Label-free structural photoacoustic tomography of intact mouse brain
Capitalizing on endogenous hemoglobin contrast, photoacoustic computed tomography (PACT), a deep-tissue highresolution imaging modality, has drawn increasing interest in neuro-imaging. However, most existing studies are limited to functional imaging on the cortical surface, and the deep-brain structural imaging capability of PACT has never been demonstrated. Here, we explicitly studied the limiting factors of deep-brain PACT imaging. We found that the skull distorted the acoustic signal and blood suppressed the structural contrast from other chromophores. When the two effects are mitigated, PACT can provide high-resolution label-free structural imaging through the entire mouse brain. With 100 μm in-plane resolution, we can clearly identify major structures of the brain, and the image quality is comparable to that of magnetic resonance microscopy. Spectral PACT studies indicate that structural contrasts mainly originate from cytochrome and lipid. The feasibility of imaging the structure of the brain in vivo has also been discussed. Our results demonstrate that PACT is a promising modality for both structural and functional brain imaging.
Additional Information© 2015 Society of Photo-Optical Instrumentation Engineers. The authors appreciate Prof. James Ballard's close reading of the manuscript, and thank Ernie Gonzales, Dr. Junjie Yao, Dr. Chi Zhang, and Chiye Li for their useful discussions and technical assistance. This work was sponsored in part by National Institutes of Health (NIH) grants DP1 EB016986 (NIH Director's Pioneer Award), R01 CA186567 (NIH Director's Transformative Research Award), R01 EB016963, R01 EB010049, and R01 CA159959. L. V. Wang has a financial interest in Microphotoacoustics, Inc., and Endra, Inc., which, however, did not support this work.
Published - 93230M.pdf