1349669 - Efficient 3D free-breathing non-CE cardiovascular MRA in 3 min in patients with congenital heart disease

Cardiovascular MRA is established for anatomical assessment in patients with congenital heart disease(CHD)¹.Conventional 3D T2-prep-bSSFP sequences rely on diaphragmatic respiratory gating(dNAV T2prep-bSSFP) to minimize the effects of respiratory motion, leading to long scan times and residual motion artefacts. A recently proposed accelerated MRA framework,which incorporates image-based navigation^2,3 with 3D-patch-based denoising(iNAV T2prep-bSSFP PROST)⁴,was prospectively evaluated against the clinical sequence.



Methods:

40 adult patients with CHD and different underlying pathologies (tetralogy of Fallot,aortic coarctation, hypoplastic left heart syndrome, atrioventricular septal defect, transposition of the great arteries) were scanned on a 1.5T system (MAGNETOM Aera, Siemens).The proposed ECG-triggered,free-breathing prototype sequence was acquired with a 4-fold undersampled variable-density Cartesian trajectory⁵(FOV: 400x300x72-108 mm³,resolution 1.5 mm³,flip angle =90°,T2-prep duration=40ms,TE/TR = 1.75/238 ms,coronal orientation).2D image navigators² were acquired at each cardiac cycle to enable 100% respiratory scan efficiency.Motion estimation and non-rigid motion correction is performed inline in the scanner software.3D-PROST denoising was performed off-line.The research sequence was compared against the clinical sequence with matching parameters(except FOV 400x300x88-120,TE/TR=1.52/294 ms,GRAPPA parallel imaging 2x undersampled,sagittal orientation).Two blinded experts recorded their diagnostic confidence for anatomical analysis(1:poor diagnostic confidence to 4: full diagnostic confidence).Diagnostic quality of the intrapericardiac structures with regards to sharpness of vascular borders and robustness to artefacts was compared between the two methods using a 1-5 Likert scale(1: non-diagnostic,5: excellent quality, ≥3: diagnostic).Signal ratio between the vessel lumen and the myocardium for the major intrapericardiac structures was also compared.



Results:

Improved quality depiction of all cardiac segments in shorter scan time was achieved with the proposed approach in comparison to the clinical [3.2±0.7min(proposed) vs 15±3.2min(clinical),P < 0.0001] (Fig1).Reconstruction time was 2±0.5min(inline) plus 1.5±0.5min(offline). Diagnostic confidence was higher for the proposed approach vs the clinical(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).Image quality scores were statistically significantly higher for the proposed approach for the systemic and pulmonary veins, left atrium, left main stem and comparable for the remaining structures(Fig2). Signal ratio comparison demonstrated comparable results with both approaches(Fig3).



Conclusion:

The proposed respiratory-motion compensation and reconstruction strategy offers a  framework for superior quality depiction of the heart and the thoracic vessels in CHD patients, in shorter and consistent scan times (~ 3min) than the clinical standard and holds promise for imminent clinical integration.