Performance of a dual, solid-state intraoperative probe system with F-18, Tc-99m, and In-111

The use of tracer-avid radiopharmaceuticals and handheld, intraoperative, r adiation-sensitive probes to localize areas of tumors promises to improve s urgical treatments of cancer. Currently several beta- and gamma -ray-emitti ng radiopharmaceuticals are proposed for use in these procedures. Therefore , intraoperative-probe systems should be capable of optimum performance wit h several different radionuclides. The goal of this study was to evaluate t he performance of a dual, solid-state probe with three of these radionuclid es (F-18, Tc-99m, and In-111), Methods: The detector unit of the intraopera tive-probe system used in this investigation consisted of a stack of two io n-implanted silicon detectors separated by 0.5 mm. The system could be oper ated in two modes: beta optimized, in which the difference between the sign als from the two detectors was calculated to correct the beta signal for ph oton contamination, and photon-optimized mode, in which the signals were su mmed. Detection sensitivity and an index measuring beta detection selectivi ty were measured in both acquisition modes with the three different radionu clides, The gamma -ray detection sensitivity of a commercially available pr obe was measured with Tc-99m and compared with the results with a solid-sta te probe. Results: beta and photon emissions (gamma -rays and annihilation photons) produced by all three radionuclides were detected by the probe. In gamma -optimized acquisition mode, the greatest gamma -detection sensitivi ty was achieved with F-18; photon sensitivity was greatest for measurements with In-111, The lowest detection sensitivities (beta and photon) were obt ained with Tc-99m. With the probe system in gamma -optimized mode, the grea test beta and photon sensitivities were achieved with F-18; th, lowest were obtained with Tc-99m. The gamma -detection sensitivity measured with Tc-99 m in gamma mode (5.59 +/- 0.41 counts per second [cps]/kBq) compared surpri singly well with the results from the commercial probe (8.75 +/- 0.47cps/kB q). Conclusion: The results from this investigation demonstrate the flexibi lity and versatility of the dual, solid-state probe system used in this stu dy. These capabilities may be used to improve existing techniques or lead t o new methods for performing radionuclide-guided surgeries.