In MI patients, anti-apoA-1 IgG is independently associated with MACE at 1-year, interfering with a currently unknown aldosterone-dependent RHR determinant. Knowing whether anti-apoA-1 IgG assessment could be of interest to identify an MI patient subset susceptible to benefit from apoA-1/IVIG therapy remains to be demonstrated.

The novel CZT camera allows a more than fivefold reduction in scan time and provides clinical information equivalent to conventional standard SPECT MPI.

The ability to obtain quantitative values of flow and myocardial flow reserve (MFR) has been perceived as an important advantage of PET over conventional nuclear myocardial perfusion imaging (MPI). We evaluated the added diagnostic value of MFR over MPI alone as assessed with 13 N-ammonia and PET/CT to predict angiographic coronary artery disease (CAD). Methods: Seventy-three patients underwent 1-d adenosine stress-rest 13 N-ammonia PET/CT MPI, and MFR was calculated. The added value of MFR as an adjunct to MPI for predicting CAD (luminal narrowing $ 50%) was evaluated using invasive coronary angiography as a standard of reference. Results: Per patient, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MPI for detecting significant CAD were 79%, 80%, 91%, 59%, and 79%, respectively. Adding a cutoff of less than 2.0 for global MFR to MPI findings improved the values to 96% (P , 0.005), 80%, 93%, 89% (P , 0.005), and 92% (P , 0.005), respectively. Conclusion: The quantification of MFR in 13 N-ammonia PET/CT MPI provides a substantial added diagnostic value for detection of CAD. Particularly in patients with normal MPI results, quantification of MFR helps to unmask clinically significant CAD.Key Words: myocardial flow reserve; 13 N-ammonia; positron emission tomography; diagnostic value; myocardial perfusion imaging Nucl Med 2012; 53:1230 53: -1234 53: DOI: 10.2967 The PET technique confers advantages over SPECT related to improved image resolution and intrinsic attenuation correction (1). In addition, in myocardial perfusion imaging (MPI) PET offers quantitative assessment of myocardial blood flow (MBF) at rest and pharmacologic stress allowing calculation of myocardial flow reserve (MFR) (2). The latter is an index to evaluate blood circulation from the epicardial coronary arteries down to the microcirculation (3), which therefore provides functional information far beyond the epicardial section of the coronary vascular tree. Relative MPI such as SPECT (or PET without quantitative measurement) relies on induction of flow heterogeneities by hyperemic stress, which may sometimes underestimate the extent of coronary artery disease (CAD), as only the most severely underperfused territory may be evidenced (4). By contrast, absolute flow and MFR may reveal the true extent of CAD even at an early stage of subclinical atherosclerotic CAD. This possibility is supported by recent results documenting an added prognostic value for MFR over PET MPI alone with either 13 N-ammonia (5) or 82 Rb (6,7). Interestingly, MFR remained predictive throughout a 10-y follow-up period (5). Although many studies have revealed a reversed correlation of increasing coronary artery lesion narrowing with decreasing hyperemic flow and MFR in the respective myocardial territory (8-10), its diagnostic added value over MPI PET has not been assessed systematically. JWe evaluated the hypothesis that patients with decreased MFR (,2.0) would have a higher probability of CAD and that, thus, MFR would co...

Aims Although cardiac hybrid imaging, fusing single-photon emission computed tomography (SPECT) myocardial perfusion imaging with coronary computed tomography angiography (CCTA), provides important complementary diagnostic information for coronary artery disease (CAD) assessment, no prognostic data exist on the predictive value of cardiac hybrid imaging. Hence, the aim of this study was to assess the prognostic value of hybrid SPECT/CCTA images. Methods and results Of 335 consecutive patients undergoing a 1-day stress/rest (99m)Tc-tetrofosmin SPECT and a CCTA, acquired on stand-alone scanners and fused to obtain cardiac hybrid images, follow-up was obtained in 324 patients (97%). Survival free of all-cause death or non-fatal myocardial infarction (MI) and free of major adverse cardiac events (MACE: death, MI, unstable angina requiring hospitalization, coronary revascularizations) was determined using the Kaplan-Meier method for the following groups: (i) stenosis by CCTA and matching reversible SPECT defect; (ii) unmatched CCTA and SPECT finding; and (iii) normal finding by CCTA and SPECT. Cox's proportional hazard regression was used to identify independent predictors for cardiac events. At a median follow-up of 2.8 years (25th-75th percentile: 1.9-3.6), 69 MACE occurred in 47 patients, including 20 death/MI. A corresponding matched hybrid image finding was associated with a significantly higher death/MI incidence (P < 0.005) and proved to be an independent predictor for MACE. The annual death/MI rate was 6.0, 2.8, and 1.3% for patients with matched, unmatched, and normal findings. Conclusion Cardiac hybrid imaging allows risk stratification in patients with known or suspected CAD. A matched defect on hybrid image is a strong predictor of MACE.

Recent advances in SPECT technology including cadmium-zinctelluride (CZT) semiconductor detector material may pave the way for absolute myocardial blood flow (MBF) measurements by SPECT. The aim of the present study was to compare K 1 uptake rate constants as surrogates of absolute MBF and myocardial flow reserve index (MFRi) in humans as assessed with a CZT SPECT camera versus PET. Methods: Absolute MBF was assessed in 28 consecutive patients undergoing adenosine stress-rest myocardial perfusion imaging (MPI) by 99m Tc-tetrofosmin CZT SPECT and 13 N-ammonia PET, and MFR was calculated as a ratio of hyperemic over resting MBF. Results from both MPI methods were compared, and correlation coefficients were calculated. The diagnostic accuracy of CZT MFRi to predict an abnormal MFR defined as PET MFR less than 2 was assessed using a receiver-operator-characteristic curve. The definition of coronary artery disease (CAD) was originally based on the presence of anatomic luminal narrowing greater than 50%. Over the past decades, however, many advances in imaging techniques have enhanced our pathophysiologic understanding of CAD. It has been recognized that many factors beyond luminal narrowing may determine whether or not an anatomic coronary lesion induces ischemia. Because this cannot be comprehensively addressed by coronary angiography alone, nuclear myocardial perfusion imaging (MPI) has been well established as a tool for providing proof of ischemia. This is mandatory for prognostically relevant target lesion revascularization in chronic stable CAD. Because revascularization of a non-flow-limiting coronary stenosis is not beneficial to the patient, neither from a prognostic nor from a symptomatic point of view, nuclear MPI has been suggested as a gatekeeper for invasive coronary angiography (1-3). MPI studies with PET have demonstrated that absolute myocardial blood flow (MBF) and flow reserve (MFR) provide incremental diagnostic (4) and prognostic (5) information over relative perfusion alone. Quantitative assessment of MBF is difficult with standard SPECT for which detectors need to rotate around the patient and for which unfavorable properties of the currently available flow tracers hamper accurate MBF quantification because of nonlinear extraction fraction with roll-off at higher flow values. The recent advances in SPECT technology including semiconductor detector material (cadmium zinc telluride [CZT]) allow acquisition in a nonrotating mode and therefore acquisition of time-activity curves. This may enable absolute MBF and MFR estimation by SPECT as recently shown in experimental animal models (6), which may pave the way for its implementation in clinical routine (7). More knowledge on the impact of the tracer properties on the values obtained from quantification is crucial.The aim of the present study was a head-to-head comparison in humans of indices of absolute MBF and MFR as assessed with 99m Tc-tetrofosmin on a CZT SPECT camera versus MBF and MFR measured with 13 N-ammonia on a PET scanner. MATERIALS AND...

Purpose Tendency is to moderate the injected activity and/or reduce acquisition time in PET examinations to minimize potential radiation hazards and increase patient comfort. This work aims to assess the performance of regular full-dose (FD) synthesis from fast/low-dose (LD) whole-body (WB) PET images using deep learning techniques. Methods Instead of using synthetic LD scans, two separate clinical WB 18F-Fluorodeoxyglucose (18F-FDG) PET/CT studies of 100 patients were acquired: one regular FD (~ 27 min) and one fast or LD (~ 3 min) consisting of 1/8th of the standard acquisition time. A modified cycle-consistent generative adversarial network (CycleGAN) and residual neural network (ResNET) models, denoted as CGAN and RNET, respectively, were implemented to predict FD PET images. The quality of the predicted PET images was assessed by two nuclear medicine physicians. Moreover, the diagnostic quality of the predicted PET images was evaluated using a pass/fail scheme for lesion detectability task. Quantitative analysis using established metrics including standardized uptake value (SUV) bias was performed for the liver, left/right lung, brain, and 400 malignant lesions from the test and evaluation datasets. Results CGAN scored 4.92 and 3.88 (out of 5) (adequate to good) for brain and neck + trunk, respectively. The average SUV bias calculated over normal tissues was 3.39 ± 0.71% and − 3.83 ± 1.25% for CGAN and RNET, respectively. Bland-Altman analysis reported the lowest SUV bias (0.01%) and 95% confidence interval of − 0.36, + 0.47 for CGAN compared with the reference FD images for malignant lesions. Conclusion CycleGAN is able to synthesize clinical FD WB PET images from LD images with 1/8th of standard injected activity or acquisition time. The predicted FD images present almost similar performance in terms of lesion detectability, qualitative scores, and quantification bias and variance.

Low-dose CTCA by electrocardiogram triggering is feasible in the vast majority of an every-day population. However, HR control is crucial, as an HR below 62 beats/min favors diagnostic image quality.

Intra- and inter-scan agreement of CAC measurement in a given data set is excellent. Inter-scanner variability is reasonable, particularly for Agatston units in the clinically most relevant range <1000. The use of different software solutions has a greater influence particularly on volume scores than the use of different scanner types.