In this study, the feasibility of utilizing 2-deoxy-2-fluoro-d-glucose (FDG) in conjunction with a positron-sensitive intraoperative probe to guide breast tumor excision was investigated.
Methods: The probe was constructed with a plastic scintillator tip coupled to a photomultiplier tube with fiber optic cable. Anticipated resolution degradation was evaluated by measurement of line spread functions in the presence of background radiation. Realistic photon background distributions were simulated with a human torso phantom and a cardiac insert. The relationship between resolution and energy threshold was measured to find the optimal discriminator settings. In addition, probe sensitivity as a function of energy threshold was determined for various size-simulated tumors. Finally, the ability to localize breast cancers in vivo was tested in a rodent model. Mammary rat tumors implanted in Lewis rats were examined after injection with FDG; these results were correlated with those of histologic analyses.
Results: Measurements of line spread functions indicated that resolution could be maximized in a realistic background photon environment by increasing the energy threshold to levels at or above the Compton continuum edge (340 keV). At this setting, the probe's sensitivity was determined to be 58 and 11 cps/muCi for 3.18- and 6.35-mm diameter simulated tumors, respectively. Probe readings correlated well with histologic results: the probe was generally able to discriminate between tumor and normal tissue.
Conclusion: This study indicates that breast cancer surgery guided by a positron-sensitive probe warrants future evaluation in breast-conserving surgery of patients with breast cancer.