11,254 results found
Article
MRI
MRI (an abbreviation of magnetic resonance imaging) is an imaging modality that uses non-ionizing radiation to create useful diagnostic images.
In simple terms, an MRI scanner consists of a large, powerful magnet in which the patient lies. A radio wave antenna is used to send signals to the bod...
Article
MRI artifacts
MRI artifacts are numerous and give an insight into the physics behind each sequence. Some artifacts affect the quality of the MRI exam, while others do not affect the diagnostic quality but may be confused with pathology.
When encountering an unfamiliar artifact, it is useful to systematically...
Article
Aliasing on MRI
Aliasing on MRI, also known as wrap-around, is a frequently encountered MRI artifact that occurs when the field of view (FOV) is smaller than the body part being imaged. The part of the body that lies beyond the edge of the FOV is projected onto the other side of the image 5.
This can be correc...
Article
Cardiac MRI
Cardiac MRI consists of using MRI to study heart anatomy, physiology, and pathology.
Advantages
In comparison to other techniques, cardiac MRI offers:
improved soft tissue definition
protocol can be tailored to likely differential diagnoses
a large number of sequences are available
dynamic...
Article
Hemorrhage on MRI
Hemorrhage on MRI has highly variable imaging characteristics that depend on:
the age of the blood
the type of hemoglobin present: oxy-, deoxy- or met-
whether or not the red blood cell walls are intact: i.e. intra- vs extracellular
the MRI sequence
Although MRI is often regarded as being i...
Article
MRI physics
The physics of MRI are complicated and much harder to understand than those underpinning image generation in plain radiography, CT or ultrasound.
What follows is a very abbreviated, 'broad strokes' description of the process. Essentially, the process can be broken down into four parts:
prepar...
Article
MRI safety
MRI scanners, although free from potentially cancer-inducing ionizing radiation found in plain radiography and CT, have a host of safety issues which must be taken very seriously. MRI safety can be divided into:
main magnetic field
varying magnetic (gradient) fields
radiofrequency
Main magne...
Article
Arthrogram (MRI)
An MR arthrogram is an MRI performed after a joint is injected with a solution containing gadolinium. Sometimes abbreviated to MRA, which can be confused with MR angiography. MRI can also be performed after an injection is not directly administered into the joint, via an indirect arthrogram. An ...
Article
MRI brain (summary)
This is a basic article for medical students and other non-radiologists
MRI brain is a specialist investigation that is used for the assessment of a number of neurological conditions. It is the main method to investigate conditions such as multiple sclerosis and headaches, and used to character...
Article
Breast MRI
Breast MRI is the most sensitive method (>90%) for the detection of breast cancer. Its role in diagnosis and management continues to evolve 13.
Terminology
Dynamic contrast-enhanced (DCE)-MRI provides information about the morphology and function of a lesion with high sensitivity but moderate ...
Article
MRI protocols
MRI protocols are a combination of various MRI sequences, designed to optimally assess a particular region of the body and/or pathological process.
There are some general principles of protocol design for each area. However, the specifics of a protocol are dependent on MRI hardware and software...
Article
Fetal MRI
Fetal MRI allows for detailed imaging of the developing fetus in utero. Fast sequences are required due to fetal movement 1. Fetal MRI is most commonly utilized when ultrasound findings are equivocal. Fetal anatomy can be evaluated in detail including the brain, upper aerodigestive tract, thorax...
Article
Synthetic MRI
Synthetic MRI is a technique that generates contrast weighted images based on measurements of tissue properties from a single acquisition.
Basic principles
With synthetic MRI, different contrast weighted images can be obtained based on quantifications of a single multiple dynamic and multiple ...
Article
Esophageal MRI
Esophageal MRI, or gastro-esophageal junction (GEJ) MRI, is a targeted mediastinal imaging protocol performed to stage and aid treatment decisions in esophageal and GEJ carcinoma. It is not yet included in major treatment guidelines, but recent literature have pointed promising accuracy compared...
Article
Functional MRI
Functional magnetic resonance imaging (fMRI) is a technique used to obtain functional information by visualizing cortical activity. fMRI detects subtle alteration in blood flow in response to stimuli or actions. It is used in two broad ways:
clinical practice
typically in presurgical patients ...
Article
MRI pulse sequences
An MRI pulse sequence is a programmed set of changing magnetic gradients. Each sequence will have a number of parameters, and multiple sequences grouped together into an MRI protocol.
Parameters
A pulse sequence is generally defined by multiple parameters, including:
time to echo (TE)
time ...
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
Ultrahigh field MRI
Ultrahigh field (UHF) magnetic resonance imaging refers to imaging done on any MRI scanner with a main magnetic field (B0) strength of 7 tesla or greater. Until recently purely a research tool, following the introduction of the first 7 T clinical scanner in 2017, there are now a slowly increasin...
Article
MRI nomenclature guidelines
MRI nomenclature guidelines help maintain uniformity across the site, and help readers get more out of your cases and articles.
Articles
MRI features in an article should follow the format under "Radiographic features".
MRI
Add a statement about general MRI features, then move into signal ch...
Article
Placental evaluation with MRI
Placental evaluation with MRI is a problem-solving technique that can be used if ultrasound evaluation is insufficient or confusing. Even if the placenta is not the main point of evaluation, it is useful to understand the appearance of the placenta on obstetric imaging for other causes.
Techniq...
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