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Published October 1, 2017 | Published
Journal Article Open

Analysis of the potential for non-invasive imaging of oxygenation at heart depth, using ultrasound optical tomography (UOT) or photo-acoustic tomography (PAT)


Despite the important medical implications, it is currently an open task to find optical non-invasive techniques that can image deep organs in humans. Addressing this, photo-acoustic tomography (PAT) has received a great deal of attention in the past decade, owing to favorable properties like high contrast and high spatial resolution. However, even with optimal components PAT cannot penetrate beyond a few centimeters, which still presents an important limitation of the technique. Here, we calculate the absorption contrast levels for PAT and for ultrasound optical tomography (UOT) and compare them to their relevant noise sources as a function of imaging depth. The results indicate that a new development in optical filters, based on rare-earth-ion crystals, can push the UOT technique significantly ahead of PAT. Such filters allow the contrast-to-noise ratio for UOT to be up to three orders of magnitude better than for PAT at depths of a few cm into the tissue. It also translates into a significant increase of the image depth of UOT compared to PAT, enabling deep organs to be imaged in humans in real time. Furthermore, such spectral holeburning filters are not sensitive to speckle decorrelation from the tissue and can operate at nearly any angle of incident light, allowing good light collection. We theoretically demonstrate the improved performance in the medically important case of non-invasive optical imaging of the oxygenation level of the frontal part of the human myocardial tissue. Our results indicate that further studies on UOT are of interest and that the technique may have large impact on future directions of biomedical optics.

Additional Information

© 2017 The Optical Society of America. Received 10 Jul 2017; revised 5 Sep 2017; accepted 11 Sep 2017; published 19 Sep 2017. The authors would like to thank Prof. Lars Edvinsson, at the Lund University Hospital, for useful discussions, and Dr. Jacqueline Gunther for observant code checking. Funding: Swedish Research Council, Lund Laser Center (LLC), through a project grant under the Lund Linneaus environment, the Knut and Alice Wallenberg Foundation, and the Science Foundation Ireland. The authors declare that there are no conflicts of interest related to this article.

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August 19, 2023
October 17, 2023