Fiber Optic-Based Method for Sensing Blood Perfusion in Intracranial Tissues

This manuscript presents feasibility of an optical fiber probe designed for detecting blood perfusion during intracranial biopsies. The probe operates alongside the biopsy needle, continuously monitoring blood to prevent internal bleeding. The proposed paper shows proof of principle of the optoelectronic system that was designed to acquire an optical signal as a digital data, discriminating if it is related to the presence of blood. The whole detecting process is composed of an optical probe which illuminates a phantom perfused with synthetic blood; the reflected signal is addressed to a spectrometer which acquires optical power with a fixed integration time. To improve blood perfusion detection, considering the significant noise expected due to diffused light within the cranium affecting the measurement, a lock-in approach was investigated. The aim of this technique is to establish a unique correlation between blood flow within a vessel and heartbeat frequency by acquiring reflected light through a fiber optic probe. This method was experimentally tested using a modulated peristaltic motor to simulate blood flow in a silicone-based artificial vein, confirming the presence of blood flowing if the fundamental harmonic in the reflected light is the same of the modulating signal. Measurements were conducted at different distances and heights from the vein, with the motor both active (simulating a heartbeat) and inactive (no blood flow). The results show that the system can reliably detect blood perfusion in the artificial vein from different distances, using a probe that is compatible with standard biopsy needles.