Performance of a dual, solid-state intraoperative probe system with 18F, 99mTc, and (111)In

The use of tracer-avid radiopharmaceuticals and handheld, intraoperative, radiation-sensitive probes to localize areas of tumors promises to improve surgical treatments of cancer. Currently several beta- and gamma-ray-emitting radiopharmaceuticals are proposed for use in these procedures. Therefore, intraoperative-probe systems should be capable of optimum performance with several different radionuclides. The goal of this study was to evaluate the performance of a dual, solid-state probe with three of these radionuclides (18F, 99mTc, and (111)In).

The detector unit of the intraoperative-probe system used in this investigation consisted of a stack of two ion-implanted silicon detectors separated by 0.5 mm. The system could be operated in two modes: beta optimized, in which the difference between the signals from the two detectors was calculated to correct the beta signal for photon contamination, and photon-optimized mode, in which the signals were summed. Detection sensitivity and an index measuring beta detection selectivity were measured in both acquisition modes with the three different radionuclides. The gamma-ray detection sensitivity of a commercially available probe was measured with 99mTc and compared with the results with a solid-state probe.

Beta and photon emissions (gamma-rays and annihilation photons) produced by all three radionuclides were detected by the probe. In beta-optimized acquisition mode, the greatest beta-detection sensitivity was achieved with 18F; photon sensitivity was greatest for measurements with (111)In. The lowest detection sensitivities (beta and photon) were obtained with 99mTc. With the probe system in gamma-optimized mode, the greatest beta and photon sensitivities were achieved with 18F; the lowest were obtained with 99mTc. The gamma-detection sensitivity measured with 99mTc in gamma mode (5.59 +/- 0.41 counts per second [cps]/kBq) compared surprisingly well with the results from the commercial probe (8.75 +/- 0.47 cps/kBq).

The results from this investigation demonstrate the flexibility and versatility of the dual, solid-state probe system used in this study. These capabilities may be used to improve existing techniques or lead to new methods for performing radionuclide-guided surgeries.