Low-dose 18F-FDG TOF-PET/MR for accurate quantification of brown adipose tissue in healthy volunteers

Abstract

Background: Positron emission tomography (PET) is increasingly applied for in vivo brown adipose tissue (BAT) research in healthy volunteers. To limit the radiation exposure, the injected 18 F-FDG tracer dose should be as low as possible. With simultaneous PET/MR imaging, the radiation exposure due to computed tomography (CT) can be avoided, but more importantly, the PET acquisition time can often be increased to match the more extensive magnetic resonance (MR) imaging protocol. The potential gain in detected coincidence counts, due to the longer acquisition time, can then be applied to decrease the injected tracer dose. The aim of this study was to investigate the minimal 18 F-FDG dose for a 10-min time-of-flight (TOF) PET/MR acquisition that would still allow accurate quantification of supraclavicular BAT volume and activity. Methods: Twenty datasets from 13 volunteers were retrospectively included from a prospective clinical study. PET emission datasets were modified to simulate step-wise reductions of the original 75 MBq injected dose. The resulting PET images were visually and quantitatively assessed and compared to a 4-min reference scan. For the visual assessment, the image quality and artifacts were scored using a 5-point and a 3-point Likert scale. For the quantitative analysis, image noise and artifacts, BAT metabolic activity, BAT metabolic volume (BMV), and total BAT glycolysis (TBG) were investigated. Results: The visual assessment showed still good image quality for the 35%, 30%, and 25% activity reconstructions with no artifacts. Quantitatively, the background noise was similar to the reference for the 35% and 30% activity reconstructions and the artifacts started to increase significantly in the 25% and lower activity reconstructions. There was no significant difference in supraclavicular BAT metabolic activity, BMV, and TBG between the reference and the 35% to 20% activity reconstructions. Conclusions: This study indicates that when the PET acquisition time is matched to the 10-min MRI protocol, the injected 18 F-FDG tracer dose can be reduced to approximately 19 MBq (25%) while maintaining image quality and accurate supraclavicular BAT quantification. This could decrease the effective dose from 1.4 mSv to 0.36 mSv.

Comparative [18F]FDG and [18F]DPA714 PET imaging and time-dependent changes of brown adipose tissue in tumor-bearing mice

“…[ 18 F]FDG PET imaging is the gold standard for the study of BAT activity in vivo [ 11 ], but its defects such as low positive rate (<5%) and poor stability in even normal physiological conditions limit the development of BAT research [ 12 , 13 ]. BAT mainly relies on fatty acids instead of glucose as the substrate of energy metabolism, so the uptake of [ 18 F]FDG in BAT is relatively little.…”

“…However, the imaging results of [ 18 F]FDG PET are quite discrepant and vulnerable to environmental influences [ 11 ]. In the retrospective studies, the prevalence or positive rate of BAT in measurement was less than 5% [ 12 , 13 ]. 99m Tc-methoyl isobutyl isonitrile (MIBI) and 123 I-meta-iodobenzylguanidine (MIBG) single-photon emission computed tomography (SPECT) can also be used in BAT imaging, but the low positive rate limits their application [ 14 ].…”

Feasibility of Low-Dose 68Ga-DOTATATE With Short Acquisition Time Using Total-Body PET/CT in Patients With Neuroendocrine Tumor

“…In addition, the image quality could also be improved using the reconstructed method of PSF and TOF. Previous study [21] reported that the TOF could accelerate the vergence for a 13 mm sphere and obtain more contact information than that without TOF information. Although the image reconstructed with PSF correction slowed the iterative convergence, it could provide a more uniform background and increased SNRL than that without PSF correction.…”

Estimation of the Internal Dose Imparted by 18F-Fluorodeoxyglucose to Tissues by Using Fricke Dosimetry in a Phantom and Positron Emission Tomography

“…Lowering the injected tracer dose means fewer positron-emitting radionuclides and thus less detected 511 keV photon pairs. Therefore, by taking into account this issue of count loss can be compensated by longer PET acquisition times (51). The scan time were calculated according to the previous study of Koopman et al A= c x w 2 x T min / t, where c is a constant which is typically 0.0533 (MBq/kg 2 ), w is the patient's body weight (in kg), T min is the minimal scan time per bed position needed to be extracted using an image coefficient of variation (COV) of 15 %, and t is the scan time per bed position (s) (52).…”