Grant: Discovery Grants Program - Individual

The long-term vision of my research program is to develop noninvasive optical imaging and monitoring techniques and translate them to human applications. Over the last 6 years, my team has built several point-of-care optical devices including a portable system that can monitor cerebral oxygen consumption, a sensitive biomarker of brain injury. We have subsequently tested the technique in preterm infants during the first 3 days of life, a period of high risk of brain injury, and neonates with excessive accumulation of fluid in the brain that causes severe injuries. Our objective over the next 5 years is to develop a similar neuromonitoring technology for adults. However, developing an adult optical neuromonitor is not trivial because, in contrast to neonates who have very thin (2-3 mm) scalp and skull, the adult extracerebral layer (i.e., scalp and skull) is very thick. Since the probes of optical device need to be placed on the scalp for noninvasive measurements, light must travel through the thick (10-15 mm) adult extracerebral layer before reaching the brain. As such, the optical signal would be overwhelmingly comprised of scalp and skull contributions (more than 80%), leading to unreliable brain measurements. To meet this challenge, we will develop a technology that can distinguish the brain signal from that of the extracerebral layer. In contrast to the traditional optical spectroscopy method used in the neonatal device (based on light of constant intensity), we will send very short (picosecond) pulses of light into the head and measure the time of travel of each photon in the tissue (i.e., their time-of-flight). Since there is an equivalence between time and distance, light that is detected right after the pulse only travel through the extracerebral layer while light that is detected long after the pulse have travelled deeper and have a high chance of probing the brain. We have shown that this approach can significantly reduce the contamination of the extracerebral layer by focusing on the late arriving photons. The new device will include a laser that simultaneously emits light pulses at dozens of wavelengths, and we will build an advanced detection system that can measure the wavelength of each photon and its time-of-flight in the tissue. The device will be tested in inert media that mimic the adult head and in juvenile pigs, to determine the reliability of the technology before human testing. Note that juvenile pigs were chosen because the thickness of their extracerebral layer is similar to that of the adult human. Given the success of our neonatal optical neuromonitor, we anticipate that this research program will lead to the development of a safe and reliable technique for adult neuromonitoring. Further, the program will create a research environment that is fair, inclusive, and welcoming to diverse perspectives, to train Canada's future scientific workforce on building and testing advanced optical devices.