Comparison of tethered and untethered helmet mounted fNIR systems for TBI application

Blast or accident related damages to brain leads to traumatic brain injury (TBI) and early detection of TBI and its severity avoids disability. Broadband near-infrared spectroscopy system of 30-1000 MHz provides accurate functional imaging that could be instrumental in diagnosis of any TBI. This paper addresses design challenges and performance comparison of helmet mounted broadband functional near infra-red (fNIR) designs of both tethered and un-tethered communications with a remote analysis unit. Performance comparison of both systems in terms of size, power consumption, and data throughput are discussed and merits of the tethered and untethered helmet mounted broadband fNIR is discussed. The photon migration of NIR light is accomplished using broadband optical transmitters and reception of diffused photons at various positions on head that are 1.5 cm away from each individual optical transmitter. Optical transmitter and receiver are custom designed to perform photon migration spectroscopy through head and brain at wavelengths of 680nm, 780nm, 820nm, and 980nm. The untethered helmet structure consists of RF electronic for reception of UWB signals of 4.5-5.5GHz and transmission of 50Mb/s data after local signal processing of the received diffused photons. Low frequency electrical connections using microcoax are employed for interfacing the broadband 30-1000MHz reference source to the multi-wavelength optical transmitters and process the received RF signal component of diffused photon density waves.