Photoacoustic monitoring of blood oxygenation during neurosurgical interventions

摘要

Multispectral photoacoustic (PA) imaging is a prime modality to monitor hemodynamics and changes in bloodoxygenation (sO_2). Although sO_2 changes can be an indicator of brain activity both in normal and in pathologicalconditions, PA imaging of the brain has mainly focused on small animal models with lissencephalic brains.Therefore, the purpose of this work was to investigate the usefulness of multispectral PA imaging in assessingsO_2 in a gyrencephalic brain. To this end, we continuously imaged a porcine brain as part of an open neurosurgicalintervention with a handheld PA and ultrasonic (US) imaging system in vivo. Throughout the experiment, wevaried respiratory oxygen and continuously measured arterial blood gases. The arterial blood oxygenation (SaO2)values derived by the blood gas analyzer were used as a reference to compare the performance of linear spectralunmixing algorithms in this scenario. According to our experiment, PA imaging can be used to monitor sO2 inthe porcine cerebral cortex. While linear spectral unmixing algorithms are well-suited for detecting changes inoxygenation, there are limits with respect to the accurate quantification of sO_2, especially in depth. Overall,we conclude that multispectral PA imaging can potentially be a valuable tool for change detection of sO_2 inthe cerebral cortex of a gyrencephalic brain. The spectral unmixing algorithms investigated in this work willbe made publicly available as part of the open-source software platform Medical Imaging Interaction Toolkit(MITK).