Calibration of the LNMRI secondary standard ionization chamber for ~(131)I capsules used in nuclear medicine

摘要

The radionuclide ~(131)I has been increasingly used in nuclear medicine therapy procedures. Nowadays, the ~(131)I source administered to the patient is manufactured in two different geometries: solution and capsules. The purpose of this study is the accurate measurement of the activity present in a ~(131)I capsule without destroys it. The methodology to determine the capsules activity is to obtain the calibration factor of an IG12 secondary standard activity measurement system based on the IG12 well-type ionization chamber set up at Brazilian national metrology laboratory for ionizing radiation (LNMRI) of institute of radiation protection and dosimetry (IRD).The result obtained, 6.4670 ± 0.0381 × 10 ~(-18) A Bq ~(-1), is quite similar to the calibration factor of the ~(131)I solution contained in the standard ampoule geometry, 6.4515 ± 0.0368 × 10 ~(-18) A Bq ~(-1). After obtaining the calibration factor it was used to measure ~(131)I therapy capsules in order to check the performance of radionuclide calibrators of some Brazilian nuclear medicine centers.