Investigating the effects of compressional and elastic photoacoustic waves to predict transcranial photoacoustic image quality for guidance of minimally invasive neurosurgeries

Patient simulations can be a powerful tool to plan placement of photoacoustic imaging components for surgical guidance. We previously used compressional-wave-only simulations to identify optimal acoustic windows for transcranial photoacoustic imaging. Elastic simulations, which include both compressional and shear waves, are expected to more accurately represent the physical transcranial acoustic process. However, elastic simulations are timing-consuming and memory intensive. This paper contains a comparison of compressional and elastic wave simulations to determine which option is more suitable for preoperative surgical planning. Compressional and elastic photoacoustic k-Wave simulations were performed based on a CT volume of a human cadaver head. Photoacoustic sources were placed in the locations of the internal carotid arteries and likely positions of neurosurgical instrument tips. Transducers received signals from three acoustic windows (i.e., the ocular, nasal, and temporal regions). Target visibility, image-based target size estimates, and target-to-instrument distances were measured using the generalized contrast-to-noise ratio, resolution, and relative source distances, respectively, for each simulation method. The generalized contrast-to-noise ratio and resolution measurements were equivalent between compressional and elastic simulations. Relative source distance measurements were within 0.1 mm of the true distances. These results indicate that it is sufficient to utilize the less time-consuming, less memory-intensive compressional wave simulations for presurgical planning.