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 continuously improved upon by countless contributing members. Our dedicated editors oversee each edit for accuracy and style. Find out more about articles.
1,141 results found
Article
60/60 sign (echocardiography)
The 60/60 sign in echocardiography refers to the coexistence of a truncated right ventricular outflow tract acceleration time (AT <60 ms) with a pulmonary arterial systolic pressure (PASP) of less than 60 mmHg (but more than 30 mmHg). In the presence of right ventricular failure, it is consisten...
Article
Aaron sign
Aaron sign is a clinical sign that is defined as a feeling of distress and pain in the epigastric, umbilical and praecordial regions, on steady pressure over McBurney point, it is suggestive of chronic appendicitis.
History and etymology
Charles Dettie Aaron (1866–1951) was an American gastroe...
Article
Abnormally eccentric gestational sac
An eccentrically-located gestational sac towards the fundus of the uterus is the normal sonographic appearance, however, an abnormally eccentric gestational sac on ultrasound may be apparent due to a number of causes:
interstitial ectopic pregnancy 1
normally implanted pregnancy in a
bicornu...
Article
Absent bow tie sign (knee)
The absent bow tie sign represents the loss of the normal appearance of the menisci on parasagittal MRI images and is suggestive of meniscal injury.
Normally the medial and lateral menisci appear as low signal triangular structures linked by a thin body located between the femoral condyles and ...
Article
Absent nasal bone
In a fetal sonographic assessment, an absent nasal bone is a feature that can sometimes be used as a surrogate marker for fetal aneuploidy.
Radiographic assessment
Antenatal ultrasound
It is assessed on a midline sagittal view. In this section, the nasal bone is often seen as a bright echogen...
Article
Absent posterior limb sign
The absent posterior limb sign is one of the main MRI findings of prognostic significance in term neonates with suspected hypoxic-ischemic brain injury. An absent posterior limb sign is defined as loss of the normally distinct hyperintensity on T1-weighted images in the posterior part of the pos...
Article
Acceleration index
Acceleration index is an indirect sonographic sign to assess renal artery stenosis 1.
Usage
Acceleration index is used in the Doppler assessment of the renal arteries when assessing for renal artery stenosis.
Measurement
Acceleration index is calculated by subtracting the initial systolic ve...
Article
Accordion sign (colon)
The accordion sign (also known as concertina sign) is seen on CT of the abdomen and refers to the similarity between the thickened edematous wall of pseudomembranous colitis and the folds of an accordion. This appearance is the result of hyperemic enhancing mucosa stretched over markedly thicken...
Article
Ace-of-spades sign (heart)
Ace-of-spades sign refers to the pathognomonic configuration of the left ventricle as seen in apical hypertrophic cardiomyopathy 1-3.
It consists of marked ventricular wall thickening at the apex resulting in cavity narrowing at the apex with a relatively normal appearance of the mid-ventricula...
Article
Adie pupil
Adie pupil (also known as tonic pupil) is caused by idiopathic degeneration of the ciliary ganglion, which sometimes occurs following a viral or bacterial illness. It is usually unilateral and typically affects young females 1.
Adie pupil represents a large dilated "tonic pupil", which does not...
Article
Adrenal congestion
Adrenal congestion is considered to possibly precede non-traumatic adrenal hemorrhage 1, and refers to adrenal gland thickening and peri-adrenal fat stranding on imaging, which are nonspecific findings. However, more research is needed to elucidate this entity.
A possible explanation for adrena...
Article
Air bronchogram
An air bronchogram occurs when endobronchial air is visible against a background of increased lung opacity. Expulsion of gas from the parenchyma is partial or complete and can be due to atelectasis and/or replacement by fluid, inflammatory cells, blood, tumor or interstitial thickening. The pers...
Article
Air bubble sign (tension pneumocephalus)
The air bubble sign is seen on CT of the brain and represents multiple small foci of air within the subarachnoid space, especially the Sylvian fissure.1
Although described as a sign of tension pneumocephalus it is also seen in pneumocephalus without elevated pressures.2
It should not be confus...
Article
Air crescent (lung)
Air crescent describes the crescent of gas between an intra-cavitary mass and the cavity wall. The intra-cavitary mass may be due to necrotic tissue or a fungus ball 6.
Terminology
The descriptor Monod sign 2 is commonly used to describe the combination of a gas crescent and a mobile fungus ba...
Article
Air-tissue interface sign - breast
Air-tissue interface sign on mammography in cases where the mass is located on the skin helps to distinguish it from intra-mammary mass so that in the skin-based lesion, due to the presence of air in the vicinity of a part of the margin, its border is pretty sharp and a narrow lucent rim around ...
Article
Air trapping
Air trapping is the retention of excess gas in lung distal to one or more obstructed airways. Subnormal reduction in volume and subnormal increase in attenuation on end-expiratory CT are diagnostic findings and the affected areas are typically sharply demarcated. Reactive vasoconstriction is oft...
Article
A-line (ultrasound)
An A-line is an ultrasonographic artifact appreciated during the insonation of an aerated lung. 1
The term may be applied to the horizontal, echogenic long path reverberation artifacts that occur beneath the pleural line at multiples of the distance between the ultrasound probe and the visceral...
Article
Alphabet inspired signs
There are many alphabet-inspired signs in radiology:
A line (US artifact)
C sign (MSK)
delta sign
delta sign (brain)
double delta sign (MSK)
empty delta sign (brain)
D sign (cardiac)
E sign
gamma sign (bicornuate uterus)
G sign (gout)
H-shaped vertebrae
H sign
H sign (sacrum)
H sig...
Article
Amniotic fluid sludge (ultrasound)
Amniotic fluid sludge is a finding in obstetric transvaginal ultrasound scanning. Defined as free-floating hyperechogenic material in close proximity to the cervical internal os within the amniotic cavity of women with intact fetal membranes 1. It images as a dense, homogenous mass 2.
Pathology...
Article
Anderson triad
The Anderson triad consists of the clinical findings of tachypnea and abdominal rigidity with lower thoracic or epigastric pain, associated with subcutaneous emphysema, which is usually related to esophageal rupture.
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