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
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...
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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
Pion therapy
Pion therapy is a form of particle therapy employing pions. Pions, or to give them their full name, negatively-charged pi mesons (π-), are a type of meson. Pion therapy is not used as a treatment modality due to its great expense and lack of clinical efficacy 1,2.
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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
Coronary MR angiography
Coronary MR angiography (coronary MRA) is a developing approach to imaging the coronary arteries.
Advantages of coronary MRA include avoidance of the intravenous iodinated contrast and ionizing radiation used in coronary CT angiography and conventional angiography.
A disadvantage of coronary M...
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...
Article
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 ...
Article
Filtered back projection
Filtered back projection is an analytic reconstruction algorithm designed to overcome the limitations of conventional back projection; it applies a convolution filter to remove blurring. It was the primary method in cross-sectional imaging reconstruction.
It utilizes simultaneous equations of ...
Article
Fetal dosimetry
NB: Please consult original article(s) and discuss with your local radiology department/radiation physicist before making any clinical decision.
Although radiation exposure to the gravid uterus is to be avoided whenever possible, and only deliberately performed after careful weighing up of the ...
Article
Gallbladder ultrasound
Gallbladder ultrasound is a non-invasive diagnostic imaging technique used to evaluate the structure and function of the gallbladder as well as the adjacent anatomy.
Preparation
Patients are typically advised to fast for 6-8 hours prior to the ultrasound examination. This allows the gallbladde...
Article
Dimensionless index (DI)
Dimensionless index (DI) is the ratio of the velocity-time integral of the left ventricular outflow tract (LVOT-VTI) to that of the aortic valve jet (AV VTI)1-2.
Dimensionless index (DI) = LVOT VTI / AV VTI
Usage
Dimensionless index is a classic marker of severity in aortic stenosis that does...
Article
Photon starvation
Photon starvation is one source of streak artifact which may occur in CT. It is seen in high attenuation areas, particularly behind metal implants. Because of high attenuation, insufficient photons reach the detector. During the reconstruction process, the noise is greatly magnified in these are...
Article
Liver protocol (MRI)
Examination of the liver with MRI requires numerous sequences and imaging at multiple times after the administration of contrast.
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
Raymond V Damadian
Raymond V Damadian (1936-2022) was a pioneer in the field of MRI and inventor of one of the first MRI scanners.
Early life
Raymond Vahan Damadian was born on 16 March 1936 in Forest Hills, New York City and was a child prodigy. He studied violin at the Juilliard School of Music for eight years...
Article
Mirror image artifact
Mirror image artifact in sonography is seen when there is a highly reflective surface (e.g. diaphragm) in the path of the primary beam.
The primary beam reflects from such a surface (e.g. diaphragm) but instead of directly being received by the transducer, it encounters another structure (e.g. ...
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