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.
16,873 results found
Article
Absent yolk sac
Absence of the yolk sac in the presence of an embryo on a transvaginal ultrasound is considered abnormal, and in general is associated with subsequent embryonic death.
See also
yolk sac
Article
Absorbed dose
Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation. It is equal to the energy deposited per unit mass of a medium, and so has the unit joules (J) per kilogram (kg), with the adopted name of gray (Gy) where 1 Gy = 1 J.kg-1.
The absorbed dose is not a good indica...
Article
Absorption (ultrasound)
In ultrasound, absorption is the reduction in intensity of the sound waves as it passes through tissue. Most of the energy lost is in the form of heat.
Article
Abusive head trauma
Abusive head trauma is a term that is used for inflicted head injury that has occurred by either shaking, impact head trauma, or both, as part of the spectrum of non-accidental injury (NAI).
Pathology
Intracranial injuries
Subdural hemorrhage in a child should be viewed with suspicion. Most o...
Article
Aceruloplasminemia
Aceruloplasminemia is an autosomal recessive type of neurodegeneration with brain iron accumulation and disorder of iron metabolism caused by a mutation in the ceruloplasmin (CP) gene resulting in the production of dysfunctional ceruloplasmin.
Epidemiology
Aceruloplasminemia is a very rare dis...
Article
Acalculia
Acalculia (or acquired dyscalculia) represents the acquired loss of the ability to perform simple arithmetic tasks secondary to CNS pathology. It is not to be confused with developmental dyscalculia, which is a different entity and represents developmental disturbance of computational ability.
...
Article
Acanthosis nigricans
Acanthosis nigricans is a cutaneous disorder characterized by symmetric hyperpigmented velvety plaques on the neck, axillae, antecubital and popliteal fossae, inframammary, and groin areas. It is associated with acquired lipodystrophy.
Pathology
The benign form of acanthosis nigricans is assoc...
Article
Acardiac twin
An acardiac twin, also known a recipient twin, refers to the haemodynamically disadvantaged twin of a twin-pair in the setting of twin reversed arterial perfusion (TRAP) sequence. The acardiac twin undergoes secondary atrophy and is non-viable.
Epidemiology
Acardiac twinning is thought to affe...
Article
Acardius acormus
Acardius acormus is a morphologic subtype of an acardiac twin in a twin reversed arterial perfusion (TRAP) sequence. This entity is the least common of the four subtypes, comprising of cephalic structures only. It is seen in approximately 5% of cases.
Article
Acardius amorphus
Acardius amorphus is a morphologic subtype of the acardiac twin in a twin reversed arterial perfusion (TRAP) sequence. This entity is the least well differentiated of the four subtypes, comprising of an amorphus mass with no recognizable structures. It is seen in approximately 20% of cases.
Article
Acardius anceps
Acardius anceps is a morphologic subtype of the acardiac twin in a twin reversed arterial perfusion (TRAP) sequence. This entity is the most well differentiated of the four subtypes, with a partly formed head, thorax, and abdomen. It is seen in approximately 10% of cases.
Article
Acardius anephus
Acardius anephus is a morphologic subtype of an acardiac twin in the twin reversed arterial perfusion (TRAP) sequence. In this entity, no cephalic or structures are present, but the lower limbs are preserved. This is the most common subtype, seen in 60-75% of cases1.
Article
ACC/AHA classification of coronary lesions
ACC/AHA classification of coronary lesions is a system used to classify coronary arterial calcific plaque burden. It is classified as
type A
discrete (<10 mm)
concentric
nonangulated segment <45º
smooth contour
little or no calcification
less than totally occlusive
not ostial in locatio...
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
Accepted abbreviations
There are a number of accepted abbreviations that we use on Radiopaedia.org. We would like the site to be as standardized as possible and we have therefore chosen our accepted abbreviations and would ask that where possible these are used:
a.k.a. not aka (short for "also known as")
c. short fo...
Article
Access guidewires
Access guidewires are interventional procedures wires used during the first steps of interventions, to secure stable access and sheaths/catheter insertion. They are quickly exchanged for a navigation wire thereafter.
The most common access wires are1:
Cope Mandril wire
Nitrex wire
Properties...
Article
Accessory abductor digiti minimi muscle (hand)
An accessory abductor digiti minimi (ADM) muscle is the most common accessory muscle of the hand and wrist, found in 24% of individuals on the hypothenar eminence. When present it is one of the intrinsic muscles of the hand.
Summary
origin:
antebrachial fascia passing anteriorly to Guyon cana...
Article
Accessory and cavitated uterine mass
Accessory and cavitated uterine mass (ACUM), also known as non-communicating accessory uterine cavity or cystic adenomyoma, is a rare uterine anomaly comprised of an accessory uterus-like mass in the uterus along the wall but with no communication to the main uterus.
Clinical presentation
This...
Article
Accessory anterior inferior tibiofibular ligament
The accessory anterior inferior tibiofibular ligament (accessory AITFL), also known as Bassett's ligament, is an anatomical variant present in many ankles. Pathological thickening of the accessory ligament is seen in the setting of inversion injury that causing the pain due to mild anterior inst...
Article
Accessory appendicular artery
The accessory appendicular artery, also known as the artery of Seshachalam, is a branch of the posterior cecal artery. It arises from the ileocolic artery, and runs in the mesoappendix.
The exact prevalence of this accessory artery and its impact upon the risk of appendicitis varies among studi...
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