Correct Response: B. Radioactive tracers are used for the medical diagnoses of organs. The tracer can be tracked as it passes through the organ by detecting the gamma radiation emitted by the radioisotope. Radioisotopes with short half-lives are used so that they do not remain in the body for long periods of time. Answer choice A is a true statement that describes the basis for medical radiography commonly known as x-rays and is most commonly performed with x-rays, not gamma rays. Answer choice C is incorrect, although radioactive isotopes are commonly used as sources of gamma rays for the destruction of malignant tumors. Radioactive tracers use smaller quantities of radioisotopes that emit relatively low-energy gamma rays. Their purpose is not for destroying tissue but for the diagnoses of organs. Answer choice D is incorrect because radioactive tracers emit gamma radiation, which is ionizing radiation. The statement would be true if it were applied to magnetic resonance imaging (MRI) rather than radioactive tracers.
