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Quantification of aortic stenosis diagnostic parameters: comparison of fast 3 direction and 1 direction phase
Juliana Serafim da Silveira1,2, Matthew Smyke1, Adam V Rich3
1Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA.
Insights
A faster, multi-directional cardiovascular magnetic resonance (CMR) technique, 3Dir PC-CMR with ReVEAL, offers improved accuracy in assessing aortic stenosis (AS) compared to traditional methods. This advanced imaging provides better hemodynamic parameter estimation than unidirectional CMR and transthoracic echocardiography (TTE).
Area of Science:
- Cardiovascular Imaging
- Medical Physics
- Flow Dynamics
Background:
- Aortic stenosis (AS) diagnosis relies on transthoracic echocardiography (TTE), but its accuracy can be limited by inconsistent results.
- Cardiovascular magnetic resonance (CMR) offers an alternative, with multi-directional phase-contrast CMR (3Dir PC-CMR) promising improved velocity measurement over unidirectional PC-CMR (1Dir PC-CMR).
- Clinical adoption of 3Dir PC-CMR has been slow due to prolonged acquisition times.
Purpose of the Study:
- To compare the accuracy of flow parameter quantification in AS patients using 1Dir PC-CMR and a novel, accelerated 3Dir PC-CMR technique (ReVEAL).
- To evaluate the performance of these CMR methods against traditional TTE for assessing AS severity.
Main Methods:
- Twenty-three AS patients underwent TTE and CMR, including 1Dir PC-CMR and accelerated 3Dir PC-CMR using the ReVEAL reconstruction method.
- Acquisition acceleration for 3Dir PC-CMR was achieved using a variable density sampling pattern and an acceleration rate of 8.
- Flow parameters and aortic valve area estimates derived from both CMR techniques were compared to TTE findings.
Main Results:
- ReVEAL-based 3Dir PC-CMR demonstrated better correlation with TTE for derived parameters compared to 1Dir PC-CMR.
- Peak velocity (Vpeak) correlations with TTE were 0.81 for 1Dir PC-CMR and 0.87 for 3Dir PC-CMR.
- TTE was observed to slightly underestimate peak velocities, likely due to its sensitivity only to flow parallel to the acoustic beam.
Conclusions:
- The ReVEAL technique enables multi-directional flow imaging with clinically feasible acquisition times, overcoming previous limitations of 3Dir PC-CMR.
- ReVEAL-based 3Dir PC-CMR provides a more accurate estimation of hemodynamic parameters in AS patients than 1Dir PC-CMR.
- Multi-directional flow imaging, by capturing all velocity vector components, has the potential to surpass TTE in cases with complex flow patterns like eccentric or multiple jets.
Background:
Aortic stenosis (AS) is a common valvular disorder, and disease severity is currently assessed by transthoracic echocardiography (TTE). However, TTE results can be inconsistent in some patients, thus other diagnostic modalities such as cardiovascular magnetic resonance (CMR) are demanded. While traditional unidirectional phase-contrast CMR (1Dir PC-CMR) underestimates velocity if the imaging plane is misaligned to the flow direction, multi-directional acquisitions are expected to improve velocity measurement accuracy. Nonetheless, clinical use of multidirectional techniques has been hindered by long acquisition times. Our goal was to quantify flow parameters in patients using 1Dir PC-CMR and a faster multi-directional technique (3Dir PC-CMR), and compare to TTE.
Methods:
Twenty-three patients were prospectively assessed with TTE and CMR. Slices above the aortic valve were acquired for both PC-CMR techniques and cine SSFP images were acquired to quantify left ventricular stroke volume. 3Dir PC-CMR implementation included a variable density sampling pattern with acceleration rate of 8 and a reconstruction method called ReVEAL, to significantly accelerate acquisition. 3Dir PC-CMR reconstruction was performed offline and ReVEAL-based image recovery was performed on the three (x, y, z) encoding pairs. 1Dir PC-CMR was acquired with GRAPPA acceleration rate of 2 and reconstructed online. CMR derived flow parameters and aortic valve area estimates were compared to TTE.
Results:
ReVEAL based 3Dir PC-CMR derived parameters correlated better with TTE than 1Dir PC-CMR. Correlations ranged from 0.61 to 0.81 between TTE and 1Dir PC-CMR and from 0.61 to 0.87 between TTE and 3Dir-PC-CMR. The correlation coefficients between TTE, 1Dir and 3Dir PC-CMR Vpeakwere 0.81 and 0.87, respectively. In comparison to ReVEAL, TTE slightly underestimates peak velocities, which is not surprising as TTE is only sensitive to flow that is parallel to the acoustic beam.
Conclusions:
By exploiting structure unique to PC-CMR, ReVEAL enables multi-directional flow imaging in clinically feasible acquisition times. Results support the hypothesis that ReVEAL-based 3Dir PC-CMR provides better estimation of hemodynamic parameters in AS patients in comparison to 1Dir PC-CMR. While TTE can accurately measure velocity parallel to the acoustic beam, it is not sensitive to the other directions of flow. Therefore, multi-directional flow imaging, which encodes all three components of the velocity vector, can potentially outperform TTE in patients with eccentric or multiple jets.
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