Dose Calibrator Assay of Preloaded Magazines for Prostate Brachytherapy
K. L. Classic, A. D. Amundson
Sealed sources of radioactive material are used in radiation oncology for treatment of cancer. Treatment of the disease site with radioactive sources is often referred to as brachytherapy. Sources can be placed temporarily or permanently depending on the treatment needs of the patient. Prostate brachytherapy usually involves permanent implantation of sealed sources and is typically performed as an outpatient procedure. In a surgical setting, radioactive sources are implanted under the guidance of fluoroscopy, ultrasound, or both. After spending time in recovery, the patient is allowed to leave if the result of an ion chamber measurement at one meter is 1 mR/h or less. Methods of seed implantation for prostate treatment include the use of preloaded needles, preloaded magazines for a Mick applicator or seeds loaded in a polyglactin ribbon. Preloaded magazines can be loaded at the site of use or by the manufacturer prior to shipment. We assayed preloaded magazines to determine whether an accurate assessment of activity could be obtained to look at variations between dose calibrators, and to examine whether an improperly loaded magazine could be recognized. This paper also describes a plastic magazine holder that was designed and built for assaying loaded magazines in a dose calibrator. The magazine holder keeps geometry constant, which facilitates assessment of total activity. We have determined that, with careful measurement and proper calibration, a fully loaded magazine can be accurately assayed in well-type chamber.
This abstract was presented at the 33rd Annual Midyear Meeting, "Instrumentation, Measurements, and Electronic Dosimetry", Laboratory Use Session, 1/30/2000 - 2/2/2000, held in Virginia Beach, VA.