mDixon ECG-gated 3-dimensional cardiovascular magnetic resonance angiography in patients with congenital cardiovascular disease

Background: Cardiovascular magnetic resonance (CMR) angiography (CMRA) is an important non-invasive imaging tool for congenital heart disease (CHD) and aortopathy patients. The conventional 3D balanced steady-state free precession (bSSFP) sequence is often confounded by imaging artifacts. We sought to compare the respiratory navigated and electrocardiogram (ECG) gated modified Dixon (mDixon) CMRA sequence to conventional non-gated dynamic multi-phase contrast enhanced CMRA (CE-CMRA) and bSSFP across a variety of diagnoses.

Methods: We included 24 patients with CHD or aortopathy with CMR performed between September 2017 to December 2017. Each patient had undergone CE-CMRA, followed by a bSSFP and mDixon angiogram. Patients with CMR-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 border 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.

Results: All scans were diagnostically adequate. Mean (SD) quality scores were 3.4 (0.7) for the mDixon, 3.2 (0.5) for the bSSFP and 3.4 (0.5) for the CE-CMRA. Qualitatively, the intracardiac anatomy and myocardium-blood pool definition were better in the bSSFP; however, mDixon images showed enhanced vessel wall sharpness with less blurring surrounding the anatomical borders distally. Coronary origins were identified in all cases. Pulmonary veins were visualized in 92% of mDixon sequences, 75% of bSSFP and 96% of CE-CMRA. 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 bSSFP, respectively. However, the size of signal void and field distortion were significantly worse in the latter, particularly for flow and metal induced artifacts.

Conclusion: In patients with congenital heart disease, ECG gated mDixon angiography yields high fidelity vascular images including better delineation of head and neck vasculature and pulmonary veins and fewer artifacts than the comparable bSSFP sequence. It should be considered as the preferred strategy for successful CHD imaging in patients with valve stenosis, vascular stents, or metallic implants.