Respiratory optimized data selection for more resilient self-navigated whole-heart coronary MR angiography

Our objective was to test a data-exclusion strategy for respiratory motion suppression by retrospectively eliminating data acquired at extreme respiratory positions for improved coronary vessel sharpness (VS) of 1-D self-navigated 3-D radial whole-heart coronary angiography acquisitions.

3-D radial self-navigated acquisitions were performed on a 1.5T scanner in volunteers during free-breathing (n = 8), in coached volunteers (n = 13) who were asked to breathe in a controlled manner to mimic cardiovascular patients presenting with Cheyne-Stokes breathing, and in free-breathing patients (n = 20). Data collected during large respiratory excursions were gradually excluded retrospectively from the reconstruction yielding 14 data sets per subject on average. The impact on VS, blood and myocardium signal-to-noise and contrast-to-noise was measured. From these results, two retrospective gating strategies were defined for the k-line elimination procedure and tested in all groups.

Maximum right coronary artery VS improvement was +7.4 and +2.7% in coached volunteers and patients (P < 0.0001 for both), respectively, and 1.6% for the free-breathing volunteers (P = 0.13). The first gating strategy was defined as a fixed undersampling factor of 5 compared to a fully sampled 3-D radial acquisition, yielding significant VS improvement in coached volunteers and patients while myocardial signal-to-noise decreased in these. The second strategy was defined as a fixed gating window of 5.7 mm, leading to similar improvements.

The presented strategies improve image quality of self-navigated acquisitions by retrospectively excluding data collected during end-inspiration.