Photoacoustic imaging
Citation, DOI, disclosures and article data
At the time the article was created Bálint Botz had no recorded disclosures.
View Bálint Botz's current disclosuresAt the time the article was last revised Andrew Murphy had no recorded disclosures.
View Andrew Murphy's current disclosures- Optoacoustic imaging
- Optoacoustic tomography
- Photoacoustic imaging (PAI)
Photoacoustic or optoacoustic imaging (PAI) is an emerging imaging modality that utilizes a hybrid approach by using optical illumination of endogenous materials or administered fluorescent tracers, and consequent detection of the ultrasound waves released due to thermoelastic expansion.
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Physics
During photoacoustic imaging, a typically nanosecond, narrow bandpass laser or LED illumination is used to excite biological tissues. Molecules absorb the optical energy and convert it to heat, which in turn results in thermoelectric expansion of the investigated tissue. This expansion generates acoustic waves that can be detected by US transducers. Clinical use of optical imaging has been hampered by the limited penetration of light in biological tissues. Photoacoustic imaging partially overcomes this limitation by using the emitted US waves for detection, increasing the maximum depth of the imaging to several centimeters.
The most promising aspect of photoacoustic imaging in clinical imaging is its ability to selectively detect naturally occurring chromophores with distinct optical absorption spectra, such as hemoglobin, lipids, melanin, and water 1.
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Current use and potential future applications
Label-free photoacoustic imaging is a non-invasive method similar to the conventional US, and can be readily utilized in a variety of tasks. It can differentiate deoxyhemoglobin and hemoglobin, thereby directly visualizing ischemia/hypoxia. Superficial, pigmented lesions (e.g. melanoma) can also be visualized directly. Label-free photoacoustic imaging of tissue vascularity has been successfully employed in e.g. imaging of breast cancers, skin tumors, psoriatic skin lesions, wound healing, and inflammation of the small joints 2-5. PAI has been also proposed as a tool to image disease activity in Crohn disease 6. With the light source easily integrated into a linear array, US transducer photoacoustic imaging can be readily utilized as an adjunct in sonography.
The clinically approved fluorophores indocyanine green, and methylene blue can also be depicted with photoacoustic imaging as can most other fluorescent tracers 1. Selective labeling with these chromophores (e.g. labeled peptides or antibodies) can open up new perspectives in clinical molecular imaging.
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See also
References
- 1. Attia ABE, Balasundaram G, Moothanchery M, Dinish US, Bi R, Ntziachristos V, Olivo M. A review of clinical photoacoustic imaging: Current and future trends. Photoacoustics. 2019 Nov 7;16:100144. doi: 10.1016/j.pacs.2019.100144. PMID: 31871888; PMCID: PMC6911900.
- 2. Li Lin, Peng Hu, Junhui Shi, Catherine M. Appleton, Konstantin Maslov, Lei Li, Ruiying Zhang, Lihong V. Wang. Single-breath-hold photoacoustic computed tomography of the breast. Nature Communications. 9 (1): 1. doi:10.1038/s41467-018-04576-z
- 3. Juan Aguirre, Mathias Schwarz, Natalie Garzorz, Murad Omar, Andreas Buehler, Kilian Eyerich, Vasilis Ntziachristos. Precision assessment of label-free psoriasis biomarkers with ultra-broadband optoacoustic mesoscopy. Nature Biomedical Engineering. 1 (5): 1. doi:10.1038/s41551-017-0068
- 4. Petri M, Petri SI, Petri JJ, Petri LJ, Petri SA, Petri DJ, Petri SD, Petri KJ, Petri. Photoacoustic imaging of real-time oxygen changes in chronic leg ulcers after topical application of a haemoglobin spray: a pilot study. (2016) Journal of wound care. doi:10.12968/jowc.2016.25.2.87 - Pubmed
- 5. van den Berg PJ, Daoudi K, Bernelot Moens HJ, Steenbergen W. Feasibility of photoacoustic/ultrasound imaging of synovitis in finger joints using a point-of-care system. Photoacoustics. 2017 Aug 31;8:8-14. doi: 10.1016/j.pacs.2017.08.002. PMID: 28913168; PMCID: PMC5587869.
- 6. Waldner MJ, Knieling F, Egger C, Morscher S, Claussen J, Vetter M, Kielisch C, Fischer S, Pfeifer L, Hagel A, Goertz RS, Wildner D, Atreya R, Strobel D, Neurath MF. Multispectral Optoacoustic Tomography in Crohn's Disease: Noninvasive Imaging of Disease Activity. Gastroenterology. 2016 Aug;151(2):238-40. doi: 10.1053/j.gastro.2016.05.047. Epub 2016 Jun 3. PMID: 27269244.
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