Biodistribution and radiation dosimetry of the 18 kDa translocator protein (TSPO) radioligand [18F]FEDAA1106: a human whole-body PET study.

PURPOSE: [(18)F]FEDAA1106 is a recently developed positron emission tomography (PET) radioligand for in vivo quantification of the 18 kDa translocator protein [TSPO or, as earlier called, the peripheral benzodiazepine receptor (PBR)]. TSPO imaging is expected to be useful for the clinical evaluation of neuroinflammatory diseases. The aim of this study was to provide dosimetry estimates for [(18)F]FEDAA1106 based on human whole-body PET measurements. METHODS: PET scans were performed for a total of 6.6 h after the injection of 183.8 ± 9.1 MBq of [(18)F]FEDAA1106 in six healthy subjects. Regions of interest were drawn on coronal images. Estimates of the absorbed doses of radiation were calculated using the OLINDA software. RESULTS: Peak uptake was largest in lungs, followed by liver, small intestine, kidney, spleen and other organs. Peak values of the percent injected dose (%ID) at a time after radioligand injection were calculated for the lungs (27.1%ID at 0.2 h), liver (21.1%ID at 0.6 h), small intestine (10.4%ID at 6.3 h), kidney (4.9%ID at 1.8 h) and spleen (4.6%ID at 0.6 h). The largest absorbed dose was found in the spleen (0.12 mSv/MBq), followed by kidneys (0.094 mSv/MBq). The calculated mean effective dose was 0.036 mSv/MBq. CONCLUSION: Based on the distribution and dose estimates, the estimated radiation burden of [(18)F]FEDAA1106 is moderately higher than that of [(18)F]fluorodeoxyglucose (FDG). In clinical studies, the administered activity of this radioligand ought to be adjusted in line with regional regulations. This result would be helpful for further clinical TSPO imaging studies.

Advancement in PET quantification using 3D-OP-OSEM point spread function reconstruction with the HRRT.

PURPOSE: Image reconstruction including the modelling of the point spread function (PSF) is an approach improving the resolution of the PET images. This study assessed the quantitative improvements provided by the implementation of the PSF modelling in the reconstruction of the PET data using the High Resolution Research Tomograph (HRRT). METHODS: Measurements were performed on the NEMA-IEC/2001 (Image Quality) phantom for image quality and on an anthropomorphic brain phantom (STEPBRAIN). PSF reconstruction was also applied to PET measurements in two cynomolgus monkeys examined with [(18)F]FE-PE2I (dopamine transporter) and with [11C]MNPA (D2 receptor), and in one human subject examined with [11C]raclopride (D2 receptor). RESULTS: PSF reconstruction increased the recovery coefficient (RC) in the NEMA phantom by 11-40% and the grey to white matter ratio in the STEPBRAIN phantom by 17%. PSF reconstruction increased binding potential (BP (ND)) in the striatum and midbrain by 14 and 18% in the [18F]FE-PE2I study, and striatal BP (ND) by 6 and 10% in the [11C]MNPA and [11C]raclopride studies. CONCLUSION: PSF reconstruction improved quantification by increasing the RC and thus reducing the partial volume effect. This method provides improved conditions for PET quantification in clinical studies with the HRRT system, particularly when targeting receptor populations in small brain structures.

Whole-body biodistribution, radiation dosimetry estimates for the PET norepinephrine transporter probe (S,S)-[18F]FMeNER-D2 in non-human primates.

BACKGROUND: (S,S)-[F]FMeNER-D2 is a recently developed norepinephrine transporter ligand which is a potentially useful radiotracer for mapping the brain and heart norepinephrine transporter in vivo using positron emission tomography. In this work, we quantified the biodistribution over time and radiation exposure to multiple organs with (S,S)-[F]FMeNER-D2. METHODS: Whole-body images were acquired for 21 time points in two cynomolgus monkeys for approximately 270 min after injection of radioligand. Compressed 3-D to 2-D planar images were used to identify organs with the highest radiation exposure at each time point. Estimates of the absorbed dose of radiation were calculated using the MIRDOSE 3.1 software program performed with the dynamic bladder and ICRP 30 gastrointestinal tract models. RESULTS: In planar images, peak values of the percent injected dose (%ID) at a time after radioligand injection were calculated for the lungs (26.76% ID at 1.42 min), kidneys (13.55% ID at 2.18 min), whole brain (5.65% ID at 4.48 min), liver (7.20% ID at 2 min), red bone marrow (5.02% ID at 2.06 min), heart (2.36% ID at 1.42 min) and urinary bladder (23% ID at 250 min). Assuming a urine voiding interval of 2.4 h, the four organs with highest exposures in microGy . MBq ( mrad . mCi) were kidneys 126 (468), heart wall 108 (399), lungs 88.4 (327) and urinary bladder 114 (422). The effective doses were estimated with and without urine voiding at a range of 123 (33) and to 131 (35.5) microGy . MBq ( mrad . mCi). CONCLUSION: The estimated radiation burden of (S,S)-[F]FMeNER-D2 is comparable to that of other F radioligands.

Biodistribution and radiation dosimetry of the norepinephrine transporter radioligand (S,S)-[18F]FMeNER-D2: a human whole-body PET study.

PURPOSE: (S,S)-[(18)F]FMeNER-D(2) is a recently developed positron-emission tomography (PET) radioligand for in vivo quantification of the norepinephrine transporter system. The aim of this study was to provide dosimetry estimates for (S,S)-[(18)F]FMeNER-D(2) based on human whole-body PET measurements. METHODS: PET scans were performed for a total of 6.4 h after the injection of 168.9 +/- 31.5 MBq of (S,S)-[(18)F]FMeNER-D(2) in four healthy male subjects. Volumes of interest were drawn on the coronal images. Estimates of the absorbed dose of radiation were calculated using the OLINDA software. RESULTS: Uptake was largest in lungs, followed by liver, bladder, brain and other organs. Peak values of the percent injected dose (%ID) at a time after radioligand injection were calculated for the lung (21.6%ID at 0.3 h), liver (5.1%ID at 0.3 h), bladder (12.2%ID at 6 h) and brain (2.3%ID at 0.3 h). The largest absorbed dose was found in the urinary bladder wall (0.039 mGy/MBq). The calculated effective dose was 0.017 mSv/MBq. CONCLUSION: Based on the distribution and dose estimates, the estimated radiation burden of (S,S)-[(18)F]FMeNER-D(2) is lower than that of [(18)F]FDG. The radioligand would allow multiple PET examinations in the same research subject per year.