Improved quantification of myocardial blood flow using highly constrained back projection reconstruction

Whole Left Ventricular Coverage Versus Conventional 3-Slice Myocardial Perfusion Magnetic Resonance Imaging for the Detection of Suspected Coronary Artery Disease

RATIONALE AND OBJECTIVES

Sliding-window conjugate-gradient highly constrained back-projection reconstruction (SW-CG-HYPR) allows whole left ventricular coverage, improved temporal and spatial resolution, and signal-to-noise ratio compared to the conventional 3-slice saturation recovery turbo-fast low-angle shot (SR-Turbo-FLASH) sequence. We prospectively compared the diagnostic value of whole leftventricular coverage myocardial perfusion magnetic resonance imaging (MRI) and conventional 3-slice technique in patients with suspected coronary artery disease (CAD).

MATERIALS AND METHODS

Thirty consecutive patients with suspected CAD who were scheduled for coronary angiography underwent myocardial perfusion MRI with both SW-CG-HYPR and SR-Turbo-FLASH in random order at 3.0 T. Perfusion defects were interpreted visually by two blinded observers and were correlated to x-ray angiographic stenoses ≥50%. Receiver-operating characteristic curve analysis was used to compare the diagnostic performance of the two imaging techniques.

RESULTS

The image quality score of SW-CG-HYPR was significantly higher than that of SR-Turbo-FLASH (3.4 ± 0.6 vs 3.0 ± 0.7, respectively; p < 0.05). In the per-patient analysis, SW-CG-HYPR provided a higher sensitivity (94% vs 89%), specificity (83% vs 75%), and diagnostic accuracy (90% vs 83%) for the detection of CAD than SR-Turbo-FLASH. In the per-vessel analysis, the diagnostic performance of SW-CG-HYPR was significantly greater than that of SR-Turbo-FLASH for the overall detection of CAD (area under receiver-operating characteristic curve: 0.96 ± 0.02 vs 0.90 ± 0.03, respectively; p < 0.05).

CONCLUSION

Whole left ventricular coverage myocardial perfusion MRI has higher diagnostic accuracy compared to conventional 3-slice technique for the detection of suspected CAD.

A model-based reconstruction technique for quantitative myocardial perfusion imaging

PURPOSE

To reduce saturation effects in the arterial input function (AIF) estimation of quantitative myocardial first-pass saturation recovery perfusion imaging by employing a model-based reconstruction.

THEORY AND METHODS

Imaging was performed with a saturation recovery prepared radial FLASH sequence. A model-based reconstruction was applied for reconstruction. By exploiting prior knowledge about the relaxation process, an image series with different saturation recovery times was reconstructed. By evaluating images with an effective saturation time of approximately 3 ms, saturation effects in the AIF determination were reduced. In a volunteer study, this approach was compared with a standard prebolus technique.

RESULTS

In comparison to the low-dose injection of a prebolus acquisition, saturation effects were further reduced in the AIFs determined using the model-based approach. These effects, which were clearly visible for all six volunteers, were reflected in a statistically significant difference of up to 20% in the absolute perfusion values.

CONCLUSION

The application of model-based reconstruction algorithms in quantitative myocardial perfusion imaging promises a significant improvement of the AIF determination. In addition to greatly reducing saturation effects that occur even for the prebolus methods, only a single bolus has to be applied. Magn Reson Med 76:880-887, 2016. © 2015 Wiley Periodicals, Inc.

Quantification of myocardial blood flow using non-electrocardiogram-triggered MRI with three-slice coverage

PURPOSE

Accurate quantification of myocardial perfusion is dependent on reliable electrocardiogram (ECG) triggering. Measuring myocardial blood flow (MBF) in patients with arrhythmias or poor ECGs is currently infeasible with MR. The purpose of this study was to demonstrate the feasibility of a non-ECG-triggered method with clinically useful three-slice ventricular coverage for measurement of MBF in healthy volunteers.

METHODS

A saturation recovery magnetization-prepared gradient recalled echo acquisition was continuously repeated during first-pass imaging. A slice-interleaved radial trajectory was employed to enable image-based retrospective triggering. The arterial input function was generated using a beat-by-beat T1 estimation method. The proposed technique was validated against a conventional ECG-triggered dual-bolus technique in 10 healthy volunteers. The technique was further demonstrated under adenosine stress in 12 healthy volunteers.

RESULTS

The proposed method produced MBF with no significant difference compared with the ECG-triggered technique. The proposed method yielded mean myocardial perfusion reserve comparable to published literature.

CONCLUSION

We have developed a non-ECG-triggered quantitative perfusion imaging method. In this preliminary study, our results demonstrate that our method yields comparable MBF compared with the conventional ECG-triggered method and that it is feasible for stress imaging.

All-systolic non-ECG-gated myocardial perfusion MRI: Feasibility of multi-slice continuous first-pass imaging

PURPOSE

To develop and test the feasibility of a new method for non-ECG-gated first-pass perfusion (FPP) cardiac MR capable of imaging multiple short-axis slices at the same systolic cardiac phase.

METHODS

A magnetization-driven pulse sequence was developed for non-ECG-gated FPP imaging without saturation-recovery preparation using continuous slice-interleaved radial sampling. The image reconstruction method, dubbed TRACE, used self-gating based on reconstruction of a real-time image-based navigator combined with reference-constrained compressed sensing. Data from ischemic animal studies (n = 5) was used in a simulation framework to evaluate temporal fidelity. Healthy subjects (n = 5) were studied using both the proposed approach and the conventional method to compare the myocardial contrast-to-noise ratio (CNR). Patients (n = 2) underwent adenosine stress studies using the proposed method.

RESULTS

Temporal fidelity of the developed method was shown to be sufficient at high heart-rates. The healthy volunteers studies demonstrated normal perfusion and no dark-rim artifacts. Compared with the conventional scheme, myocardial CNR for the proposed method was slightly higher (8.6 ± 0.6 versus 8.0 ± 0.7). Patient studies showed stress-induced perfusion defects consistent with invasive angiography.

CONCLUSION

The presented methods and results demonstrate feasibility of the proposed approach for high-resolution non-ECG-gated FPP imaging of 3 myocardial slices at the same systolic phase, and indicate its potential for achieving desirable image quality (high CNR and no dark-rim artifacts).

Quantification of myocardial blood flow using non-ECG-triggered MR imaging

PURPOSE

MR myocardial perfusion imaging is dependent on reliable electrocardiogram (ECG) triggering for accurate measurement of myocardial blood flow (MBF). A non-ECG-triggered method for quantitative first-pass imaging may improve clinical feasibility in patients with poor ECG signal. The purpose of this study is to evaluate the feasibility of a non-ECG-triggered method for myocardial perfusion imaging in a single slice.

METHODS

The proposed non-ECG-triggered technique uses a saturation-recovery magnetization preparation and golden-angle radial acquisition for integrated arterial input function (AIF) measurement. Image based self-gating with a temporal resolution of 42.6 ms is used to generate a first-pass image series with consistent cardiac phase. The AIF is measured using beat-by-beat T1 estimation of the ventricular blood pool. The proposed technique was performed on 14 healthy volunteers and compared against a conventional ECG-triggered dual-bolus acquisition.

RESULTS

The proposed method produced MBF with no significant difference compared with ECG-triggered technique (mean of 0.63 ± 0.22 mL/min/g to 0.73 ± 0.21 mL/min/g).

CONCLUSION

We have developed a non-ECG-triggered perfusion imaging method with T1 based measurement of the AIF in a single slice. In this preliminary study, our results demonstrate that MBF measured using the proposed method is comparable to the conventional ECG-triggered method.