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
Mass attenuation coefficient
The mass attenuation coefficient (MAC) is a quantity used in calculations involving the penetration and energy deposition of photons (such as X-rays and gamma rays) in various materials, including biological tissues and shielding substances.
Definition
The MAC is defined as the linear attenuat...
Article
Technetium-99m agents
Technetium agents based on the technetium-99m (Tc-99m) radioisotope are frequently used agents in medical imaging. A radiopharmaceutical labeled with Tc-99m constitutes a co-ordination complex in which ligands bond to a central atom of Tc-99m by co-ordinate covalent bonds 4 .
The radioactive te...
Article
Photoluminescence
Photoluminescence is a type of luminescence in which energy source for material to absorb, store and convert to light are electromagnetic radiation. Photoluminescent materials have important applications in radiology.
Types
Fluorescence refers to the near instantaneous emission of light follow...
Article
Half-value layer
Half-value layer (HVL) is the thickness of a material required to reduce the air kerma of an X-ray or gamma-ray beam to half its original value. HVL is most accurately measured under narrow-beam geometry, as broad-beam setups allow scatter to reach the detector, leading to an underestimation of ...
Article
Electron
Electrons are fundamental subatomic particles involved in various atomic processes, including those relevant to X-ray production and interactions with matter.
Properties
Subatomic particle with a mass of 9.109 × 10⁻³¹ kg (~0.0005 relative mass to proton).
Carries a -1 charge (-1.6 × 10⁻19 C)....
Article
Linear attenuation coefficient
Linear attenuation coefficient (µ) is a constant that describes the fraction of attenuated incident photons in a monoenergetic beam per unit thickness of a material 1. It includes all possible interactions including coherent scatter, Compton scatter and photoelectric effect 1. Its complement is ...
Article
Incisural line
The incisural line is a midsagittal line connecting the Galenic venous confluence point (which includes the internal cerebral veins, the mesencephalic veins, and the basal veins of Rosenthal) with the base of the dorsum sella 1.
It is a fixed anatomically-based line of reference at the tentoria...
Article
Tuberculum-venous confluence line
The tuberculum-venous confluence line is a midsagittal line formed by the interconnection between the Galenic venous confluence (which includes the internal cerebral veins, the mesencephalic veins, and the basal veins of Rosenthal) and the tuberculum sella 1.
This is an artificial reference lin...
Article
Heterozygous HTRA1-related cerebral small vessel disease
Heterozygous HTRA1-related cerebral small vessel disease, also known as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy type 2 (CADASIL2), is a very rare monogenic cerebral small vessel disease.
Heterozygous HTRA1-related cerebral small vessel disease ...
Article
Pseudo-Meigs syndrome
Pseudo-Meigs syndrome refers to a clinical syndrome of pleural effusion and ascites associated with an ovarian tumor that is not a fibroma or a fibroma-like tumor.
Pathology
Entities that have been reported to result in pseudo Meigs syndrome include
Krukenberg tumors
colon carcinoma metastas...
Article
Jejunoileal diverticulitis
Jejunoileal diverticulitis (plural diverticulitides), an acute inflammation of diverticula of the jejunum or ileum, is much rarer than colonic diverticulitis.
Epidemiology
The jejunum is a more common site of acquired diverticula of the small bowel than the ileum 1.
Clinical presentation
Div...
Article
Small intestine diverticular disease
Small intestine diverticular disease is an uncommon form of diverticular disease and can be classified into disease affecting the:
Meckel diverticulum
Meckel diverticulitis
non Meckel diverticular disease
duodenum - duodenal diverticulosis
duodenal diverticulitis
jejunum and ileum - jejuno...
Article
Gastrinoma
Gastrinomas are the second most common pancreatic endocrine tumor and the most common type in the setting of multiple endocrine neoplasia type I (MEN I).
Epidemiology
Most gastrinomas are sporadic, although some are seen in the setting of multiple endocrine neoplasia type I (MEN I). In general...
Article
Multiple endocrine neoplasia type 1
Multiple endocrine neoplasia type 1 (MEN1), also known as Wermer syndrome, is an autosomal dominant genetic disease that results in proliferative lesions in multiple endocrine organs, particularly the pituitary gland, pancreas, and parathyroid glands.
There are other multiple endocrine neoplas...
Article
Pancreatic neuroendocrine tumors
Pancreatic neuroendocrine tumors (pNET), also known as endocrine tumors of the pancreas, arise from pancreatic ductal stem cells and include some distinct tumors that match the cell type of origin.
Terminology
Pancreatic neuroendocrine tumors have commonly been referred to as "islet cell tumo...
Article
Parathyroid adenoma
Parathyroid adenomas are benign tumors of the parathyroid glands and are the most common cause of primary hyperparathyroidism.
Epidemiology
Associations
There is an association with multiple endocrine neoplasia types I (MEN1) and IV (MEN4).
Clinical presentation
Patients typically present w...
Article
Pituitary microadenoma
Pituitary microadenomas are a minority of all pituitary adenomas but can pose imaging and management challenges on account of their size and protean clinical presentations.
By definition, a microadenoma is less than 10 mm in size. If the same tumor is greater than 10 mm in size, it is then con...
Article
Zollinger-Ellison syndrome
Zollinger-Ellison syndrome (ZES) is a clinical syndrome that occurs secondary to elevated gastrin levels produced by a gastrinoma.
Clinical presentation
The syndrome presents with abdominal pain but can also present with diarrhea or other complaints as well. Diagnosis is often delayed by 5-7 ...
Article
Hip dislocation
Hip dislocation is a relatively rare entity and may be congenital or acquired. It has a relatively high morbidity.
Epidemiology
Hip dislocations account for ~5% of all dislocations 3.
Pathology
There are numerous patterns of dislocation 1,9:
posterior hip dislocation (most common ~85%)
a...
Article
Small bowel follow-through
Small bowel follow-through is a fluoroscopic technique designed to obtain high-resolution images of the small bowel. The motility of the small bowel can also be grossly evaluated.
Indications
The small bowel follow-through can be useful for the evaluation of:
strictures
obstruction
divertic...
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