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.
716 results found
Article
Virtual grid
Virtual grid software is a relatively new innovation utilizing no physical grid at all. Instead, the original purpose of a grid is replicated by an algorithm 1 based on fundamental mathematics (i.e. Laplace transformation, wavelet transformation and Gaussian decomposition) which iteratively reco...
Article
Dual energy CT
Dual energy CT, also known as spectral CT, is a computed tomography technique that uses two separate x-ray photon energy spectra, allowing the interrogation of materials that have different attenuation properties at different energies.
Technique
Whereas conventional single-energy CT produces a...
Article
T1 mapping - myocardium
T1 mapping is a magnetic resonance imaging technique used to calculate the T1 time of a certain tissue and display them voxel-vice on a parametric map. It has been used for myocardial tissue characterization 1-6 and has been investigated for other tissues 5.
Terminology
Native T1 is referred t...
Article
T2 mapping - myocardium
T2 mapping is a magnetic resonance imaging technique used to calculate the T2 times of a certain tissue and display them voxel-vice on a parametric map. It has been used for tissue characterization of the myocardium 1-5 and has been investigated for cartilage 6,7 and other tissues 4.
T2 mapping...
Article
T2* mapping - myocardium
T2* mapping is a magnetic resonance imaging technique used to calculate the T2* time of tissue and display them voxel-vice on a parametric map. It is used for myocardial tissue characterization 1-4 and has been investigated for other tissues 5,6.
Clinical applications
T2* relaxation time has b...
Article
Sequential CT image acquisition
Sequential CT scanning, also referred to as "scan-move-scan" or "step and shoot", was the conventional method of image acquisition in computed tomography before the advent of helical CT.
Terminology
In sequential scanning, the patient is moved forward along the longitudinal axis of the CT sca...
Article
Digital radiography
Digital radiography is based on capturing and storing the radiograph using discrete (digital) values 1 as opposed to conventional film radiography, which uses analog (continuous) values. It removes the requirement of dark room procedures.
Terminology
The term digital radiography is often used ...
Article
Scintillator (gamma camera)
The scintillator is the component of a gamma camera which receives the gamma rays emitted from a radionuclide in a nuclear medicine scan and converts it to visible light photons. It is located just behind the collimator device.
A scintillator crystal may have properties of phosphorescence, wher...
Article
Shoulder protocol (MRI)
The MRI shoulder protocol encompasses a set of different MRI sequences for the routine assessment of the shoulder joint.
Note: This article aims to frame a general concept of an MRI protocol for the assessment of the shoulder joint. Protocol specifics will vary depending on MRI scanner type, sp...
Article
MR enterography
MR enterography (MRE), also known as MRI small bowel study, is a non-invasive technique for the diagnosis of small bowel disorders.
Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's...
Article
Whole-body diffusion-weighted MRI
Whole-body diffusion-weighted MRI (WB-MRI) is an advanced imaging technique that combines anatomical and functional MRI sequences to provide a comprehensive assessment of the whole-body in a single examination.
WB-MRI uses the properties of diffusion-weighted imaging for oncological disease sta...
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
Alpha decay
Alpha decay (a.k.a. α decay) is the radioactive process in which an alpha (α) particle (containing two neutrons and two protons) is ejected from the nucleus. An alpha particle is identical to the nucleus of a helium atom. All nuclei with an atomic number (Z) greater than 82, are considered unsta...
Article
MR cisternography
MR cisternography is an MR imaging technique useful in evaluating abnormalities in subarachnoid cisterns 1,2. It is the intracranial equivalent to MR myelography and can similarly be non-contrast-enhanced or, less commonly, contrast-enhanced (off-label).
Clinical applications
MR cisternography...
Article
Photomultiplier tube (Gamma camera)
The photomultiplier tube array of a Gamma camera detects the visible light produced by the scintillator and converts it to a measurable electronic signal 1.
A series of photomultiplier tubes are mounted behind the scintillation crystal 1. Each photomultiplier tube is composed of a tightly seal...
Article
Arterial spin labeling MR perfusion
Arterial spin labeling (ASL) MR perfusion is an MR perfusion technique which does not require intravenous administration of contrast (unlike DSC perfusion and DCE perfusion). Instead, it exploits the ability of MRI to magnetically label arterial blood below the imaging slab. The parameter most ...
Article
3D fast spin echo (MRI sequence)
3D fast spin-echo sequences are MRI pulse sequences that are able to rapidly image relatively large volumes of tissue with high resolution whilst retaining many of the advantages of fast spin-echo sequences.
They are able to create the same weightings as traditional 2D sequences (i.e., T1, T2,...
Article
MR fingerprinting
MR fingerprinting (MRF) describes an approach to the acquisition and evaluation of MRI data that is aimed at generating quantitative multiparametric data from a single acquisition.
The underlying process is acquiring data in a pseudorandom manner resulting in a unique pattern of signal evoluti...
Article
Ultrasound (introduction)
Ultrasound (US) is an imaging technology that uses high-frequency sound waves to characterize tissue. It is a useful and flexible modality in medical imaging, and often provides an additional or unique characterization of tissues, when compared to other modalities such as conventional radiograph...
Article
X-ray artifacts
X-ray artifacts can present in a variety of ways including abnormal shadows noted on a radiograph or degraded image quality, and have been produced by artificial means from hardware failure, operator error and software (post-processing) artifacts.
There are common and distinct artifacts for fi...
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