Purpose: To compare single photon emission computed tomography (SPECT) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) and positron emission tomography (PET) with FDG to evaluate malignancies.
Materials and methods: PET and SPECT, with fluorine-18 sodium fluoride, were performed sequentially in a cylindric phantom that contained different size spheres with activity ratios of 5:1, 10:1, and 15:1. PET and SPECT were also performed in 24 patients with known or suspected malignancies.
Results: Sensitivities of PET and SPECT were 2,238 cpm/microCi (82.8 cpm/MBq) and 129 cpm/microCi (4.8 cpm/MBq), respectively (reconstructed spatial resolution, 7 and 17 mm, respectively [13-cm radius of rotation]). In the phantom studies, lesions of 1.5 and 1.3 cm or more in diameter were detected with a ratio of 5:1 and 10:1, respectively, and an information density of 150 counts per square centimeter. At FDG PET, 46 hypermetabolic lesions consistent with tumor were depicted in patients; at FDG SPECT, 36 (78%) were depicted. Sensitivity of FDG SPECT was 92% for detection of malignancies 1.8 cm or more in diameter seen at FDG PET.
Conclusion: Findings at FDG SPECT can help differentiate benign from malignant lesions.