Using cardiac phase to order reconstruction [CAPTOR]: A method to improve diastolic images
Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1061, USA. Journal of Magnetic Resonance Imaging
(Impact Factor: 3.21).
09/1997; 7(5):794-8. DOI: 10.1002/jmri.1880070505
A method is proposed to reconstruct multiphase images that accurately depicts the entire cardiac cycle. A segmented, gradient-recalled-echo sequence (FASTCARD) was modified to acquire data continuously. Images were reconstructed retrospectively by selecting views from each heartbeat based on cardiac phase rather than the time elapsed from the QRS complex. Cardiac phase was calculated using a model that compensates for beat-to-beat heart rate changes. Images collected using cardiac phase to order reconstruction (CAPTOR) depict the entire cardiac cycle and lack the temporal gap that is characteristic of prospectively reconstructed sequences. Time-volume curves of the left ventricle capture the contribution of atrial contraction to end-diastolic volume (EDV). Transmitral phase-contrast flow measurements show a second peak inflow (alpha wave) that is absent in the standard sequence. Because atrial contraction contributes to ventricular EDV, images using CAPTOR potentially may provide a more reliable measure of EDV, stroke volume, and ejection fraction than standard techniques.
Available from: Steve W Leung
- "A recent study of quantitative perfusion in normal volunteers suggested that there was a modest increase in stress MBF in diastole compared to systole . For quality assurance reasons, we analyzed the timing of slices within the cardiac cycle using the approach described by Feinstein et al . Since only one AIF slice was acquired for each RR interval (for base, mid and apical slices) the prepulse delay was not significant. "
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ABSTRACT: Regadenoson, dipyridamole and adenosine are commonly used vasodilators in myocardial perfusion imaging for the detection of obstructive coronary artery disease. There are few comparative studies of the vasodilator properties of regadenoson, adenosine and dipyridamole in humans. The specific aim of this study was to determine the relative potency of these three vasodilators by quantifying stress and rest myocardial perfusion in humans using cardiovascular magnetic resonance (CMR).
Fifteen healthy normal volunteers, with Framingham score less than 1% underwent vasodilator stress testing with regadenoson (400 mug bolus), dipyridamole (0.56 mg/kg) and adenosine (140 mug /kg/min) on separate days. Rest perfusion imaging was performed initially. Twenty minutes later, stress imaging was performed at peak vasodilation, i.e. 70 seconds after regadenoson, 4 minutes after dipyridamole infusion and between 3--4 minutes of the adenosine infusion. Myocardial blood flow (MBF) in ml/min/g and myocardial perfusion reserve (MPR) were quantified using a fully quantitative model constrained deconvolution.
Regadenoson produced higher stress MBF than dipyridamole and adenosine (3.58 +/-0.58 vs. 2.81+/- 0.67 vs. 2.78 +/- 0.61 ml/min/g, p = 0.0009 and p = 0.0008 respectively). Regadenoson had a much higher heart rate response than adenosine and dipyridamole respectively (95 +/- 11 vs. 76 +/- 13 vs. 86 +/- 12 beats/ minute) When stress MBF was adjusted for heart rate, there were no differences between regadenoson and adenosine (37.8 +/- 6 vs. 36.6 +/- 4 mul/sec/g, p = NS), but differences between regadenoson and dipyridamole persisted (37.8 +/- 6 vs. 32.6 +/- 5 mul/sec/g, p = 0.03). The unadjusted MPR was higher with regadenoson (3.11+/-0.63) when compared with adenosine (2.7 +/-0.61, p = 0.02) and when compared with dipyridamole (2.61 +/- 0.57, p = 0.04). Similar to stress MBF, these differences in MPR between regadenoson and adenosine were abolished when adjusted for heart rate (2.04 +/- 0.34 vs. 2.12 +/- 0.27, p = NS), but persisted between regadenoson and dipyridamole (2.04 +/- 0.34 vs. 1.77 +/- 0.33, p =0.07) and between adenosine and dipyridamole (2.12 +/- 0.27 vs. 1.77 +/- 0.33, p =0.01).
Based on fully quantitative perfusion using CMR, regadenoson and adenosine have similar vasodilator efficacy and are superior to dipyridamole.
Available from: Lilia M. Sierra-Galan
- "Left ventricular systolic function and mass were evaluated in continuous short-axis slices using either electrocardiogram (ECG)-gated cine MRI in steady state free precession (SSFP) (Barkhausen et al., 2001) or an ECG-gated fast gradient echo cine sequence (FGRE). Both sequences imaged the entire cardiac cycle(Feinstein et al., 1997). For the SSFP cine method, the scan parameters selected included a slice thickness of 8 mm, in-plane resolution of 1:5 £ 1:9 mm=pixel; and temporal resolution of 41 ms (12 views per segment, TR ¼ 3:4 ms; TE 0.8 to 1.0 ms). "
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ABSTRACT: Assessment of left ventricular function is important in patients with heart disease. We hypothesized that regional wall motion assessed qualitatively by cine magnetic resonance imaging (MRI) can predict the left ventricular ejection fraction (EF).
The correlations between MRI EF and the American Society of Echocardiography (ASE) score index and a modified ASE score index were established in 117 subjects. The model was tested in the next 86 patients. Interobserver variability was studied in 30 patients. Radionuclide EF was compared in 81 patients. Cine MRI studies were performed on a 1.5 T scanner.
From the initial 117 patients, there was a linear correlation between the ASE score index and MRI (r = 0.85), but the relationship improved by including a category of hyperkinetic wall motion (r = 0.90). Using these correlations to predict MRI EF in the next 86 patients, there was a good agreement (r = 0.93 for the ASE score index and r = 0.97 for the modified ASE score index). Correlations between radionuclide EF and the EF predicted by the modified ASE score index or the MRI EF by planimetry were similar (r = 0.91 vs. r = 0.90, respectively). Four observers tested the model and achieved comparable results (r = 0.88 to 0.95).
There is a close relationship between ejection fraction and the ASE score index or modified ASE score index. This correlation can provide an objective prediction of ejection fraction based solely on a qualitative reading of regional wall thickening.
Available from: Sari Kivistö
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