JUNCTION PLANE DOSIMETRY IN DIFFERENT TECHNIQUES OF COBALT-60 HEAD AND NECK IRRADIATION
Abstract
Study of dose at the junction between lateral and anterior field in irradiation technique of head and neck cancer with a Cobalt-60 teletherapy machine was performed in anthropomorphic rando phantom with TLD-100 chips as dosemeters. Doses were compared in three different techniques ; straight field (Technique 1), couch turntable in lateral field (Technique 2) and couch turntable in lateral field with a half beam block device in anterior field ( Technique 3). When normalize dose at any point of the junction as a percentage of the dose at the center of lateral field, the mean doses in Technique | , Technique 2 and Technique 3 are 112.56 ± 13.51%, 103.69 ± 12.29% and 97.20 ± 12.25% respectively. Measurements were done three times in each technique to assess for the setup reproducibility. It was found that only the reproducibility in Technique 1 and 2 was acceptable. This report is an attempt to investigate the dosimetry at the junction plane in different techniques of head and neck irradiation and suggest an appropriate technique which provides a reproducibly uniform dose distribution across JAN. - APR. 2001. Volume VII Number| the junction of head and neck irradiation with the Cobalt-60 teletherapy machine.
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