Using cardiac phase to order reconstruction [CAPTOR]: A method to improve diastolic images
ABSTRACT 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.
SourceAvailable from: Debiao Li[Show abstract] [Hide abstract]
ABSTRACT: PurposeTo develop a cardiac and respiratory self-gated four-dimensional (4D) coronary MRA technique for simultaneous cardiac anatomy and function visualization. MethodsA contrast-enhanced, ungated spoiled gradient echo sequence with self-gating (SG) and 3DPR trajectory was used for image acquisition. Data were retrospectively binned into different cardiac and respiratory phases based on information extracted from SG projections using principal component analysis. Each cardiac phase was reconstructed using a respiratory motion-corrected self-calibrating SENSE framework, and those belong to the quiescent period were retrospectively combined for coronary visualization. Healthy volunteer studies were conducted to evaluate the efficacy of the SG method, the accuracy of the left ventricle (LV) function parameters and the quality of coronary artery visualization. ResultsSG performed reliably for all subjects including one with poor electrocardiogram (ECG). The LV function parameters showed excellent agreement with those from a conventional cine protocol. For coronary imaging, the proposed method yielded comparable apparent signal to noise ratio and coronary sharpness and lower apparent contrast to noise ratio on three subjects compared with an ECG and navigator-gated Cartesian protocol and an ECG-gated, respiratory motion-corrected 3DPR protocol. ConclusionA fully self-gated 4D whole-heart imaging technique was developed, potentially allowing cardiac anatomy and function assessment from a single measurement. Magn Reson Med 72:1208-1217, 2014. (c) 2014 Wiley Periodicals, Inc.Magnetic Resonance in Medicine 11/2014; 72(5). DOI:10.1002/mrm.25450 · 3.40 Impact Factor
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ABSTRACT: Introduction: MR tagging provides for regional quantification of myocardial function. Two key factors currently limit the usefulness of previous techniques: 1) tag fading due to T1 and 2) Loss of 10-30% of the cardiac cycle in gated sequences due to trigger windowing. This abstract presents results from a new sequence that combines a tagging method that allows for tag persistence through the entire cardiac cyle (CSPAMM, Ref. 1) with one that allows acquisition of the entire cardiac cycle in a single breathhold (CAPTOR, Ref. 2). The purpose of this study was to quantify regional cardiac function of all phases of the cardiac cycle including atrial systole. Results are shown for Normal Subjects (NS) and Hypertrophic Cardiomyopathy (HCM). Methods: Images were acquired with a 1.5T GE cardiac MRI scanner. Both CSPAMM and CAPTOR were implemented in a Fast Gradient Echo sequence with an Echo-Train readout (FGRE-ET). A 4D B-spline motion analysis method used long axis images to track through plane motion (Ref. 3). Slice following techniques were not used (Ref. 1). Longitudinal displacements were assumed to be small in the motion analysis performed on two HCMs in which no long axis images were acquired. Three NS and four HCM patients were examined. Heart rates (bpm) were 59.1±5.8 in NS and 60.9±7.7 in HCM. Images were segmented using a 3-D template with spatial and temporal interpolation (Ref. 4). Tags were automatically tracked with little intervention using Findtags (Ref. 5). Figure 1 Results: The regional and global mechanics of both NS and HCM patients were quantified. Figure 1 shows global midwall left ventricular circumferential strain (Ecc), computed from averages of regional assessments, in each of seven patients. The maximum global midwall circumferential shortening strains were -17.1%±0.8% in the NS group and -11.5%±3.8% in the HCM (p<0.057). The rate of systolic shortening (%strain/second) in the NS group was 84.7%/s±7.6%/s and 59.2%/s±10.0%/s in the HCM group (p<0.012). The rate of diastolic lengthening in the NS group was 99.5%/s±3.0%/s and 32.2%/s±27.8%/s in the HCM group (p<0.016). In two of the HCM patients, there is no diastasis phase despite low heart rates. A new measure, presented here, is called the Atrial Systolic Response Ratio (ASRR). ASRR, similar to the E/A ratio (Ref. 5), is the ratio of stretch due to atrial systole in proportion to the stretch due to total diastolic filling. ASRR is an index of ventricular diastolic function. ASRR for global midwall Ecc was 14.1%±3.6% in the NS group. This was found to be regionally homogenous. ASRR in the HCM group was 29.7%±9.2% (p<0.036). This quantifies a near two-fold increase of dependence on atrial systole for complete diastolic lengthening. HCM patients exhibited greater regional heterogeneity of ASRR than the NS group. Regional assessment of midwall Ecc ASRR is shown in Figure 2. Some of the regions in the HCM patients show function similar to the average NS data. Other regions are markedly different from the same region in the average NS, suggesting impaired regional diastolic function. HCM exam #06437 might be overlooked upon global function assessment (Fig. 1), but shows marked regional dysfunction compared to the average NS assessment (Fig. 3).
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ABSTRACT: Purpose. 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). Methods. 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. Results. 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). Conclusions. 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.Journal of Cardiovascular Magnetic Resonance 07/2009; 5(3). · 5.11 Impact Factor