Author: Steven Brown, Mike Hopkins, Jerimy C. Polf, Scott Sawyer, Benjamin L. Viglianti 👨🔬
Affiliation: H3D, inc, University of Michigan, M3D, Inc, M3D Imaging 🌍
Purpose: We characterized the sensitivity, energy dependence, and calibrated dose rate for a radiation imaging survey meter (RAVIN Cam; M3d inc., Ann Arbor MI) based on cadmium zinc telluride (CZT) crystals for gamma detection and imaging of medical isotopes.
Methods: We measured the sensitivity (counts-per-second/mCi) of the RAVIN Cam as well as energy spectrum and dose rates (mrem/hr) for 99mTc, I-123, Lu-177, In-111, I-131, F-18, and Cs-137 isotopes at distances from 10 cm to 50 cm. We determined the change in sensitivity as a function of distance, as well as the energy response of the RAVIN (at 30 cm) for gamma energies from 140 keV to 662 keV. We then compared the measured dose rate for the RAVIN to calculated dose rates using the known isotope activity and published dose rate constants for the tested isotopes.
Results: The measured signal decreased as a function of ~1/r (where r = the distance from the detector) for all isotopes across the tested energy range. Additionally, the sensitivity of the camera varied by a factor of 3x across the tested energy range. Finally, when corrected for the energy dependence, the measured dose rate was within ±20% (accuracy required by Nuclear Regulatory Commission regulations) of the calculated values across the full range of common medical isotopes tested.
Conclusion: The new RAVIN Cam imaging survey meter can accurately image and detect the presence of medical isotopes, as well as determine their dose rate. This provides a new hand-held imager for medical workers to quickly and accurately image, locate, and determine strength of radiation contamination within medical clinics, to help improve speed and efficiency of radio-isotope contamination localization and cleanup as well as patient discharge surveys.