Theoretical, simulated, and experimental photoacoustic approaches to detect the internal carotid artery during minimally invasive neurosurgery

Real-time intraoperative guidance during the minimally invasive neurosurgical procedure known as endonasal transsphenoidal surgery is often limited to endoscopy and computed tomography. These imaging options are suboptimal when localizing internal carotid arteries (ICAs) either obscured by tissue or shifted relative to preoperative locations due to anatomical disruptions during surgery. Accidental damage to these critical structures has severe surgical complications, such as patient hemorrhage, stroke, and death. Photoacoustic imaging is a promising imaging technique to provide real-time intraoperative guidance of the subsurface ICAs. However, interactions with bone along the optical and acoustic pathways degrade photoacoustic image quality. In this dissertation, novel theoretical, simulated, and experimental approaches are employed to address image quality limitations, yielding the following three fundamental contributions to the proposed photoacoustic technology. First, a new photoacoustic-specific spatial coherence theory was derived and developed, followed by the development of PhocoSpace, an open-source software package to utilize this theory. This foundational theory supports the implementation of advanced coherence-based beamforming techniques to enable ICA detection and generally improve photoacoustic image quality in bony environments, with broader applications that extend beyond these tasks. Second, intraoperative ICA tracking tasks most beneficial for coherence-based beamforming were differentiated from those better suited to more traditional amplitude-based beamforming techniques. Third, a novel approach employing patient-specific simulations is presented to identify naturally occurring acoustic windows for photoacoustic receiver placements that minimize acoustic interactions with bone. These contributions demonstrate that strategic use of acoustic windows and coherence-based beamforming techniques address photoacoustic image degradation in the presence of bone and ultimately generate interpretable photoacoustic images of the ICAs. From presurgical planning to intraoperative monitoring, a new paradigm for photoacoustic detection of the ICAs during minimally invasive neurosurgery is established. Beyond ICA detection, the contributions herein extend to photoacoustic-based detection of other critical structures (e.g., nerves or other blood vessels) lying within optically and acoustically challenging environments