Photothermal tomographic imaging of optically absorbing inclusions in human skin in vivo

Katja Arh; Sara Klopčič; Tomaž Cvetko; Boris Majaron

doi:10.1117/12.3000045

12 March 2024 Photothermal tomographic imaging of optically absorbing inclusions in human skin in vivo

Katja Arh, Sara Klopčič, Tomaž Cvetko, Boris Majaron

Proceedings Volume 12816, Photonics in Dermatology and Plastic Surgery 2024; 1281606 (2024) https://doi.org/10.1117/12.3000045
Event: SPIE BiOS, 2024, San Francisco, California, United States

Abstract

The concept of photothermal tomography (PTT) involves spatially and temporally resolved detection of blackbody emission from the sample surface after irradiation with a short light pulse. In principle, this allows reconstruction of the light-induced temperature field inside the sample, thus enabling three-dimensional imaging of absorbing structures in strongly scattering biological tissues and organs. However, development of accurate and robust PTT methodology has proven difficult due to the large size and severe ill-posedness of the underlying inverse problem, aggravated by the inherently low signal-to-noise ratios of active infrared radiometry. We discuss here our recently developed PTT system and its first application to human skin in vivo. The experimental setup involves a medical-grade laser emitting milisecond pulses at 532 nm, and a fast mid-infrared camera equipped with a microscope objective. A custom code written in Python is used to reconstruct three-dimensional images of the absorbing structures by performing iterative multidimensional minimization of the difference between the analytically predicted and experimental radiometric record, using a projected v-method algorithm. The described approach produces a rather sharp and high-contrast tomographic image of a tattoo layer in a human volunteer’s skin with the onset depth of ~0.15 mm. No evident artifacts or even noise appear elsewhere in the reconstructed volume. Applying quadratic binning of the radiometric record significantly reduced the computational load, enabling us to reconstruct a volume of 5.6 x 2.8 x 0.9 mm³ with nominal resolution of 25 x 25 x 15 μm³ using a personal computer in less than one minute.

Conference Presentation

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Katja Arh, Sara Klopčič, Tomaž Cvetko, and Boris Majaron "Photothermal tomographic imaging of optically absorbing inclusions in human skin in vivo", Proc. SPIE 12816, Photonics in Dermatology and Plastic Surgery 2024, 1281606 (12 March 2024); https://doi.org/10.1117/12.3000045

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