Photomultiplier tube artifacts on 67Ga-citrate imaging caused by loss of correction floods due to an off-peak status of one head of a dual-head γ-camera.

UNLABELLED: γ-cameras use flood-field corrections to ensure image uniformity during clinical imaging. A loss or corruption of the correction data of one head of a dual-head camera can result in an off-peak artifactual appearance. We present our experience with the occurrence of such an incident on a (67)Ga scan. METHODS: A patient was referred for a whole-body (67)Ga scan to evaluate for causes of neutropenic fever. Whole-body planar and static images of the head, chest, abdomen, pelvis, and lower extremities in multiple projections were obtained. RESULTS: Whole-body images showed decreased image quality on the anterior view obtained with detector 1 and an unremarkable posterior image obtained with detector 2. A problem with detector 2 was suspected, and additional static images were obtained after rotation of the detector heads. The posterior images taken with detector 1 showed photomultiplier tube outlines. The anterior images taken with detector 2 showed improved count and image quality. It was later found that the uniformity map for detector 2 had been lost and that this software malfunction led to the resulting imaging problem. CONCLUSION: When artifacts with an off-peak appearance are seen on scintigraphic images, evaluation of possible causes should include not only isotope window settings but also an incorrect or corrupted uniformity map.

FDG for therapy of metabolically active tumors.

(18)F-2-deoxy-2-fluoro-D-glucose ((18)F-FDG, later referred to as (19)FDG) has been extensively used in diagnostic positron emission tomography (PET) in oncology for many years. FDG is a glucose analog that is taken by cells in a similar fashion as glucose and is phosphorylated by hexokinase to (18)F-FDG-6-phosphate but cannot undergo further glycolysis, and hence is trapped in the cell. Metastatic cancer remains a major cause of death men and women, surpassed only by heart disease. Despite the enormous research efforts resulting in emergence of novel drug candidates, there is little progress in improving the survival of patients with many types of solid tumors. Thus, novel therapies to combat metastatic cancer are urgently needed. With a physical half-life of almost 2 hours, (18)F emits energetic positrons with high abundance (96%) and a path length in tissue of ∼0.1-0.2 cm. Theoretically, these positrons can kill cancer cells in the same manner as electrons by damaging DNA and cellular machinery and inducing apoptosis/necrosis of the tumor cells. Several years ago, we explored, in a first series of comprehensive studies, the therapeutic potential of FDG in experimental breast cancer and showed its efficacy and safety. Since then, FDG therapy has been shown to be effective and safe in experimental melanoma, colon cancer, as well as in eliminating in vitro the endothelial cells in blood vessels, which supply the tumors with nutrients. The next step forward in translation of FDG therapy into the clinic should be a phase II clinical trial. Also, recent developments in targeted PET imaging could increase the range of PET pharmaceuticals potentially useful for positron therapy of metastatic cancers because of increased specificity of these tracers in comparison with FDG.