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.
More than 200 results
Article
Tissue weighting factor
The tissue weighting factor (WT) is a measure of relative contribution of an organ or tissue to the total health detriment due to stochastic effects resulting from a uniform irradiation of the entire body 1. It accounts for the variable sensitivity to ionizing radiation and size of a given organ...
Article
Gray (SI unit)
The gray (symbol Gy) is the SI unit of absorbed dose. It is defined as the absorption of one joule of energy originating from ionizing radiation per kilogram of matter 1,2, i.e. Gy = 1 J/kg.
Terminology
One gray is a large unit and is usually used with a prefix, e.g. milligray (mGy), microgray...
Article
Effective dose
The effective dose (E) is a hypothetical equivalent dose uniformly applied to the whole body, which would result in the same health detriment through stochastic effects as the partial-body exposition being considered. It is calculated by summating the equivalent doses (HT) delivered to irradiate...
Article
Rem (unit)
The rem (an acronym for roentgen equivalent man) was the cgs unit of effective dose and was officially replaced by the sievert many years ago (1 Sv = 100 rem) 1.
One rem was a large quantity of radiation, and therefore for practical day to day use the millirem (mrem), representing one-thousand...
Article
Sievert (SI unit)
The sievert (symbol Sv) is the SI unit of equivalent dose and effective dose. It is dimensionally equivalent to one joule per kilogram 1.
Although sievert and gray (Gy) are dimensionally equivalent SI units of dose, they cannot be used interchangeably. Sievert is applicable only in context of r...
Article
Crawford and Schorry classification of congenital tibial dysplasia
The Crawford and Schorry classification, sometimes referred to simply as the Crawford classification, is used to describe congenital tibial dysplasia.
Usage
The Crawford and Schorry classification is mostly descriptive and does not offer much guidance on the treatment of the condition 1-3.
Cl...
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Crawford classification (disambiguation)
There are two distinct and unrelated classification systems which are commonly referred to as the Crawford classification:
Crawford classification thoracoabdominal aneurysms
Crawford (and Schorry) classification of congenital tibial dysplasia
Article
Traumatic posterior fossa subdural hematoma in neonates
Traumatic posterior fossa subdural hematoma (TPFSH) in neonates is a traumatic complication at birth. It is extremely rare. Although traumatic posterior fossa subdural hematoma is a very rare condition, it is clinically critical as it may compress the ventricular system or the brainstem and can ...
Article
Impending testicular infarction
Impending testicular infarction is a rare complication of epididymo-orchitis which can be diagnosed by absence or reversal of diastolic flow in intra-testicular arteries 1,2.
Clinical presentation
Patients may present with worsening of symptoms of epididymo-orchitis despite proper treatment.
...
Article
Cardiac ischemia protocol (MRI)
The cardiac MRI ischemia or stress protocol encompasses a set of different MRI sequences for the assessment of myocardial ischemia.
Note: This article aims to frame a general concept of a cardiac MRI protocol in the setting of vasodilator stress perfusion testing.
Protocol specifics will vary ...
Article
Ganglioneuroma
Ganglioneuromas are fully differentiated neuronal tumors that do not contain immature elements and potentially occur anywhere along with the peripheral autonomic ganglion sites.
On imaging, usually, they present as well-defined solid masses and can be quite large at presentation. Generally, th...
Article
Video
Video files are useful in a very limited number of situations, but should not be used for routine stacks of scrollable images (such as CT or MRI).
When to use video
Rarely is video mandatory, but some studies do benefit from this. The reasons to use video include:
ultrasound cine clips
car...
Article
Buffalo hump
A buffalo hump describes lipomatosis of the posterior neck and interscapular region. It may be idiopathic or caused by a variety of underlying medical conditions:
idiopathic
Cushing syndrome 1
Cushing disease
steroid therapy
HIV-associated lipodystrophy 2
Madelung disease (usually in the s...
Article
de Carvalho index of patellar height
The de Carvalho index is used to measure patellar height and identify patella alta. It is similar to the Caton-Deschamps index and relies upon the length of the patellar articular surface and its distance from the tibia. This helps in reducing erroneous measurements in those with long patellar b...
Article
Iliotibial band
The iliotibial band (ITB) or tract is a thick band of fascia along the lateral aspect of the thigh.
Gross anatomy
The ITB is a thickening in the fascia lata. Superiorly, it splits to enclose and anchor the aponeurosis of tensor fasciae latae and posteriorly most of the tendon of gluteus maximu...
Article
Magnetic Resonance Index of Activity (Crohn disease)
The Magnetic Resonance Index of Activity (MaRIA) scoring system assesses ileocolonic Crohn disease activity on contrast-enhanced MRI enterography. The segmental index represents disease severity in one bowel segment whilst assessing six defined anatomic regions; these can be combined into a glob...
Article
Clermont score (Crohn disease)
The Clermont score or DWI-MaRIA scoring system assesses ileocolonic Crohn disease activity on noncontrast MRI enterography. It is based on the earlier Magnetic Resonance Index of Activity (MaRIA) index, however, it does not require intravenous gadolinium by substituting relative contrast enhance...
Article
MELD score (chronic liver disease)
The MELD score (Model for End-stage Liver Disease) is a classification used to grade chronic liver disease in preparation for liver transplantation in adults. The score has prognostic value in terms of three-month mortality.
Usage
Three-month mortality of patients with chronic liver disease pe...
Article
Medical abbreviations and acronyms (P)
This article contains a list of commonly used medical abbreviations and acronyms that start with the letter P and may be encountered in medicine and radiology (please keep the main list and any sublists in alphabetic order).
A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R ...
Article
Chiari malformations
Chiari malformations are a group of structural conditions characterized by congenital caudal 'displacement' of the cerebellar tonsils below the foramen magnum, often with associated caudal displacement of brainstem.
Terminology
The description of 'malformation' may not be accurate for Chiari 0...
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