Application of an [(18)F]fluorodeoxyglucose-sensitive probe for the intraoperative detection of malignancy

Abstract

Background: Whole-body positron emission tomography (PET) has been shown to be a highly sensitive method for detecting malignancy not imaged by conventional modalities. We have adapted a hand-held gamma-ray-sensitive probe to detect the radiation emission from the [(18)F]fluorodeoxyglucose (FDG) used in PET imaging. This pilot study was devised to examine the feasibility of using a hand-held probe to intraoperatively differentiate normal from tumor-bearing tissue.

Materials and methods: A commercially available gamma probe was adapted to detect the radioactivity released from FDG and examined to determine the in vitro sensitivity for localization of a FDG point source. Eight consecutive patients underwent resection of metastatic colon cancer or melanoma; each received a preoperative injection of 7--10 mCi of FDG. The gamma probe was used to determine radioactive counts per second from tumor and normal tissue, and ratios of tumor to adjacent normal background were calculated.

Results: In vitro studies with a FDG point source demonstrated the probe could identify the source with a 50% reduction in maximum counts 1.7 +/- 0.1 cm from the source (full-width half-maximum measurement). Based on the results of their preoperative PET scans 17 tumors were identified from the 8 patients. Of the 17 tumors assessed the in vivo tumor-to-background ratios varied from 1.16:1 to 4.67:1 for the melanoma patients (13 tumors) and from 1.19:1 to 7.92:1 for colon cancer patients (4 tumors). Thirteen tumors were resected; four (2 patients) were unresectable.

Conclusions: This study demonstrates the use of a hand-held gamma-ray-sensitive probe to intraoperatively differentiate the radioactivity released from FDG from tumor-bearing and adjacent normal tissue. While further studies are necessary for us to optimize the use of this probe, the intraoperative detection of FDG-avid malignancies may ultimately improve our ability to completely resect patients with metastatic disease.