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Proceedings Paper

Multispectral photoacoustic imaging of nerves with a clinical ultrasound system
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Paper Abstract

Accurate and efficient identification of nerves is of great importance during many ultrasound-guided clinical procedures, including nerve blocks and prostate biopsies. It can be challenging to visualise nerves with conventional ultrasound imaging, however. One of the challenges is that nerves can have very similar appearances to nearby structures such as tendons. Several recent studies have highlighted the potential of near-infrared optical spectroscopy for differentiating nerves and adjacent tissues, as this modality can be sensitive to optical absorption of lipids that are present in intra- and extra-neural adipose tissue and in the myelin sheaths. These studies were limited to point measurements, however. In this pilot study, a custom photoacoustic system with a clinical ultrasound imaging probe was used to acquire multi-spectral photoacoustic images of nerves and tendons from swine ex vivo, across the wavelength range of 1100 to 1300 nm. Photoacoustic images were processed and overlaid in colour onto co-registered conventional ultrasound images that were acquired with the same imaging probe. A pronounced optical absorption peak centred at 1210 nm was observed in the photoacoustic signals obtained from nerves, and it was absent in those obtained from tendons. This absorption peak, which is consistent with the presence of lipids, provides a novel image contrast mechanism to significantly enhance the visualization of nerves. In particular, image contrast for nerves was up to 5.5 times greater with photoacoustic imaging (0.82 ± 0.15) than with conventional ultrasound imaging (0.148 ± 0.002), with a maximum contrast of 0.95 ± 0.02 obtained in photoacoustic mode. This pilot study demonstrates the potential of photoacoustic imaging to improve clinical outcomes in ultrasound-guided interventions in regional anaesthesia and interventional oncology.

Paper Details

Date Published: 3 March 2014
PDF: 7 pages
Proc. SPIE 8943, Photons Plus Ultrasound: Imaging and Sensing 2014, 89430W (3 March 2014); doi: 10.1117/12.2036717
Show Author Affiliations
Jean Martial Mari, Univ. College London (United Kingdom)
Simeon West, Univ. College Hospital (United Kingdom)
Paul C. Beard, Univ. College London (United Kingdom)
Adrien E. Desjardins, Univ. College London (United Kingdom)


Published in SPIE Proceedings Vol. 8943:
Photons Plus Ultrasound: Imaging and Sensing 2014
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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