Performance evaluation of a position-sensitive SiPM-based gamma camera for intraoperative imaging

Abstract

Abstract Background The POSiCS camera is a handheld and wireless, small field-of-view gamma camera developed for use in radio-guided surgery (RGS), with sentinel lymph node biopsy (SLNB) as its benchmark application. This compact and lightweight detector (about $$350\,\textrm{g}$$ ) maps tissues labeled with a $${^{99m}\hbox {Tc}}$$ radiotracer to highlight target lesions. By enabling intraoperative visualization close to the surgical field, POSiCS aims to reduce invasiveness and operative time, improve localization accuracy, and minimize post-operative complications. Methods The performances of two hardware configurations were tested: high-sensitivity and high-resolution, to meet application-specific needs. Tests assessed key parameters, including extrinsic spatial resolution, energy resolution, and sensitivity, as well as shielding effectiveness and response to different gamma energies. Characterization of the camera’s sensitivity and energy resolution employed a Flood (flat) $${^{99m}\hbox {Tc}}$$ source, while the determination of spatial resolution and lateral collimator penetration was performed using a $${^{57}\hbox {Co}}$$ point source. The response to $${^{177}\hbox {Lu}}$$ was also investigated, given its growing role in theranostics, by imaging a cavity filled with the radionuclide and evaluating the reconstruction performance of POSiCS across its different gamma-ray emissions.. Results In direct contact, the spatial resolution was $$1.9\pm 0.1\,\textrm{mm}$$ in high-sensitivity mode and $$1.4\pm 0.1\,\textrm{mm}$$ in high-resolution mode. System sensitivity at $$2\,\textrm{cm}$$ source-detector distance was $$481\pm 14\,\mathrm {cps/MBq}$$ and $$134\pm 8\,\mathrm {cps/MBq}$$ , respectively. Both modes showed an energy resolution of about 20% at 140 keV, though the high-resolution collimator exhibited increased scatter due to its larger tungsten content. Conclusion The POSiCS camera combines compactness, ease of use, and reliable performance, making it suitable for RGS. Its interchangeable configurations allow balancing between sensitivity and resolution depending on surgical needs. The results demonstrate millimeter-scale resolution and adequate sensitivity for $${^{99m}\hbox {Tc}}$$ , confirming its suitability for intraoperative use. Imaging with $${^{177}\hbox {Lu}}$$ was also proven possible, although achieved only with the 55 keV and 113 keV photopeaks. These outcomes support the camera’s potential for broader clinical deployment and further development toward advanced intraoperative nuclear imaging.