Design and evaluation of a prototype radio-ultrasound guided system for simultaneous, dual-modality intraoperative localization

Due to limitations in individual image guidance modalities, such as gamma probes or ultrasound imaging, up to 25% of patients must undergo a revision surgery following breast-conserving surgery. Although previous studies have shown that hybrid imaging systems combining complementary molecular and anatomical imaging provide a more thorough and accurate assessment of cancerous lesions, hybrid systems have seldom been used in the operating room due to difficulties in combining the modalities. To address this need, we developed an innovative radio-ultrasound guided system by incorporating a focused gamma probe that provides spot detection of radioisotopes in a remote focal zone. The objective of this study was to design, fabricate, and evaluate the spatial resolution and sensitivity of a prototype radio-ultrasound guided system and assess its feasibility for real-time localization. The hybrid system was realized by clipping an ultrasound transducer and a focused gamma probe into a two-part, 3D-printed receptacle, aligning the gamma focal region within the ultrasound imaging plane for unobstructed, simultaneous imaging. In a phantom test, the focused gamma probe achieved a lateral resolution of 5.3 mm, an axial resolution of 10.2 mm, and a sensitivity of 3.2 cps/kBq. Simultaneously, the system acquired high-resolution ultrasound images consistent with the given imaging protocol. Testing also confirmed that the hybrid imaging display allowed the device to be guided by hand for real-time localization. Overall, this work presents a unique and practical approach to couple a focused gamma probe with ultrasound imaging, allowing surgeons to precisely identify and quantify radiolabeled lesions within the anatomy.