Camera-based Cardiac Triggering in Functional Cardiac MR

Motivation: Contactless cardiac triggering makes cardiac and cardiovascular MRI (cMRI) more accessible by improving patient comfort, reducing complexity, and facilitating swift workflow. Goal(s): In this work we quantitatively assess performance of remote photoplethysmography (rPPG) triggering in selected functional cMRI (Flow, T1 mapping) sequences. Approach: Building on in-bore camera hardware we developed a cardiac trigger detection method for cMRI that extracts a rPPG signal acquired at the patient's forehead. The reconstructed images, flow metrics and T1 are quantitatively compared to standard ECG triggering. Results: MR image qualities and derived quantities of the studied volunteer and patient cohort are comparable for rPPG and ECG triggering. Impact: The presented work provides evidence that flow quantification and T1 mapping is feasible with contactless cardiac cycle detection. The proposed method allows cardiac MRI without placement of ECG electrodes, thus increasing accessibility of cardiac MR.