Tissue optical clearing for fNIRS studies in radiotherapy

Functional near infrared spectroscopy (fNIRS) is a non-invasive and safe method to measure hemodynamics of the cerebral cortex. The use fNIRS in combination with brain radiotherapy is currently of our high interest since it provides a method to measure tissue oxygenation levels during irradiation. This can potentially help to advance the field of personalized cancer treatment. However, one limitation of the fNIRS technique is associated with penetration depth into tissues. Tissue optical clearing (TOC) could potentially improve the efficiency of fNIRS and for this use of radiopaque solutions, such as Omnipaque T (iohexol), VisipaqueT (iodixanol), etc., are proposed as effective optical clearing agents (OCA). The presented study experiments the feasibility of using TOC for fNIRS measurements in radiotherapy. The effectiveness of isosmotic VisipaqueT and an OCA with a high osmolarity, a solution of 70% glycerol with 10% DMSO, was evaluated when using chicken samples.