Albedos for 4-, 10-, and 18-MV bremsstrahlung x-ray beams on concrete, iron, and lead--normally incident.
Backscattering of radiation incident on a solid medium has been treated with some success as a reflection phenomenon. The concept of albedo has been used in the literature to deal with this problem. A Monte Carlo program has been used in this study to simulate the generation of bremsstrahlung beams from medical linear accelerators. The accuracy of the calculated spectra have been checked indirectly by calculating TPRs and comparing them with measured values. The dose albedos for 60Co and 137Cs beams normally incident on concrete have been calculated and compared with experimentally determined values in the literature. The generated energy spectra are then used to calculate the albedo factors for 4-, 10-, and 18-MV bremsstrahlung x-ray beams normally incident on concrete, iron, and lead. The number albedo decreases with increase in the atomic number of the reflecting medium. However, for high-energy photons, the dose albedo increases with increase in the atomic number of the medium. This is an important factor that needs to be considered in the design of shielding. The calculated energy spectra can be used in other problems and the albedo factors can be applied in practical shielding design for medical linear accelerators.
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Department of Radiation Oncology, Massachusetts General Hospital, Boston 02114.
D002588:Cesium Radioisotopes; D003037:Cobalt Radioisotopes; D003252:Construction Materials; D004867:Equipment Design; D006801:Humans; D007501:Iron; D007854:Lead; D008962:Models, Theoretical; D009010:Monte Carlo Method; D010315:Particle Accelerators / Q000295:instrumentation*; D011827:Radiation; D011829:Radiation Dosage; D011835:Radiation Protection; D012822:Silicon Dioxide; D014965:X-Rays
D002588:Cesium Radioisotopes; D003037:Cobalt Radioisotopes; D007854:Lead; D012822:Silicon Dioxide; D007501:Iron