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Objectives The bombesin derivative RM2 is a GRPr antagonist with strong binding affinity to prostate cancer (PCa). In this study, the impact of [68Ga]Ga-RM2 positron emission tomography-computed tomography (PET-CT) for the detection of primary PCa was compared with that of [18F]FCH PET-CT and multiparametric magnetic resonance imaging (mpMRI). Methods This phase I/II study was conducted in 30 biopsy-positive PCa subjects. The patients were stratified into high (10 patients), intermediate (10 patients), and low risk (10 patients) for extraglandular metastases as defined by National Comprehensive Cancer Network (NCCN) criteria (NCCN Clinical Practice Guidelines in Oncology, 2016). The prostate gland was classified in 12 anatomic segments for data analysis of the imaging modalities as well as histopathologic findings. The segment with the highest radiotracer uptake was defined as the “index lesion.” All cases were scheduled to undergo prostatectomy with pelvic lymph node (LN) dissection in intermediate- and high-risk patients. Intraprostatic and pelvic nodal [68Ga]Ga-RM2 and [18F]FCH PET-CT findings were correlated with mpMRI and histopathologic results. Results Of the 312 analyzed regions, 120 regions (4 to 8 lesions per patient) showed abnormal findings in the prostate gland. In a region-based analysis, overall sensitivity and specificity of [68Ga]Ga-RM2 PET-CT in the detection of primary tumor were 74% and 90%, respectively, while it was 60% and 80% for [18F]FCH PET-CT and 72% and 89% for mpMRI. Although the overall sensitivity of [68Ga]Ga-RM2 PET-CT was higher compared to that of [18F]FCH PET-CT and mpMRI, the statistical analysis showed only significant difference between [68Ga]Ga-RM2 PET-CT and [18F]FCH PET-CT in the intermediate-risk group (p = 0.01) and [68Ga]Ga-RM2 PET-CT and mpMRT in the high-risk group (p = 0.03). In the lesion-based analysis, there was no significant difference between SUVmax of [68Ga]Ga-RM2 and [18F]FCH PET-CT in the intraprostatic malignant lesions ([68Ga]Ga-RM2: mean SUVmax: 5.98 ± 4.13, median: 4.75; [18F]FCH: mean SUVmax: 6.08 ± 2.74, median: 5.5; p = 0.13). Conclusions [68Ga]Ga-RM2 showed promising PET tracer for the detection of intraprostatic PCa in a cohort of patients with different risk stratifications. However, significant differences were only found between [68Ga]Ga-RM2 PET-CT and [18F]FCH PET-CT in the intermediate-risk group and [68Ga]Ga-RM2 PET-CT and mpMRT in the high-risk group. In addition, GRP-R-based imaging seems to play a complementary role to choline-based imaging for full characterization of PCa extent and biopsy guidance in low- and intermediate-metastatic-risk PCa patients and has the potential to discriminate them from those at higher risks. Key Points • [68Ga]Ga-RM2 is a promising PET tracer with a high detection rate for intraprostatic PCa especially in intermediate-risk prostate cancer patients. • GRPr-based imaging seems to play a complementary role to choline-based or PSMA-based PET/CT imaging in selected low- and intermediate-risk PCa patients for better characterization and eventually biopsy guidance of prostate cancer disease.

BACKGROUND: Bioprosthetic valve thrombosis may have implications for valve function and durability.OBJECTIVES: Using a novel glycoprotein IIb/IIIa receptor radiotracer 18F-GP1, we investigated whether positron emission tomography (PET)-computed tomography (CT) could detect thrombus formation on bioprosthetic aortic valves.METHODS: Ex vivo experiments were performed on human platelets and explanted bioprosthetic aortic valves. In a prospective cross-sectional study, patients with either bioprosthetic or normal native aortic valves underwent echocardiography, CT angiography, and 18F-GP1 PET-CT.RESULTS: Flow cytometric analysis, histology, immunohistochemistry, and autoradiography demonstrated selective binding of 18F-GP1 to activated platelet glycoprotein IIb/IIIa receptors and thrombus adherent to prosthetic valves. In total, 75 participants were recruited: 53 with bioprosthetic valves (median time from implantation 37 months [IQR: 12-80 months]) and 22 with normal native aortic valves. Three participants had obstructive valve thrombosis, and a further 3 participants had asymptomatic hypoattenuated leaflet thickening on CT angiography. All bioprosthetic valves, but none of the native aortic valves, demonstrated focal 18F-GP1 uptake on the valve leaflets: median maximum target-to-background ratio 2.81 (IQR: 2.29-3.48) vs 1.43 (IQR: 1.28-1.53) (P < 0.001). Higher 18F-GP1 uptake was independently associated with duration of valve implantation and hypoattenuated leaflet thickening. All 3 participants with obstructive valve thrombosis were anticoagulated for 3 months, leading to resolution of their symptoms, improvement in mean valve gradients, and a reduction in 18F-GP1 uptake.CONCLUSIONS: Adherence of activated platelets is a common and sustained finding on bioprosthetic aortic valves. 18F-GP1 uptake is higher in the presence of thrombus, regresses with anticoagulation, and has potential use as an adjunctive clinical tool. (18F-GP1 PET-CT to Detect Bioprosthetic Aortic Valve Thrombosis; NCT04073875).

BACKGROUND: The PET tracer (4S)-4-(3-[(18)F]fluoropropyl)-l-glutamate ((18)F-FSPG) targets the system x(C)(–) cotransporter, which is overexpressed in various tumors. PURPOSE: To assess the role of (18)F-FSPG PET/CT in intracranial malignancies. MATERIALS AND METHODS: Twenty-six patients (mean age, 54 years ± 12; 17 men; 48 total lesions) with primary brain tumors (n = 17) or brain metastases (n = 9) were enrolled in this prospective, single-center study (ClinicalTrials.gov identifier: NCT02370563) between November 2014 and March 2016. A 30-minute dynamic brain (18)F-FSPG PET/CT scan and a static whole-body (WB) (18)F-FSPG PET/CT scan at 60–75 minutes were acquired. Moreover, all participants underwent MRI, and four participants underwent fluorine 18 ((18)F) fluorodeoxyglucose (FDG) PET imaging. PET parameters and their relative changes were obtained for all lesions. Kinetic modeling was used to estimate the (18)F-FSPG tumor rate constants using the dynamic and dynamic plus WB PET data. Imaging parameters were correlated to lesion outcomes, as determined with follow-up MRI and/or pathologic examination. The Mann-Whitney U test or Student t test was used for group mean comparisons. Receiver operating characteristic curve analysis was used for performance comparison of different decision measures. RESULTS: (18)F-FSPG PET/CT helped identify all 48 brain lesions. The mean tumor-to-background ratio (TBR) on the whole-brain PET images at the WB time point was 26.6 ± 24.9 (range: 2.6–150.3). When (18)F-FDG PET was performed, (18)F-FSPG permitted visualization of non-(18)F-FDG–avid lesions or allowed better lesion differentiation from surrounding tissues. In participants with primary brain tumors, the predictive accuracy of the relative changes in influx rate constant K(i) and maximum standardized uptake value to discriminate between poor and good lesion outcomes were 89% and 81%, respectively. There were significant differences in the (18)F-FSPG uptake curves of lesions with good versus poor outcomes in the primary brain tumor group (P < .05) but not in the brain metastases group. CONCLUSION: PET/CT imaging with (4S)-4-(3-[(18)F]fluoropropyl)-l-glutamate ((18)F-FSPG) helped detect primary brain tumors and brain metastases with a high tumor-to-background ratio. Relative changes in (18)F-FSPG uptake with multi-time-point PET appear to be helpful in predicting lesion outcomes. Clinical trial registration no. NCT02370563 © RSNA, 2022 Online supplemental material is available for this article.

We aimed to explore whether the imaging of antiporter system x(C)(−) of immune cells with (4S)-4-(3-(18)F-fluoropropyl)-l-glutamate ((18)F-FSPG) PET can assess inflammatory bowel disease (IBD) activity in murine models and patients (NCT03546868). Methods: (18)F-FSPG PET imaging was performed to assess IBD activity in mice with dextran sulfate sodium-induced and adoptive T-cell transfer–induced IBD and a cohort of 20 patients at a tertiary care center in South Korea. Immunohistochemical analysis of system x(C)(−) and cell surface markers was also studied. Results: Mice with experimental IBD showed increased intestinal (18)F-FSPG uptake and xCT expression in cells positive (+) for CD11c, F4/80, and CD3 in the lamina propria, increases positively associated with clinical and pathologic disease activity. (18)F-FSPG PET studies in patients, most of whom were clinically in remission or had mildly active IBD, showed that PET imaging was sufficiently accurate in diagnosing endoscopically active IBD and remission in patients and bowel segments. (18)F-FSPG PET correctly identified all 9 patients with superficial or deep ulcers. Quantitative intestinal (18)F-FSPG uptake was strongly associated with endoscopic indices of IBD activity. The number of CD68(+)xCT(+) and CD3(+)xCT(+) cells in 22 bowel segments from patients with ulcerative colitis and the number of CD68(+)xCT(+) cells in 7 bowel segments from patients with Crohn disease showed a significant positive association with endoscopic indices of IBD activity. Conclusion: The assessment of system x(C)(−) in immune cells may provide diagnostic information on the immune responses responsible for chronic active inflammation in IBD. (18)F-FSPG PET imaging of system x(C)(−) activity may noninvasively assess the IBD activity.

MPG Movie file - 4626K, Y94-9392 H460 Tumor PET

Purpose:18F-labeled small molecules targeting adaptations of tumor metabolism possess the potential for early tumor detection with high sensitivity and specificity by positron emission tomography (PET) imaging. Compounds tracing deranged pathways other than glycolysis may have advantages in situations where 2-[18F]fluoro-2-deoxy-d-glucose (FDG) has limitations. The aim of this study was the generation of a metabolically stable 18F-labeled glutamate analogue for PET imaging of tumors.Experimental Design: Derivatives of l-glutamate were investigated in cell competition assays to characterize the responsible transporter. An automated radiosynthesis was established for the most promising candidate. The resulting 18F-labeled PET tracer was characterized in a panel of in vitro and in vivo tumor models. Tumor specificity was investigated in the turpentine oil-induced inflammation model in rats.Results: A fluoropropyl substituted glutamate derivative showed strong inhibition in cell uptake assays. The radiosynthesis was established for (4S)-4-(3-[18F]fluoropropyl)-l-glutamate (BAY 94-9392). Tracer uptake studies and analysis of knockdown cells showed specific transport of BAY 94-9392 via the cystine/glutamate exchanger designated as system xC−. No metabolites were observed in mouse blood and tumor cells. PET imaging with excellent tumor visualization and high tumor to background ratios was achieved in preclinical tumor models. In addition, BAY 94-9392 did not accumulate in inflammatory lesions in contrast to FDG.Conclusions: BAY 94-9392 is a new tumor-specific PET tracer which could be useful to examine system xC− activity in vivo as a possible hallmark of tumor oxidative stress. Both preclinical and clinical studies are in progress for further characterization. Clin Cancer Res; 17(18); 6000–11. ©2011 AACR.

Supplementary Figure 1: 79 patients enrolled in study.

Purpose: We determined the maximum tolerated dose (MTD), safety, pharmacokinetics, pharmacodynamics, and preliminary activity of OSI-906, a potent, oral, dual inhibitor of insulin-like growth factor-1 receptor (IGF1R) and insulin receptor (IR), in patients with advanced solid tumors.Experimental Design: This was a multicenter, open-label, dose escalation phase I study evaluating three intermittent dosing schedules of once-daily OSI-906 [schedule (S) 1, days 1–3 every 14 days; S2, days 1–5 every 14 days; S3, days 1–7 every 14 days]. A fed-fasting expansion cohort was included in the study.Results: Seventy-nine patients were enrolled: 62 in S1, 4 in S2, and 13 in S3. S2 was discontinued. Dose-limiting toxicity comprised grade 3–4 hyperglycemia, vomiting, fatigue, and prolonged QTc interval. The MTD and recommended phase II dose of OSI-906 was 600 mg for both S1 and S3 schedules. Other common adverse events were grade 1–2 nausea, vomiting, fatigue, and diarrhea. The pharmacokinetics of OSI-906 was dose linear, and the terminal half-life ranged between 2 and 6 hours. High-fat meals had a moderate effect on the pharmacokinetics of OSI-906. At the MTD, inhibition of IGF1R and IR was observed in peripheral blood mononuclear cells. An increase in plasma IGF1 concentrations, an indirect measure of IGF1R signaling inhibition, was seen at doses ≥ 450 mg. Two patients with adrenocortical carcinoma achieved partial responses.Conclusion: The MTD of 600 mg was well tolerated and associated with preliminary antitumor activity. These data support further evaluation of OSI-906 in solid tumors. Clin Cancer Res; 21(4); 693–700. ©2014 AACR.See related commentary by Yee, p. 667

Supplementary Materials Table 1. Ratio of area under the curve during the time interval between consecutive dosing (AUCtau) on day 3 to AUCtau on day 1 (schedule 1 [S1]) Table 2. Ratio of area under the curve during the time interval between consecutive dosing (AUCtau) on day 5 (S2) or day 7 (S3) to AUCtau on day 1.

PDF file- 354K, Detailed information on chemistry, radiochemistry and additional biological characterization

Importance Individuals who are amyloid-positive with subjective cognitive decline and clinical features increasing the likelihood of preclinical Alzheimer disease (SCD+) are at higher risk of developing dementia. Some individuals with SCD+ undergo amyloid-positron emission tomography (PET) as part of research studies and frequently wish to know their amyloid status; however, the disclosure of a positive amyloid-PET result might have psychological risks. Objective To assess the psychological outcomes of the amyloid-PET result disclosure in individuals with SCD+ and explore which variables are associated with a safer disclosure in individuals who are amyloid positive. Design, Setting, and Participants This prospective, multicenter study was conducted as part of The Amyloid Imaging to Prevent Alzheimer Disease Diagnostic and Patient Management Study (AMYPAD-DPMS) (recruitment period: from April 2018 to October 2020). The setting was 5 European memory clinics, and participants included patients with SCD+ who underwent amyloid-PET. Statistical analysis was performed from July to October 2022. Exposures Disclosure of amyloid-PET result. Main Outcomes and Measures Psychological outcomes were defined as (1) disclosure related distress, assessed using the Impact of Event Scale–Revised (IES-R; scores of at least 33 indicate probable presence of posttraumatic stress disorder [PTSD]); and (2) anxiety and depression, assessed using the Hospital Anxiety and Depression scale (HADS; scores of at least 15 indicate probable presence of severe mood disorder symptoms). Results After disclosure, 27 patients with amyloid-positive SCD+ (median [IQR] age, 70 [66-74] years; gender: 14 men [52%]; median [IQR] education: 15 [13 to 17] years, median [IQR] Mini-Mental State Examination [MMSE] score, 29 [28 to 30]) had higher median (IQR) IES-R total score (10 [2 to 14] vs 0 [0 to 2]; P P P P P = .06) and Depression (–1.0 [–2.0 to 0.0] vs –1.0 [–3.0 to 0.0]; P = .46) deltas (score after disclosure – scores at baseline). In patients with amyloid-positive SCD+, despite the small sample size, higher education was associated with lower disclosure-related distress (ρ = –0.43; P = .02) whereas the presence of study partner was associated with higher disclosure-related distress (W = 7.5; P = .03). No participants with amyloid-positive SCD+ showed probable presence of PTSD or severe anxiety or depression symptoms at follow-up. Conclusions and Relevance The disclosure of a positive amyloid-PET result to patients with SCD+ was associated with a bigger psychological change, yet such change did not reach the threshold for clinical concern.

BackgroundThe diagnosis and management of myocardial infarction is increasingly complex andestablishing the presence of intracoronary thrombosis has major implications for both theclassification and treatment of myocardial infarction.ObjectivesTo investigate whether positron emission tomography (PET) and computed tomography (CT)could non-invasively detect in vivo thrombus formation in human coronary arteries using anovel glycoprotein IIb/IIIa receptor antagonist-based radiotracer, 18F-GP1.MethodsIn a single centre observational case-control study, patients with or without acute myocardialinfarction underwent coronary 18F-GP1 PET-CT angiography. Coronary artery 18F-GP1 uptakewas assessed visually and quantified using maximum target-to-background ratios.Results18F-GP1 PET-CT angiography was performed in 49 patients with, and 50 patients without,acute myocardial infarction (61±9 years, 75% male). Coronary 18F-GP1 uptake was apparentin 39 (80%) of the 49 culprit lesions in patients with acute myocardial infarction. False negativescans appeared to relate to time delays to scan conduct and low thrombus burden in smallcalibre distal arteries. On multivariable regression analysis, culprit vessel status was the onlyindependent variable associated with higher 18F-GP1 uptake. Extra-coronary cardiac 18F-GP1findings included a high frequency of infarct-related intramyocardial uptake (35%) as well asleft ventricular (8%) or left atrial (2%) thrombus.ConclusionsCoronary 18F-GP1 PET-CT angiography is the first non-invasive selective technique to identifyin vivo coronary thrombosis in patients with acute myocardial infarction. This novel approachcan further define the role and location of thrombosis within the heart and has the potential toinform the diagnosis, management, and treatment of patients with acute myocardial infarction.

INTRODUCTION: We aim to study the effect of a more precise diagnosis, by means of amyloid positron emission tomography (PET), on institutionalization, mortality, and health-care costs.METHODS: Between October 27, 2014 and December 31, 2016, we offered amyloid PET to all patients as part of their diagnostic work-up. Patients who accepted to undergo amyloid PET (n = 449) were propensity score matched with patients without amyloid PET (n = 571, i.e., no PET). Matched groups (both n = 444) were compared on rate of institutionalization, mortality, and health-care costs in the years after diagnosis.RESULTS: Amyloid PET patients had a lower risk of institutionalization (10% [n = 45] vs. 21% [n = 92]; hazard ratio [HR] = 0.48 [0.33-0.70]) and mortality rate (11% [n = 49] vs. 18% [n = 81]; HR = 0.51 [0.36-0.73]) and lower health-care costs in the years after diagnosis compared to matched no-PET patients (β = -4573.49 [-6524.76 to -2523.74], P-value < 0.001).DISCUSSION: A more precise diagnosis in tertiary memory clinic patients positively influenced the endpoints of institutionalization, death, and health-care costs.

The first candidate PI-2014 was tested in healthy controls and subjects with Alzheimer's disease (AD). As PI-2014 displayed off-target binding to monoamine oxidase A (MAO-A), a new lead with improved binding to Tau and decreased MAO-A binding was required. For compound optimization, Tau binding assays based on both human AD brain homogenate and Tau-paired helical filaments were employed. Furthermore, two MAO-A screening assays based on (1) human-recombinant MAO-A and (2) displacement of 2-fluoro-ethyl-harmine from mouse brain homogenate were employed. Removing the N-methyl group from the tricyclic core resulted in compounds displaying improved Tau binding. For the final round of optimization, the cyclic amine substituents were replaced by pyridine derivatives. PI-2620 (2-(2-fluoropyridin-4-yl)-9H-pyrrolo[2,3-b:4,5-c']dipyridine) emerged as a best candidate displaying high Tau binding, low MAO-A binding, high brain uptake, and fast and complete brain washout. Furthermore, PI-2620 showed Tau binding on brain sections from corticobasal degeneration, progressive supranuclear palsy, and Pick's disease.

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 4-repeat tauopathies (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±7y, 39 female), 79 patients with other neurodegenerative diseases (67±12y, 35 female) and twelve age-matched controls (69±8y, 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, p18F]PI-2620 perfusion imaging mirrors known topology of regional hypoperfusion in 4RTs. Single region hypoperfusion is not specific for 4RTs, but perfusion pattern expression provides an additive value for the discrimination of 4RTs from other neurodegenerative diseases and correlates closer with clinical severity than tau pattern expression.

Tau aggregates accumulate in the Alzheimer's disease (AD) brain according to the established Braak staging scheme and spread from transentorhinal over limbic regions to the neocortex. To impact the management of AD patients, an in vivo tool for tau Braak staging is needed. First-generation tau tracers have limited performance in detecting early stages of tau. Therefore, we tested the corresponding capability of the next-generation tau tracer

Early after [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) [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 other neurodegenerative diseases (AUC: 0.850). Discrimination by the combined perfusion-tau pattern expression (AUC: 0.903) exceeded that of the sole tau pattern expression (AUC: 0.864) and the discriminatory power of the combined perfusion-tau pattern expression was replicated in the external dataset (AUC: 0.917). Perfusion but not tau pattern expression was associated with PSP rating scale (R = 0.402; p = 0.0012) and activities of daily living (R = - 0.431; p = 0.0005).[

The bombesin derivative RM2 is a GRPr antagonist with strong binding affinity to prostate cancer (PCa). In this study, the impact of [This phase I/II study was conducted in 30 biopsy-positive PCa subjects. The patients were stratified into high (10 patients), intermediate (10 patients), and low risk (10 patients) for extraglandular metastases as defined by National Comprehensive Cancer Network (NCCN) criteria (NCCN Clinical Practice Guidelines in Oncology, 2016). The prostate gland was classified in 12 anatomic segments for data analysis of the imaging modalities as well as histopathologic findings. The segment with the highest radiotracer uptake was defined as the "index lesion." All cases were scheduled to undergo prostatectomy with pelvic lymph node (LN) dissection in intermediate- and high-risk patients. Intraprostatic and pelvic nodal [Of the 312 analyzed regions, 120 regions (4 to 8 lesions per patient) showed abnormal findings in the prostate gland. In a region-based analysis, overall sensitivity and specificity of [[• [

Progressive supranuclear palsy (PSP) is a 4-repeat tauopathy movement disorder that can be imaged by the (18)F-labeled tau PET tracer 2-(2-([(18)F]fluoro)pyridin-4-yl)-9H-pyrrolo[2,3-b:4,5-c′]dipyridine ((18)F-PI-2620). The in vivo diagnosis is currently established on clinical grounds and supported by midbrain atrophy estimation in structural MRI. Here, we investigate whether (18)F-PI-2620 tau PET has the potential to improve the imaging diagnosis of PSP. Methods: In this multicenter observational study, dynamic (0–60 min after injection) (18)F-PI-2620 PET and structural MRI data for 36 patients with PSP, 22 with PSP–Richardson syndrome, and 14 with a clinical phenotype other than Richardson syndrome (i.e., variant PSP) were analyzed along with data for 10 age-matched healthy controls (HCs). The PET data underwent kinetic modeling, which resulted in distribution volume ratio (DVR) images. These and the MR images were visually assessed by 3 masked experts for typical PSP signs. Furthermore, established midbrain atrophy parameters were measured in structural MR images, and regional DVRs were measured in typical tau-in-PSP target regions in the PET data. Results: Visual assessments discriminated PSP patients and HCs with an accuracy of 63% for MRI and 80% for the combination of MRI and (18)F-PI-2620 PET. As compared with patients of the PSP–Richardson syndrome subgroup, those of the variant PSP subgroup profited more in terms of sensitivity from the addition of the visual (18)F-PI-2620 PET to the visual MRI information (35% vs. 22%). In quantitative image evaluation, midbrain-to-pons area ratio and globus pallidus DVRs discriminated best between the PSP patients and HCs, with sensitivities and specificities of 83% and 90%, respectively, for MRI and 94% and 100%, respectively, for the combination of MRI and (18)F-PI-2620 PET. The gain of sensitivity by adding (18)F-PI-2620 PET to MRI data was more marked in clinically less affected patients than in more affected patients (37% vs. 19% for visual, and 16% vs. 12% for quantitative image evaluation). Conclusion: These results provide evidence for an improved imaging-based PSP diagnosis by adding (18)F-PI-2620 tau PET to structural MRI. This approach seems to be particularly promising at earlier disease stages and could be of value both for improving early clinical PSP diagnosis and for enriching PSP cohorts for trials of disease-modifying drugs.

Background/Introduction Bioprosthetic valve thrombosis (BPVT) is an important clinical entity eventually following both bioprosthetic surgical and transcatheter aortic valve replacement. Although dynamic contrast-enhanced 4D-MDCT has improved the diagnosis of BPVT, more sensitive and pathology-specific non-invasive imaging tools are lacking. Recently, the glycoprotein IIb/IIIa receptor targeted, elarofiban-derived PET/CT imaging radiotracer [18F]GP1 has been successfully used for visualization of acute venous and arterial thrombi. Purpose We hypothesized that [18F]GP1 PET/CT imaging is suitable to detect BPVT. Methods In this proof-of-concept study, patients after bioprosthetic aortic valve replacement with symptomatic, severe hemodynamic valve dysfunction and confirmed hypoattenuated leaflet thickening (HALT) in dynamic 4D-MDCT were offered to participate in compassionate use examinations to undergo PET/CT imaging with the investigational [18F]GP1 PET tracer at baseline and after a 12-week course of therapeutic oral anticoagulation. Results This case series reports on three patients after aortic valve replacement. Two patients with symptomatic, obstructive BPVT as confirmed by echocardiography and 4D-MDCT fulfilled specified criteria and underwent [18F]GP1 PET/CT imaging. [18F]GP1 PET/CT clearly distinguished between blood pool activity and thrombotic foci. Clot-to-blood ratios at baseline were 8.2 and 4.5, respectively. A 12-week trial of therapeutic oral anticoagulation was associated with a regression of mean transprosthetic pressure gradient and reversal of HALT. Follow-up 4D-MDCT corroborated thrombus resolution in both patients. Correspondingly, [18F]GP1 PET/CT imaging demonstrated decreased tracer uptake in both patients. Clot-to-blood ratio at follow-up visit decreased to 1.2 and 2.9, respectively. While absent tracer uptake was seen in patient #1, residual tracer uptake was observed in patient #2 suggestive of ongoing platelet aggregation. One asymptomatic SAVR patient was examined with [18F]GP1 PET/CT for a different compassionate use and no thrombotic foci were detected on the leaflets. Conclusions [18F]GP1 PET/CT is a novel imaging technique in patients with obstructive BPVT. In a head-to-head comparison we show that [18F]GP1 PET/CT may have incremental diagnostic value over dynamic contrast-enhanced 4D-MDCT alone by detection of sites of ongoing platelet aggregation at the molecular level. [18F]GP1 PET/CT may serve as a novel, highly sensitive tool to overcome some limitations of current diagnostic imaging modalities for detecting BPVT and may prove useful for the monitoring and guidance of therapeutic interventions. Funding Acknowledgement Type of funding sources: Other. Main funding source(s): Life Molecular Imaging provided material for [18F]GP1 radiolabeling free of charge as part of an ongoing research collaboration.

Background Coronary artery thrombus is typically present in type 1 myocardial infarction, but small volumes in the setting of an uncertain culprit lesion may be beyond the detection limit of current imaging modalities. Purpose Using a novel glycoprotein IIb/IIIa-receptor radiotracer, 18F-GP1, we investigated whether positron emission tomography-computed tomography (PET-CT) could detect thrombus formation in coronary arteries. Methods In a single centre cross-sectional study, patients over 40 years of age with myocardial infarction were recruited after myocardial infarction and underwent underwent CT angiography and 18F-GP1 PET-CT. Stable patients with and without coronary artery disease formed a control cohort. Coronary artery 18F-GP1 uptake was visually assessed and quantified using maximum target-to-background ratios (TBRmax). Results Ninety-four (44 post-myocardial infarction and 50 control patients) were included in the cross-sectional analysis. The mean age of the post-myocardial infarction group was 61±9 years, three-quarters were male and two thirds had presented with ST elevation on electrocardiography. 34 (80%) patients post-myocardial infarction, but none of the control patients, demonstrated focal 18F-GP1 uptake in the coronary arteries. Of 42 vessels with an angiographic culprit lesion, 35 (83%) had 18F-GP1 uptake which was significantly higher than non-culprit vessels (p A patient with ectatic vessel and visual thrombus demonstrated the most intense 18F-GP1 uptake (TBRmax 2.0, highest in the cohort) in the region of heaviest thrombus burden (Figure 2). Extra-coronary uptake was seen in regions of left ventricular thrombus, left atrial appendage thrombus, pulmonary thromboembolism and intramyocardial microvascular obstruction. Conclusions 18F-GP1 PET-CT is able to detect coronary artery thrombus in culprit lesions following myocardial infarction, as well as extra-coronary thrombotic pathologies that may be important in guiding patient management. 18F-GP1 is highly specific in recognising a culprit lesion from a non-culprit lesion both visually as well as quantitatively. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Figure 1Figure 2

Purpose: Overexperssion of Gastrin-releasing-peptide receptor (GRPr) in prostate carcinoma (PCa) suggests new means in the detection of prostate cancer foci. The bombesin derivative RM2 (DOTA-4-amino-1-carboxy­methyl­piperidine-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2) is a GRPr antagonist with strong binding affinity. Based on promising results from a first-in-man study on PCa detection in patients with local disease, a Phase I/II study was initiated and the ability of [68Ga]Ga-RM2 PET/CT to detect PCa lesions was compared with [18F]fluoromethylcholine ([18F]FCH) PET/CT and multiparameteric prostate Magnetic Resonance Imaging (mpMRI).Methods: This Phase I/II study was conductedwith a pre-specified interim analysis following the enrollment of 30 biopsy-positive PCa subjects, stratified into low, intermediate and high pretreatment risk of extra-glandular metastases with reference to NCCN criteria. Each subject had PCa detected by transrectal ultrasound guided prostate biopsy and subjects were scheduled to undergo prostatectomy with pelvic lymph node (LN) dissection in intermediate and high risk patients. Following administration of an intravenous dose of 140 MBq of [68Ga]Ga-RM2,imaging was conducted at 60 min. p.i.. Twenty-five (25/30) subjects had concomitant [18F]FCH PET/CT imaging. All patients underwent mpMRI. Intra-prostatic and pelvic nodal PET/CT findings were correlated with histopathologic results.Results: High uptake of [68Ga]Ga-RM2 was seen in pancreas and the urinary system with very low background uptake in the rest of the abdomen or thorax. Despite of high bladder activity, focal intraprostatic uptake was readily well detectable. Of overall 312 analyzed regions, 120 regions (4 to 8 lesions per-patient) showed abnormal finding in the prostate gland. In a region-based analysis overall sensitivity and specificity of [68Ga]Ga-RM2 PET/CT in the detection of primary tumor were 74% and 90%, respectively; while it was 60% and 80% for [18F]FCH PET/CT and 72% and 89% for mpMRI. Although, the overall sensitivity of [68Ga]Ga-RM2 PET/CT was higher comparing to [18F]FCH PET/CT and mpMRI; however, the statistical analysis showed only significant difference between [68Ga]Ga-RM2 PET/CT and [18F]FCH PET/CT in intermediate-risk group (P=0.01) and [68Ga]Ga-RM2 PET/CT and mpMRT in high-risk group (p=0.03). [68Ga]Ga-RM2 PET/CT correctly detected 2 histopathologically verified LN metastases in 2 high risk patients; while 18F-FCH PET/CT only identified the LN lesion in 1 patient.Conclusion: [68Ga]Ga-RM2 is a promising new PET-tracer with a high detection rate for intraprostatic PCa. While index lesion detection rates were similar in both PET/CT studies, the improved specificity of [68Ga]Ga-RM2 for canver versus BPH renders it notably better than [18F]FCH in the detection of intraprostatic lesions. In addition, GRP-R-based imaging seems to play a complementary role to Choline-based imaging for full characterization of PCa extent, biopsy guidance in low and intermediate metastatic risk PCa patients and has the potential to discriminate them from whom of those at higher risks.Trial Registeration number: EudraCT-Nr.: 2014-003027-21, Date: 10 June, 2014

We observed the candidate dual quasar J2122−0026 with speckle interferometric imaging at the Gemini-North Observatory. Results of our one-hour high resolution ‘Alopeke imaging observation agree with and confirm Hubble Space Telescope imaging of the pair separated at ∼0.″5. These observations show that sub-arcsec dual quasar candidates as faint as r ∼ 19 can be observed and detected using speckle imaging at Gemini. “Do not go where the path may lead, go instead where there is no path and leave a trail.” Ralph Waldo Emerson