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
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. ...
Article
Charles Thurstan Holland
Charles Thurstan Holland (1863-1941) was a pioneering radiologist who played a pivotal role in establishing radiology as a specialty in its own right.
Early life
Charles Thurstan Holland was born in Bridgwater, Somerset on 7 March 1863. He studied medicine at University College Hospital in...
Article
Magnetic shimming
Magnetic shimming refers to the process of reducing magnetic field inhomogeneities. It is an important aspect of optimizing image quality. Field inhomogeneities can be the result by both intrinsic magnet properties and the surrounding environment of the MR magnet – such as the presence of nearby...
Article
Gustav Bucky
Gustav Bucky (1880-1963) was a German-born, American radiologist who pioneered the development of anti-scatter grids in projectional radiography with his invention, the Bucky diaphragm.
Early life
Gustav Peter Bucky was born in the city of Leipzig, Germany on 3 September 1880 2,3,5. He had a k...
Article
Taurine
Taurine is one of the compounds examined in MR spectroscopy. It resonates at 3.4 ppm chemical shift. It is elevated in medulloblastomas.
Article
Tumor specific MRI contrast agents
Tumor specific MRI contrast agents are pharmaceuticals that are targeted to tumors, either specifically or nonspecifically. Monoclonal antibodies are targeted to specific tumors such as adenocarcinoma of the colon. Metalloporphyrins exhibit affinity for many tumor types including carcinoma, sarc...
Article
MRI sequence parameters
Listed in the table below are the most common acquisition parameters for commonly used MRI pulse sequences (in msec).
For a general introduction to these sequences please refer to MRI sequences (basic).
The specific parameters for any given study varies from one manufacturer to another, and fr...
Article
Law of Bergonié and Tribondeau
The law of Bergonie and Tribondeau is that the radiosensitivity of a biological tissue is directly proportional to the mitotic activity and inversely proportional to the degree of differentiation of its cells. This law underpins the field of radiation-oncology, although such a general law may no...
Article
Slew rate
Slew rate refers to the speed at which a gradient can be turned on and off, and is defined as the maximum gradient strength of the gradient divided by the rise time.
MR imaging is a product of magnetic field gradients which are created by magnetic gradient coils. The quality and performance of...
Article
Nephrogenic systemic fibrosis
Nephrogenic systemic fibrosis (NSF), also known as nephrogenic fibrosing dermopathy, occurs almost exclusively in patients with renal impairment and is associated with the administration of gadolinium-based contrast agents (GBCAs) used in MRI.
The American College of Radiology (ACR) has divide...
Article
Valence shell
The valence shell of an atom is the outermost shell of the electron cloud. It plays a large part in determining the chemical, thermal, optical and
electrical properties of the element. This occurs because it often not
full and movement of electrons may occur between it and a) electrons
from o...
Article
T2 relaxation
T2 relaxation, also known as spin-spin relaxation or transverse relaxation, refers to the progressive dephasing of spinning dipoles resulting in decay in the magnetization in the transverse plane (Mxy). Following a radiofrequency pulse, this form of relaxation occurs with the time constant T2, w...
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
Sono-elastography
Sono-elastography is the term used when ultr...
Article
Inverse Fourier transformation
The inverse Fourier transform is a mathematical formula that converts a signal in the frequency domain ω to one in the time (or spatial) domain t.
A time domain signal f(t) is obtained by demodulating a frequency domain signal F(ω) using a special sinusoidal wave ejωt across all time (from nega...
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