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.

903 results found
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Falling snow sign (spermatocele)

The falling snow sign describes the appearance of movement of internal echoes in spermatoceles away from the transducer, resulting in an appearance similar to falling snow when color Doppler is applied. The sign can be used to aid in the diagnosis of a spermatocele.
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Fascial tail sign

The fascial tail sign is the linear extension along the fascia/muscular aponeurosis from a deeper tumor. Although classically described in desmoid tumors 1, the sign can be seen in other soft tissue tumors: fibrosarcoma leiomyoma neurofibroma myxofibrosarcoma 5 undifferentiated sarcoma (fo...
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Fascicular sign

Fascicular sign is a finding on T2-weighted MRI images that suggests a lesion of neurogenic origin. It is characterized by multiple small ring-like structures with peripheral hyperintensity representing the fascicular bundles within the nerves. It is found in various neurogenic tumors, includin...
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Fat halo sign (inflammatory bowel disease)

The fat halo sign refers to a feature seen on CT examination of the abdomen, and represents infiltration of the submucosa with fat, between the muscularis propria and the mucosa. It is characterized by an inner (mucosa) and outer (muscularis propria and serosa) ring of enhancing bowel wall along...
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Fat ring sign (mesenteric panniculitis)

The fat ring sign (also known as a fat halo sign) describes preservation of fat around the mesenteric vessels and around soft tissue nodules on a background of diffuse fat stranding in patients with mesenteric panniculitis or mesenteric lipomas.  This finding may help distinguish mesenteric pan...
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Fat stranding on CT

Fat stranding is a common sign seen on CT wherever fat can be found. It is most commonly seen in abdomen/pelvis, but can also be seen in retroperitoneum, thorax and subcutaneous tissues. It can be helpful in localizing both acute and chronic pathology. Radiographic features CT Fat stranding c...
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Fat stranding (summary)

This is a basic article for medical students and other non-radiologists Fat stranding is a sign that is seen on CT. It describes the change in attenuation of fat around an inflamed structure and is a very helpful signpost for intra-abdominal pathology. Reference article This is a summary arti...
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FBI sign (lipohemarthrosis)

The FBI sign is an acronym referring to the components that form a lipohemarthrosis. It stands for: fat blood interface
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Feeding vessel sign

Feeding vessel sign consists of a distinct vessel leading directly to a nodule or a mass. This sign indicates either that the lesion has a haematogenous origin or that the disease process occurs near small pulmonary vessels.  A number of vessel-related non-neoplastic disorders of the lung produ...
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Female prostate sign

Female prostate sign is a characteristic imaging sign seen in patients with a large urethral diverticulum.  A large urethral diverticulum in females surrounds the urethra, and elevates the base of the bladder, mimicking the typical appearance of enlarged prostate in males.
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Festooned dura (CSF leak)

The festooned appearance of the spinal dural sac has been described in cases of CSF leak resulting in the combination of epidural fluid and craniospinal hypotension/hypovolemia. The theca collapses down upon the cord but kept attached at multiple points by the epidural ligaments 1. 
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Fetal cardiothoracic circumference ratio

Fetal cardiothoracic (C/T) circumference ratio is a parameter than can be used in assessment of fetal cardiac and thoracic/chest wall anomalies. It is the ratio of the cardiac circumference to the thoracic circumference and may be easily measured on fetal ultrasound/echocardiography.  Radiograp...
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Fetal maceration

Fetal maceration is one of the signs of fetal death. It is a destructive aseptic process that appears between 12 to 24 hours after fetal death. It may not be seen in a pregnancy earlier than 6 months. In this a separation of the skin from head and trunk occurs giving a bubble-like appearance.
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Figure 3 sign (aortic coarctation)

The figure 3 sign is seen in aortic coarctation and is formed by prestenotic dilatation of the aortic arch and left subclavian artery, indentation at the coarctation site (also known as the "tuck"), and post-stenotic dilatation of the descending aorta. On barium studies of the esophagus in pati...
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Figure of eight appearance

The following lesions may resemble a figure of eight (sometimes referred to as snowman shaped): supracardiac variety of total anomalous pulmonary venous return 1 pituitary macroadenoma with suprasellar extension 2 intraspinal neurofibroma with extraspinal extension through neural foramina di...
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Finger clubbing

Finger clubbing, also called "drumstick fingers", is a common clinical sign in patients with heart or lung disease. The term is used to describe an enlargement of the distal phalanges of the fingers, giving them a drumstick or club-like appearance.  Clinical Presentation Finger clubbing presen...
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Finger in glove sign (lung)

The finger in glove sign can be seen on either a chest radiograph or CT chest and refers to the characteristic sign of a bronchocoele. The same appearance has also been referred to as: rabbit ear appearance mickey mouse appearance toothpaste-shaped opacities Y-shaped opacities V-shaped opac...
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Fishhook ureters

Fishhook ureters, also known as J-shaped ureters or hockey stick ureters describe the appearance of the distal ureter in patients with significant benign prostatic hypertrophy. It has also been used to describe the appearance of a retrocaval ureter  in type 1 or low loop variety. As the right ur...
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Fishtail pancreas

Fishtail pancreas (also known as pancreas bifidum or bifid tail of the pancreas) is a rare anatomical variant of the pancreas produced by a branching anomaly during its development. It is named as such due to the fishtail-like appearance of the pancreas. Epidemiology It is a rare anatomical an...
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Fissure for ligamentum teres sign

The fissure for ligamentum teres sign or extrahepatic ligamentum teres sign is a radiographic sign of pneumoperitoneum. It represents the outline of the ligamentum teres (remnant of an obliterated left umbilical vein) with free abdominal gas in a supine patient, as seen on a plain abdominal radi...
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Fistula test

The fistula test is used when examining a patient with recurrent vertigo. A finger is abruptly applied to the external meatus which causes a pulse of air-transmitted pressure. If nystagmus is induced in association with vertigo, it indicates bony destruction within the inner ear e.g. cholesteat...
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Flame sign (spinal cord metastasis)

The flame sign has been described as a helpful MRI sign of spinal cord metastases, enabling them to be distinguished from other enhancing spinal cord lesions (e.g. ependymoma, astrocytoma and hemangioblastoma) 1.  Radiographic features MRI The flame sign is seen on sagittal post contrast T1 w...
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Flat floor of fourth ventricle sign

The flat floor of fourth ventricle sign is useful in detecting a pontine mass and is a sign of mass effect. The normal floor of the fourth ventricle (remember that the floor is anterior) normally slopes upwards towards the midline, with the facial colliculi visible on either side.  It is a non-...
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Flat waist sign

The flat waist sign refers to flattening of the left heart border, specifically the contours of the aortic arch and adjacent pulmonary trunk. It is seen in severe left lower lobe collapse and is caused by leftward displacement and rotation of the heart. It is different to the straight left hear...
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Fleck sign (disambiguation)

The radiographic fleck sign refers to an avulsion fracture in the lower limb at either of two sites: fleck sign (ankle) due to superior peroneal retinaculum injury fleck sign (foot) due to Lisfranc injury
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Fleck sign (foot)

The fleck sign in the foot is a small bony fragment seen in the Lisfranc space (between the base of the 1st and 2nd metatarsal) associated with avulsion of the Lisfranc ligament (at the base of the 2nd metatarsal). It is a very subtle, but important finding, since it predisposes to Lisfranc inju...
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Fleischner sign (disambiguation)

Fleischner sign can refer to two distinctly separate signs: Fleischner sign (enlarged pulmonary artery) Fleischner sign (tuberculosis of ileocecal junction)
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Fleischner sign (enlarged pulmonary artery)

The Fleischner sign refers to a prominent central pulmonary artery that can be commonly caused either by pulmonary hypertension or by distension of the vessel by a large pulmonary embolus. It can be seen on chest radiographs, CT pulmonary angiography (CTPA), and MR pulmonary angiography (MRPA). ...
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Fleischner sign (tuberculosis of ileocecal junction)

The Fleischner sign (also known as the inverted umbrella sign), refers to a widely gaping, thickened, patulous ileocecal valve and a narrowed, ulcerated terminal ileum associated with tuberculous involvement of the ileocecum. See also gastrointestinal tuberculosis Stierlin sign not to be con...
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Flip-flop effect

The so-called flip-flop effect refers to a confusing MRI appearance of the skeletal system and subcutaneous tissues. It is seen in a variety of severe fat depletion conditions responsible for diffuse bone marrow serous atrophy and modification or loss of the subcutaneous fat. Not to be confused...
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Floating aorta sign

The floating aorta sign refers to the displacement of the abdominal aorta away from the vertebral column. It is a radiographic sign of retroperitoneal masses. Radiographic findings On lateral lumbar spine radiographs, the expected location of the posterior aortic wall is expected to be ≤10 mm...
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Floating balls sign

The floating balls sign refers to the appearance of multiple mobile globules/spherules of solid, usually fatty, tissue within an adnexal cyst. It is pathognomonic for ovarian mature cystic teratoma 1,2.  Terminology Alternative names include the meat balls 3 or truffle sign 4. When a single l...
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Floating head appearance

A floating head appearance refers to imaging features observed typically on antenatal ultrasound with certain skeletal dysplasias such as achondrogenesis.   Against the background of a poorly-mineralized spine, a normally ossified skull is seen giving an impression of a floating head.
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Floating viscera sign

The floating viscera sign is an angiographic sign that occurs when there is visualization of branches of the abdominal aorta (e.g. celiac axis, superior mesenteric artery, and renal arteries) during aortography with little or no visualization of the aortic lumen. The floating viscera sign indic...
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Fluid bronchogram sign

The fluid bronchogram sign can be seen on chest CT or ultrasound as the presence of fluid attenuation material within respiratory bronchioles with surrounding collapsed or consolidated lung. The presence of this sign suggests endobronchial obstruction as a precipitating cause for consolidation/...
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Fluid color sign

The fluid color sign is a diagnostic sign to differentiate a pleural effusion from pleural thickening by means of color Doppler ultrasound. In the case of pleural effusion a color signal is seen in the pleural fluid during respiratory and cardiac movement, whereas this color signal is not seen i...
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Fluid sign (vertebral collapse)

The fluid sign is one of the radiological features of osteoporotic fractures, and can be helpful in distinguishing them from metastatic vertebral fractures, as it is seen more often in osteoporotic fractures and is rarely seen in metastatic fractures 1. It is not as helpful as identifying a para...
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Foamy esophagus sign

Foamy esophagus is an appearance seen on a single contrast barium study in Candida esophagitis with associated scleroderma/achalasia (stasis). Pathology Pathophysiologic basis of the foamy esophagus is uncertain. Stasis is a predisposing factor. Foam is produced directly by the fungal organism...
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Focal hepatic hot spot sign

The focal hepatic hot spot sign can be seen on technetium 99m sulfur colloid scans of the liver and spleen, as well as CT studies. Radiographic features It occurs as a focal area of increased radiopharmaceutical uptake in the medial segment of the left hepatic lobe (segment IV) due to superior...
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Fogging phenomenon (cerebral infarct)

The fogging phenomenon is seen on non-contrast CT of the brain and represents a transient phase of the evolution of cerebral infarct where the region of cortical infarction regains a near-normal appearance.  {{youtube:http://www.youtube.com/watch?v=LuX3VV__2w0}} During the first week following...
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Football sign (pneumoperitoneum)

The football sign is seen in cases of massive pneumoperitoneum, where the abdominal cavity is outlined by gas from a perforated viscus. The median umbilical ligament and falciform ligament are sometimes included in the description of this sign, as representing the sutures. Which football is use...
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Fountain sign (acute idiopathic scrotal edema)

The fountain sign is sonographic sign described in acute idiopathic scrotal edema (AISE). It refers to the appearance of the pattern of vascularity seen during transverse color Doppler sonography of the scrotum with both testes together 1. In these transverse views in patients with AISE, marked...
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Fragment-in-notch sign (knee)

The fragment-in-notch sign is closely related to, can be thought of as a failed, double PCL sign, in so far as it represents a meniscal fragment lying in the intercondylar notch, but not paralleling the posterior cruciate ligament (PCL).  Although both signs are most frequently seen in the sett...
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Frimann-Dahl sign

The Frimann-Dahl sign is a diagnostic sign demonstrated when three dense lines, representing the sigmoid walls, are seen converging to the site of obstruction in sigmoid volvulus and associated with empty rectal gas 1. History and etymology Johan Frimann-Dahl (1902-82) was a Norwegian Professo...
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Frostberg inverted 3 sign

Frostberg inverted 3 sign is a radiological sign seen on a barium examination where there is effacement and distortion of the mucosal pattern on the medial wall of the second part of the duodenum due to focal mass and local edema. It is most commonly associated with carcinoma of the head of the ...
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Fruit-inspired signs

There are many fruit-inspired signs in radiology: apple core sign (disambiguation) apple core sign (colon) apple core sign (femur) apple-peel intestinal atresia banana sign banana fracture berry aneurysm bunch of grapes sign lemon sign pear-shaped bladder strawberry gallbladder straw...
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Funneling of the internal cervical os

Cervical funnelling is a sign of cervical incompetence and represents the dilatation of the internal part of the cervical canal and reduction of the cervical length. Greater than 50% funnelling before 25 weeks is associated with ~80% risk of preterm delivery. Radiographic features Good scanni...
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Funnel trachea

Funnel trachea is a colloquialism for a congenital long-segment intrathoracic tracheal stenosis.  The diameter of the trachea immediately below the cricoid is normal, and becomes progressively more stenotic caudally. The posterior, membranous portion of the trachea may be partially or completel...
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Gage sign

The Gage sign is a V-shaped lucent defect at the lateral portion of the epiphysis and/or adjacent metaphysis. It is pathognomonic for Legg-Calve-Perthes disease. It may occur early in the disease and is one of the five indicators of a worse prognosis, which are: Gage sign  calcification later...
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Galaxy sign (lungs)

The so-called galaxy sign, initially described as the sarcoid galaxy, represents a coalescent granuloma seen in a minority of patients with pulmonary sarcoidosis 1. The same appearance can be seen in tuberculosis 2,3. In other words, it represents a mass-like region composed of numerous smaller ...
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Gallbladder ghost triad

Gallbladder ghost triad is a term used on ultrasound studies when there is a combination of three gallbladder features on biliary atresia: atretic gallbladder, length less than 19 mm irregular or lobular contour  lack of smooth/complete echogenic mucosal lining with an indistinct wall The te...
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Garland triad

Garland triad, also known as the 1-2-3 sign or pawnbroker's sign, is a lymph node enlargement pattern on chest radiographs which has been described in sarcoidosis: right paratracheal nodes right hilar nodes left hilar nodes Hilar lymphadenopathy is symmetrical and usually massive. These so-c...
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Garrington sign (teeth)

Garrington sign is thickening of the periodontal ligament/membrane space of involved teeth in the setting of gnathic osteosarcoma. Symmetrical widening of the space can be seen early in the disease process due to infiltration of tumor cells. 
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Genu recurvatum

Genu recurvatum describes the malalignment or deformity of the knee joint with extension beyond neutral (i.e. hyperextension).  Pathology Genu recurvatum can be associated with subluxation or dislocation of the knee joint.  Etiology congenital arthrogryposis multiplex congenita congenital ...
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Geographic skull

A geographic skull is a radiographic appearance which is seen in eosinophilic granuloma (EG) and characterized by destructive lytic bone lesions, the edges of which may be bevelled, scalloped or confluent. See also geographic appearance
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Geyser sign (shoulder)

The geyser sign may occur in some cases of long-standing rotator cuff tear and advanced degenerative change of the shoulder.  Clinical presentation It may present as a pseudotumor above the AC joint. Pathology Chronic rotator cuff degenerative change and full-thickness tearing leads to insta...
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Ghon lesion

Ghon lesion, sometimes called Ghon focus, represents a tuberculous caseating granuloma (tuberculoma) and represents the sequelae of primary pulmonary tuberculosis infection. Terminology Radiologically, this term is used quite loosely to refer to a calcified granuloma; technically, the Ghon les...
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Ghost meniscus

A ghost meniscus, also known as the empty meniscus sign, refers to a large radial tear that has completely transected the meniscus or, alternatively, previous meniscectomy. Radiographic features MRI On MRI knee when the slice plane is exactly in line with the meniscal tear this can produce ei...
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Ghost sign (cervical spine)

The ghost sign is a feature that has been described in a clay shoveler fracture as seen on the AP projection of a cervical spine radiograph. It is caused by the appearance of a "double spinous process" on C6 or C7 resulting from caudal displacement of the avulsed spinous process fragment, giving...
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Ghost sign (Charcot joint)

The ghost sign is seen when a Charcot joint is complicated by an osteomyelitis. It is most commonly seen in the setting of a diabetic foot.  It refers to the poor definition of the margins of a bone on a T1 weighted image, which reappears after contrast injection 1.
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Ghost vertebra

Ghost vertebra is a sign, that is generally used synonymously with bone-within-a-bone vertebra, and as such, the causes form a subset of those causing bone within a bone appearance 2: Thorotrast administration: bone within a bone appearance due to temporary growth arrest 1 stress line rickets...
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Ginkgo leaf sign (disambiguation)

The ginkgo leaf sign can refer to: ginkgo leaf sign (chest) of chest wall surgical emphysema ginkgo leaf sign (spine) of spinal meningioma
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Ginkgo leaf sign (subcutaneous emphysema)

The ginkgo leaf sign of the chest, also referred as the ginkgo leaf sign of subcutaneous emphysema, is a radiographic appearance seen with extensive subcutaneous emphysema of the chest wall. Gas outlines the fibers of the pectoralis major muscle and creates a branching pattern that resembles the...
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Giraffe pattern

Giraffe pattern (also known as the pseudonodular appearance) is a distinctive ultrasound appearance characteristic of Hashimoto thyroiditis. Bonavita originally described a thyroid gland with multiple echogenic nodules, separated from one another by bands of hypoechogenicity, reminiscent of a gi...
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Girdlestone procedure

The Girdlestone procedure (also known as a femoral head ostectomy or Girdlestone resection arthroplasty) is an excision arthroplasty of the hip. The procedure inevitably results in limb shortening. Indications  peri-prosthetic infection aseptic loosening recurrent dislocation failed interna...
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Glenoid labrum ovoid mass sign

The glenoid labrum ovoid mass (GLOM) sign (seen on MRI) is useful when a torn anterior glenoid labrum retracts superiorly. Seen typically on a T2 axial image through the glenohumeral joint as a low signal ovoid mass anterior to the glenoid labrum. Sometimes this can be the only sign of a torn la...
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Goblet sign (ureter)

The goblet sign, also known as the champagne glass sign, refers to the appearance of the ureter when it is focally dilated by an intraluminal mass. It is best seen when the ureter is opacified by retrograde contrast (retrograde ureterogram). Presence of this sign indicates the pathology to be ch...
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Golden arches sign (knees)

The Golden arches sign is a nuclear medicine sign often seen on bone scan in patients with total knee prosthesis. The femoral condylar prosthesis results in two central photopenic regions with two 'hot' arches formed around the periprosthetic region. This finding is non-specific and may sugges...
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Golden S-sign (lung lobe collapse)

The Golden S-sign is seen on both PA chest radiographs and on CT scans. It is named because this sign resembles a reverse S shape, and is therefore sometimes referred to as the reverse S-sign of Golden. Although typically seen with right upper lobe collapse, the S-sign can also be seen with the...
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Grey cortex sign (stress fracture)

The grey cortex sign was described as an early sign of stress (fatigue) fractures on plain radiographs and refers to subtle ill-definition/lucency of the cortex at the site of microfracture. However, plain radiography is insensitive (~25%, range 15-25%) for the detection of early-stage injuries....
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Griesinger sign (mastoid)

The Griesinger sign refers to edema of the postauricular soft tissues overlying the mastoid process as a result of thrombosis of the mastoid emissary vein. It is a complication of acute otomastoiditis and may be associated with dural sinus occlusive disease (DSOD). It is said to be a pathognomon...
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Gull-wing appearance (phalanges)

The gull-wing appearance (also known as seagull erosions) is seen in erosive osteoarthritis (EOA), typically on posteroanterior radiographs (of the hands/fingers) and is highly specific.  The combination of cartilage space loss, central subchondral erosions, and marginal osteophyte proliferatio...
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Gut signature sign

The gut signature sign is an ultrasound term used to describe the appearance of the gastrointestinal wall. Radiographic features  Ultrasound The bowel wall has five layers, composed of alternating hyperechoic and hypoechoic appearances. Anatomically these layers are as follows (innermost to o...
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Guttman test (larynx)

The Guttman test is a clinical test relating to the function of the larynx. In normal subjects, frontal pressure on the thyroid cartilage lowers the tone of voice produced and lateral pressure produces a higher tone of voice. The opposite is true with paralysis of the cricothyroid muscle.
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Hematocrit effect

The hematocrit effect with fluid-fluid levels is the result by layering of heavier cellular elements of blood located dependent to a liquid supernatant. It can be seen on CT or MRI. It is most frequently seen in the setting of anticoagulation therapy or coagulopathy. See also signal flare phen...
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Hemorrhage exclusion sign (prostate)

The hemorrhage exclusion sign can be a useful MRI finding following prostate biopsy. Pathology The normal prostate produces high concentrations of citrate, which among other properties, acts as an anticoagulant 1. As tumor cells are dysfunctional, they will produce lower levels of citrate than...
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Hemosiderin cap sign

The hemosiderin cap sign refers to an MR imaging feature in some spinal tumors where a cap of T2 hypointense hemosiderin is above and/or below the tumor due to previous hemorrhage.  It is most often associated with spinal cord ependymomas (20-33% of cases) 1. It may also be seen in hemangioblas...
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Hair on end sign (mnemonic)

The hair on end sign refers to a radiographic appearance of the diploic space of the skull vault which results from a thickening of trabeculae as the diploic space expands. These trabeculae are perpendicular in orientation, interspersed by radiolucent marrow hyperplasia along the skull vault. I...
Article

Hairy kidney sign (Erdheim-Chester disease)

The hairy kidney sign refers to the soft tissue rind of perirenal infiltration seen on cross-sectional imaging studies in Erdheim-Chester disease, and is considered to be pathognomonic of this disease. The ‘‘hairy’’ description refers to the associated thickening of the bridging perirenal septa ...
Article

Hairy pleural plaque

Hairy pleural plaques are a manifestation of asbestos-related disease. They arise from the visceral pleura, typically from an interlobar fissure. The hairiness stems from short radially-oriented linear regions of fibrosis extending from the plaque into the adjacent lung parenchyma. Compared to ...
Article

Halberd pelvis

A halberd pelvis refers to a pathognomonic appearance of the pelvis seen in metatropic dysplasia, a rare form of spondyloepimetaphyseal dysplasia. hypoplastic ilia with narrow sacrosciatic notches horizontal acetabular roofs with small associated notches superior to their lateral borders prom...
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Halo sign (chest)

The halo sign in chest imaging is a feature seen on lung window settings (typically HRCT), ground glass opacity surrounding a pulmonary nodule or mass and represents hemorrhage. It is typically seen in angioinvasive aspergillosis. Pathology Histopathologically, it represents a focus of pulmona...
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Halo sign (osseous)

Halo sign in bone imaging imaging refers to a presence of a hyperintense rim around the osseous lesion on T2-weighted MRI, which showed to be an indicator of a metastatic lesion 1.
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Hampton hump

Hampton hump refers to a dome-shaped, pleural-based opacification in the lung most commonly due to pulmonary embolism and lung infarction (it can also result from other causes of pulmonary infarction (e.g. vascular occlusion due to angioinvasive aspergillosis). While a pulmonary embolism is expe...
Article

Hampton line

The Hampton line is a thin millimetric radiolucent line seen at the neck of a gastric ulcer in barium studies (profile view), indicating its benign nature. It is caused by a thin line of mucosa overhanging the ulcer's crater. History and etymology It was originally described by Aubrey Otis Ham...
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Hanging noose sign

Hanging noose sign in obstetric imaging is a rarely described but classical finding of a true umbilical cord knot. It demonstrates a transverse section of the umbilical cord surrounded by a loop of umbilical cord and changes in the pressure of the knot can be demonstrated with the fetal movement...
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Harlequin eye deformity

The harlequin eye deformity is characterized by elevation of the superolateral corner of the orbit. It may be seen in unilateral (plagiocephaly) or bilateral (brachycephaly) coronal suture synostosis. History and etymology The term harlequin eye derives from the appearance of the eyes on a har...
Article

Harrison sulcus

The Harrison sulcus or Harrison groove refers to a groove at the lower end of the rib cage seen in young children/infants with abnormally weak bones (e.g. rickets) or chronic respiratory disease (e.g. severe asthma). The lower chest is drawn in with flaring of the rib margin. The exact cause is ...
Article

Hatchet sign (ankylosing spondylitis)

Hatchet sign refers to the limited erosion of the lateral aspect of the humeral head that produces a hatchet-shaped deformity. This finding is typically associated with ankylosing spondylitis. In the absence of osteoporosis and the presence of sclerosis, this sign helps to differentiate it from...
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Hawkins sign (talus)

The Hawkins sign describes subchondral lucency of the talar dome seen in AP view that occurs secondary to subchondral atrophy 6-8 weeks after a talar neck fracture 1. This indicates that there is sufficient vascularity in the talus, and is therefore unlikely to develop avascular necrosis of the...
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Haystack sign (pneumomediastinum)

The haystack sign on chest radiographs in pediatric patients is indicative of pneumomediastinum. The pediatric heart is surrounded above and below with gas, giving it an appearance of a haystack from Monet's paintings. 
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Head cheese sign (lungs)

The head cheese sign refers to a juxtaposition of regions with three (or sometimes more) different densities/regions of different attenuation within the lungs: ground glass opacities (high attenuation) mosaic attenuation pattern (low attenuation) normal lung tissue (normal attenuation) A mix...
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Heel pad sign

Increased heel pad thickness, also known as the heel pad sign, is seen in a number of conditions and relates to an increase in the soft-tissue thickness of the heel pad on lateral ankle radiographs.   The heel pad should normally be <21 mm. However, in certain situations, this is increased: ac...

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