J. Neba, J. Wuestemann, P. Matthies, F. Pinto, A. Menzel, K. Schwenkenbecher, T. Barthel, O. S. Grosser, M. Lassmann Intraoperative molecular imaging investigation using a CZT detecor World Congress on Medical Physics and Biomedical Engineering, Prague, Czech Republic, June 2018 (bib)
	In molecular imaging, the spatial and energy resolutions are important to be optimized as well as other camera calibration parameters. To investigate the effectiveness of using a handheld gamma camera as a major aid in intraoperative molecular imaging surgery, the sensitivity of the device should also be a top priority. Method: Using a commercial handheld cadmium zinc telluride (CZT) solid state gamma detector (CrystalCam?), the sensitivity, spatial and energy resolutions were investigated under different conditions but same collimation (LEHS Tungsten). Sensitivity data were acquired from 50 to 350mm source-detector-distance (steps: 50mm) by using a Co-57 point source in air (activity: 610.88 kBq, energy window: 122.1 keV ± 10 %), acquisition duration of 90s. The spatial resolution was investigated using an in-house mini-parallel bar phantom of ca. 2mm thick. The investigation of the image resolution was by point spread function measurements from 50 to 150mm (steps: 50mm), acquisition duration of 120s. Acquisitions were exported using the manufacturer's software (Crystal-Imager) and further processed with ImageJ?. Data plots and analysis was performed on spreadsheets. Adequate count statistics (error below 1%) were achieved in all measurements; and no significant dead-time corrections. Results: The sensitivity versus source-detector-distance response showed an estimated 3.23 cps/MBq/mm loss with increasing point source distance. Interestingly, the 2mm spatial resolution was achieved when using the correct homogeneity correction matrix. The PSF expressed the image resolution of 3.23%, 4.62% and 6.62% at 50, 100, and 150mm SDD respectively, corresponding to count rates of 700, 640 and 480cps. Conclusion: The investigations show that the CrystalCam? can effectively localize "small" lesions up to about 2mm apart and within a relatively small time scale. The high sensitivity and good spatial resolution, in combination with its light-weight and fast and ease of use, make the CrystalCam? very suitable for intraoperative molecular/targeted imaging surgery.
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