Multisoftware Reproducibility Study of Stress and Rest Myocardial Blood Flow Assessed with 3D Dynamic PET/CT and a 1-Tissue-Compartment Model of 82Rb Kinetics.
Journal - Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Routine quantification of myocardial blood flow (MBF) requires robust and reproducible processing of dynamic image series. The goal of this study was to evaluate the reproducibility of 3 highly automated software programs commonly used for absolute MBF and flow reserve (stress/rest MBF) assessment with 82Rb PET imaging. METHODS: Dynamic rest and stress 82Rb PET scans were selected in 30 sequential patient studies performed at 3 separate institutions using 3 different 3-dimensional PET/CT scanners. All 90 scans were processed with 3 different MBF quantification programs, using the same 1-tissue-compartment model. Global (left ventricle) and regional (left anterior descending, left circumflex, and right coronary arteries) MBF and flow reserve were compared among programs using correlation and Bland-Altman analyses. RESULTS: All scans were processed successfully by the 3 programs, with minimal operator interactions. Global and regional correlations of MBF and flow reserve all had an R2 of at least 0.92. There was no significant difference in flow values at rest (P = 0.68), stress (P = 0.14), or reserve (P = 0.35) among the 3 programs. Bland-Altman coefficients of reproducibility (1.96 × SD) averaged 0.26 for MBF and 0.29 for flow reserve differences among programs. Average pairwise differences were all less than 10%, indicating good reproducibility for MBF quantification. Global and regional SD from the line of perfect agreement averaged 0.15 and 0.17 mL/min/g, respectively, for MBF, compared with 0.22 and 0.26, respectively, for flow reserve. CONCLUSION: The 1-tissue-compartment model of 82Rb tracer kinetics is a reproducible method for quantification of MBF and flow reserve with 3-dimensional PET/CT imaging.
Will 3-dimensional PET-CT enable the routine quantification of myocardial blood flow?
Journal - Journal of nuclear cardiology : official publication of the American Society of Nuclear Cardiology (United States )
Quantification of myocardial blood flow (MBF) and flow reserve has been used extensively with positron emission tomography (PET) to investigate the functional significance of coronary artery disease. Increasingly, flow quantification is being applied to investigations of microvascular dysfunction in early atherosclerosis and in nonatherosclerotic microvascular disease associated with primary and secondary cardiomyopathies. Fully three-dimensional (3D) acquisition is becoming the standard imaging mode on new equipment, bringing with it certain challenges for cardiac PET, but also the potential for MBF to be measured simultaneously with routine electrocardiography (ECG)-gated perfusion imaging. Existing 3D versus 2D comparative studies support the use of 3D cardiac PET for flow quantification, and these protocols can be translated to PET-CT, which offers a virtually noise-free attenuation correction. This technology combines the strengths of cardiac CT for evaluation of anatomy with cardiac PET for quantification of the hemodynamic impact on the myocardium. High throughput clinical imaging protocols are needed to evaluate the incremental diagnostic and prognostic value of this technology.
|ISSN : ||1532-6551|
|Mesh Heading : ||Coronary Angiography Coronary Artery Disease Coronary Vessels Humans Image Enhancement Image Interpretation, Computer-Assisted Imaging, Three-Dimensional Positron-Emission Tomography Subtraction Technique Tomography, X-Ray Computed methods methods trends|
|Mesh Heading Relevant : ||Coronary Circulation trends diagnosis radionuclide imaging trends trends trends|
Detection of serial changes in absolute myocardial perfusion with 82Rb PET.
Journal - Journal of nuclear medicine : official publication, Society of Nuclear Medicine (UNITED STATES )
Serial changes in myocardial perfusion may represent an important marker of disease progression or regression or the effects of therapy for patients with coronary artery disease (CAD). Quantitative methods have not been developed for the assessment of serial changes in perfusion. The objective of this study was to use receiver operator characteristic (ROC) analysis to determine the sensitivity and specificity of direct paired comparisons (DPCs) to detect changes in absolute myocardial perfusion measured with 82Rb PET. METHODS: Repeated dynamic 82Rb PET scans were obtained on 8 dogs at rest and during hyperemia induced with dobutamine (n = 4) or atrial pacing (n = 4). Radiolabeled microspheres were used to verify perfusion changes. Polar maps of absolute 82Rb retention and associated SD were estimated from the dynamic images. Paired comparisons were then performed using a t test on each of the 532 polar map sectors. Rest-rest and stress-stress differences were used to assess specificity and reproducibility, and stress-rest differences were used to assess sensitivity. RESULTS: 82Rb retention differences of 20% over baseline were detected with 85%-90% sensitivity and specificity, using the optimal DPC probability value and image smoothness. The average 82Rb retention differences correlated well with microspheres (r = 0.74; P = 0.001). Reproducibility of the mean retention values was 4.7% +/- 2.1%. As reproducibility varies, the DPC probability value can be adjusted to maintain specificity. These ROC results are directly applicable to other image modalities that produce measurements with similar SEs (3.7% +/- 0.9%). CONCLUSION: The developed method of DPCs is sensitive and specific for the detection of changes in absolute myocardial perfusion measured with 82Rb PET.
|ISSN : ||0161-5505|
|Mesh Heading : ||Animals Coronary Vessels Dobutamine Dogs Heart Hyperemia Microspheres Physical Exertion ROC Curve Reproducibility of Results Rubidium Radioisotopes Sensitivity and Specificity radionuclide imaging diagnostic use physiology diagnostic use|
|Mesh Heading Relevant : ||Coronary Circulation Tomography, Emission-Computed physiology radionuclide imaging pharmacokinetics|
The Effects of Continuous Positive Airway Pressure on Myocardial Energetics in Patients With Heart Failure and Obstructive Sleep Apnea
Journal - Journal of the American College of Cardiology
OBJECTIVES: We sought to examine the short-term and longer term (6-week)effects of continuous positive airway pressure (CPAP) on myocardialenergetics.
BACKGROUND: Obstructive sleep apnea (OSA) and heart failure (HF) are bothstates of increased afterload and metabolic demand. Treatmentwith CPAP may initially reduce stroke volume but subsequentlyimproves left ventricular function. However, it is not clearwhether CPAP therapy favorably affects myocardial energeticsand hence improves cardiac efficiency.
METHODS: Twelve patients with HF were divided into two groups: 7 patientswith OSA were treated with CPAP (group I), and 5 patients withoutOSA served as a control group (group II). Oxidative metabolismwas measured using the mono-exponential fit of the myocardial[11C] acetate positron emission tomography time-activity curve(k-mono). Myocardial efficiency was derived using the work metabolicindex (WMI = [heart rate x stroke volume index x systolic bloodpressure]/k-mono) measured at baseline, during short-term CPAP,and after 6 ± 3 weeks of CPAP.
RESULTS: In group I, short-term CPAP tended to reduce SVI (p = 0.063)and reduced oxidative metabolism (p = 0.031). Work metabolicindex did not change. However, longer term CPAP improved leftventricular ejection fraction (38.4 ± 3.3% to 43.4 ±4.8%, p = 0.031), tended to reduce oxidative metabolism (0.047± 0.012 to 0.040 ± 0.008 min–1, p = 0.078),and improved WMI (7.13 ± 2.82 x 106 to 8.17 ±3.06 x 106 mm Hg·ml/m2, p = 0.031). In group II (control),these parameters did not change.
CONCLUSIONS: In this cohort of patients with HF and OSA, short-term CPAPdecreased oxidative metabolism and tended to decrease SVI, butdid not alter cardiac efficiency. Longer term CPAP improvedcardiac efficiency, indicating an energy-sparing effect. Theseeffects may contribute to the benefits of CPAP therapy.Abbreviations: AHI = apnea/hypopnea index • CPAP = continuous positive airway pressure • HF = heart failure • LV = left ventricle/ventricular • LVEF = left ventricular ejection fraction • MVO2
= myocardial oxygen consumption • OSA = obstructive sleep apnea • PET = positron emission tomography • SVI = stroke volume index • WMI = work metabolic index
Treadmill Exercise Produces Larger Perfusion Defects Than Dipyridamole Stress N-13 Ammonia Positron Emission Tomography
Journal - Journal of the American College of Cardiology
OBJECTIVES: The aim of this study was to compare treadmill exercise (TEX)and dipyridamole stress on the uptake and retention of N-13ammonia.
BACKGROUND: Size and severity of stress-induced myocardial perfusion defectsare clinically important. Because ammonia uptake and retentionseems to be related to perfusion, viability, and metabolism,exercise stress might induce larger perfusion defects than dipyridamolestress.
METHODS: Twenty-six patients underwent TEX and dipyridamole stress N-13ammonia positron emission tomography (PET). Images were assessedwith a 17-segment model and a five-point score. Summed stressscore (SSS), summed rest score (SRS), and summed differencescore (SDS) were calculated. Left ventricular (LV) defect sizeswere measured quantitatively with a 70% threshold for abnormalperfusion.
RESULTS: Compared with dipyridamole stress, TEX yielded larger SSS (9.1± 5.7 vs. 6.9 ± 5.9; p < 0.01), SDS (5.8 ±4.7 vs. 3.7 ± 4.6; p < 0.02), and percentage of LVstress defect (19.3 ± 11.5% vs. 13.8 ± 13.6%;p < 0.02).
CONCLUSIONS: In patients achieving adequate exercise, TEX N-13 ammonia PETmyocardial perfusion imaging (MPI) yields larger stress perfusiondefects than dipyridamole stress and might reflect the truemyocardial ischemic burden. Treadmill exercise might be thepreferred method of stress for routine N-13 ammonia PET MPI.Abbreviations: CAD = coronary artery disease • LV = left ventricle/ventricular • MPI = myocardial perfusion imaging • PET = positron emission tomography • SDS = summed difference score • SPECT = single-photon emission tomography • SRS = summed rest score • SSS = summed stress score • TEX = treadmill exercise
Positron emission tomography and recovery following revascularization (PARR-1): the importance of scar and the development of a prediction rule for the degree of recovery of left ventricular function
Journal - Journal of the American College of Cardiology
OBJECTIVES: The aim of this study was to determine whether the extent ofviability or scar is important in the amount of recovery ofleft ventricular (LV) function, and to develop a model for predictingrecovery after revascularization that could be tested in a randomizedtrial.
BACKGROUND: F-18-fluorodeoxyglucose (FDG) positron emission tomography (PET)is used to define viable myocardium in patients with coronaryartery disease (CAD) and severe LV dysfunction and to guiderevascularization decisions. Whether this approach improvesclinical outcomes has not been tested in a randomized trial.Before doing so, an objective model for prediction of recoveryis required.
METHODS: A total of 82 patients with CAD and an ejection fraction (EF)35% had FDG PET perfusion imaging before revascularization.Complete follow-up was available on 70 patients (86%). Patientshad radionuclide angiograms at baseline and three months post-revascularization.
RESULTS: Diabetes (p = 0.029), time to operation (p = 0.008), and scarscore (p = 0.001) were significant independent predictors ofthe change in EF. Previous coronary artery bypass graft confoundedthe effect of age. There was a significant interaction betweenthe perfusion tracer used and mismatch score (p = 0.02). Themultivariable prediction model incorporating PET and clinicalvariables had a goodness of fit with p = 0.001. Across tertilesof scar scores (I, small: 0% to 16%; II, moderate: 16% to 27.5%;III, large: 27.5% to 47%), the changes in EFs were 9.0 ±1.9%, 3.7 ± 1.6%, and 1.3 ± 1.5% (p = 0.003: Ivs. III), respectively.
CONCLUSIONS: In patients with severe LV dysfunction, the amount of scar wasa significant independent predictor of LV function recoveryafter revascularization. A combination of PET and clinical parameterspredicts the degree of recovery. This model is being appliedin a large randomized controlled trial to determine the effectivenessof therapy guided by FDG PET.Abbreviations: CAD • coronary artery disease • EF • ejection fraction • FDG • F-18-fluorodeoxyglucose • LV • left ventricle/ventricular • PET • positron emission tomography • RNA • radionuclide angiogram/angiography • SPECT • single photon emission computed tomography • Tc • technetium