Calibration of the LNMRI Secondary Standard Ionization Chamber for I capsules used in nuclear medicine.

The radionuclide I has been increasingly used in nuclear medicine therapy procedures. Nowadays, the 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 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 A Bq, is quite similar to the calibration factor of the I solution contained in the standard ampoule geometry, 6.4515 ± 0.0368 × 10 A Bq. After obtaining the calibration factor it was used to measure I therapy capsules in order to check the performance of radionuclide calibrators of some Brazilian nuclear medicine centers. [ABSTRACT FROM AUTHOR]