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.
715 results found
Article
Intravenous MRI contrast agents
Intravenous MRI contrast agents include chelates of paramagnetic ions, both ionic and non-ionic. Gadolinium-based contrast agents (GBCAs) are the most common type. The particulates, sequestered in the liver, spleen, and lymph nodes, the intravascular agents, confined to the blood pool, and tumor...
Article
Dark-field radiography
Dark-field radiography is an emerging medical imaging technology. While conventional x-ray imaging is based on the differential attenuation of various organs and tissues, dark-field radiography utilizes ultra-small angle x-ray scattering similar to dark-field computed tomography.
Clinical appli...
Article
Shear wave elastography
Shear wave elastography is a developing variation of ultrasound imaging.
The concept is similar to strain elastography, but instead of using transducer pressure to compare a shift in an ultrasound A-line (thereby measuring changes in strain), a higher intensity pulse is transmitted to produce s...
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
Factors affecting T1
Factors affecting T1 and T2 relaxation times of different tissues are generally based on molecular motion, size and interactions.
The protons giving rise to an NMR signal are mainly those in cell water and lipids (i.e. protons that are free to move), while those in protein and solids usually do...
Article
Adrenal glands ultrasound
Adrenal glands ultrasound, is an imaging method that can provide valuable information regarding their size, shape, and structure. As a result, it can aid in diagnosing various pathological conditions related to adrenal gland function.
Techniques
Several ultrasound techniques can be employed to...
Article
MRI
MRI (an abbreviation of magnetic resonance imaging) is an imaging modality that uses non-ionizing radiation to create useful diagnostic images.
In simple terms, an MRI scanner consists of a large, powerful magnet in which the patient lies. A radio wave antenna is used to send signals to the bod...
Article
Tube arcing
Tube arcing occurs when there is a short-circuit within the tube, typically from the cathode to the tube envelope. The result is a temporary loss of x-ray output and a localized artifact.
A number of causes of tube arcing are recognized 1:
insulator surface flashover
insulator breakdow...
Article
MR liver iron quantification
MR liver iron quantification is a non-invasive means of measuring liver iron concentration, a key indicator in the management of patients with hemochromatosis (primary or secondary).
Advantages
Apart from being non-invasive, sampling occurs in a large cross-section of the liver, as opposed to ...
Article
Brown adipose tissue
Brown adipose tissue (BAT) (also known as brown fat) is one of two types of adipose tissue (the other one being white fat) important for producing thermal energy (heat, non-shivering thermogenesis), especially in the newborn. It constitutes ~5% of body mass in the newborn and tends to reduce mar...
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
Diffusion-weighted imaging in acute ischemic stroke
Diffusion-weighted imaging (DWI) is a commonly performed MRI sequence for the evaluation of acute ischemic stroke and is very sensitive in the detection of small and early infarcts. Conventional MRI sequences (T1WI, T2WI) may not demonstrate an infarct for 6 hours, and small infarcts may be hard...
Article
Lead equivalent personal protection equipment
Lead equivalent personal protection equipment (PPE) should be available in all radiology departments and operating suites. There are three traditional principles for ionizing radiation safety: time, distance, and shielding. It is important to remember that all three principles have a part to pla...
Article
Wilhelm Roentgen
Wilhelm C Roentgen (1845-1923) was a German physicist who is celebrated globally for his discovery of x-rays on 8 November 1895.
Early life
Wilhelm Conrad Roentgen (Röntgen in German) was born on 27 March 1845 in Lennep, Germany. He attended the primary and secondary school run by Martinus Her...
Article
Nuclear medicine
Nuclear medicine in vivo is the practice of utilizing small amounts of radioactive substances (unsealed radioactive sources) to diagnose, monitor and treat disease. The utilization of radiopharmaceuticals (radionuclide + pharmaceutical) offers a unique perspective on both disease and cancer trea...
Article
X-ray tube
An x-ray tube functions as a specific energy converter, receiving electrical energy and converting it into two other forms of energy: x-radiation (1%) and heat (99%). Heat is considered the undesirable product of this conversion process; therefore x-radiation is created by taking the energy from...
Article
Enteric contrast medium (CT)
Enteric contrast media can be given to patients before their CT exam to improve its diagnostic accuracy. Historically, a combination of oral and intravenous contrast media were always given prior to a CT abdomen. Contemporaneously, improved CT scanners mean that oral contrast agents are no longe...
Article
Cone beam effect
Cone beam effect artifacts are seen in multidetector row CT (cone beam CT) acquisitions 1. Modern CT scanners use more detector arrays to increase the number of sections acquired per rotation. This causes the x-ray beams to become cone-shaped as opposed to fan-shaped 2. As a result instead of co...
Article
Modality
Modality is the term used in radiology to refer to one form of imaging, e.g. CT. It is often used in the plural form, e.g. "various modalities can be employed to evaluate this liver lesion."
More generally, in clinical medicine, the term 'modality' refers to different types of procedures and th...
Article
Mass attenuation coefficient
The mass attenuation coefficient (also known as the mass absorption coefficient) is a constant describing the fraction of photons removed from a monochromatic x-ray beam by a homogeneous absorber per unit mass.
It is equivalent to the linear attenuation coefficient divided by the density of the...
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