166 Aim: Myocardial blood flow (MBF) quantification is a promising noninvasive tool for evaluating CAD, assisting in diagnosis, treatment, and risk stratification. Several analysis software packages are validated for MBF quantification.We compared results of MBF obtained using three software packages used in clinical routine with this latest SiPM generation scanner.
Methods: In total, 111 patients (70M/41F) underwent dynamic 82Rb-PET at rest and during adenosine stress on a latest generation SiPM PET/CT (Siemens Biograph Vision 600). Data were processed with: (1) Corridor4DM, (2) FlowQuant and (3) Syngo.PET MBF. MBF and myocardial flow reserve (MFR) polar maps were computed. Comparisons used Pearson’s correlation ρ (measuring precision), Bland-Altman limit-of-agreement and Lin’s concordance correlation ρc=ρ·Cb(Cbmeasuring systematic bias).
Results: Lin’s concordance and Pearson’s correlation values were similar, suggesting no systematic bias between Corridor4DM and FlowQuant with an excellent precision ρ for rest and stress MBF (ρ=0.717, ρc=0.714, Cb=0.996 and ρ=0.908, ρc=0.845, Cb=0.930, respectively) and for MFR (ρ=0.803, ρc=0.726, Cb=0.904). A good precision was measured between Corridor4DM and Syngo.PET (MBF: ρ=0.579, ρc=0.419, Cb=0.724 for rest and ρ=0.923, ρc=0.892, Cb=0.967 for stress; MFR: ρ=0.531, ρc=0.465, Cb=0.874) and between FlowQuant and Syngo.PET (MBF: ρ=0.676, ρc=0.466, Cb=0.689 for rest and ρ=0.868, ρc=0.851, Cb=0.980 for stress; MFR: ρ=0.624, ρc=0.415, Cb=0.665). Although no mean bias was observed on Bland-Altman plots, Syngo.PET provided slightly lower MFR values than FlowQuant and Corridor4DMdue to higher rest flow values.
Conclusions: Concordance between software packages was excellent for MBF and MFR, despite slightly lower values by Syngo.PET at higher MFR values. Therefore, comparison of outcomes from the three software packages assessing quantification of MBF can be applied in clinical practice.
Angiogenesis is an essential part of the cardiac repair process after myocardial infarction, but its spatiotemporal dynamics remain to be fully deciphered.68Ga-NODAGA-Arg-Gly-Asp (RGD) is a PET tracer targeting αvβ3 integrin expression, which is a marker of angiogenesis. Methods: In this prospective single-center trial, we aimed to monitor angiogenesis through myocardial integrin αvβ3 expression in 20 patients with ST-segment elevation myocardial infarction (STEMI). In addition, the correlations between the expression levels of myocardial αvβ3 integrin and the subsequent changes in 82Rb PET/CT parameters, including rest and stress myocardial blood flow (MBF), myocardial flow reserve (MFR), and wall motion abnormalities, were assessed. The patients underwent 68Ga-NODAGA-RGD PET/CT and rest and stress 82Rb-PET/CT at 1 wk, 1 mo, and 3 mo after STEMI. To assess 68Ga-NODAGA-RGD uptake, the summed rest 82Rb and 68Ga-NODAGA-RGD images were coregistered, and segmental SUVs were calculated (RGD SUV). Results: At 1 wk after STEMI, 19 participants (95%) presented increased 68Ga-NODAGA-RGD uptake in the infarcted myocardium. Seventeen participants completed the full imaging series. The values of the RGD SUV in the infarcted myocardium were stable 1 mo after STEMI (1 wk vs. 1 mo, 1.47 g/mL [interquartile range (IQR), 1.37-1.64 g/mL] vs. 1.47 g/mL [IQR, 1.30-1.66 g/mL]; P = 0.9), followed by a significant partial decrease at 3 mo (1.32 g/mL [IQR, 1.12-1.71 g/mL]; P = 0.011 vs. 1 wk and 0.018 vs. 1 mo). In segment-based analysis, positive correlations were found between RGD SUV at 1 wk and the subsequent changes in stress MBF (Spearman ρ: r = 0.17, P = 0.0033) and MFR (Spearman ρ: r = 0.31, P < 0.0001) at 1 mo. A negative correlation was found between RGD SUV at 1 wk and the subsequent changes in wall motion abnormalities at 3 mo (Spearman ρ: r = -0.12, P = 0.035). Conclusion: The present study found that αvβ3 integrin expression is significantly increased in the infarcted myocardium 1 wk after STEMI. This expression remains stable after 1 mo and partially decreases after 3 mo. Initial αvβ3 integrin expression at 1 wk is significantly weakly correlated with subsequent improvements in stress MBF, MFR, and wall motion analysis.
334 Objectives: Quantification of myocardial blood flow (MBF) has added diagnostic and prognostic value over relative perfusion imaging alone, but requires accurate first-pass dynamic imaging to capture the arterial blood input function. The newest digital PET systems using SiPM technologies have smaller detectors and more counting channels compared to PMT-based systems, potentially reducing detector dead-time losses and increasing dynamic range. This study evaluated the high-count-rate (CR) accuracy of a digital PET system with 3.2mm detectors and 16-to-25 SiPM-to-crystal coupling.
Methods: 2200 MBq (60 mCi) of 82Rb was injected into the myocardium compartment of an anthropomorphic torso phantom (Data Spectrum) and scanned for 10 min using a 25 cm axial field-of-view (FOV) digital PET-CT scanner (Siemens Biograph Vision 600). Dynamic images were reconstructed (40 x 15 sec) with all corrections enabled. Time-activity-curves were measured in the heart wall and plotted as a function of total activity in the FOV, and as a function of the prompt coincidence CR (Trues + Scatter + Randoms). Dynamic range was determined as the maximum CR with residual bias<10% in the measured myocardial time-activity data, following the methodology of Renaud et al (J Nucl Med 2017;58(1):103). The corresponding total phantom activity in the FOV was used to estimate the maximum injected dose-by-weight to use for accurate first-pass imaging in patients. Peak first-pass CR was measured as a function of body-weight in N=38 patients, and verified against the predicted phantom CR values.
Results: Bias in the measured heart-wall activity was <10% with up to 610 MBq (16.5 mCi) in the cardiac phantom. The prompt CR at this activity was 11.7 Mcps, corresponding to an estimated dose of 12 MBq/kg in a 50kg patient. The patient sample had mean body-weight = 81±19 kg and BMI = 28±6 kg/m2. Patient scans performed using 5-6 MBq/kg (N=21) resulted in a peak CR of 4.8±0.7 Mcps that increased slightly with body weight (R2=0.10, p=0.04), and was consistent with the values predicted by the phantom scan (3.9-4.9 Mcps) representing a 50 kg patient. Patient scans with 6-8 MBq/kg (N=17) showed greater dependence of peak CR with body-weight (R2=0.66, p<0.001), approaching the 11.7 Mcps limit at ~130 kg. In a subset of patients ≤65kg receiving a fixed dose of 370 MBq (N=10), the peak CR tended to decrease with body-weight (R2=0.17, p=0.07).
Conclusions: Weight-based dosing up to 6 MBq/kg resulted in peak first-pass CR values well below the accuracy limit of 11.7 Mcps on the Siemens Biograph Vision 600. Patient doses of 6-8 MBq/kg resulted in <10% bias in the peak CR for patients up to 130 kg on average, and should still provide accurate MBF quantification. These results should be confirmed in a larger cohort and in larger patients exceeding 130 kg (285 lbs).
References: Renaud JM, Yip K, Guimond J, Trottier M, Pibarot P, Turcotte E, Maguire C, Lalonde L, Gulenchyn K, Farncombe T, Wisenberg G, Moody J, Lee B, Port SC, Turkington TG, Beanlands RS, deKemp RA. Characterization of 3-Dimensional PET Systems for Accurate Quantification of Myocardial Blood Flow. J Nucl Med. 2017 Jan;58(1):103-109. doi: 10.2967/jnumed.116.174565.
Background: Diagnostic performance of positron emission tomography using white blood cells labeled with fluorine-18-fluorodeoxyglucose (18F-FDG-WBC PET or PET/CT) in patients with suspicious infectious diseases has been evaluated in several studies; however, there is no consensus about the diagnostic accuracy of this method. Therefore, a systematic review and meta-analysis was carried out on this topic. Methods: A comprehensive computer literature search screening PubMed/MEDLINE, Embase and Cochrane library databases through March 2019 was performed. Pooled sensitivity, specificity, positive and negative likelihood ratios (LR+ and LR−), and diagnostic odds ratio (DOR) of 18F-FDG-WBC PET or PET/CT in patients with infectious diseases were calculated. Results: Eight studies on the use of 18F-FDG-WBC PET or PET/CT in suspicious infectious diseases were discussed in the systematic review. The meta-analysis of seven studies (236 patients) provided these pooled results on a per patient-based analysis: sensitivity was 86.3% [95% confidence interval (95%CI) 75–92.9%], specificity 92% (95%CI 79.8–97.1%), LR+ 6.6 (95%CI: 3.1–14.1), LR− 0.2 (95%CI: 0.12–0.33), DOR 43.5 (95%CI: 12.2–155). A statistically significant heterogeneity was not detected. Conclusions: Despite limited literature data, 18F-FDG-WBC PET or PET/CT demonstrated a good diagnostic accuracy for the diagnosis of infectious diseases; nevertheless, larger studies are needed.
Abstract BackgroundIntegrin alpha-V-beta-3 (αvβ3) pathway is involved in intraplaque angiogenesis and inflammation and represents a promising target for molecular imaging in cardiovascular diseases such as atherosclerosis. The aim of this study was to assess the clinical correlates of arterial wall accumulation of 68 Ga-NODAGA-RGD, a specific α v β 3 integrin ligand for PET. Materials and methodsThe data of 44 patients who underwent 68 Ga-NODAGA-RGD PET/CT scans were retrospectively analyzed. Tracer accumulation in the vessel wall of major arteries was analyzed semi-quantitatively by blood-pool-corrected target-to-background ratios. Tracer uptake was compared with clinically documented atherosclerotic cardiovascular disease, cardiovascular risk factors and calcified plaque burden. Data were compared using the Mann-Whitney U test and Spearman correlation. Results 68 Ga-NODAGA-RGD arterial uptake was significantly higher in patients with previous clinically documented atherosclerotic cardiovascular disease (mean TBR 2.44 [2.03-2.55] vs. 1.81 [1.56-1.96], p = 0.001) and showed a significant correlation with prior cardiovascular or cerebrovascular event ( r = 0.34, p = 0.024), BMI ( r = 0.38, p = 0.01), plaque burden ( r = 0.31, p = 0.04), and hypercholesterolemia ( r = 0.31, p = 0.04).Conclusions 68 Ga-NODAGA-RGD holds promise as a non-invasive marker of disease activity in atherosclerosis, providing information about intraplaque angiogenesis.
Abstract Background Physiological focal radiopharmaceutical uptake in the head and uncinate process of the pancreas may be seen on somatostatin receptor-based PET/CT and might lead to false-positive results for neuroendocrine tumours (NETs). We aimed to perform a systematic review and a meta-analysis about the prevalence of this finding. Methods We performed a comprehensive computer literature search across several databases until July 2020. Pooled prevalence of physiological focal uptake on somatostatin receptor-based PET/CT in the pancreas was calculated on a per-examination-based analysis and 95% confidence interval values (95% CI) were reported. Results Six studies (684 patients and 829 PET/CT scans) were included. The pooled prevalence of physiological uptake in the head and uncinate process of the pancreas on somatostatin receptor-based PET/CT imaging was 34% (95% CI 19.5–48.7%) with average SUVmax values ranging from 5 to 12.6. Heterogeneity was seen across the selected studies. Conclusions High radiopharmaceutical uptake in the head and uncinate process of the pancreas is frequent at somatostatin receptor-based PET/CT and it should be recognized by nuclear medicine physicians to prevent unnecessary additional investigations. In addition, next generation PET/CT tomographs might increase the prevalence of this finding.
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