A radioassay is an in vitro test to detect hormones, drugs and medicines in smallest concentrations.

Radiographs are x-ray pictures of the internal body. A radiograph looks like a photographic negative; this kind of impression is caused by representing the least dense structures (for example air) as dark areas and the structures with high density as white areas.

Radiographic noise is a fluctuation in optical density on radiographic or mammographic images, often as a result of low radiation dose.

See also Electronic Noise.

Radiography is a synonym for the examination of the structure of materials by nondestructive methods, for example with radiation. Radiography is used for both medical and industrial applications.
Autoradiography describes the imaging of an object using radiations produced by the radioactive decay of nuclides in the object.
Sometimes, imaging modalities without use of radiation such as MRI and ultrasound are grouped in radiography due to the fact that the radiology staff handles different forms of medical imaging. Treatment using radiation is known as radiotherapy.

See also Diagnostic Imaging and Conventional Radiography.

(RIA) A radioimmunoassay is an in vitro assay test in which very small quantities of hormones, drugs and other substances in blood, urine, etc. can be measured by using specific antibodies or antigens which have been labeled with radioactive tracers. Since the patient does not receive the radioactive material, there is no patient radiation exposure.
Radioimmunoassays are usually replaced by fluoroimmunoassay and enzymimmunoassay to avoid the use of radioactive materials.

See also Bioassay, Fluorescent Immunoassay, Protein Binding Assay, Radioassay, and Berson Salomon.