1349664 - Efficient 3D iT2prep-BOOST for contrast-free thoracic aortic lumen and vessel wall imaging

Background: In clinical routine, bright-and black-blood MRI sequences are acquired sequentially for the assessment of aortic disease¹. 3D diaphragmatic navigator-gated T2-prep bSSFP bright-blood sequences allow luminal assessment and 2D breath-held turbo-spin echo sequences enable vessel wall imaging. Limitations include the prolonged scan times and image misregistration between the two contrasts, impeding robust clinical interpretation. We proposed to investigate the feasibility and evaluate the performance of a novel, accelerated, respiratory motion-compensated, 3D cardiac MRI technique for simultaneous contrast-free aortic lumen and aortic wall imaging(iT2Prep-BOOST)²_.

Methods:

25 patients with aortopathy (14 male,31±10 years old) were scanned at a 1.5T system(MAGNETOM Aera, Siemens, Germany). The proposed 3D free-breathing, ECG-triggered bSSFP iT2prep-BOOST prototype sequence [coronal orientation,1.3mm³ isotropic resolution, FOV=300x400x104-156mm³, T2-prep=40ms,TI=110ms,TE/TR=1.41/3.24ms, image-based navigation for translational and non-rigid motion correction] utilised an interleaved acquisition framework, where a T2Prep-IR preparation module was applied before data acquisition in odd heartbeats and no preparation was applied in even heartbeats² (Fig 1). The first bright-blood dataset was used for lumen visualization, while subtraction of the two bright-blood datasets was used to create the black-blood dataset for vessel wall imaging. The research sequence was compared against the clinical sequences [T2prep-bSSFP(sagittal orientation,1.4mm³ isotropic,FOV=240×400×134-168mm³,T2prep=40ms,TR/TE=3.5/1.7ms, diaphragmatic navigator) & 2D breath-held HASTE(axial orientation,1.6mm in-plane resolution,8mm slice thickness)]. Two blinded experts recorded their diagnostic confidence using 4-point Likert scale(3≥ diagnostic). Co-axial aortic dimensions were obtained with both methods and compared with Bland-Altman analysis. One additional patient was scanned with the proposed approach and with the clinically-indicated aortic CT to investigate the feasibility in chronic dissection.



Results:

The average scan time for the conventional sequences (T2-prep bSSFP and HASTE) was 13.2±3.2 min versus 8.0±1.5min(P< 0.001) for the proposed 3D iT2Prep-BOOST. Image quality of the aortic lumen with the bright-blood iT2Prep-BOOST was comparable or superior to the conventional T2-prep bSSFP. The 3D black-blood iT2prep-BOOST provided vessel wall imaging with improved coverage compared to the 2D HASTE(Fig.2). Diagnostic confidence was higher for the proposed approach compared to the clinical for both reviewers (Reviewer 1: 4(3.5, 4) vs 3(2.5, 3),P=0.007; Reviewer 2: 4(4, 4) vs 4 (3, 4),P=0.009). Aortic dimensions in bright-blood images were in good agreement with conventional imaging (Fig.3).



Conclusion:

The accelerated iT2prep-BOOST sequence provides high quality depiction of the aortic lumen and wall with a predictable scan time of 8 min. This approach is promising for the comprehensive evaluation of aortic disease.