(CTDI) The computed tomography dose index is most commonly used dose descriptor, which represents the dose to a location (e.g., depth) in a scanned volume.
This index describes the dose from a single rotation of a CT scanner. CTDI must be corrected for pitch or couch increment to receive the dose for a series of slices. The CTDI100 is measured using a 100 mm long ionization chamber. The CTDIair is the value of CTDI determined free-in-air.
Different definitions of CTDI exist and are used in different applications.

Material that allows heat or electric current to flow.

See also Semiconductor, Electric Field Strength, Electric Flux Density, Electromagnetic Lens, Tesla, and Thermal Units Per Hour.

Conventional (also called analog, plain-film or projectional) radiography is a fundamental diagnostic imaging tool in the detection and diagnosis of diseases. X-rays reveal differences in tissue structures using attenuation or absorption of x-ray photons by materials with high density (like calcium-rich bones).
Basically, a projection or conventional radiograph shows differences between bones, air and sometimes fat, which makes it particularly useful to asses bone conditions and chest pathologies. Low natural contrast between adjacent structures of similar radiographic density requires the use of contrast media to enhance the contrast.
In conventional radiography, the patient is placed between an x-ray tube and a film or detector, sensitive for x-rays. The choice of film and intensifying screen (which indirectly exposes the film) influence the contrast resolution and spatial resolution. Chemicals are needed to process the film and are often the source of errors and retakes. The result is a fixed image that is difficult to manipulate after radiation exposure. The images may be also visualized on fluoroscopic screens, movies or computer monitors.
X-rays emerge as a diverging conical beam from the focal spot of the x-ray tube. For this reason, the radiographic projection produces a variable degree of distortion. This effect decreases with increased source to object distance relative to the object to film distance, and by using a collimator, which let through parallel x-rays only.
Conventional radiography has the disadvantage of a lower contrast resolution. Compared with computed tomography (CT) and magnetic resonance imaging (MRI), it has the advantage of a higher spatial resolution, is inexpensive, easy to use, and widely available. Conventional radiography can give high quality results if the technique selected is proper and adequate. X-ray systems and radioactive isotopes such as Iridium-192 and Cobalt-60 for generating penetrating radiation, are also used in non-destructive testing.

See also Computed Radiography and Digital Radiography.

A coronary angiogram (or cardiac catheterization) is the radiographic visualization of the coronary arteries after the introduction of a contrast agent. A coronary angiography can be performed for both diagnostic and interventional (treatment) purposes.
A catheter, inserted into a major blood vessel has to be maneuvered up to the coronary arteries to inject a blood compatible iodinated contrast material (dye). The x-ray visible catheter allows injecting a small amount of contrast agent selectively in the coronary arteries or the heart chambers. Continuous images are recorded (movies or cineangiogram) in multiple views from different angles are in order to ascertain the precise location and severity of coronary artery blockages. Digitized images are also saved on computer and replayed onto a video screen as needed.
A coronary angiogram is more invasive and requires more patient recovery time than coronary CT angiography. In the past, the gold standard for detecting atherosclerotic plaque was a coronary angiography and intravascular ultrasound. Today, the American Heart Association considers CT scanning to be one of the most effective, non-invasive methods for the detection of calcification in the coronary arteries.

See also Interventional Radiology.

The craniocaudal view is routinely used for mammography. The vertical x-ray beam is directed from cranial to caudal through the breast.