Spatial optimization of transthoracic diffuse optics for myocardial ischemia in mice: a Monte Carlo study.

Abstract

Significance: Continuous, noninvasive assessment of myocardial ischemia in intact mouse models poses a significant technical challenge. Conventional diffuse optical techniques are mostly limited to ex vivo hearts or open-chest animal models due to severe signal attenuation and tissue interference caused by the complex thoracic anatomy. Empirical placement of photoelectric probes over the cardiothorax further undermines the sensitivity and specificity of cardiac signal detection.

Aim: This study aims to systematically characterize photon transport dynamics within the mouse thorax, determine the optimal light Source-Detector (S-D) spatial configuration, and quantitatively evaluate the theoretical feasibility of transthoracic diffuse optics for detecting varying degrees of myocardial ischemia.

Approach: Using a high-fidelity 3D voxelized model derived from realistic mouse anatomical data, we performed Monte Carlo photon transport simulations at 800 nm. A high-density virtual array of sources and detectors was deployed on the body surface to determine the optimal S-D positions for cardiac signal extraction. Myocardial ischemia was simulated by modulating the optical coefficients of myocardial tissue, enabling the investigation of the relationship between surface-captured optical signals and ischemia severity.

Results: The simulations identified an optimized S-D configuration that maximizes the detection sensitivity for deep myocardial signals while minimizing interference from overlying tissues. Notably, under this configuration, the diffuse optical signals collected at the body surface showed a strong linear correlation with the degree of myocardial ischemia.

Conclusions: An optimized S-D configuration was demonstrated for establishing a linear correlation between optical signal variations and ischemic severity. This study provides a theoretical framework toward diffuse optics for in vivo assessment of cardiac hemodynamics and tissue oxygenation in murine models.