Label-free intraoperative nerve detection and visualization using ratiometric diffuse reflectance spectroscopy

Throckmorton, Graham A.; Haugen, Ezekiel; Thomas, Giju; Willmon, Parker; Baba, Justin S.; Solórzano, Carmen C.; Mahadevan‐Jansen, Anita

doi:10.1038/s41598-023-34054-6

Cited by 3 publications

(2 citation statements)

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“…Comparisons across spectroscopic absorbance measurements and photoacoustic amplitude spectra similarly revealed negligible optical absorption changes between the control (i.e., ulnar) and regenerated (i.e., median) nerve samples. Given this similarity, our newly introduced nerve optical absorption characterization results may be employed as a future reference spectrum for photoacoustic imaging of other similarly myelinated nerves (i.e., other than healthy ulnar and regenerated median nerves) and may also be utilized for other optics-based nerve imaging techniques (e.g., diffuse reflectance spectroscopy 63 ). As with any optics-based application, there are also possible cases in which the information provided by the 1725 nm peak may not be useful (e.g., if there is significant spectral overlap with other chromophores of interest, as observed in Fig.…”

Section: Discussionmentioning

confidence: 99%

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Optical absorption spectra and corresponding in vivo photoacoustic visualization of exposed peripheral nerves

Graham,

Sharma,

Padovano

et al. 2023

J. Biomed. Opt.

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Multispectral photoacoustic imaging has the potential to identify lipid-rich, myelinated nerve tissue in an interventional or surgical setting (e.g., to guide intraoperative decisions when exposing a nerve during reconstructive surgery by limiting operations to nerves needing repair, with no impact to healthy or regenerating nerves). Lipids have two optical absorption peaks within the NIR-II and NIR-III windows (i.e., 1000 to 1350 nm and 1550 to 1870 nm wavelength ranges, respectively) which can be exploited to obtain photoacoustic images. However, nerve visualization within the NIR-III window is more desirable due to higher lipid absorption peaks and a corresponding valley in the optical absorption of water.Aim: We present the first known optical absorption characterizations, photoacoustic spectral demonstrations, and histological validations to support in vivo photoacoustic nerve imaging in the NIR-III window.Approach: Four in vivo swine peripheral nerves were excised, and the optical absorption spectra of these fresh ex vivo nerves were characterized at wavelengths spanning 800 to 1880 nm, to provide the first known nerve optical absorbance spectra and to enable photoacoustic amplitude spectra characterization with the most optimal wavelength range. Prior to excision, the latter two of the four nerves were surrounded by aqueous, lipid-free, agarose blocks (i.e., 3% w/v agarose) to enhance acoustic coupling during in vivo multispectral photoacoustic imaging using the optimal NIR-III wavelengths (i.e., 1630 to 1850 nm) identified in the ex vivo studies.Results: There was a verified characteristic lipid absorption peak at 1725 nm for each ex vivo nerve. Results additionally suggest that the 1630 to 1850 nm wavelength range can successfully visualize and differentiate lipid-rich nerves from surrounding water-containing and lipid-deficient tissues and materials.Conclusions: Photoacoustic imaging using the optimal wavelengths identified and demonstrated for nerves holds promise for detection of myelination in exposed and isolated nerve tissue during a nerve repair surgery, with possible future implications for other surgeries and other optics-based technologies.

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Section: Discussionmentioning

confidence: 99%

“…As noted above, purely optical imaging methods have the potential to utilize the new optical characterizations presented herein. 63 The benefits of photoacoustic imaging relative to purely optical imaging methods include better penetration depth and spatial resolution. 64 Although the optical penetration depth in Fig.…”

Section: Discussionmentioning

confidence: 99%