Performancee evaluation of a dual Micro-SPECT detector system [abstract]

Abstract

The ability to conduct radiopharmaceutical research in vivo is largely dependent on nuclear imaging hardware and is subject to its limitations. The inability of clinical instrumentation to conduct non-invasive tracer bio-kinetics has spurred the development of dedicated pre-clinical imaging systems such as Micro-SPECT. Pixelated NaI(Tl) detectors are a relatively new attempt to further increase Micro-SPECT viability in conducting longitudinal research. The goal of this experiment is to evaluate a dual pixelated NaI(Tl) gamma-ray Micro-SPECT system and its ability to conduct routine preclinical studies. The SPECT detectors each have an area of 150 mm x 150 mm composed of 4624 (2 mm x 2 mm x 10 mm) NaI(Tl) scintillators coupled to position sensitive photomultiplier tubes. Various tungsten pinhole collimators are used depending on the amount of radioactivity in the SPECT field of view. The Micro-SPECT images are reconstructed using an OSEM routine with sub-voxel capabilities. The sensitivities and efficiencies of the SPECT detectors were determined for Tc-99m and In-111. The practical and optimum SPECT system resolutions were determined using commercial phantoms and evaluated in a Tc-99m-MDP SPECT/CT scan. Longitudinal SPECT/CT studies were performed on tumor bearing models using a receptor targeted radiopharmaceutical at 1, 4, 24, 48 and 72 hours post injection. System sensitivities of 340 cps/MBq and efficiencies of 0.03% were achieved at 25 mm from the 2 mm pinhole aperture. The spatial resolution of the SPECT was determined to optimally be 1.6 mm and practically 2.4 mm using a hot-rod reconstructed Tc-99m phantom scanned for 16 hours and 30 minutes respectively. Bone and tumor SPECT studies revealed excellent target tissue/organ visualization. Longitudinal Micro-SPECT/CT studies were conducted successfully over a 72 hour period post injection. These findings suggest that pixelated NaI(Tl) detector technology is capable of repeated imaging in the same subject.

The ability to conduct radiopharmaceutical research in vivo is largely dependent on nuclear imaging hardware and is subject to its limitations. The inability of clinical instrumentation to conduct non-invasive tracer bio-kinetics has spurred the development of dedicated pre-clinical imaging systems such as Micro-SPECT. Pixelated NaI(Tl) detectors are a relatively new attempt to further increase Micro-SPECT viability in conducting longitudinal research. The goal of this experiment is to evaluate a dual pixelated NaI(Tl) gamma-ray Micro-SPECT system and its ability to conduct routine preclinical studies. The SPECT detectors each have an area of 150 mm x 150 mm composed of 4624 (2 mm x 2 mm x 10 mm) NaI(Tl) scintillators coupled to position sensitive photomultiplier tubes. Various tungsten pinhole collimators are used depending on the amount of radioactivity in the SPECT field of view. The Micro-SPECT images are reconstructed using an OSEM routine with sub-voxel capabilities. The sensitivities and efficiencies of the SPECT detectors were determined for Tc-99m and In-111. The practical and optimum SPECT system resolutions were determined using commercial phantoms and evaluated in a Tc-99m-MDP SPECT/CT scan. Longitudinal SPECT/CT studies were performed on tumor bearing models using a receptor targeted radiopharmaceutical at 1, 4, 24, 48 and 72 hours post injection. System sensitivities of 340 cps/MBq and efficiencies of 0.03% were achieved at 25 mm from the 2 mm pinhole aperture. The spatial resolution of the SPECT was determined to optimally be 1.6 mm and practically 2.4 mm using a hot-rod reconstructed Tc-99m phantom scanned for 16 hours and 30 minutes respectively. Bone and tumor SPECT studies revealed excellent target tissue/organ visualization. Longitudinal Micro-SPECT/CT studies were conducted successfully over a 72 hour period post injection. These findings suggest that pixelated NaI(Tl) detector technology is capable of repeated imaging in the same subject.