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
Magnetic resonance neurography
Magnetic resonance neurography (MRN) is a relatively new non-invasive imaging technique for dedicated assessment of peripheral nerves.
It is used to assess peripheral nerve entrapments and impingements as well as localization and grading of nerve injuries and lesions.
Dedicated high-resolution...
Article
Spatial resolution
Spatial resolution refers to the ability of an imaging modality to differentiate two adjacent structures as being distinct from one another. Other related terms include definition or visibility of detail.
Spatial resolution is expressed in line pairs per mm (lp mm).
The absence of spatial reso...
Article
Nuclide
A nuclide is a nuclear-centric term describing an atomic species by its nuclear composition and nuclear energy state.
A nuclide has a specific number of protons and neutrons and will additionally have a specific energy state of its nucleus.
Radionuclides are unstable nuclides that undergo radi...
Article
PET-MRI
PET-MRI is a hybrid imaging technique utilizing the functional uptake information of positron emission tomography (PET) with the anatomical and soft tissue detail of magnetic resonance imaging (MRI).
Early systems were tested in the late 2000s with commercial availability from 2010 1,2. The ava...
Article
RadLex
RadLex is a lexicon of radiological information that has been produced by the Radiological Society of North America (RSNA). It is an ontological system whose principle aim is to develop a useful vocabulary for radiologists.
In the words of the RSNA
"As images, imaging reports, and medical re...
Article
Ultrasound artifacts
Ultrasound artifacts are commonly encountered and familiarity is necessary to avoid false diagnoses. In some cases, specific artifacts can even offer valuable diagnostic information. For instance, some artifacts may be indicative of certain pathologies. They are not to be confused with ultrasou...
Article
Reverse Bernheim phenomenon
Reverse Bernheim phenomenon, also known as reverse Bernheim syndrome or reverse Bernheim effect, describes the compromise of left ventricular filling caused by the interventricular septum bulging into the left ventricle. When there is right ventricular pressure and volume overload, the intervent...
Article
Doppler waveforms
Doppler waveforms refer to the morphology of pulsatile blood flow velocity tracings on spectral Doppler ultrasound. Waveforms differ by the vascular bed (peripheral, cerebrovascular, and visceral circulations) and the presence of disease.
Radiographic features
Ultrasound
Doppler
Most authori...
Article
Radiofrequency shielding
Radiofrequency or RF shielding is a technique for creating electromagnetic (EM) isolation, which is critical during the acquisition of MR images. RF shielding serves to both prevent external EM interference from contaminating the target tissue signal, and to ensure that signals generated by MR i...
Article
MRI contrast agents
MRI contrast agents have become an indispensable part of contemporary magnetic resonance imaging. Although MRI was initially hoped to provide a means of making definitive diagnoses without administering contrast media, it has been found that the addition of contrast agents in many cases improves...
Article
Beta decay
Beta decay represents radioactive decay in which a beta particle is emitted. Beta particles may be either electrons or positrons (β- or β+), having negative or positive charge respectively. The kinetic energy of beta particles has a continuous spectrum.
Beta minus decay
If the number of neutro...
Article
Radiofrequency transmitter
The radiofrequency (RF) transmitter is the generator of the radiofrequency current which is delivered to the transmitting coil. This creates a signal which is used to excite protons in the imaging field. Radiofrequency coils can be both transmitters and receivers of the radiofrequency signal or ...
Article
Compression in mammography
In mammography, compression of the breast is performed to reduce its thickness. By doing so, the following benefits are achieved:
improved subject contrast (by reducing scattered radiation)
improved density uniformity
improved visualization of breast tissue near chest wall (by spreading out s...
Article
Elastography
Elastography is a newer technique that exploits the fact that a pathological process alters the elastic properties of the involved tissue. This change in elasticity is detected and imaged using elastography.
Radiographic technique
Sonoelastography
Sonoelastography is the term used when ultras...
Article
Gradient echo sequences
Gradient echo sequences (GRE) are an alternative technique to spin-echo sequences, differing from it in two principal points:
utilization of gradient fields to generate transverse magnetization
flip angles of less than 90°
Compared to the spin-echo and inversion recovery sequences, gradient e...
Article
Creatine peak
Creatine is one of the compounds examined in MR spectroscopy. It resonates at 3.0 ppm chemical shift (with a second usually smaller peak at 3.95 ppm 2).
It is found in metabolically active tissues (brain, muscle, heart), where it is important in the storage and transfer of energy. It tends to b...
Article
Receiver operating characteristic curve
The receiver operating characteristic (ROC) curve is a statistical relationship used frequently in radiology, particularly with regards to limits of detection and screening.
The curves on the graph demonstrate the inherent trade-off between sensitivity and specificity:
y-axis: sensitivity
x-a...
Article
Image compression
Image compression is a technique applied to digital images to decrease the amount of space required to store an image and increase the speed with which the image can be retrieved or transmitted.
Compression may be lossless or lossy:
lossless compression retains all original data, for example P...
Article
Grids
Grids are placed between the patient and the x-ray film to reduce the scattered radiation reaching the detector (produced mainly by the Compton effect) and thus improve image contrast.
They are made of parallel strips of high attenuating material such as lead with an interspace filled with low ...
Article
Positron emission tomography
Positron emission tomography (PET) is a modern non-invasive imaging technique for quantification of radioactivity in vivo. It involves the intravenous injection of a positron-emitting radiopharmaceutical, waiting to allow for systemic distribution, and then scanning for detection and quantificat...
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