Materials that stop or attenuate radiation that is passed through the body, creating an outline on film of the organ(s) being examined. Contrast agents, sometimes called "dyes," do not contain radioisotopes. When such agents are used, exposure to radiation results only from the X-ray equipment…

The process of assigning clinical trial participants to treatment or control groups using an element of chance (e.g. like flipping a coin) to determine the assignments in order to reduce bias.

The plan that outlines how individuals will be recruited for the study and how the study will reach the recruitment goal.

Acronym for Roentgen Equivalent in Man; the unit of measurement for a dose of an ionizing radiation that produces the same biological effect as a unit of absorbed does (1 rad) of ordinary X-rays. One millirem is equal to 1/1000 of a rem.

A period in which the signs and symptoms of a disease are diminished or in abeyance. The term "remission" is used when one cannot say with confidence that the disease has been cured.

A systematic investigation, including research development, testing, and evaluation, designed to develop or contribute to generalizable knowledge.

A systematic investigation is an activity that is planned in advance and that uses data…

An ethical principle discussed in the Belmont Report requiring that individual autonomy be respected and persons with diminished autonomy be protected.

The plan that details the methods in which the study will use in order to retain study participation in the trial.

Research conducted by reviewing records from the past (e.g., birth and death certificates, medical records, school records, or employment records) or by obtaining information about past events elicited through interviews or surveys. Case control studies are an example of this type of research.…

The probability of harm or injury (physical, psychological, social, or economic) occurring as a result of participation in a research study. Both the probability and magnitude of possible harm may vary from minimal to significant. Federal regulations define only "minimal risk."