Coherent-Excitation PACT With Frequency-Compensated Reconstruction for High-Contrast Deep-Tissue Imaging

Photoacoustic computed tomography (PACT) synergizes optical absorption contrast with ultrasonic resolution for noninvasive biomedical imaging yet faces limitations in signal-to-noise ratio (SNR), resolution, and contrast. This study introduces a coherent-excitation PACT system integrating interferometric optical excitation and Frequency-Compensated Filtered Back Projection (FC-FBP) reconstruction. The proposed method utilizes phase-locked dual-pulse interferometric excitation to amplify photoacoustic emissions; for the isolated chicken heart, the resolution is improved by 7.9% compared to the single-pulse protocol. The FC-FBP algorithm compensates for frequency-dependent acoustic attenuation via depth-adaptive Gaussian filtering, enhancing the projected signal in the target area while suppressing speckle artifacts. Through experimental validation, we confirm that the coherent-excitation scheme enables simultaneous optimization of optical fluence distribution and acoustic coherence; hence, it can be used to resolve previously indistinguishable hemoglobin oxygenation gradients in murine tumor models. This advancement establishes a high-sensitivity PACT framework, showing potential for real-time intraoperative imaging and dynamic metabolic monitoring in clinical applications.