高エネルギー6MVX線治療における二次電子除去フィルタの評価

概要

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When using high energy X-rays, the dose increases at the skin surface and build-up region of beam contamination of secondary electrons coming out from the inner suface of the lineac head. At our radiotherapy department, many cases of external otitis from severe skin reactions, particularly resulting from whole brain irradiation of primary and metastatic brain tumors with a 6MV X-ray lineac, have been encountered. An investigation was made of the physical aspects of a 6 MV X-ray lineac, have been encountered. An investigation was made of the physical aspects of a 6 MV X-ray bean using three electron filters, lead lucite, lead glass and lucite to remove secondary electrons. Transparent materials for filters should be preferable for locating the light field. The following results were obtained : 1) For removing secondary electrons, a lead lucite filter was found best. 2) The lead lucite filter proved most effective for removing secondary electrons from the area of treatment. It reduced the dose of irradiation to the skin surface and build-up region, and furthermore improved the depth dose relative to that without filters. 3) From a clinical standpoint, skin reactions such as external otitis remarkably decreased using a lead lucite filter. 4) It thus appears necessary to use a high energy X-ray with newly designed filters to reduce beam contamination of secondary electrons.
1988-05-01