Answer to Question #792 Submitted to "Ask the Experts"

In diagnostic nuclear medicine, radioactive materials in the form of compounds labeled with radionuclides are injected into or swallowed by the patient. Alternately, the patient may breathe a radioactive gas or aerosol. Radiation from the patient is used to provide a pictorial image or measurement that correlates to the location of the radioactive material in the patient. In these cases, the patient becomes a source of radiation and remains so until the radioactive material decays or is excreted from the body.

Radiation therapy is usually characterized as one of three types: (1) Unsealed radioactive materials, in the form of compounds or elemental radionuclides, are injected into or swallowed by the patient. Because of the chemical nature of the material, it will be taken up by specific organs or tissues to disrupt the growth of tumors and cancers. (2) In brachytherapy, radioactive materials in encased or sealed sources are placed into the patient to irradiate tissue that is close to the sealed sources. The sealed sources may be removed after a period of time or left permanently in the patient. (3) Teletherapy radiation therapy involves exposing the entire patient, or only a limited area, to radiation from sealed radionuclide sources or linear accelerators, which use high-energy electron beams or radiation emitted from radionulcides.

For patients, radiation protection is ensured (1) by performing only those tests and treatments that are necessary, (2) by using calibrated equipment to provide the best test results or treatment outcomes, (3) by using standard tests, procedures, and administrative controls, and (4) by having knowledgeable and trained personnel. The overriding principal is that any test or treatment should offer the maximum benefit to the patient and limit the radiation exposure.

Because patient care in nuclear medicine and radiation therapy requires the routine use of radioactive material and sources of radiation, the technologists expect to receive exposure in the course of their duties. The principal sources include the handling of radioactive material during its compounding and administration to patients, the need to position the patients for imaging, the attending of patients who had radioactive therapy sources or compounds administered to them, and the operation of equipment used in brachytherapy and teletherapy. To keep exposures as low as reasonably achievable, or ALARA, technologists receive special training in procedures and have available equipment that will provide shielding to keep their exposures below regulatory guidelines. In principle, the training, available equipment, and procedures are designed to minimize the time with the radiation sources, allow for maximizing distances between the technologist and radiation source, and provide the use of appropriate shielding when working with radiation sources, including the patient. Equipment such as lead syringe holders and syringe shields reduce the technologists' hand and body exposure while injecting patients with radioactive material. Portable lead panels on wheels are used to reduce the exposure of the technologists and staff when brachytherapy implants are placed into patients. Lead and concrete are used in the walls around nuclear medicine clinics and treatment rooms to shield adjacent areas occupied by the technologist and public.

Requests for further information on the role of technologists in nuclear medicine may be addressed to the Society of Nuclear Medicine Technologist Section. Another professional organization concerned with the professional training and development of technologists on clinical competency in radiation therapy is the American Registry of Radiologic Technologists.

John Jacobus, MS, CHP