monod sign (often spelt Monad sign) simply describes air that surrounds a mycetoma (most commonly an aspergilloma) in a pre existing pulmonary cavity 1-3. It should not be confused with the air crescent sign which is seen in recovering angioinvasive aspergillosis 4. The air crescent sign herald...
Article

Moose head appearance

The moose head 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 the viking helmet sign.
Article

More black sign

The more black sign is a normal finding in lateral chest x-ray, and refers to the gradual increased apparent radiolucency (blackness) of the vertebral bodies, when proceeding from upper to lower chest. This is due to the increased proportion of the chest comprised of air containing lungs over di...
Article

Morning glory sign

Morning glory sign of progressive supranuclear palsy (PSP) and multisystem atrophy, not to be confused with morning glory syndrome, refers to the appearance of the midbrain on axial imaging 1. Graphically this is identified on a axial image at the level of the midbrain by drawing 1:   a horizo...
Article

Mosaic attenuation pattern in lung

Mosaic attenuation is the description given to the appearance at CT where there is a patchwork of regions of differing attenuation.  It is a non-specific finding, which may be seen in any of the following: obstructive small airways disease: low attenuation regions are abnormal and reflect decre...
Article

Mosaic pattern of bone

The mosaic bone pattern, also referred to as the jigsaw pattern, of bone is seen in Paget disease, where thickened, disorganized trabeculae lead to areas of sclerosis are interspersed with lucent and more normal bone. See also Other Paget disease related signs: blade of grass sign tam o' sha...
Article

Mother in law sign

The mother in law sign is perhaps uncharitably (depends on the mother in law I suppose) used to describe lesions that enhance early during the arterial phase and remain opacified well after the venous phase. The joke is that a mother in law comes early and stays late.  It is most frequently equ...
Article

Moulage sign

The moulage sign is related to sprue, in particular coeliac disease. It occurs where there is a dilated jejunal loop with complete loss of jejunal folds 1. It is said to appear like a tube into which wax has been poured. History and etymology Moulage (French: casting/moulding) is the art of ap...
Article

Mount Fuji sign

Mount Fuji sign is seen on cross sectional imaging and implies tension pneumocephalus is present.  The sign refers to the presence of air (pneumocephalus) between the tips of the frontal lobes giving the appearance of Mount Fuji. It suggests that the pressure of the air is at least greater than...
Article

Mushroom cap sign

Mushroom cap sign is one of the important signs of deep rectosigmoid endometriosis seen on T2 weighted MRI sequence. It indicates the submucosal involvement in rectosigmoid region. Radiographic appearance MRI Hypertrophic muscularis propria appears as heterogeneous low signal intensity surrou...
Article

Mushroom sign of pyloric stenosis

The mushroom sign (also called umbrella sign) is a radiological sign described in pyloric stenosis on barium examination. This sign refers to the impression made by the hypertrophic pylorus on the duodenal cap. See also shoulder sign cervix sign of pyloric stenosis target sign of pyloric st...

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