National calibration and measurement capability (CMC) of radiotherapy ionization chambers in terms of absorbed dose to water D w in 60Co energy

According to the Mutual Recognition Agreement (MRA) of the International Committee of Weights and Measures (CIPM) the Secondary Standard Dosimetry Laboratory (SSDL) of the Instituto Nacional de Investigaciones Nucleares (ININ) is the Designated Institute (DI) by the Centro Nacional de Metrología (CENAM) before the CIPM to establish and maintain the national standard for dosimetric quantities of ionizing radiation. In particular, the SSDL’s main purpose is to provide assistance for quality assurance (QA) and calibration services in terms of absorbed dose to water (Dw ) to radiotherapy centers in Mexico, that employ external 60Co photon beams or high-energy x-rays for treatment of malignant neoplasia. Specifically, to achieve tumor control in the patient the absorbed dose should be given with an expanded uncertainty U(k = 2) ≤ 5%. Hence the SSDL-ININ has developed the Dw ’s Calibration and Measurement Capabilities (CMC) for the calibration of ionization chambers, by a coefficient calibration NDw with U (k = 2) ≤l%, based on the International Atomic Energy Agency Technical Report Series 398 international practice code.