Laser HeartBeat: Feasibility of a Contactless Optical Gating Method for Cardiac MRI

Area of Science:

• Biomedical Engineering
• Medical Imaging Physics

Background:

• Robust cardiac gating is essential for high-quality cardiac magnetic resonance (CMR) imaging.
• Traditional methods like electrocardiography (ECG) face limitations due to electromagnetic interference and setup complexities.

Purpose of the Study:

• To introduce Laser HeartBeat (Laser HB), a novel contactless gating technique for CMR.
• To evaluate the feasibility and performance of Laser HB in realistic MRI environments, including interference and occlusion scenarios.

Main Methods:

• Developed an MRI-compatible optical module for contactless acquisition of defocused laser speckle patterns from chest-wall micro-vibrations.
• Implemented a real-time processing pipeline with a dedicated Laser HB trigger algorithm to extract cardiac motion surrogates and generate gating signals.
• Conducted out-of-bore and in-bore studies to assess performance under electromagnetic interference and occlusion.

Main Results:

• Laser HB demonstrated 97.6% availability with high beat-wise precision, recall, and F1 scores (0.946/0.946/0.943).
• The system achieved a low average trigger delay of 22.6 ms relative to the ECG R-peak.
• Integration of the Laser HB system showed a minimal impact on MRI signal-to-noise ratio (SNR), decreasing it by only 2.8.

Conclusions:

• Laser HeartBeat provides a viable, MRI-compatible, contactless gating solution for CMR imaging.
• The method reduces setup burden, enhances workflow efficiency, and improves patient comfort.
• Laser HB offers a promising alternative to conventional gating techniques, especially in challenging MRI conditions.