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
Intravenous MRI contrast agents
Intravenous MRI contrast agents include chelates of paramagnetic ions, both ionic and non-ionic. Gadolinium-based contrast agents (GBCAs) are the most common type. The particulates, sequestered in the liver, spleen, and lymph nodes, the intravascular agents, confined to the blood pool, and tumor...
Article
Zero fill artifact
Zero fill artifact is one of many MRI artifacts and is due to data in the K-space array missing or set to zero during scanning. The abrupt change from signal to no signal results in artifacts in the images showing alternating bands of shading and darkness, often in an oblique direction.
A spike...
Article
Relaxation
Relaxation is the process in which spins release the energy received from a radiofrequency pulse. MRI signal is influenced, among other factors, by different types of relaxation:
T1 relaxation (spin-lattice or longitudinal relaxation)
T2 relaxation (spin-spin or transverse relaxation)
T2* rel...
Article
Superparamagnetism
Superparamagnetic materials consist of individual domains of elements that have ferromagnetic properties in bulk. Their magnetic susceptibility is between that of ferromagnetic and paramagnetic materials.
The figure illustrates the effect of a superparamagnetic material (grey circle) on the ma...
Article
Central point artifact
The central point artifact is a focal dot of increased signal in the center of an image. It is caused by a constant offset of the DC voltage in the receiver. After Fourier transformation, this constant offset gives the bright dot in the center of the image as shown in the diagram.
The axial MRI...
Article
MKS system
The MKS (or mks) system (or meter-kilogram-second) of units predated the current International System of Units (also known as SI), which is the current iteration of the metric system.
Although many fields, including most of the healthcare sciences have abandoned the MKS system for everyday work...
Article
Inversion recovery sequences
Inversion recovery pulse sequences are a type of MRI sequence used to selectively null the signal for certain tissues (e.g. fat or fluid).
Inversion recovery can also generate heavily T1-weighted images and was originally developed for this purpose.
Physics
Basically, an inversion recovery (I...
Article
Fringe field (MRI)
The fringe field is the peripheral magnetic field outside of the magnet core. It is important because it can cause interference with nearby electronic devices, such as pacemakers. Although the strength of the magnetic fields decreases with distance from the core of the magnet, the effect of the ...
Article
Units of measurement
For units of measurement the use of SI units (both base and derived units) in articles and cases on Radiopaedia.org is preferred. This is in line with best scientific practice and helps maintain consistency across the site.
Terminology
By scientific convention:
for eponymous units, the full n...
Article
Schuller's view
Schuller's view is a oblique radiographic projection used to demonstrate the petrous temporal bone, internal auditory canal and bony labyrinth. It has an increasingly limited role in contemporary clinical practice because of the universal use of CT and MRI for imaging the temporal bone.
Patien...
Article
Antoine Henri Becquerel
Antoine Henri Becquerel (1852-1908) was a French scientist renowned for his work and subsequent discovery of radioactivity for which he was awarded the Nobel Prize for physics in 1903.
Early life
Antoine Henri Becquerel was born on 15 December 1852 in Paris, France to a family of nobility and ...
Article
CheckList for EvaluAtion of Radiomics research (CLEAR)
The CheckList for Evaluation of Radiomics Research (CLEAR) is a 58-item reporting guideline designed specifically for radiomics. It aims to improve the quality of reporting in radiomics research 1. CLEAR is endorsed by the European Society of Radiology (ESR) and the European Society of Medical I...
Article
Inhomogeneity artifact
The inhomogeneity artifact is a type of magnetic resonance imaging artifact that occurs due to multiple factors, such as irregular anatomical area (for example, shoulder, hips, ankles), presence of metallic objects or inhomogeneity of the main field.
The inhomogeneity artifact appears as hyperi...
Article
Negative enhancement integral
The negative enhancement integral in MR perfusion is used to calculate the relative cerebral blood volume (rCBV). It represents the area described by the baseline and the signal loss due to passage of contrast bolus in tissue.
Article
Low-field magnetic resonance imaging
Low-field magnetic resonance imaging is an emerging approach to MRI imaging, which aims to provide diagnostic image quality using devices with several magnitude lower field strength (typically well under 0.1T) than most stationary units.
The reduced field strength of these devices allows improv...
Article
Photon-counting computed tomography
Photon-counting computed tomography (PCCT) is a technology in CT that could represent the next major technological milestone in the field. Briefly, photon-counting CT uses energy-resolving detectors, thereby enabling scanning at multiple energies.
Technique
Physical principles
Clinical CT sys...
Article
Anode angle
The anode angle refers to the angle the target surface of the anode sits at in relation to the vertical.
Most x-ray tubes have an anode angle of 12-15 degrees but greater or lesser angles can also be used depending on the application. The degree of angulation of the anode affects the effective...
Article
CT gastrointenstinal bleed (protocol)
A CT gastro-intestinal bleed protocol utilizes a multiphasic technique to detect active gastrointestinal bleeding (as well as other potential non-bleeding bowel disease 1.
Note: This article is a general guideline for evaluating CT gastrointestinal bleeds. Protocol factors are variable as they...
Article
Diffusion kurtosis imaging
Diffusion kurtosis imaging (DKI) is an advanced neuroimaging modality which is an extension of diffusion tensor imaging by estimating the kurtosis (skewed distribution) of water diffusion based on a probability distribution function. It provides a high order diffusion of water distribution and a...
Article
Glutamine-Glutamate peak
Glutamate-Glutamine (Glx) peak is one of the regions assessed on MR spectroscopy, and resonates between 2.2 and 2.4 ppm chemical shift. It overlaps with the GABA peak and cannot be routinely separated from each other. The concentration of these two brain metabolites increases in hepatic and hypo...
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