Diffuse optical spectroscopy (DOS) and imaging methods have been widely applied to noninvasive detection of brain activity. We have designed and implemented a low cost, portable, real-time one-channel time-resolved DOS system for neuroscience studies. Phantom experiments were carried out to test the performance of the system. We further conducted preliminary human experiments and demonstrated that enhanced sensitivity in detecting neural activity in the cortex could be achieved by the use of late arriving photons.
Stroke is the second leading cause of death worldwide. Rapid and precise diagnosis is essential to expedite clinical
decision and improve functional outcomes in stroke patients; therefore, real-time imaging plays an important role to
provide crucial information for post-stroke recovery analysis. In this study, based on the multi-wavelength laser and 18.5
MHz array-based ultrasound platform, a real-time handheld photoacoustic (PA) system was developed to evaluate
cerebrovascular functions pre- and post-stroke in rats. Using this system, hemodynamic information such as cerebral
blood volume (CBV) can be acquired for assessment. One rat stroke model (i.e., photothrombotic ischemia (PTI)) was
employed for evaluating the effect of local ischemia. For achieving better intrinsic PA contrast, Vantage and COMSOL
simulations were applied to optimize the light delivery (e.g., interval between two arms) from customized fiber bundle,
while phantom experiment was conducted to evaluate the imaging performance of this system. Results of phantom
experiment showed that hairs (~150 μm diameter) and pencil lead (500 μm diameter) can be imaged clearly. On the
other hand, results of in vivo experiments also demonstrated that stroke symptoms can be observed in PTI model poststroke.
In the near future, with the help of PA specific contrast agent, the system would be able to achieve blood-brain
barrier leakage imaging post-stroke. Overall, the real-time handheld PA system holds great potential in disease models
involving impairments in cerebrovascular functions.
This paper emphasizes on the stability of the diffused signal acquired by a time domain diffuse optical tomography system. The robustness of the system is enhanced to make it perform consistently over a longer period of time.