A novel imaging beta probe for radioguided surgery

Gamma-sensitive intraoperative probes are routinely used in the assessment of conditions that include the spread of breast cancer into the lymphatic system, by detecting radiation emitted by radiopharmaceuticals such as ¹⁸F-FDG, ^99mTc, ¹³¹I, ¹¹¹In and ¹²⁵I. However, a major drawback of existing gamma probes is their inability to distinguish between radiation emitted by tissue directly in front of them and background emissions from surrounding areas, seriously degrading the user's ability to localize the source of emitted radiation. To address this issue, we have developed a novel, hand-held, digital probe (termed the Imaging Beta Probe or IBP), designed to rapidly localize and provide real-time, high-resolution images of suspect tissues by detecting emitted beta radiation with high sensitivity. Here we report preliminary test results for this newlydesigned probe. The beta sensor consists of a thin microstructured CsI:TI film optically coupled to a highly sensitive electron-multiplying charged coupled device (EMCCD) photodetector via a high-resolution, coherent, fiberoptic conduit. The microcolumnar structure of the CsI:TI scintillator constrains the spread of scintillation light to typically <100 mm, allowing the detection of beta radiation with high spatial resolution. Preliminary data acquired with the probe, in conj unction with low-energy β-emitting radiolabels such as ³H, demonstrates the high sensitivity of our design. The evaluation of the probe using standard clinical phantoms as well as operational data obtained on mice models is discussed.