Irradiation dose for personnel during brachytherapy of malignant neoplasms with 32P microsources

Abstract

Experimental measurements of the local absorbed radiation dose in the most irradiated parts of the bodies of personnel (the skin of the hands and palms, eyes, thorax, and abdomen of operators) by means of high sensitivity TLD-500K thermoluminescence detectors are reported. It is found that, for 32 P microsources with a total activity of 100 MBq, after 6 hours of work without protective x-ray gloves during a simulation of placing a real preparation in the region of the liver of an adult phantom, the maximum local irradiation dose to the hands (the skin of the left middle finger and thumb) from bremsstrahlung with deduction of the natural background and without special protective measures is 0.54 ± 0.001 mGy, the minimum dose (skin on the palm of the right hand) is 0.1 ± 0.01 mGy, and the irradiation of the thorax, abdomen, and eyes of the operator is less than 0.12 mGy. This presents no radiation hazard, even for repeated work with these sources.Intratissue radiation therapy of malignant neoplasms (brachytherapy) using silicon microparticles with embedded 32 P offers promise in clinical applications for treatment of cancer of the liver and pancreas. This method is highly effective[1] and does not require operator intervention. 32 P, a pure β emitter, irradiates the tumor selectively in the region where the preparation has been inserted. The preparation is introduced through the skin; the tumor volume is injected repeatedly in accordance with a dosimetric plan for the operation. As the β particles pass through the surrounding materials, penetrating bremsstrahlung γ radiation is produced, which, given the high activity of the therapeutic preparations being used, may irradiate the medical personnel conducting the operation. There are no published data on the irradiation dose for medical personnel (the operators) by bremsstrahlung γ radiation during this kind of therapy. Here, for the first time, we present the results of some measurements of the irradiation of personnel, specifically, of the absorbed radiation dose to the skin of the fingers and palms of operators, as well to the surface of the thorax and around the abdomen and eyes. The experiments were conducted on a volunteer operator simulating the introduction of a real radioactive preparation in a tissue-equivalent phantom of the body of an adult human. The resulting data are of interest for the radiation safety of personnel who practice this method of radiotherapy.Materials and Methods of Study. An average of one β particle is emitted in each decay event for 32 P. The maximum energy of the β particle is 1710.3 keV and the average is 694.8 keV, the half life is 14.29 days, and the maximum range in biological tissue is 0.812 cm with a half attenuation thickness of 0.076 cm in biological tissue [2]. The maximum energy of the bremsstrahlung is 1710.3 keV. The exact characteristics of the bremsstrahlung γ emission (spectrum, average energy, intensity) depend on the material surrounding the source (its effective atomic number, density, size, and configuration), as w...