Comparative study of physiological FDG uptake in small structures between silicon photomultiplier-based PET and conventional PET

• Published in: Annals of nuclear medicine 2024-02, Vol.38 (2), p.131-138
• Main Authors: Watanabe, Shiro, Hirata, Kenji, Magota, Keiichi, Takenaka, Junki, Wakabayashi, Naoto, Shinyama, Daiki, Yasuda, Koichi, Homma, Akihiro, Kudo, Kohsuke
• Format: Article
• Language: English
• Subjects: Accumulation; Adrenal glands; Blood; Comparative studies; Computed tomography; Epididymis; Evaluation; Fluorodeoxyglucose F18; Head and Neck Neoplasms; Humans; Imaging; Liver; Male; Malignancy; Medicine; Medicine & Public Health; Nuclear Medicine; Original Article; Photomultiplier tubes; Physiology; Pituitary; Pituitary gland; Positron emission; Positron emission tomography; Positron Emission Tomography Computed Tomography - methods; Radiology; Silicon; Spatial discrimination; Spatial resolution; Spinal cord; Thresholds; Tomography
• ISSN: 0914-7187; 1864-6433
• DOI: 10.1007/s12149-023-01884-3

Objective Silicon photomultiplier-based positron emission tomography/computed tomography (SiPM-PET/CT) has the superior spatial resolution to conventional PET/CT (cPET/CT). This head-to-head comparison study compared the images of physiological 18 F-fluorodeoxyglucose (FDG) accumulation in small-volume structures between SiPM-PET/CT and cPET/CT in patients scanned with both modalities, and we investigated whether the thresholds that are reported to be useful for differentiating physiological accumulations from malignant lesions can also be applied to SiPM-PET/CT. Methods We enrolled 21 consecutive patients with head and neck malignancies who underwent whole-body FDG-PET/CT for initial staging or a follow-up evaluation (October 2020 to March 2022). After being injected with FDG, all patients underwent PET acquisition on both Vereos PET-CT and Gemini TF64 PET-CT systems (both Philips Healthcare) in random order. For each patient, the maximum standardized uptake value (SUVmax) was measured in the pituitary gland, esophagogastric junction (EGJ), adrenal glands, lumbar enlargement of the spinal cord, and epididymis. We measured the liver SUVmean and the blood pool SUVmean to calculate the target-to-liver ratio (TLR) and the target-to-blood ratio (TBR), respectively. Between-groups differences in each variable were examined by a paired t-test. We also investigated whether there were cases of target uptake greater than the reported threshold for distinguishing pathological from physiological accumulations. Results Data were available for 19 patients. Ten patients were in Group 1, i.e., the patients who underwent SiPM-PET first, and the remaining nine patients who underwent cPET first were in Group 2. In the SiPM-PET results, the SUVmax of all targets was significantly higher than that obtained by cPET in all patients, and this tendency was also observed when the patients were divided into Groups 1/2. The TLRs of all targets were significantly higher in SiPM-PET than in cPET in all patients, and SiPM-PET also showed significantly higher TBRs for all targets except the EGJ ( p  = 0.052). Conclusions The physiological uptake in the small structures studied herein showed high accumulation on SiPM-PET. Our results also suggest that the thresholds reported for cPET to distinguish pathological accumulations likely lead to false-positive findings in SIPM-PET evaluations.