Hybrid optoacoustic and ultrasound biomicroscopy monitors’ laser-induced tissue modifications and magnetite nanoparticle impregnation

Abstract

Tissue modification under laser radiation is emerging as one of the advanced applications of lasers in medicine, with treatments ranging from reshaping and regeneration of cartilage to normalization of the intraocular pressure. Laser-induced structural alterations can be studied using conventional microscopic techniques applied to thin specimen. Yet, development of noninvasive imaging methods for deep tissue monitoring of structural alterations under laser radiation is of great importance, especially for attaining efficient feedback during the procedures. We developed a fast scanning biomicroscopy system that can simultaneously deliver both optoacoustic and pulse-echo ultrasound contrast from intact tissues and show that both modalities allow manifesting the laser-induced changes in cartilage and sclera. Furthermore, images of the sclera samples reveal a crater developing around the center of the laser-irradiated spot as well as certain degree of thickening within the treated zone, presumably due to pore formation. Finally, we were able to observe selective impregnation of magnetite nanoparticles into the cartilage, thus demonstrating a possible contrast enhancement approach for studying specific treatment effects. Overall, the new imaging approach holds promise for development of noninvasive feedback control systems that could guarantee efficacy and safety of laser-based medical procedures.

Control of optical transparency and infrared laser heating of costal cartilage via injection of iohexol

“…However, the problem is complicated when the temperature cannot be directly measured in clinical procedure working in contact modes with tissue or for the short laser pulses. In that case the feedback control systems based on the laser‐induced alterations of the tissue optical properties or optoacoustic signal are being developed .…”

Short and long-term phototoxicity in cells expressing genetic reporters under nanosecond laser exposure

“…For this, the fast scanning setup employed a coaxially aligned scanning head, comprising the focused illumination and ultrasound detector which scans across a planar field of view of 4x4 mm² within 25 s. The laser PRF was set at ~6.2 kHz. Three-dimensional image volumes are then rendered using nearest neighbor interpolation of the zig-zag trajectory of the scanning head into a regular two-dimensional grid [31]. The effect of oscillations in the energy of the laser pulses is corrected using the signals of a photodiode (DET10A/M, Thorlabs, Newton, New Jersey, USA) placed in the optical path.…”

Combining microscopy with mesoscopy using optical and optoacoustic label-free modes

“…There have been many approaches that attempt to combine different contrast mechanisms in microscopy. Optoacoustic microscopy in particular has been combined with second harmonic generation (SHG) microscopy 10 , two-photon and confocal fluorescence microscopy 11 , optical coherence tomography (OCT) 12 , pulse-echo ultrasound imaging 13 and single-photon excitation autofluorescence imaging 14 . However, hybrid implementations achieving multi-scale optical imaging have not been common.…”