Statistical gating of ballistic signals enables nanosecond-pulse laser-scan imaging (NPLSI) of myocardial injury in a beating heart

Myocardial injury remains a critical complication in cardiac surgery, posing significant challenges for intraoperative detection and intervention. Existing methods, including biochemical assays and imaging techniques, either involve invasive procedures or are limited by poor spatial resolution and vulnerability to motion artifacts. Here, we propose a nanosecond-pulse laser-scan imaging (NPLSI) method for monitoring myocardial injury in a beating heart. The nanosecond laser pulses achieve motion-blur-free data acquisition. A statistical gating method is developed to extract ballistic signals from confounding multiple scattering signals, achieving accurate characterization of myocardial optical properties. We validated the NPLSI method using Monte Carlo simulations and preclinical experiments in 30 rabbits with myocardial ischemia. Across simulations with varying tissue optical parameters, the statistical-gating method estimated the ballistic component with a mean relative error of 4.85% ± 3.82%. In the ligation region, the normalized systolic ballistic signal showed a significant overall effect of time (F(4, 116) = 17.967, p < 0.001) and a significant linear increasing trend across the five post-ligation time points (F(1, 29) = 23.156, p < 0.001), consistent with the progressive increase in serum troponin levels. These results demonstrate that NPLSI enables non-contact and label-free imaging of dynamic myocardial optical changes in a beating heart. Our work advances the integration of NPLSI-based human organ-scale monitoring into clinical cardiac surgery.