RT Journal Article
SR Electronic
T1 Assessment of incidental pituitary uptake on FDG PET/CT scan: Digital vs. conventional PET/CT
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1294
OP 1294
VO 61
IS supplement 1
A1 Osamu Manabe
A1 Kenji Hirata
A1 Keiichi Magota
A1 Daiki Shinyama
A1 Ronee Asad
A1 Sho Furuya
A1 Naoto Numata
A1 Noriko Oyama-Manabe
A1 Tohru Shiga
A1 Kohsuke Kudo
YR 2020
UL http://jnm.snmjournals.org/content/61/supplement_1/1294.abstract
AB 1294Introduction: The physiological uptake of the pituitary gland is rarely met in the study of conventional PET (CPET). FDG accumulation in the sellar is warranted further diagnostic evaluation for the clinical decision making because pituitary incidentaloma shows obvious uptake and is fairly common in the general population. Fully digital PET (DPET) camera provides true digital photon counting with 1-to-1 crystal coupling which leads to higher count rate detection efficiency across a more uniform scintillator distribution compared to CPET with photomultiplier tubes. DPET might be used to detect small biologically active disease. However, physiological uptake in the sellar might produce a false-positive result for the DPET. Our aim of this study is to identify the incidence of focal pituitary uptake on FDG DPET compared to CPET. Methods: We retrospectively analyzed consecutive 45 patients who underwent FDG DPET from April to December 2019. For the control group, 41 consecutive patients who underwent an FDG CPET for evaluating in 2019 were retrospectively analyzed. Patients who were < 20 years old and patients who were suffered or suspected brain tumor were excluded. Positive FDG accumulation in the pituitary gland is defined as increased FDG uptake localized in the sellar area that is greater than background activity in adjacent tissues. We investigated the glucose metabolic status of the sellar using maximum of standardized uptake value (SUVmax) to place a 10-mm-in-diameter spherical volume of interest within the sellar area. The CPET is a Gemini TF 64 (Philips Healthcare, Cleveland, OH) which transaxial and axial fields of view were 57.6 cm and 18.0 cm, respectively. Images were reconstructed using OSEM algorism reinforced with time-of-flight algorithm but without point spread function correction. The reconstructed images had a matrix size of 144 × 144 and a voxel size of 4.0 × 4.0 × 4.0 mm. The DPET is a Vereos (Philips Healthcare, Cleveland, OH) which transaxial and axial fields of view were 67.6 cm and 16.4 cm, respectively. Images were reconstructed using OSEM algorism. Both time-of-flight algorithm and point spread function correction were applied. The reconstructed images had a matrix size of 338 × 338 and a voxel size of 2.0 × 2.0 × 2.0 mm. Data are expressed as means ± standard deviations (SDs). A p value of < 0.05 was considered significant. The Wilcoxon signed-rank test was used for inter-group comparisons. Fisher’s exact test was used to compare discrete data. Statistical calculations were carried out using SAS (JMP ver. 14, SAS, Cary, NC, USA). Results: Gender, age and fasting blood glucose level showed no significant differences between the patients scanned by DPET and CPET. Incidentally detected focal FDG accumulation in the pituitary gland was found in 23 of 45 patients (52.3%) on DPET which was significantly higher compared to 5 of 41 patients (12.2%) on CPET (p = 0.0001). The representative case of DPET was shown in Figure A-C, with significantly elevated FDG metabolic activity as SUVmax 6.3 in the pituitary gland. The SUVmax on DPET was significantly higher than that on CPET (4.1 ± 3.9 vs. 2.5 ± 0.6, p < 0.0001) (Figure D). Conclusions: Improved photon counting technology in the digital PET/CT can detect the physiological uptake of the pituitary gland. Although incidental FDG uptake on CPET is an unusual finding, the prevalence of physiological uptake in the pituitary gland is high (52.3%) on DPET. Therefore, we have to pay attention not to overestimate the pituitary diseases.