A phantom assessment of portable imaging and radio-guided surgery systems with technetium-99m and fluorine-18

To perform a detailed analysis of the performance of mobile intraoperative imaging systems and gamma probes in a phantom set-up, and compare this with a conventional gamma camera.

Two separate experiments were performed. In the first, a modified Jaszczak phantom equipped with five (99m)Tc-filled hot spheres (0.5-20 ml) was analyzed using Sentinella, declipseSPECT and a conventional gamma camera under three conditions: no background, spheres on the surface of the background activity, and totally immersed spheres (contrast level in both 1: 8). In the second experiment, two phantom spheres (0.5 and 2 ml) filled with (99m)Tc and (18)F (infinite contrast, 1: 4 and 1: 8) were measured using the hand-held probes Navigator and GammaLocator DXI. Data analysis consisted of signal-to-background ratios and determination of the full-width at half-maximum (FWHM). A visual scoring was performed by three nuclear medicine physicians.

At infinite contrast, (99m)Tc-filled spheres with volumes of at least 2 ml could be detected adequately with all systems (e.g. 2 ml sphere, FWHM: ECAM 11 mm, declipseSPECT 9 mm, Navigator 13 mm, GammaLocator 12 mm). Under decreased contrast conditions, the results for all systems were impaired and the 0.5 ml phantom sphere filled with either (99m)Tc or (18)F was only detected accurately by the GammaLocator (FWHM range: 13-17 mm).

All systems are suitable for intraoperative sentinel node detection with nearly infinite signal-to-background contrast. At a lower contrast, the GammaLocator performed best for the detection of small volumes at low-contrast ratios regardless of the radionuclide.