Is alanine/ESR dosimetry now an alternative to ferrous sulphate dosimetry?.

For some decades ferrous sulphate (Fricke) dosimetry was considered to be the method of choice for the calibration of therapy level dosimeters in terms of absorbed dose to water. Attempts to replace the Fricke by alanine/ESR dosimeters failed because of inadequate precision at the absorbed dose level of 40 Gy so far used for intercomparisons with Fricke dosimeters. The present paper, however, shows by a means of comparative measurements with ion chamber and thermoluminescent dosimeters that a coefficient of variation of lower than 0.5% can be achicved for the alanine at the 30 Gy absorbed dose level. Together with further advantages of the alanine/ESR technique, e.g., its easy handling and reliability, this result is encouraging to use alanine as an alternative to Fricke dosimeters for the transfer of the quantity absorbed dose to water.For some decades ferrous sulphate (Fricke) dosimetry was considered to be the method of choice for the calibration of therapy level dosimeters in terms of absorbed dose to water. Attempts to replace the Fricke by alanine/ESR dosimeters failed because of inadequate precision at the absorbed dose level of 40 Gy so far used for intercomparisons with Fricke dosimeters. The present paper, however, shows by a means of comparative measurements with ion chamber and thermoluminescent dosimeters that a coefficient of variation of lower than 0.5% can be achieved for the alanine at the 30 Gy absorbed dose level. Together with further advantages of the alanine/ESR technique, e.g., its easy handling and reliability, this result is encouraging to use alanine as an alternative to Fricke dosimeters for the transfer of the quantity absorbed dose to water