Purpose: In patients with cancer, performance was assessed of a commercially available triple-head gamma camera fitted with ultra-high energy parallel-hole collimators performing single photon emission computed tomography (SPECT) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG). Results were compared with those of positron emission tomography (PET) with FDG.
Materials and methods: Performance characteristics were first determined in phantom studies for FDG PET and triple-head gamma camera SPECT systems. In 13 patients with malignancies, FDG PET was followed by SPECT of the same region, and imaging results were independently assessed.
Results: Sensitivity of the PET and SPECT systems was 58.3 counts/MBq/min and 4.5 counts/MBq/min, respectively. Reconstructed spatial resolution was approximately 7 mm for PET and 20 mm for SPECT. All known cancer foci were detected at PET. SPECT depicted 11 of the 22 lesions detected at PET, but only five of the 14 lesions less than 3 cm in diameter.
Conclusion: FDG SPECT performed with a specially collimated triple-head gamma camera depicted some cancers but had an unacceptably low sensitivity compared with PET for lesions less than 3 cm in diameter. PET is preferable for detecting small cancers.