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.
717 results found
Article
C-arm
C-arm is a term employed to refer to image intensifiers used in a variety of settings, including interventional suites and operating theaters. The machine is similar to the letter ''C'' in its appearance with the x-ray tube on one end and the image intensifier on another.
Article
Superparamagnetic iron oxide
Superparamagnetic iron oxides (SPIOs) are a class of MR contrast agents composed of nanoparticles of iron oxide crystals coated in carbohydrates. They are used to image vasculature and the liver via shortening T1 and T2/T2* relaxation times.
The main agent currently used is ferumoxytol (Ferahem...
Article
Acoustic impedance
Acoustic impedance (Z) is a physical property of tissue. It describes how much resistance an ultrasound beam encounters as it passes through a tissue.
Acoustic impedance depends on:
the physical density of the tissue (d, in kg/m3)
the velocity of the soundwave transmitted through the tissue m...
Article
Contrast enhancement
Contrast enhancement is a ubiquitous term in radiology and can be used in three ways.
Firstly, it may refer to any method of exaggerating the visible difference between adjacent structures on imaging by administering contrast media/agents. This includes differentiating between normal structure...
Article
Power Doppler
Power Doppler is a technique that uses the amplitude of Doppler signal to detect moving matter. Power Doppler:
is independent of velocity and direction of flow, so there is no possibility of signal aliasing
is independent of angle, allowing detection of smaller velocities than color Doppler, f...
Article
Peak systolic velocity (Doppler ultrasound)
Peak systolic velocity (PSV) is an index measured in spectral Doppler ultrasound. On a Doppler waveform, the peak systolic velocity corresponds to each tall “peak” in the spectrum window 1.
Explanation
When traveling with their greatest velocity in a vessel (i.e. during systole), red blood cel...
Article
Kerma
Kerma is a measure of energy transferred from radiation to matter and is an acronym for kinetic energy released to matter. It is related to, but not the same as absorbed dose. Kerma is measured by the SI unit, the gray (joules per kilogram) 1,3.
Kerma measures the amount of energy that is trans...
Article
Speckle artifact
Speckle artifact may be encountered in ultrasound. It is caused by the scattering of waves from the surface of small structures within a certain tissue. The artifact produces a textured appearance.
Because speckle can make it harder to distinguish soft tissue differences, modern ultrasound mac...
Article
Thallium-201 scintigraphy
Thallium-201 (Tl-201) is a radiopharmaceutical used for scintigraphy, primarily of the myocardium. The element thallium is treated by the body as an analog of potassium; it is produced in a cyclotron by bombarding thallium-203 with protons.
Characteristics
thallium is a monovalent cation
usua...
Article
Gadolinium contrast agents
Gadolinium-based contrast media (GBCM), gadolinium-based contrast agents (GBCAs), or simply gadolinium contrast agents, are molecular complexes containing the rare earth metal gadolinium, chelated to a carrier ligand. They are a type of paramagnetic contrast agent, which are the primary class of...
Article
Superb microvascular imaging (ultrasound)
Superb microvascular imaging (SMI) or microvascular flow imaging (MVI/MV-flow - the name varying by manufacturers) is a ultrasound imaging technique that aims to visualize low velocity and small diameter blood vessel flow. Unlike conventional color and power Doppler imaging, superb microvascular...
Article
Mechanical index
The mechanical index (MI) is an attempt to measure part of an ultrasound beam's bioeffects. The mechanical index is found on most ultrasound display screens, along with the thermal index.
Mechanical index is an indication of an ultrasound beam's ability to cause cavitation-related bioeffects, a...
Article
PET-CT (overview)
PET-CT imaging is a form of dual-modality imaging that utilizes the advantages of both positron emission tomography (PET) and computed tomography (CT).
PET imaging excels at detailing physiologic or biologic phenomena through the administration of positron-emitting radiopharmaceuticals. The bi...
Article
T1 weighted image
T1 weighted image (also referred to as T1WI or the "spin-lattice" relaxation time) is one of the basic pulse sequences in MRI and demonstrates differences in the T1 relaxation times of tissues.
A T1WI relies upon the longitudinal relaxation of a tissue's net magnetization vector (NMV). Basicall...
Article
Diastolic pseudogating
Diastolic pseudogating appears as periodic bright and dark signal in arteries such as the aorta as one progresses through a series of images. Synchronisation of the cardiac cycle and the pulse sequence results in high signal in the artery during diastole when blood is relatively stationary and l...
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Double oblique multiplanar reconstruction
Double oblique is a type of multiplanar reconstruction used in cardiac cross-sectional imaging. It is useful for an accurate assessment of the ascending aorta and aortic annulus, and is particularly useful for pre- and post-procedure evaluation of a transcatheter aortic valve replacement (TAVR)....
Article
Air gap technique (mammography)
The air gap technique is utilized for the magnification mammography view.
Magnification mammography is a high dose imaging technique which is generally utilized as a follow-up to a standard mammogram image series when a focal area needs to be more clearly examined 1. The air gap technique is ut...
Article
LaPlace's law
LaPlace's law is useful in thinking about dilated tubular structures, such as the bowel or vessels (e.g. aortic aneurysms). The relationship between wall tension and radius shows why more dilated regions of a tube develop more wall stress and therefore are at higher risk for perforation:
wall t...
Article
Partial volume averaging (CT artifact)
Partial volume artifact occurs when tissues of widely different absorption are encompassed on the same CT voxel producing a beam attenuation proportional to the average value of these tissues.
The latest generation of CT scanners with an associated reduction in the volume of a voxel has substa...
Article
Chemical exchange saturation transfer
Chemical exchange saturation transfer (CEST) imaging is a novel molecular MR technique that enables imaging certain compounds at concentrations that are too low to impact the contrast of standard MR imaging and too low to directly be detected in MRS at typical water imaging resolution 1.
Amide ...
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