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PURPOSE: Early after [18F]PI-2620 PET tracer administration, perfusion imaging has potential for regional assessment of neuronal injury in neurodegenerative diseases. This is while standard late-phase [18F]PI-2620 tau-PET is able to discriminate the 4-repeat tauopathies progressive supranuclear palsy and corticobasal syndrome (4RTs) from disease controls and healthy controls. Here, we investigated whether early-phase [18F]PI-2620 PET has an additive value for biomarker based evaluation of 4RTs. METHODS: Seventy-eight patients with 4RTs (71 ± 7 years, 39 female), 79 patients with other neurodegenerative diseases (67 ± 12 years, 35 female) and twelve age-matched controls (69 ± 8 years, 8 female) underwent dynamic (0-60 min) [18F]PI-2620 PET imaging. Regional perfusion (0.5-2.5 min p.i.) and tau load (20-40 min p.i.) were measured in 246 predefined brain regions [standardized-uptake-value ratios (SUVr), cerebellar reference]. Regional SUVr were compared between 4RTs and controls by an ANOVA including false-discovery-rate (FDR, p < 0.01) correction. Hypoperfusion in resulting 4RT target regions was evaluated at the patient level in all patients (mean value - 2SD threshold). Additionally, perfusion and tau pattern expression levels were explored regarding their potential discriminatory value of 4RTs against other neurodegenerative disorders, including validation in an independent external dataset (n = 37), and correlated with clinical severity in 4RTs (PSP rating scale, MoCA, activities of daily living). RESULTS: Patients with 4RTs had significant hypoperfusion in 21/246 brain regions, most dominant in thalamus, caudate nucleus, and anterior cingulate cortex, fitting to the topology of the 4RT disease spectrum. However, single region hypoperfusion was not specific regarding the discrimination of patients with 4RTs against patients with other neurodegenerative diseases. In contrast, perfusion pattern expression showed promise for discrimination of patients with 4RTs from

Background 4‐repeat (4R) tauopathies are neurodegenerative diseases characterized by cerebral accumulation of 4R tau pathology. The most prominent 4R‐tauopathies are progressive‐supranuclear‐palsy (PSP) and corticobasal‐syndrome (CBS) characterized by tau accumulation in subcortical nuclei as well as cortical neuronal dysfunction, as shown by PET‐assessed hypoperfusion and glucose hypometabolism. Yet, there is a spatial mismatch between subcortical tau deposition patterns and cortical neuronal dysfunction and it is unclear how these two pathological brain changes are interrelated. Here, we hypothesized that subcortical tau pathology induces diaschisis‐like neuronal dysfunction in functionally connected cortical regions. Method We included 47 patients with clinically diagnosed PSP or CBS who underwent structural MRI and 18F‐PI‐2620 tau‐PET. PI‐2620 PET was recorded using a dynamic one‐shot, two‐stop acquisition protocol, to determine an early 0.5‐2.5min post‐tracer‐injection perfusion window for assessing cortical neuroinjury in 200 cortical ROIs of the Schaefer atlas, as well as a 20‐40min post‐tracer‐injection window to determine 4R‐tau load in 32 subcortical ROIs of the TIAN atlas. We determined tau epicenters as 10% of subcortical ROIs with highest tau‐PET, and assessed the connectivity of tau epicenters to cortical ROIs using an age‐matched 3T resting‐state fMRI template derived from 69 healthy elderly. Using linear regression, we assessed whether i) higher subcortical tau‐PET was associated with overall reduced cortical perfusion and ii) whether cortical hypoperfusion was observed preferentially in regions closely connected to subcortical tau epicenters. Result As hypothesized, higher subcortical tau‐PET was associated with lower cortical perfusion (R=‐0,37, p‐value: <0,011, Fig.1). Using group‐average tau‐PET and perfusion‐PET, we found that the seed‐based connectivity pattern of subcortical tau epicenters predicted cortical perfusion patterns, whe

Zyklotrone bilden als Ressource medizinischer Radionuklide eine zentrale Infrastruktur für die Entwicklung neuer und die Produktion klinisch etablierter Radiotracer zur molekularen Hybridbildgebung. Da die letzte umfassende Veröffentlichung zu Zyklotronen ca. 15 Jahre alt ist, wurde eine Statuserhebung zu den für die Nuklearmedizin und Radiopharmazie in Deutschland, Österreich und der Schweiz (D-A-CH-Länder) betriebenen Zyklotronen angestrebt.

Background: Cyclotrons form a central infrastructure and are a resource of medical radionu- clides for the development of new radiotracers as well as the production and supply of clini- cally established radiopharmaceuticals for patient care in nuclear medicine. Aim: To provide an updated overview of the number and characteristics of cyclotrons that are currently in use within radiopharmaceutical sciences and for the development of radiopharma- ceuticals to be used for patient care in Nuclear Medicine in Germany (D), Austria (A) and Switzerland (CH). Methods: Publicly available information on the cyclotron infrastructure was (i) consolidated and updated, (ii) supplemented by selective desktop research and, last but not least, (iii) vali- dated by members of the committee of the academic “Working Group Radiochemistry and Radiopharmacy” (AGRR), consisting of radiochemists and radiopharmacists of the D-A-CH countries and belonging to the German Society of Nuclear Medicine (DGN), as well as the Radiopharmaceuticals Committee of the DGN. Results: In total, 39 cyclotrons were identified that are currently being operated for medical radionuclide production for imaging and therapy in Nuclear Medicine clinics, 29 of them in Germany, 4 in Austria and 6 in Switzerland. The majority of the cyclotrons reported (69%) are operated by universities, university hospitals or research institutions close to a university (clinic), less by/in cooperation with industrial partners (26%) or a (non-university) clinic/PET-center (5%). Most of the cyclotrons (82%) are running with up to 18 MeV proton beams, which is sufficient for the production of the currently most common cyclotron-based radionuclides for PET imaging. Discussion: The data presented provide an academically-updated overview of the medical cy- clotrons operated for the production of radiopharmaceuticals and their use in Nuclear Medi- cine in the D-A-CH countries. In this context, we discuss current developments and trends with a

Background Dynamic 60‐minute positron‐emission‐tomography (PET) imaging with the novel tau radiotracer [18F]PI‐2620 facilitated accurate discrimination between patients with progressive supranuclear palsy (PSP) and healthy controls (HCs). We now aimed to investigate if shorter acquisition and static time windows of [18F]PI‐2620 tau‐PET can be used for imaging of patients with PSP. Method We evaluated 37 patients at five different centers with probable or possible PSP Richardson syndrome (PSP‐RS) together with ten HCs. [18F]PI‐2620 PET was performed by a dynamic 60 minute scan. Distribution volume ratios (DVRs, multilinear reference tissue model 2, cerebellar reference) were calculated using full and truncated scan durations (0‐60, 0‐50, 0‐40, 0‐30, and 0‐20 minutes p.i.). Standardized uptake value ratios (SUVrs, cerebellar reference) were obtained from static imaging windows with 20 minutes duration (20‐40, 30‐50, and 40‐60 minutes p.i.). All DVR and SUVr data were compared with regard to their potential to discriminate patients with PSP‐RS from HCs in predefined subcortical and cortical target regions (effect size, receiver operating area under the curve (AUC), multi‐region classifier). Finally, we tested if shorter [18F]PI‐2620 PET imaging can also be applied to patients with Alzheimer’s disease (n=11). Result The effect size of 0‐50 and 0‐40 DVR was equivalent to 0‐60 DVR (averaged Cohen’s d: 1.22 and 1.16 vs. 1.26), whereas the performance dropped for 0‐30 or 0‐20 DVR. The 20‐40 SUVr indicated the best performance of all short static acquisition windows (averaged Cohen’s d: 0.99). The globus pallidus internus discriminated patients with PSP and healthy controls at a similarly high level for 0‐60 DVR (AUC: 0.96), 0‐40 DVR (AUC: 0.96), and 20‐40 SUVr (AUC: 0.94). The multi‐region classifier sensitivity of these time windows was consistently 86%. 0‐40 DVR showed similar performance in Alzheimer’s disease when compared to 0‐60 DVR. Conclusion Short dynamic acquisiti

The novel tau-PET tracer [18F]PI-2620 detects the 3/4-repeat-(R)-tauopathy Alzheimer's disease (AD) and the 4R-tauopathies corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP). We determined whether [18F]PI-2620 binding characteristics deriving from non-invasive reference tissue modelling differentiate 3/4R- and 4R-tauopathies. Ten patients with a 3/4R tauopathy (AD continuum) and 29 patients with a 4R tauopathy (CBS, PSP) were evaluated. [18F]PI-2620 PET scans were acquired 0-60 min p.i. and the distribution volume ratio (DVR) was calculated. [18F]PI-2620-positive clusters (DVR ≥ 2.5 SD vs. 11 healthy controls) were evaluated by non-invasive kinetic modelling. R1 (delivery), k2 & k2a (efflux), DVR, 30-60 min standardized-uptake-value-ratios (SUVR30-60) and the linear slope of post-perfusion phase SUVR (9-60 min p.i.) were compared between 3/4R- and 4R-tauopathies. Cortical clusters of 4R-tau cases indicated higher delivery (R1SRTM: 0.92 ± 0.21 vs. 0.83 ± 0.10, p = 0.0007), higher efflux (k2SRTM: 0.17/min ±0.21/min vs. 0.06/min ± 0.07/min, p < 0.0001), lower DVR (1.1 ± 0.1 vs. 1.4 ± 0.2, p < 0.0001), lower SUVR30-60 (1.3 ± 0.2 vs. 1.8 ± 0.3, p < 0.0001) and flatter slopes of the post-perfusion phase (slope9-60: 0.006/min ± 0.007/min vs. 0.016/min ± 0.008/min, p < 0.0001) when compared to 3/4R-tau cases. [18F]PI-2620 binding characteristics in cortical regions differentiate 3/4R- and 4R-tauopathies. Higher tracer clearance indicates less stable binding in 4R tauopathies when compared to 3/4R-tauopathies.

Radiochemical conversion is an important term to be included in the “Consensus nomenclature rules for radiopharmaceutical chemistry”. Radiochemical conversion should be used to define reaction efficiency by measuring the transformation of components in a crude reactionmixture at a given time,whereas radiochemical yield is better suited to define the efficiency of an entire reaction process including, for example, separation, isolation, filtration, and formulation.