Quick Fire Session
SCMR 22nd Annual Scientific Sessions
Cardiovascular magnetic resonance angiography (MRA) is an important non-invasive imaging tool for congenital heart disease (CHD) and aortopathy patients. The standard ECG gated balanced 3D-Steady-State Free Precession (SSFP) sequence is often confounded by imaging artifacts. We sought to compare the respiratory navigated and ECG gated multi-echo Dixon (mDixon) MRA sequence to conventional non-gated dynamic multi-phase contrast enhanced MRA (CE-MRA) and SSFP across a variety of diagnoses.
We included 24 patients with CHD or aortopathy with cardiovascular magnetic resonance (CMR) performed between September to December 2017. Each patient had undergone CE-MRA, followed by a SSFP and mDixon angiogram. Patients with MR-incompatible implants or contraindications to contrast were excluded. The studies were rated according to image quality at a scale from 1 (poor) to 4 (excellent) based on diagnostic adequacy, artifact burden, vascular boarder delineation, myocardium-blood pool contrast, and visualization of pulmonary and systemic veins and coronaries. Contrast-to-Noise Ratio (CNR), Signal-to-Noise Ratio (SNR) and quantitative vascular measurements were compared between the two gated sequences. Bland-Altman plots were generated to compare paired measures.
All scans were diagnostically adequate. Mean (SD) quality scores were 3.4 (0.7) for the mDixon, 3.2 (0.5) for the SSFP and 3.4 (0.5) for the CE-MRA.The Bland-Altman plots revealed acceptable agreement between the SSFP-mDixon, CE-MRA-SSFP and CE-MRA-mDixon pairs with respect to their average image quality scores, SNR and CNR (Figure 1). Qualitatively, the intracardiac anatomy and myocardium-blood pool definition were better in the SSFP; however, mDixon images showed enhanced vessel wall sharpness with less blurring surrounding the anatomical boarders distally. Coronary origins were identified in all cases. Pulmonary veins were visualized in 92% of mDixon sequences, 75% of SSFP and 96% of CE-MRA, (Figure 2).Similarly, neck veins were identified in 92%, 83% and 96% respectively. Artifacts prevented vascular measurement in 6/192 (3%) and 4/192 (2%) of total vascular measurements for the mDixon and SSFP, respectively. However, the size of signal void and field distortion was significantly worse in the latter, particularly for flow and metal induced artifacts, (Figure 3).There was no meaningful difference between all mDixon and SSFP vascular diameter estimates irrespective of the vessel type and size.
mDixon ECG gated angiography yields high fidelity vascular images with improved delineation of head and neck vasculature and pulmonary veins and fewer artifacts compared to the SSFP sequence. It should be considered as the preferred strategy for successful CHD imaging in patients with valve stenosis, vascular stents, or metallic implants.