Portable PET probes are a novel tool for intraoperative localization of tumor deposits

Six-to-eight-week-old athymic mice were injected with one of four possible tumor cell lines: gastric, pancreas, squamous cell and breast cancer. After tumors reached at least 1 cm in size, they were euthanized and imaged with a micro-PET imager. Hand-held gamma and beta probes were then used in vivo and ex vivo to measure high-energy gamma and beta emissions.The portable PET probes detected high-energy gamma and beta emissions from all tumors evaluated. These emissions were reproducible and we established that beta emissions correlate with high-energy gamma emissions and conventional PET scans. There was a strong positive correlation (R = 0.8) between gamma and beta counts. Beta emission showed a stronger correlation than gamma emission with overall tissue radioactivity.This study is the first to demonstrate that gamma emission detected by conventional PET imaging correlates with beta emissions. This study shows that compared to detection of gamma emissions, beta counts may offer superior real-time localization of tumor deposits. Intraoperative portable PET probe may become a useful way to exploit tumor biology and PET technology to guide real-time tissue characterization during surgery.Positron emission tomography (PET) scans using fluorodeoxyglucose (FDG), an analog of glucose labeled with the positron-emitting fluorine-18, is based on the recognition that malignancies accumulate FDG at greater rates than normal tissue [1]. PET scans have helped increase accuracy of identifying occult sources of cancer and to improve the staging of patients with potentially curable cancer by finding distant sites of tumor spread. However, difficulty remains in pinpointing specific sites of tumor and identifying small cancer deposits as the resolution of PET scans is at best about 1 cm [2]. Unsuspected intra-abdominal disease is still frequently first detected at the time of surgery [3]. Diagnostic laparoscopy is indicated for staging and to determine resectability prior to extensi