Modified optical fiber sensors for intravital monitoring

Sensing using optical fibers is quite an established technology and is increasingly used in the field of bio-medical sensing applications owing to its small size, light weight, immunity towards electromagnetic interference, biocompatibility, sensitivity, and the ease with which it can be integrated with standard catheters leading to a designated point of inspection. Fiber Bragg gratings (FBGs), due to their ease of multiplexing, inherent sensitivity towards strain, and thereby pressure, can be suitably designed to make a novel pressure sensor for diagnosing and monitoring angiogenesis in brain tumors and for assessing vascular lesions inside coronary arteries. However, standard FBGs have a poor pressure sensitivity of 4pm/MPa (0.5fm/mmHg), which is insufficient to detect a few mmHg blood pressure changes. By utilizing the mechanical properties of modified FBGs with an elastomeric material coating, it is possible to improve the transduction mechanism of effectively translating pressure to strain and increase the resolution and sensitivity by two orders of magnitude (53.4 times) compared to standard FBGs. These modified FBGs could then be used to monitor respective pressure indices, i.e., Intracranial Pressure (ICP) and Instantaneous wave-free Ratio (iFR), by integrating them with catheters or endoscopes and using appropriate signal-processing algorithms. Moreover, a simulation of the modification of the blood vessel flow with respect to the secondary vessel formation is done to study the impact of different blood vessel formations during angiogenesis on pressure, thereby co-relating flow patterns to angiogenesis.