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We recently developed a positron emission tomography (PET) probe, [sup18/supF]PM-PBB3, to detect tau lesions in diverse tauopathies, including mixed three-repeat and four-repeat (3R + 4R) tau fibrils in Alzheimer's disease (AD) and 4R tau aggregates in progressive supranuclear palsy (PSP). For wider availability of this technology for clinical settings, bias-free quantitative evaluation of tau images without a priori disease information is needed.We aimed to establish tau PET pathology indices to characterize PSP and AD using a machine learning approach and test their validity and tracer capabilities.Data were obtained from 50 healthy control subjects, 46 patients with PSP Richardson syndrome, and 37 patients on the AD continuum. Tau PET data from 114 regions of interest were subjected to Elastic Net cross-validation linear classification analysis with a one-versus-the-rest multiclass strategy to obtain a linear function that discriminates diseases by maximizing the area under the receiver operating characteristic curve. We defined PSP- and AD-tau scores for each participant as values of the functions optimized for differentiating PSP (4R) and AD (3R + 4R), respectively, from others.The discriminatory ability of PSP- and AD-tau scores assessed as the area under the receiver operating characteristic curve was 0.98 and 1.00, respectively. PSP-tau scores correlated with the PSP rating scale in patients with PSP, and AD-tau scores correlated with Mini-Mental State Examination scores in healthy control-AD continuum patients. The globus pallidus and amygdala were highlighted as regions with high weight coefficients for determining PSP- and AD-tau scores, respectively.These findings highlight our technology's unbiased capability to identify topologies of 3R + 4R versus 4R tau deposits. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Background A family of BF2-chelated tetraaryl-azadipyrromethenes was developed as non-porphyrin photosensitizers for photodynamic therapy. Among the developed photosensitizers, ADPM06 exhibited excellent photochemical and photophysical properties. Molecular imaging is a useful tool for photodynamic therapy planning and monitoring. Radiolabeled photosensitizers can efficiently address photosensitizer biodistribution, providing helpful information for photodynamic therapy planning. To evaluate the biodistribution of ADPM06 and predict its pharmacokinetics on photodynamic therapy, we synthesized [18F]ADPM06 and evaluated its in vivo properties. Results [18F]ADPM06 was automatically synthesized by Lewis acid-assisted isotopic 18F-19F exchange using ADPM06 and tin (IV) chloride at room temperature for 10 min. Radiolabeling was carried out using 0.4 µmol of ADPM06 and 200 µmol of tin (IV) chloride. The radiosynthesis time was approximately 60 min, and the radiochemical purity was > 95% at the end of the synthesis. The decay-corrected radiochemical yield from [18F]F- at the end of irradiation was 13 ± 2.7% (n = 5). In the biodistribution study, radioactivity levels in the heart, lungs, liver, pancreas, spleen, kidney, small intestine, muscle, and brain gradually decreased over 120 min after the initial uptake. The mean radioactivity level in the bone was the highest among all organs investigated and increased for 120 min after injection. Upon co-injection with ADPM06, the radioactivity levels in the blood, heart, and brain significantly increased, whereas those in the lung, liver, pancreas, kidney, small intestine, muscle, and bone were not affected. In the metabolite study of the plasma in mice, the percentage of radioactivity corresponding to [18F]ADPM06 was 76.3 ± 1.6% (n = 3). In a positron emission tomography study using MDA-MB-231-HTB-26 tumor-bearing mice, radioactivity accumulated in the bone at a relatively high level and in the tumor at a moderate level for 60 min after injection. Conclusions We synthesized [18F]ADPM06 using an automated 18F-labeling synthesizer and evaluated the biodistribution of [18F]ADPM06 in mice, which may be useful for predicting the pharmacokinetics of ADPM06 in photodynamic therapy.

BackgroundAccumulating evidence indicated decreased levels of glutamate (Glu) and N-acetylaspartate (NAA) in the posterior cingulate cortex (PCC) in Alzheimer’s disease (AD) brains. However, the levels of these metabolites in the other brain regions and the associations with abnormal protein of AD remain to be elucidated.MethodsWe enrolled 19 patients with AD and 26 healthy controls (HC). We performed magnetic resonance spectroscopic imaging (MRSI) to evaluate Glu/creatine (Cr) and NAA/Cr ratios and measure plasma neurofilament light chain (NfL) levels. We examined tau and amyloid-β depositions with standardized uptake value ratios (SUVRs) of florzolotau (18F) and11C-PiB positron emission tomography, respectively. Heatmaps were created to visualize Z scores of Glu/Cr and NAA/Cr ratios using HC data.ResultsIn the AD brains, Z-score maps demonstrated reduced Glu/Cr and NAA/Cr ratios in the gray matter, including the right dorsolateral prefrontal cortex (DLPFC) and PCC; Glu/Cr ratios negatively correlated with florzolotau (18F) SUVRs in the PCC; mini-mental state examination total scores correlated with Glu/Cr (P < 0.001, r = 0.72) and NAA/Cr ratios (P < 0.001, r = 0.75) in the right DLPFC; and blood NfL levels were increased and negatively correlated with the Glu/Cr (P = 0.040, r = −0.50) and NAA/Cr ratios (P = 0.003, r = −0.68) in the right DLPFC.ConclusionsOur findings indicated that decreased Glu/Cr levels correlated with tau pathologies of AD in the PCC. MRSI is capable of providing spatial information on neural function, enabling the identification of vulnerabilities in the right DLPFC in AD pathology.

Supplementary Files contain (1) Supplementary Materials and Methods for �V�3 expression analysis, autoradiography and histological analysis, and hematology and hepatorenal function; (2) Supplementary Tables S1-S5; and (3) Supplementary Figures S1-S5. Table S1Effects of 37 MBq (1 nmol) of 64Cu-cyclam-RAFT-c(-RGDfK-)4 {plus minus} GF/Lys on hepatorenal functions of U87MG tumor-bearing mice; Table S2Blood cell counts of U87MG tumor-bearing mice at various time points post-injection of 37 MBq (1 nmol) of 64Cu-cyclam-RAFT-c(-RGDfK-)4 {plus minus} GF/Lys; Table S3Blood cell counts of U87MG tumor-bearing mice at various time points after single dose administrations of 37 and 74 MBq of 64Cu-cyclam-RAFT-c(-RGDfK-)4; Table S4Effects of 74 MBq (2 nmol) of 64Cu-cyclam-RAFT-c(-RGDfK-)4 + GF/Lys on hepatorenal functions of normal mice; Table S5Human absorbed doses extrapolated from the biodistribution data of 64Cu-cyclam-RAFT-c(-RGDfK-)4 in U87MG tumor-bearing mice

Figure S1The treatment outcomes of radiotherapy with 37 MBq (1 nmol) of 64Cu-cyclam-RAFT-c(-RGDfK-)4; Figure S2Toxicity studies in normal mice that were injected with 74 MBq of 64Cu-cyclam-RAFT-c(-RGDfK-)4; Figure S3Preliminary study of U87MG tumors excised at day 13 p.i. of 37 MBq of 64Cu-cyclam-RAFT-c(-RGDfK-)4 for the changes in microvasculature; Figure S4Positive correlation between the tumor volume and the corresponding WBC in U87MG tumor-bearing mice; Figure S5Biodistribution of 64Cu-cyclam-RAFT-c(-RGDfK-)4 at various peptide doses (0.00510 nmol) in U87MG tumor-bearing mice.

The files contain (1) Supplementary Materials and Methods for αVβ3 expression analysis, autoradiography and histological analysis, and hematology and hepatorenal function; (2) Supplementary Tables S1-S5; and (3) Supplementary Figures S1-S5. Table S1â^'Effects of 37 MBq (1 nmole) of 64Cu-cyclam-RAFT-c(-RGDfK-)4 {plus minus} GF/Lys on hepatorenal functions of U87MG tumor-bearing mice; Table S2â^'Blood cell counts of U87MG tumor-bearing mice at various time points post-injection of 37 MBq (1 nmole) of 64Cu-cyclam-RAFT-c(-RGDfK-)4 {plus minus} GF/Lys; Table S3â^'Blood cell counts of U87MG tumor-bearing mice at various time points after single dose administrations of 37 and 74 MBq of 64Cu-cyclam-RAFT-c(-RGDfK-)4; Table S4â^'Effects of 74 MBq (2 nmole) of 64Cu-cyclam-RAFT-c(-RGDfK-)4 + GF/Lys on hepatorenal functions of normal mice; Table S5â^'Human absorbed doses extrapolated from the biodistribution data of 64Cu-cyclam-RAFT-c(-RGDfK-)4 in U87MG tumor-bearing mice; Figure S1â^'The treatment outcomes of radiotherapy with 37 MBq (1 nmole) of 64Cu-cyclam-RAFT-c(-RGDfK-)4; Figure S2â^'Toxicity studies in normal mice that were injected with 74 MBq of 64Cu-cyclam-RAFT-c(-RGDfK-)4; Figure S3â^'Preliminary study of U87MG tumors excised at day 13 p.i. of 37 MBq of 64Cu-cyclam-RAFT-c(-RGDfK-)4 for the changes in microvasculature; Figure S4â^'Positive correlation between the tumor volume and the corresponding WBC in U87MG tumor-bearing mice; Figure S5â^'Biodistribution of 64Cu-cyclam-RAFT-c(-RGDfK-)4 at various peptide doses (0.005â^'10 nmole) in U87MG tumor-bearing mice.

ObjectiveIncreasing evidence suggests that reactive astrocytes are associated with Alzheimer’s disease (AD). However, its underlying pathogenesis remains unknown. Given the role of astrocytes in energy metabolism, reactive astrocytes may contribute to altered energy metabolism. It is hypothesized that lactate, a glucose metabolite, is produced in astrocytes and subsequently shuttled to neurons as an energy substrate. This study aimed to examine alterations in brain lactate levels and their association with astrocytic activities in AD.Methods30 AD and 30 cognitively unimpaired (CU) subjects were enrolled. For AD subjects, amyloid and tau depositions were confirmed by positron emission tomography using [11C]PiB and [18F]florzolotau, respectively. Lactate and myo-inositol, an astroglial marker, in the posterior cingulate cortex (PCC) were quantified by magnetic resonance spectroscopy (MRS). These MRS metabolites were compared with plasma biomarkers, including glial fibrillary acidic protein (GFAP) as another astrocytic marker.ResultsLactate and myo-inositol levels were higher in AD than in CU (p< 0.05). Lactate levels correlated with myo-inositol levels (r= 0.272,p= 0.047). Lactate and myo-inositol levels were positively associated with the Clinical Dementia Rating sum-of-boxes scores (p< 0.05). Significant correlations were noted between myo-inositol levels and plasma GFAP and tau phosphorylated at threonine 181 levels (p< 0.05).InterpretationWe found high lactate levels accompanied by an increased astrocytic marker in the PCC in AD. Thus, impaired lactate shuttle of reactive astrocytes may disrupt energy regulation, resulting in surplus lactate levels. Myo-inositol and plasma GFAP may reflect similar astrocytic changes.

We have developed 8-amino-3-(2S,5R-dimethyl-1-piperidyl)-[1,2,4]triazolo[4,3- a]pyrazine-5-[11C]carbonitrile ([11C]MTP38) as a PET tracer for the imaging of phosphodiesterase 7. For the fully automated production of [11C]MTP38 routinely and efficiently for clinical applications, we determined the radiosynthesis procedure of [11C]MTP38 using [11C]hydrogen cyanide ([11C]HCN) as a PET radiopharmaceutical. Radiosynthesis of [11C]MTP38 was performed using an automated 11C-labeling synthesizer developed in-house within 40 min after the end of irradiation. [11C]MTP38 was obtained with a relatively high radiochemical yield (33 ± 5.5% based on [11C]CO 2 at the end of irradiation, decay-corrected, n = 15), radiochemical purity (>97%, n = 15), and molar activity (47 ± 12 GBq/µmol at the end of synthesis, n = 15). All the results of the quality control (QC) testing for the [11C]MTP38 injection complied with our in-house QC and quality assurance specifications. We successfully automated the radiosynthesis of [11C]MTP38 for clinical applications using an 11C-labeling synthesizer and sterile isolator. Taken together, this protocol provides a new radiopharmaceutical [11C]MTP38 suitable for clinical applications.

Purpose: Monoacylglycerol lipase (MAGL) regulates cannabinoid neurotransmission and the pro-inflammatory arachidonic acid pathway by degrading endocannabinoids. MAGL inhibitors may accordingly act as cannabinoid-potentiating and anti-inflammatory agents. Although MAGL dysfunction has been implicated in neuropsychiatric disorders, it has never been visualized in vivo in human brain. The primary objective of the current study was to visualize MAGL in the human brain using the novel PET ligand 18F-T-401. Methods: Seven healthy males underwent 120-min dynamic 18F-T-401-PET scans with arterial blood sampling. Six subjects also underwent a second PET scan with 18F-T-401 within 2 weeks of the first scan. For quantification of MAGL in the human brain, kinetic analyses using one- and two-tissue compartment models (1TCM and 2TCM, respectively), along with multilinear analysis (MA1) and Logan graphical analysis were performed. Time-stability and test-retest reproducibility of 18F-T-401-PET were also evaluated.Results: 18F-T-401 showed rapid uptake and gradual washout from the brain. Logan graphical analysis showed linearity in all subjects, indicating reversible radioligand kinetics. Using a metabolite-corrected arterial input function, MA1 estimated regional total distribution volume (VT) values by best identifiability. VT values were highest in the cerebral cortex, moderate in the thalamus and putamen, and lowest in white matter and the brainstem, which was in agreement with regional MAGL expression in the human brain. Time-stability analysis showed that MA1 estimated VT values with a minimal bias even using truncated 60-min scan data. Test-retest reliability was also excellent with the use of MA1. Conclusions: Here, we provide the first demonstration of in vivo visualization of MAGL in the human brain. 18F-T-401 showed excellent test-retest reliability, reversible kinetics, and stable estimation of VT values consistent with known regional MAGL expressions. PET with 18F-T-401-PET is promising tool for measurement of central MAGL.

The tendency to avoid punishment, called behavioral inhibition system, is an essential aspect of motivational behavior. Behavioral inhibition system is related to negative affect, such as anxiety, depression and pain, but its neural basis has not yet been clarified. To clarify the association between individual variations in behavioral inhibition system and brain 5-HT2A receptor availability and specify which brain networks were involved in healthy male subjects, using [18F]altanserin positron emission tomography and resting-state functional magnetic resonance imaging. Behavioral inhibition system score negatively correlated with 5-HT2A receptor availability in anterior cingulate cortex. A statistical model indicated that the behavioral inhibition system score was associated with 5-HT2A receptor availability, which was mediated by the functional connectivity between anterior cingulate cortex and left middle frontal gyrus, both of which involved in the cognitive control of negative information processing. Individuals with high behavioral inhibition system displays low 5-HT2A receptor availability in anterior cingulate cortex and this cognitive control network links with prefrontal-cingulate integrity. These findings have implications for underlying the serotonergic basis of physiologies in aversion.

Purpose Monoacylglycerol lipase (MAGL) regulates cannabinoid neurotransmission and the pro-infammatory arachidonic acid pathway by degrading endocannabinoids. MAGL inhibitors may accordingly act as cannabinoid-potentiating and antiinfammatory agents. Although MAGL dysfunction has been implicated in neuropsychiatric disorders, it has never been visualized in vivo in human brain. The primary objective of the current study was to visualize MAGL in the human brain using the novel PET ligand 18F-T-401. Methods Seven healthy males underwent 120-min dynamic 18F-T-401-PET scans with arterial blood sampling. Six subjects also underwent a second PET scan with 18F-T-401 within 2 weeks of the frst scan. For quantifcation of MAGL in the human brain, kinetic analyses using one- and two-tissue compartment models (1TCM and 2TCM, respectively), along with multilinear analysis (MA1) and Logan graphical analysis, were performed. Time-stability and test–retest reproducibility of 18F-T-401-PET were also evaluated. Results 18F-T-401 showed rapid uptake and gradual washout from the brain. Logan graphical analysis showed linearity in all subjects, indicating reversible radioligand kinetics. Using a metabolite-corrected arterial input function, MA1 estimated regional total distribution volume (VT) values by best identifability. VT values were highest in the cerebral cortex, moderate in the thalamus and putamen, and lowest in white matter and the brainstem, which was in agreement with regional MAGL expression in the human brain. Time-stability analysis showed that MA1 estimated VT values with a minimal bias even using truncated 60-min scan data. Test–retest reliability was also excellent with the use of MA1. Conclusions Here, we provide the frst demonstration of in vivo visualization of MAGL in the human brain. 18F-T-401 showed excellent test–retest reliability, reversible kinetics, and stable estimation of VT values consistent with known regional MAGL expressions. PET with 18F-T-401-PET is promising tool for measurement of central MAGL.

Corticobasal degeneration (CBD) is the most common neuropathological substrate for clinically diagnosed corticobasal syndrome (CBS), while identifying CBD pathology in living individuals has been challenging. This study aimed to examine the capability of positron emission tomography (PET) to detect CBD-type tau depositions and neuropathological classification of CBS.

Histamine H3 receptor antagonists and inverse agonists have been extensively developed to treat sleep–wake, neurocognitive, and allied disorders. However, potential adverse effects, including insomnia, hampered the clinical use of these drugs, possibly due to their persistent interaction with the target molecules. The purpose of the present study was to estimate the pharmacokinetics and pharmacodynamics of enerisant, a novel antagonist and inverse agonist for histamine H3 receptors. To measure the histamine H3 receptor occupancy by enerisant, positron emission tomography studies using [11C]TASP457, a specific radioligand for histamine H3 receptors, were performed in 12 healthy men at baseline and at 2 h after oral administration of enerisant hydrochloride. For three of these subjects, two additional scans were performed at 6 and 26 h after the administration. Relationships between the receptor occupancy by enerisant and its dose and plasma concentrations were then analyzed. Administration of enerisant hydrochloride decreased the radioligand binding in a dose-dependent manner. The estimated receptor occupancy values at 2 h varied as a function of its dose or plasma concentration. The time course of the occupancy showed persistently high levels (> 85%) in the two subjects with higher doses (25 and 12.5 mg). The occupancy was also initially high at 2 h and 6 h with the lower dose of 5 mg, but it decreased to 69.7% at 26 h. The target engagement of enerisant was demonstrated in the brains of living human subjects. The occupancy of histamine H3 receptors by enerisant at 2 h can be predicted by applying the plasma concentration of enerisant to Hill’s plot. The preliminary time-course investigation showed persistently high brain occupancy with high doses of enerisant despite the decreasing plasma concentration of the drug. Five milligrams or less dose would be appropriate for the treatment for narcolepsy with initially high occupancy allowing for effective treatment of narcolepsy, and then the occupancy level would be expected to decrease to a level to avoid this drug’s unwanted side effect of insomnia at night, although further research is warranted to confirm the statement since the expected decrease is based on the finding in one subject. This study was retrospectively registered with ClinicalTrials.gov (NCT04631276) on November 17, 2020.

Histamine H receptor antagonists and inverse agonists have been extensively developed to treat sleep-wake, neurocognitive, and allied disorders. However, potential adverse effects, including insomnia, hampered the clinical use of these drugs, possibly due to their persistent interaction with the target molecules. The purpose of the present study was to estimate the pharmacokinetics and pharmacodynamics of enerisant, a novel antagonist and inverse agonist for histamine H receptors.

先進核医学基盤研究部では、臨床診断・治療や生体機能の計測に有用な放射性核種標識薬剤の開発、標識薬剤合成に必要な放射性核種の製造及び標識・分析技術の開発研究を行っている。また、新規放射性薬剤を開発し、多種多様な動物モデルを含めた動物実験による薬剤の有効性と前臨床評価、臨床共同研究を実施している。さらに、安全で高品位な標識核種及び診断・治療用の放射性薬剤を製造し、脳機能イメージング研究部、分子イメージング診断治療研究部のみならずQST病院や外部の大学・研究機関・企業の研究者に広く提供している。 当研究部によって製造される臨床研究用の放射性薬剤は、1）HIMACや量子メスを用いた腫瘍の治療効果の評価や転移の有無などの判定、2）がん患者への診断・治療研究、3）認知症をはじめとする各種の脳疾患の診断、治療効果の評価及び病態発生メカニズムの解明研究などに利用されている。本報告書では、新規標識薬剤の開発状況及び放射性核種・薬剤の製造状況を報告する。

Patients with progressive supranuclear palsy (PSP) frequently exhibit apathy but the neuropathological processes leading to this phenotype remain elusive. We aimed to examine the involvement of tau protein depositions, oxidative stress (OS), and neuronal loss in the apathetic manifestation of PSP. Twenty patients with PSP and twenty-three healthy controls were enrolled. Tau depositions and brain volumes were evaluated via positron-emission tomography (PET) using a specific probe

【背景・目的】ADPM06はaza-BODIPY類であり、光線力学療法（PDT）用の光感受性物質として開発された。ADPM06を用いたPDTでは、様々な腫瘍モデルにおいて短時間近赤外レーザー照射により腫瘍の縮退効果がみられた。我々は、ADPM06の安全性を評価するために、18Fを標識したADPM06を開発し、インビボ評価を行った。 【方法】[18F]ADPM06は、同位体交換反応を用いて合成を行った。18F-はSepPak QMAからテトラブチルアンモニウムを用いて溶出し、乾燥後、塩化スズ（IV）入りADPM06アセトニトリル溶液中で室温10分間反応させ、18Fを標識した。インビボ実験はマウスを用いて体内動態を評価した。 【結果】[18F]ADPM06は18F標識自動合成装置を用い、合成時間60分程度、10％程度の放射化学的収率で合成でき、注射液とした。[18F]ADPM06投与後のマウス体内放射能分布は、測定可能な全ての臓器において、投与後120分まで初期取り込みの後に徐々に減少した。 【結論】[18F]ADPM06を注射液として合成でき、体内動態をインビボで評価することができた。, 第62回日本核医学会学術総会

Background/Aims: [18F]Fluoroalkyl groups are essential labeling units because they are considered as surrogates for [11C]methyl moieties, and are coupled to the same functional units as the [11C]methyl group. Many [18F]fluoroalkyated PET tracers have been developed. In general, 18F-fluoroalkylation using [18F]fluoroalkyl reagents requires multi-step radiosynthesis procedures and a multi-pot 18F-labeling synthesizer. To overcome these limitations, a straightforward one-pot method for 18F-fluoroethylation without azeotropic drying of [18F]F- was developed [1]. We have used an improved one-pot 18F-fluoroethylaion method to synthesize 18F-fluoroethylated tracers [2]. In this study, we further modified this one-pot method suitable for 18F-fluoromethylation, and simplified the automated radiosynthesis of two [18F]fluoromethylated tracers using this method. Methods: We synthesized [18F]fluoromethyl tosylate in a mixture of 18F- in K222/K2CO3 acetonitrile solution including 2% water, bis(tosyloxy)methane and cesium carbonate. Without purification of [18F]fluoromethyl tosylate, we directly added a labeling precursor to this mixture for the simplified one-pot 18F-fluoromethylation. Using this procedure equipped to a 18F-labeling synthesizer, [18F]FCho (a PET tracer for imaging tumor) and [18F]FMeNER-D2 (a PET tracer for imaging norepinephrine transporter) were automatically synthesized by the reactions of their corresponding labeling precursors with [18F]fluoromethyl tosylate, respectively. Results: Using the simplified one-pot 18F-fluoromethylation procedure in the automated radiosynthesis, we achieved [18F]FCho and [18F]FMeNER-D2 in approximately 10% of radiochemical yield from 18F- at the end of irradiation (EOI). Radiosynthesis times and radiochemical purities of two 18F-labeled tracers were approximately 60 min after EOI and over 95%, respectively. Conclusions: We have successively synthesized [18F]FCho and [18F]FMeNER-D2 using the simplified one-pot 18F-fluoromethylation method, and achieved automation for all radiosynthesis processes using an 18F-labeling synthesizer. The present method provides a shorter synthesis time and automated procedures with one-pot for the 18F-fluoromethylation strategy., 第13回世界核医学会(13th Congress of the World Federation of Nuclear Medicine and Biology)

Positron emission tomography (PET) has been used to investigate changes in the concentration of endogenous neurotransmitters. Recently, this technique has been applied to the imaging of serotonin2A receptors using [18F]altanserin. In these measurements, a reduction in binding potential (BP) suggests an increase in endogenous serotonin levels caused by pharmacological or cognitive stimulations, and the sensitivity of BP reduction depends on the characteristics of [18F]altanserin. In this study, we evaluated an analytical method for estimating the changes in endogenous serotonin levels based on PET scans with [18F]altanserin at baseline and stimulated states and validated it using simulations and small animal PET studies. First, in the simulations, the time-activity curves at baseline and the stimulated states were generated using an extended compartment model including the competition for the receptors between the administered [18F]altanserin and endogenous serotonin. In the stimulated state, the magnitude and onset of the endogenous serotonin elevation were altered to varying degrees. In these time-activity curves, BP was estimated using the simplified reference tissue model (SRTM), and the reduction in BP was evaluated by comparison with that of the baseline state. Next, the proposed method was applied to mouse PET studies. Endogenous serotonin levels were elevated by treatment with selective serotonin reuptake inhibitors (SSRIs), and PET studies were performed twice, once with and once without treatment. In both scans, BP was estimated using the SRTM with the cerebellum as a reference region, and the reduction in BP after SSRI treatment was evaluated. In the simulations, the BP estimate of the stimulated state was smaller than that of the baseline state, and their reduction was related to the amount of change in the serotonin concentration. BP reduction was also affected by the onset of serotonin elevation. In the mouse studies, the BP of the cerebral cortex decreased in the scans with SSRI treatment. The reduction in BP estimated using the SRTM from [18F]altanserin-PET studies at baseline and in stimulated states can detect changes in the binding conditions of serotonin2A receptors. This may be useful for investigating the elevation of endogenous serotonin levels caused by stimulations.

Positron emission tomography (PET) has been used to investigate changes in the concentration of endogenous neurotransmitters. Recently, this technique has been applied to the imaging of serotonin receptors using [18F]altanserin. In these measurements, a reduction in binding potential (BP) suggests an increase in endogenous serotonin levels caused by pharmacological or cognitive stimulations, and the sensitivity of BP reduction depends on the characteristics of [18F]altanserin. In this study, we evaluated an analytical method for estimating the changes in endogenous serotonin levels based on PET scans with [18F]altanserin at baseline and stimulated states and validated it using simulations and small animal PET studies.

Fluctuations of neuronal activities in the brain may underlie relatively slow components of neurofunctional alterations, which can be modulated by food intake and related systemic metabolic statuses. Glutamatergic neurotransmission plays a major role in the regulation of excitatory tones in the central nervous system, although just how dietary elements contribute to the tuning of this system remains elusive. Here, we provide the first demonstration by bimodal positron emission tomography (PET) and magnetic resonance spectroscopy (MRS) that metabotropic glutamate receptor subtype 5 (mGluR5) ligand binding and glutamate levels in human brains are dynamically altered in a manner dependent on food intake and consequent changes in plasma glucose levels. The brain-wide modulations of central mGluR5 ligand binding and glutamate levels and profound neuronal activations following systemic glucose administration were further proven by PET, MRS, and intravital two-photon microscopy, respectively, in living rodents. The present findings consistently support the notion that food-associated glucose intake is mechanistically linked to glutamatergic tones in the brain, which are translationally accessible in vivo by bimodal PET and MRS measurements in both clinical and non-clinical settings.

Fluctuations of neuronal activities in the brain may underlie relatively slow components of neurofunctional alterations, which can be modulated by food intake and related systemic metabolic statuses. Glutamatergic neurotransmission plays a major role in the regulation of excitatory tones in the central nervous system, although just how dietary elements contribute to the tuning of this system remains elusive. Here, we provide the first demonstration by bimodal positron emission tomography (PET) and magnetic resonance spectroscopy (MRS) that metabotropic glutamate receptor subtype 5 (mGluR5) ligand binding and glutamate levels in human brains are dynamically altered in a manner dependent on food intake and consequent changes in plasma glucose levels. The brain-wide modulations of central mGluR5 ligand binding and glutamate levels and profound neuronal activations following systemic glucose administration were further proven by PET, MRS, and intravital two-photon microscopy, respectively, in living rodents. The present findings consistently support the notion that food-associated glucose intake is mechanistically linked to glutamatergic tones in the brain, which are translationally accessible in vivo by bimodal PET and MRS measurements in both clinical and non-clinical settings.

Objectives: Metabotropic glutamate receptor 1 (GRM1) is aberrantly overexpressed in a wide variety of human solid tumors, such as melanoma，but not in normal peripheral organs (1). Therefore, GRM1 can be a widely–applicable target for the theranostics in oncology. Here, a novel small-molecular radiopharmaceutical pair, 3-iodo- N-[4-[6-(methylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-N-[11C]methylbenzamide ([11C]1) and 3-211At-astato-N-[4-[6-(methylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-N-methylbenzamide ([211At]1), was designed and developed to target the GRM1 for the theranostics in melanomas (Fig.1). Method: [ 11C]1 was synthesized by reacting a N-desmethyl precursor with [11C]CH3OTf in the presence of NaOH at room temperature for 5 min. Radiolabeling of [211At]1 was performed by reaction of aryl tin precursor with NCS-containing 211At/MeOH solution. The theranostic potentials of the radiopharmaceutical pair were explored for PET imaging and radiotherapy in GRM1-positive B16F10 melanoma-bearing mice. Results: [ 11C]1 and [211At]1 were obtained with a radiochemical purity of greater than 99% and radiochemical yields of 19 ± 8 % and 46 ± 3%, respectively, based on the total radioactivity of used radionuclides. In vivo PET imaging of [ 11C]1 clearly visualized the targeted melanomas with a good tumor-to-background contrast (Fig. 1A). Ex vivo biodistribution study verified the persistent increase of [ 11C]1, which reached 12.29 ± 2.44 %ID/g tissue at 90 min in the targeted melanomas, and rapidly cleared from nontarget organs after intravenous injection. In the therapeutic studies, [211At]1 exhibited unequivocal and durable antitumor efficacy with only a single treatment (2.96 MBq) in the melanoma model, compared to the controls (0.38 ± 0.02 cm3 vs. 7.88 ± 1.28 cm3 at 13 days post-therapy) (Fig. 1B). No decrease in body weight, and no liver and kidney damage were observed through the examination period in melanoma mice injected with 2.96 MBq of [211At]1. Conclusion: The novel small-molecular radiopharmaceutical pair successfully visualized the GRM1-positive melanomas by [ 11C]1 with high contrast PET images, and further treated by [211At]1 without significant toxicity. The results highlight the good potential of using [ 11C]1 and [211At]1 as theranostic agents for the management of GRM1-positive tumors and should be further investigated in the theranostic field of oncology in the clinic., SNMMI2022

Objectives: A family of the BF2-chelated tetraaryl-azadipyrromethenes (ADPMs) was developed as a nonporphyrin photosensitizer (PS) for photodynamic therapy (PDT) [1]. Among ADPMs, ADPM06 displayed excellent photochemical and photophysical properties [1]. In addition, PDT using ADPM06 elicited impressive complete response rates in various tumor models when a short drug-light interval was applied [2]. Molecular imaging is a promising PDT planning and monitoring tool, and the PS biodistribution is a relevant issue for PDT planning that radiolabeled PSs may address efficiently. To evaluate efficiency for PDT using ADPM06 and also side effects of ADPM, we synthesized [18F]ADPM06 using an automated 18F-labeling synthesizer, and evaluated its in vivo properties. Methods: [18F]ADPM06 was synthesized using an automated 18F-labeling synthesizer by Lewis acid-assisted isotopic 18F-19F exchange [3]. The [18F]F– was extracted from a Sep-Pak Accell Plus QMA Carbonate Plus Light cartridge with a mixture of tetrabutylanmmonium bicarbonate aqueous solution and acetonitrile. The solution was concentrated by evaporation at 100 °C for 10 min under nitrogen gas flow. After the reaction vessel was cooled, the mixture of ADPM06 in acetonitrile and tin(IV) chloride (SnCl4) solution was added to the reaction vessel, and then was agitated using magnetic stirrer at room temperature for 10 min. After the reaction, the mixture was diluted with water for injection, and transferred to the injector for semi-preparative radio-HPLC. The HPLC fractions were collected in a flask, to which Tween 80 in ethanol was added prior to radiosynthesis. The solution was subsequently evaporated to dryness and the residue was dissolved in physiological saline. The product was analyzed by HPLC with radioactivity and UV-VIS detection. The in vivo biodistribution study was performed using mice. Results: To radio-synthesize efficiently [18F]ADPM06, we performed semi-automated radiosynthesis. By increasing the concentration of SnCl4 from 100 to 400 μmol, the radiochemical conversion (RCC) of [18F]ADPM06 from [18F]TBAF was increased until 60%. Also, the RCC using 0.8 μmol of ADPM06 was 1.2-fold higher than that using 0.4 μmol of ADPM06. In the radiosynthesis using an automated 18F-labeling synthesizer, we successfully synthesized [18F]ADPM06 for in vivo applications. The radiochemical yield (RCY) from [18F]F- was 13 ± 2.7 % (n = 5; 0.4 μmol of ADPM06, 200 μmol of SnCl4) at the end of irradiation. The radiosynthesis time was within 60 min, and radiochemical purity remained >95% after maintaining it for 1 hour after the end of synthesis. In the biodistribution study within 120 min after the injection, radioactivity levels in heart, lung, liver, pancreas, spleen, kidney, small intestine, muscle, and brain gradually decreased after initial uptake. Conclusions: We enabled to synthesize [18F]ADPM06 using an automated 18F-labeling synthesizer, and to evaluate biodistribution of [18F]ADPM06 in mice.

Glutamatergic neurons and cingulate cortices have crucial roles in the cognitive dysfunction of Alzheimer's disease (AD). This study aimed to evaluate regional vulnerabilities of the glutamatergic system in AD at the level of the cingulate gyrus in relation to tau and amyloid-β (Aβ) depositions. Combining MRSI and PET, we found that the glutamatergic system in the posterior cingulate cortex (PCC) is vulnerable to tau deposits but not Aβ from the early stage of AD, and glutamate in the PCC region may be a marker of disease progression in AD., 2022 Joint Annual Meeting ISMRM-ESMRMB

Purpose Phosphodiesterase (PDE) 7 is a potential therapeutic target for neurological and inflammatory diseases, although in vivo visualization of PDE7 has not been successful. In this study, we aimed to develop [11C]MTP38 as a novel positron emission tomography (PET) ligand for PDE7. Methods [11C]MTP38 was radiosynthesized by 11C-cyanation of a bromo precursor with [11C]HCN. PET scans of rat and rhesus monkey brains and in vitro autoradiography of brain sections derived from these species were conducted with [11C]MTP38. In monkeys, dynamic PET data were analyzed with an arterial input function to calculate the total distribution volume (VT). The non-displaceable binding potential (BPND) in the striatum was also determined by a reference tissue model with cerebellar reference. Finally, striatal occupancy of PDE7 by an inhibitor was calculated in monkeys according to changes in BPND. Results [11C]MTP38 was synthesized with radiochemical purity ≥99.4% and molar activity of 38.6 ± 12.6 GBq/μmol. Autoradiography revealed high radioactivity in the striatum and its reduction by non-radiolabeled ligands, in contrast with unaltered autoradiographic signals in other regions. In vivo PET after radioligand injection to rats and monkeys demonstrated that radioactivity was rapidly distributed to the brain and intensely accumulated in the striatum relative to the cerebellum. Correspondingly, estimated VT values in the monkey striatum and cerebellum were 3.59 and 2.69 mL/cm3, respectively. The cerebellar VT value was unchanged by pretreatment with unlabeled MTP38. Striatal BPND was reduced in a dose-dependent manner after pretreatment with MTP-X, a PDE7 inhibitor. Relationships between PDE7 occupancy by MTP-X and plasma MTP-X concentration could be described by Hill’s sigmoidal function. Conclusion We have provided the first successful preclinical demonstration of in vivo PDE7 imaging with a specific PET radioligand. [11C]MTP38 is a feasible radioligand for evaluating PDE7 in the brain and is currently being applied to a first-in-human PET study.

Purpose: Phosphodiesterase (PDE) 7 is a potential therapeutic target for neurological and inflammatory diseases, although in-vivo visualization of PDE7 has not been successful. In this study, we aimed to develop [11C]MTP38 as a novel positron emission tomography (PET) ligand for PDE7. Methods: [11C]MTP38 was radiosynthesized by 11C-cyanation of a bromo precursor with [11C]HCN. PET scans of rat and rhesus monkey brains and in-vitro autoradiography of brain sections derived from these species were conducted with [11C]MTP38. In monkeys, dynamic PET data were analyzed with an arterial input function to calculate the total distribution volume (VT). The non-displaceable binding potential (BPND) in the striatum was also determined by a reference tissue model with cerebellar reference. Finally, striatal occupancy of PDE7 by an inhibitor was calculated in monkeys according to changes in BPND. Results: [11C]MTP38 was synthesized with radiochemical purity ≥ 99.4% and molar activity of 38.6 ± 12.6 GBq/μmol. Autoradiography revealed high radioactivity in the striatum and its reduction by non-radiolabeled ligands, in contrast with unaltered autoradiographic signals in other regions. In-vivo PET after radioligand injection to rats and monkeys demonstrated that radioactivity was rapidly distributed to the brain and intensely accumulated in the striatum relative to the cerebellum. Correspondingly, estimated VT values in the monkey striatum and cerebellum were 3.59 and 2.69 mL/cm3, respectively. The cerebellar VT value was unchanged by pretreatment with unlabeled MTP38. Striatal BPND was reduced in a dose-dependent manner after pretreatment with MTP-X, a PDE7 inhibitor. Relationships between PDE7 occupancy by MTP-X and plasma MTP-X concentration could be described by Hill’s sigmoidal function. Conclusion: We have provided the first successful preclinical demonstration of in-vivo PDE7 imaging with a specific PET radioligand. [11C]MTP38 is a feasible radioligand for evaluating PDE7 in the brain and is currently being applied to a first-in-human PET study.

Purpose Phosphodiesterase 7 (PDE7) is an enzyme that selectively hydrolyses cyclic adenosine monophosphate, and its dysfunction is implicated in neuropsychiatric diseases. However, in vivo visualization of PDE7 in human brains has hitherto not been possible. Using the novel PET ligand 11C-MTP38, which we recently developed, we aimed to image and quantify PDE7 in living human brains. Methods Seven healthy males underwent a 90-min PET scan after injection of 11C-MTP38. We performed arterial blood sampling and metabolite analysis of plasma in six subjects to obtain a metabolite-corrected input function. Regional total distribution volumes (VTs) were estimated using compartment models, and Logan plot and Ichise multilinear analysis (MA1). We further quantified the specific radioligand binding using the original multilinear reference tissue model (MRTMO) and standardized uptake value ratio (SUVR) method with the cerebellar cortex as reference. Results PET images with 11C-MTP38 showed relatively high retentions in several brain regions, including in the striatum, globus pallidus, and thalamus, as well as fast washout from the cerebellar cortex, in agreement with the known distribution of PDE7. VT values were robustly estimated by two-tissue compartment model analysis (mean VT = 4.2 for the pallidum), Logan plot, and MA1, all in excellent agreement with each other, suggesting the reversibility of 11C-MTP38 binding. Furthermore, there were good agreements between binding values estimated by indirect method and those estimated by both MRTMO and SUVR, indicating that these methods could be useful for reliable quantification of PDE7. Because MRTMO and SUVR do not require arterial blood sampling, they are the most practical for the clinical use of 11C-MTP38-PET. Conclusion We have provided the first demonstration of PET visualization of PDE7 in human brains. 11C-MTP38 is a promising novel PET ligand for the quantitative investigation of central PDE7.

[11C]K-2, a radiotracer exhibiting high affinity and selectivity for α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs), is suitable for the quantification of AMPARs in living human brains and potentially useful in the identification of epileptogenic foci in patients. This study aimed to estimate the radiation doses of [11C]K-2 in various organs and calculate the effective dose after injection of [11C]K-2 in healthy human subjects. Twelve healthy male subjects were registered and divided into two groups (370 or 555 MBq of [11C]K-2), followed by 2 h whole-body scans. We estimated the radiation dose of each organ and then calculated the effective dose for each subject. The highest uptake of [11C]K-2 was observed in the liver, while the brain also showed relatively high uptake. The urinary bladder exhibited the highest radiation dose. The kidneys and liver also showed high radiation doses after [11C]K-2 injections. The effective dose of [11C]K-2 ranged from 5.0 to 5.2 μSv/MBq. Our findings suggest that [11C]K-2 is safe in terms of the radiation dose and adverse effects. The injection of 370–555 MBq (10 to 15 mCi) for PET studies using this radiotracer is applicable in healthy human subjects and enables serial PET scans in a single subject.

Recently, we produced 11 C-labeled 2-((1E,3E)-4-(6-(methylamino)pyridin-3-yl)buta-1,3-dienyl)benzo[d]thiazol-6-ol ([11 C]PBB3) as a clinically useful positron emission tomography (PET) tracer for in vivo imaging of tau pathologies in the human brain. To overcome the limitations (i.e., rapid in vivo metabolism and short half-life) of [11 C]PBB3, we further synthesized 18 F-labeled 1-fluoro-3-((2-((1E,3E)-4-(6-(methylamino)pyridine-3-yl)buta-1,3-dien-1-yl)benzo[d]thiazol-6-yl)oxy)propan-2-ol ([18 F]PM-PBB3). [18 F]PM-PBB3 is also a useful tau PET tracer for imaging tau pathologies. In this study, we developed a routine radiosynthesis and quality control testing of [18 F]PM-PBB3 for clinical applications. [18 F]PM-PBB3 was synthesized by direct 18 F-fluorination of the tosylated derivative, followed by removal of the protecting group. [18 F]PM-PBB3 was obtained with sufficient radioactivity (25 ± 6.0% of the nondecay-corrected radiochemical yield at the end of synthesis, EOS), radiochemical purity (98 ± 0.6%), and molar activity (350 ± 94 GBq/μmol at EOS; n = 53). Moreover, [18 F]PM-PBB3 consistently retained >95% of radiochemical purity for 60 min without undergoing photoisomerization using a new UV-cutoff light (yellow light) fixed in the hot cell to monitor the synthesis. All the results of the quality control testing for the [18 F]PM-PBB3 injection complied with our in-house quality control and quality assurance specifications. We have accomplished >200 production runs of [18 F]PM-PBB3 in our facility for various research purposes.

Recently, we produced 11C‐labeled 2‐((1E,3E)‐4‐(6‐(methylamino)pyridin‐3‐yl)buta‐1,3‐dienyl)benzo[d]thiazol‐6‐ol ([11C]PBB3) as a clinically useful positron emission tomography (PET) tracer for in vivo imaging of tau pathologies in the human brain. To overcome the limitations (i.e., rapid in vivo metabolism and short half‐life) of [11C]PBB3, we further synthesized 18F‐labeled 1‐fluoro‐3‐((2‐((1E,3E)‐4‐(6‐(methylamino)pyridine‐3‐yl)buta‐1,3‐dien‐1‐yl)benzo[d]thiazol‐6‐yl)oxy)propan‐2‐ol ([18F]PM‐PBB3). [18F]PM‐PBB3 is also a useful tau PET tracer for imaging tau pathologies. In this study, we developed a routine radiosynthesis and quality control testing of [18F]PM‐PBB3 for clinical applications. [18F]PM‐PBB3 was synthesized by direct 18F‐fluorination of the tosylated derivative, followed by removal of the protecting group. [18F]PM‐PBB3 was obtained with sufficient radioactivity (25 ± 6.0% of the nondecay‐corrected radiochemical yield at the end of synthesis, EOS), radiochemical purity (98 ± 0.6%), and molar activity (350 ± 94 GBq/μmol at EOS; n = 53). Moreover, [18F]PM‐PBB3 consistently retained >95% of radiochemical purity for 60 min without undergoing photoisomerization using a new UV‐cutoff light (yellow light) fixed in the hot cell to monitor the synthesis. All the results of the quality control testing for the [18F]PM‐PBB3 injection complied with our in‐house quality control and quality assurance specifications. We have accomplished >200 production runs of [18F]PM‐PBB3 in our facility for various research purposes.

Objective: Despite accumulating evidence for impaired glutamatergic neurotransmission in Alzheimer’s disease (AD) brains, its significance in neurofunctional and neuropathological alterations remains elusive. The aim of this study is to evaluate the associations between glutamatergic dysfunctions and tau depositions across cortical regions in AD patients using magnetic resonance spectroscopic imaging (MRSI). Methods: We enrolled 16 patients with AD, consisting of cases with mild cognitive impairment due to AD and AD dementia, and 15 healthy controls (HCs). We performed tau and amyloid-β (Aβ) PET with 18F-PM-PBB3 and 11C-PiB, respectively, and single-plane MRSI for evaluating a glutamate/creatine (Glu/Cr) ratio at the level of the cingulate gyrus. PET probe retentions were quantified as standardized uptake value ratio (SUVR) using the cerebellar cortex as a reference region. Results: Z-score maps of the AD group compared to the HC group showed marked tau and Aβ depositions in extensive cortical gray matter regions, and reduced glutamate levels in more confined areas (Figures 1-3). Glutamate levels were correlated with tau but not Aβ burdens in some regions, including the posterior cingulate cortex (PCC) (Figures 4). In an analysis of combined voxels covering PCC, Glu/Cr ratios were correlated negatively with tau deposits in the AD group (r = -0.53, p < 0.05) and positively with mini-mental state examination scores (r = 0.74, p < 0.05) in AD dementia cases. Conclusions: MRSI revealed the regionally variable vulnerability of the glutamatergic system to tau depositions in AD brains. In PCC, tau accumulations are likely to induce disrupted glutamine transmissions, aggravating cognitive functions., AD/PD 2022