0547
Whole-Heart Cardiovascular Magnetic Resonance Angiography (CMRA) with iNAV-based Non-Rigid Motion-Corrected Reconstruction at 0.55T
Carlos Castillo-Passi1,2,3, Michael G. Crabb1, Camila Muñoz1, Karl P. Kunze1,4, Radhouene Neji 1,4, Pablo Irarrazaval2,3,5, Claudia Prieto1,3,5, and Rene M. Botnar1,2,3,5
1School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 2Institute for Biological and Medical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile, 3Millennium Institute for Intelligent Healthcare Engineering, Santiago, Chile, 4MR Research Collaborations, Siemens Healthcare Limited, Camberley, United Kingdom, 5Electrical Engineering Department, Pontificia Universidad Católica de Chile, Santiago, Chile
1School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 2Institute for Biological and Medical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile, 3Millennium Institute for Intelligent Healthcare Engineering, Santiago, Chile, 4MR Research Collaborations, Siemens Healthcare Limited, Camberley, United Kingdom, 5Electrical Engineering Department, Pontificia Universidad Católica de Chile, Santiago, Chile
Synopsis
Keywords: Heart, Low-Field MRI
In this work, we demonstrate the feasibility of free-breathing whole-heart magnetic resonance angiography (CMRA) at 0.55T. We implemented an image navigator (iNAV)-based non-rigid motion-corrected reconstruction with 100% respiratory scan efficiency and patch-based low-rank (PROST) denoising. The research sequence was validated on three healthy subjects, showing that whole-heart CMRA provides good depiction of the coronary arteries at 0.55T in under 6 minutes scan time.Introduction
The potential clinical value of free-breathing whole-heart magnetic resonance angiography (CMRA) with image navigator (iNAV)-based non-rigid motion-corrected reconstruction and 100% respiratory scan efficiency has been recently demonstrated at 1.5T1. The feasibility of this approach has also been shown at 3T2 and 7T3. However, it is unknown if 3D whole-heart CMRA is feasible at 0.55T due to the lower signal-to-noise ratio (SNR). Compared to 1.5T, the SNR at 0.55T is 4.5 times smaller, as the SNR is proportional to B03/2. In this study, we sought to investigate the feasibility of iNAV-based4 non-rigid motion-corrected 3D CMRA on the latest 0.55T MR scanner generation, which could make CMRA potentially more accessible and affordable.Methods
The proposed accelerated whole-heart CMRA framework was performed in three healthy subjects on a 0.55T scanner (MAGNETOM Free.Max, Siemens Healthcare, Erlangen, Germany) using a 3D bSSFP research sequence with an undersampled variable-density cartesian trajectory with spiral-like profile order (VD-CASPR). T2 preparation (T2-Prep) and Fat Saturation (FAT SAT) pre-pulses were performed before the acquisition at each heartbeat. A 2D iNAV4 preceded each spiral-like arm acquisition to enable beat-to-beat 2D translational and bin-to-bin 3D non-rigid respiratory motion correction of the heart with 100% respiratory scan efficiency (Fig.1). Estimated bin-to-bin non-rigid 3D motion fields are incorporated into a non-rigid motion-compensated reconstruction. Motion-compensated reconstruction was performed with iterative SENSE (itSENSE) with and without patch-based low-rank denoising (PROST)5. Acquisitions parameters included: FOV = 312 x 312 x 120 mm, resolution = 1.5 mm3, flip-angle = 90 deg, TR = 5.48 ms, TE = 2.74 ms, T2-Prep duration = 50 ms, FAT SAT flip-angle = 130 deg, 3x undersampling, total scan time ~ 6min. Shimming box, REST slab location, and trigger delay were set following the steps described in Fig. 2. Free-breathing 2D CINE was performed to determine the subject-specific trigger delay (mid-diastole) and acquisition window (~120ms).Results
itSENSE reconstructions without and with non-rigid motion reconstructions are shown in Fig.3, together with the proposed non-rigid motion-corrected reconstruction with additional PROST denoising. Both itSENSE reconstructions show low SNR at low field. Non-rigid motion correction reduces respiratory motion artifacts (itSENSE non-rigid), whereas the proposed approach greatly increases image quality due to the further incorporation of PROST denoising, which partially compensates for low SNR at low field. Reformatted images along the right (RCA) and circumflex (LCX) coronary arteries are shown in Fig.3. The proposed CMRA sequence at 0.55T showed a good depiction of the coronary arteries in all three subjects despite the relatively low resolution used in this preliminary study (Fig. 4). A video going across the slices for Subject #1 is shown in Figure 5.Conclusions
In this work, we showed a first proof of concept of iNAV-based whole-heart CMRA at 0.55T in ~6min scan time. Future work will focus on further parameter optimization, increasing spatial resolution, and evaluation in healthy subjects and patients with cardiovascular disease.Acknowledgements
This work was supported by the following grants: (1) EPSRC P/V044087/1,(2) BHF programme grant RG/20/1/34802, (3) Wellcome/EPSRC Centre for Medical Engineering (WT 203148/Z/16/Z), (4) Millennium Institute for Intelligent Healthcare Engineering ICN2021_004, (5) FONDECYT 121074, 1210637 and 1210638, (6) IMPACT, Center of Interventional Medicine for Precision and Advanced Cellular Therapy, ANID FB210024, (7) PhD program in Biological and Medical Engineering of the Pontificia Universidad Católica de Chile.References
1. Hajhosseiny R, Rashid I, Bustin A, Munoz C, Cruz G, Nazir MS, et al. Clinical comparison of sub-mm high-resolution non-contrast coronary CMR angiography against coronary CT angiography in patients with low-intermediate risk of coronary artery disease: a single center trial. Journal of Cardiovascular Magnetic Resonance [Internet]. BioMed Central; 2021; 23:57.
2. Munoz, C., Neji, R., Cruz, G., Mallia, A., Jeljeli, S., Reader, A.J., Botnar, R.M. and Prieto, C. (2018), Motion-corrected simultaneous cardiac positron emission tomography and coronary MR angiography with high acquisition efficiency. Magn. Reson. Med, 79: 339-350. https://doi.org/10.1002/mrm.26690
3. S Paul, R Tomi-Tricot, C Munoz, K Kunze, S Malik, J V Hajnal, P Bridgen, T Wilkinson, S Giles, R Neji, R Razavi, C Prieto, R M Botnar. (2022), High resolution motion compensated contrast-free free-breathing 3D CMRA at 7T using single transmit coil. ISMRM 2022. London, UK.
4. Henningsson M, Koken P, Stehning C, Razavi R, Prieto C, Botnar RM. Whole-heart coronary MR angiography with 2D self-navigated image reconstruction. Magn Reson Med. 2012;67(2):437–45.
5. Bustin A, Rashid I, Cruz G, Hajhosseiny R, Correia T, Neji R, et al. 3D whole-heart isotropic sub-millimeter resolution coronary magnetic resonance angiography with non-rigid motion-compensated PROST. Journal of Cardiovascular Magnetic Resonance. 2020;22.
Figures
Figure 1. Proposed CMRA sequence at 0.55T. T2 preparation (T2-Prep) (T2-Prep duration of 50 ms) and fat saturation (FAT SAT) (flip-angle of 130 deg) pre-pulses are incorporated to improve visualization of the coronary arteries. 2D image navigators (iNAVs) are incorporated to estimate 2D translation respiratory motion correction at each heartbeat, enabling beat-to-beat translational and bin-to-bin non-rigid respiratory motion. 3D whole-heart CMRA acquisition was a 3x accelerated bSSFP with a variable-density cartesian trajectory with spiral-like profile order (VD-CASPR).
Figure 2. Planning steps for the proposed free-breathing iNAV-based whole-heart CMRA at 0.55T. Firstly, a cardiac localizer is used to set the 3D FOV, shimming box (around the heart), and REST slabs (on the arms). Secondly, a free-breathing 2D CINE is performed to determine the subject-specific trigger delay (mid-diastole or late-systole) and acquisition window. Lastly, the proposed whole-heart CMRA sequence is performed.
Figure 3. 3D whole-heart CMRA at 0.55T. Comparison between itSENSE reconstruction without motion correction (Top Left) and with non-rigid motion corrected (MC) reconstruction (Top Middle), together with the proposed non-rigid MC reconstruction with PROST denoising (Top Right). The proposed approach greatly increases image quality due to the further incorporation of PROST denoising, which partially compensates for the low SNR at low field. The reformatted images at the bottom display the right (RCA) and circumflex (LCX) coronary arteries.
Figure 4. Reformatted images of the three healthy volunteers show a good depiction of the coronary arteries despite the relatively low resolution of the prototype sequence.
Figure 5 (Click me!). Video going across the slices for Subject #1. The resolution is 1.5 mm3 isotropic with a FOV = 312x312x120 mm. Video compression artifacts may be visible due to the maximum file size allowed in the submission.
DOI: https://doi.org/10.58530/2023/0547