An accurate and inexpensive gamma camera-based system for wipe testing.

Abstract

UNLABELLED: Radiation safety regulations require regular wipe testing to detect possible radioactive contamination. The objective of this work was to develop and test an accurate, convenient and inexpensive means of performing wipe tests with a conventional gamma camera. METHODS: An array of fifteen 3.2 x 3.2-cm square holes was chiseled through a previously-damaged collimator, substantially increasing the gamma camera's sensitivity for wipe testing. The sensitivity and the minimum detectable activity (MDA) were evaluated using low-activity sources of 99mTc, 111In, 67Ga, 201TI and 131I. RESULTS: The wipe testing system had a sensitivity of 2.5 cpm/Bq for 131I, 2.9 cpm/Bq for 67Ga, 3.8 cpm/Bq for 99mTc, 4.1 cpm/Bq for 201TI and 4.3 cpm/Bq for 111In. In all cases, the MDA was less than 35 Bq for a 2-min counting time and an open-energy window. CONCLUSION: The gamma camera wipe test system provides an accurate, inexpensive and easy method of meeting regulatory requirements for contamination monitoring of radioisotopes commonly used in nuclear medicine.