In vivo simultaneous imaging with 99m Tc and 18 F using a Compton camera

We have been developing a medical imaging technique using a Compton camera. This study evaluates the feasibility of clear imaging with 99m Tc and 18 F simultaneously, and demonstrates in vivo imaging with 99m Tc and/or 18 F. We used a Compton camera with silicon and cadmium telluride (Si/CdTe) semiconductors. We estimated the imaging performance of the Compton camera for 141 keV and 511 keV gamma rays from 99m Tc and 22 Na, respectively. Next, we simultaneously imaged 99m Tc and 18 F point sources to evaluate the cross-talk artifacts produced by a higher energy gamma-ray background. Then, in the in vivo experiments, three rats were injected with 99m Tc-dimercaptosuccinic acid and/or 18 F-fluorodeoxyglucose and imaged. The Compton images were compared with PET images. The rats were euthanized, and the activities in their organs were measured using a well counter. The energy resolution and spatial resolution were measured for the sources. No apparent cross-talk artifacts were observed in the practical-activity ratio ( 99m Tc: 18 F = 1:16). We succeeded in imaging the distributions of 99m Tc and 18 F simultaneously, and the results were consistent with the PET images and well counter measurements. Our Si/CdTe Compton camera can thus work as a multi-tracer imager, covering various SPECT and PET probes, with less cross-talk artifacts in comparison to the conventional Anger cameras using a collimator. Our findings suggest the possibility of human trials.