Fingertip beta imager based on the SiPM technology

We have implemented the low-profile SENSL 16ch SPMArray2 module in a small prototype of a beta/positron imager. The SiPM sensor has a 0.5-1mm thick plastic scintillator optically coupled via thin (1-2mm) glass window for better light spread between the sixteen 3mm SiPM pads to allow center of gravity position calculations of the scintillation light flashes. In the initial studies, aluminized Mylar foil and Teflon tape were used for a top surface reflector, and black Tedlar foil for a light-tight mechanical barrier. Sensitivity of 3-5 counts/sec per nanoCi was measured with one layer of 50 micron Teflon and 50 micron Tedlar each. For two Tedlar layers the sensitivity was lower by about 10 percent with the applied broad energy window. Intrinsic spatial resolution was estimated at approximately 2.5mm, with the un-collimated positron beam distribution limiting the measurement. The position information can be used as a finer indication when the hot spots are located within the ~10mm×10mm useful FOV of the device. According to the initial plans, the imager will be evaluated as a tool assisting with checking the cancer margin adequacy in breast cancer excision (lumpectomy). Before surgery, the patient will obtain systemic injection of positron biomarker, such as F18-FDG, the same that was used to detect the cancer in the PET procedure. Attached to the surgeons fingertip, the imager will be used to scan the surface of the post-extraction cavity for residual positron activity as an indication of non-sufficient cancer margins, to allow for immediate in-situ correction. The imager is planned as another instrument in the set of complementary imaging and non-imaging tools to assist with breast cancer surgeries, not to replace other tools.