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Published September 2015 | Accepted Version
Journal Article Open

Photoacoustic tomography imaging and estimation of oxygen saturation of hemoglobin in ocular tissue of rabbits


This study evaluated in vivo imaging capabilities and safety of qualitative monitoring of oxygen saturation of hemoglobin (sO_2) of rabbit ciliary body tissues obtained with acoustic resolution (AR) photoacoustic tomography (PAT). AR PAT was used to collect trans-scleral images from ciliary body vasculature of seven New Zealand White rabbits. The PAT sO_2 measurements were obtained under the following conditions: when systemic sO_2 as measured by pulse oximetry was between 100% and 99% (level 1); systemic sO_2 as measured by pulse oximetry was between 98% and 90% (level 2); and systemic sO_2 as measured by pulse oximetry was less than 90% (level 3). Following imaging, histological analysis of ocular tissue was conducted to evaluate for possible structural damage caused by the AR PAT imaging. AR PAT was able to resolve anatomical structures of the anterior segment of the eye, viewed through the cornea or anterior sclera. Histological studies revealed no ocular damage. On average, sO_2 values (%) obtained with AR PAT were lower than sO_2 values obtained with pulse oximetry (all p < 0.001): 86.28 ± 4.16 versus 99.25 ± 0.28, 84.09 ± 1.81 vs. 95.3 ± 2.6, and 64.49 ± 7.27 vs. 71.15 ± 10.21 for levels 1, 2 and 3 respectively. AR PAT imaging modality is capable of qualitative monitoring for deep tissue sO_2 in rabbits. Further studies are needed to validate and modify the AR PAT modality specifically for use in human eyes. Having a safe, non-invasive method of in vivo imaging of sO_2 in the anterior segment is important to studies evaluating the role of oxidative damage, hypoxia and ischemia in pathogenesis of ocular diseases.

Additional Information

© 2015 Elsevier Ltd. Received 3 December 2014, Revised 27 May 2015, Accepted 30 May 2015, Available online 3 June 2015. Stella Hennen and Wenxin Xing contributed equally to this work. Conflict of Interest: Stella N. Hennen: none; Wenxin Xing: none; Ying-Bo Shui: none; Yong Zhou: none; Kalishman Jennifer: none; Andrews-Kaminsky, Lisa: none; Michael Kass: none; Beebe, David: none; Maslov, Konstantin: Microphotoacoustics, Inc., which, however, did not support this work; Wang, Lihong: Microphotoacoustics, Inc. and Endra, Inc., which, however, did not support this work. Sources of Funding: This work is supported, in part, by a Faculty Diversity grant, Washington University in St. Loius, # 93711 (SNH) and by National Institutes of Health grants R01 EB008085, R01 CA134539, U54 CA136398, R01 CA159959, DP1 EB016986 (NIH Director's Pioneer Award) (LVW).

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