Accuracy of Gamma Probes in Localizing Radioactivity: In-Vitro Assessment and Clinical Implications

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Abstract
Background Radioguided surgery (RGS) uses gamma probes to localize radioactive targets. We examined the in-vitro localizing properties of commercially available gamma probes for three common RGS radioisotopes: technetium-99m (99mTc), indium-111 (111In), and iodine-125 (125I). Methods The linear and angular localizing properties of five gamma probes were assessed. Radioactive counts in air were obtained at multiple energy threshold settings for each radioisotope. The full width half maximum (FWHM) and angular half maximum (AHM) were calculated to determine localizing acccuracy. Results The FWHM of the five probes ranged from 1.2 to 3.4 cm for 99mTc, 1.8 to 2.7 cm for 111In and 1.6 to 2.8 cm for 125I. AHM of the probes ranged from 20 to 49 degrees for 99mTc, 14 to 35 degrees for 111In, and 18 to 47 degrees for l25I. The ranking of probe accuracy depended on the radioisotope studied. Absolute count rates varied with energy threshold settings for each probe and radioisotope. Probes required individualized ene...