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AffiliationFEDERAL RESEARCH CENTER A.V. GAPONOV-GREKHOV INSTITUTE OF APPLIED PHYSICS OF THE RUSSIAN ACADEMY OF SCIENCES,

Research area 05 - FUNDAMENTAL RESEARCH IN MEDICINE, 05-602 - Physical methods of medical diagnostics. Tomography

KeywordsOptoacoustics, raster scanning, clinical angiography, portable microscope, cardiovascular diseases, microvasculature.

Annotation
Morpho-functional pathological changes in the microcirculatory bed associated with the development of a large group of socially significant diseases and leading to disabling complications are being actively studied in terms of prediction, diagnosing and new treatment perspectives for a number of potentially life-threatening conditions that are important for modern health care. The use of non-invasive clinical diagnostics of peripheral vessels pathology is limited either by their infrastructural and technical complexity (MRI and PET), or by the resolution insufficient for imaging the microvascular bed (MRI, ultrasound), by the requirement to introduce additional substances (angiography, CT-angiography, MRT-angiography, iontophoresis) and by depth of investigation (optical methods). The aim of this project is to create a new approach to the medical diagnosis of vascular pathologies, based on the development and clinical application of new technologies of raster-scan optoacoustic visualization. The developed angiographic device will be based on the so-called optoacoustic (OA) microscopy with acoustic resolution, actively developed by P.V.Subochev's group in the department of radiophysical methods in medicine, IAP RAS. OA microscopy is based on the mechanical scanning of the investigated biological tissue with a compact OA probe consisting of a spherically-focused single-element ultrasound antenna and a fiber-optic illumination system. As part of the preliminary work, the project team developed a stationary OA microscope that allows the implementation of angiography of soft biological tissues with a spatial resolution of 30 um at a depth of up to 3 mm. However, the previously developed stationary OA microscope had significantly limited clinical applications, having a significant weight (1 kg), a long scanning time (5 minutes) and not allowing scanning at the OA probe positions differing from the vertical. To reach the project goal, we have planned a number of profound technological improvements in the existing experimental approaches to raster-scan OA angiography. During the first year of the project, a numerical model of OA probe will be developed and verified, designed to optimize its technical characteristics. Based on the results of the optimization, a compact OA probe weighing no more than 10 grams will be developed and tested on phantoms simulating the acoustic and optical properties of human superficial tissues in normal conditions and in pathologies. During the second year of the project, a deep processing of the moving part of the previously developed stationary OA microscope will be completed, aimed at ensuring its clinical use in a handheld mode with fast (up to 30 seconds) scanning time due to the use of a compact OA probe. In parallel with the improvement of portability of the OA scanner (Figure 3a), improvement of the reconstructive algorithms designed to convert OA data into angiographic images in real time will be carried out. For the purpose of preliminary in vivo testing of a portable OA microscope, a study of the vascular network of the superficial tissues of healthy volunteers of various age groups will be conducted. The capabilities of the device for determining the functional and structural features of the microvasculature of the skin of volunteers will be determined according to the parameters of vessels size, shape, depth, blood supply and density. The third year of the project is completely devoted to the study of the capabilities of the device developed by OA in a clinical setting. Based on the results of clinical trials, numerical methods for the quantitative characterization of OA angiograms (calculation of vascular density and diameter) will be developed. The ergonomics of the OA scanner for the physician and patient will be improved. As a result, the new portable OA microscope will provide clinicians with unique opportunities to study vascular pathologies unattainable when using other modern methods of angiography.

Expected results
The project is dedicated to the development of a portable optoacoustic scanner for the clinical diagnosis of vascular pathologies. Unlike optical or acoustic imaging methods, optoacoustics is based on recording ultrasonic pulses generated by laser radiation and combine the advantages of optics and ultrasound, providing highly specific molecular optical contrast without loss of spatial resolution due to scattering of photons at great depths. During the implementation of the project, it is planned to solve eight tasks divided into three years and associated with thorough theoretical and experimental research: 1. within the task of numerical OA modelling, the problem of optimization of the technical characteristics of OA probe for raster-scan OA angiography will be solved (the first year of the project); 2. based on the results of numerical optimization, a compact OA probe weighing less than 10 grams will be developed, consisting of a focused ultrasound antenna with a broadband amplifier and a fiber-optic illumination system (the first year of the project); 3. on phantoms imitating the acoustic and optical properties of real biological tissues under normal and pathological conditions, the achieved characteristics of the OA probe will be determined: spatial resolution lesss than 30 um and diagnostics depth more than 3 mm (first year of the project); 4. based on the compact OA probe, a portable (handheld) OA microscope weighing up to 300 grams with a fast (up to 30 seconds) three-dimensional scanning time will be developed and automated (the second year of the project); 5. accelerated OA reconstruction algorithms will be developed to convert OA data from a portable OA microscope to real-time angiographic images (second year of the project); 6. within the task of preliminary in vivo testing of a portable OA microscope on healthy volunteers of different age groups, the device will be examined to determine the functional and structural features of the microvasculature of the skin by the parameters of vessels size, shape, depth, blood supply and density; 7. for the study of the clinical capabilities of the portable OA microscope, angiographic OA microcirculation studies will be performed on groups of patients with confirmed diagnoses, as well as on the control group without identified vascular pathologies (the third year of the project); 8. Based on the results of clinical trials, the ergonomics of the OA scanner for the physician and patient will be improved; numerical methods will be developed to characterize the OA angiograms (the third year of the project). The stated results will have an important scientific and social significance. The area of practical application of the results of the project is medical diagnostics. The results of the work can be used: - by scientific organizations for the study of tissue microcirculation, as well as for creation of new methods of biomedical diagnostics; - by governmental and commercial structures working in the field of development and commercialization of new research and medical diagnostic devices; - public and private clinics for the diagnosis of vascular pathologies.

Annotation of the results obtained in 2021
Additional hardware and software improvements of the developed OA microscope were made. Before moving to the clinical conditions, a complete disassembly of the OA of the microscope and maintenance of the main components were carried out. Technologies for additional protection of the piezoelectric surface of an ultrasonic antenna have been developed and applied. Sealing of the optical chamber containing the laser and passive optical components was provided. The fluoroplastic guides of the fast piezoscanner M-664 were replaced. To enable separate visualization of blood-filled structures of different sizes, an additional program code has been implemented that separates the initial spectrum of OA signals into two frequency subranges of 1-25 MHz and 25-50 MHz. In collaboration with the group of Prof. Daniel Ryazansky (ETH Zurich) the maximum resolution of the ultrasonic antenna of the OA scanner at a level of less than 30 microns was demonstrated. Ergonomics of the OA scanner for the doctor and patient was improved. Two types of interfaces between the OA scanner and the patient (sterilizable immersion chambers and disposable rings with a biocompatible adhesive coating) have been developed. Specialized painting of all parts of the OA microscope was carried out. The capabilities of OA microscope for determining the structural features of superficial tissues vascular bed with a number of vasculopathies were evaluated in clinic (Clinic of the Institute of Applied Physics, Russian Academy of Sciences). The study included volunteers without identified vascular pathologies, as well as patients with previously diagnosed venous thrombosis, chronic venous and arterial insufficiency of various degrees, diabetes mellitus with microangiopathy and chronic arterial insufficiency of various degrees, Raynaud's syndrome. Verification of such signs of circulatory disorders as blood content, density, diameter, tortuosity of vessels was carried out in comparison with normal tissues separately for peripheral and large vessels. An increase in blood content of superficial tissues has been shown in pathological conditions such as venous thrombosis and diabetes mellitus with pathological neoangiogenesis without severe arterial insufficiency. A decrease in vascular density was revealed in Raynaud's syndrome, chronic arterial insufficiency of the 3rd degree. An increase in the diameter of vessels and their tortuosity in venous thrombosis was demonstrated. For Raynaud's syndrome, OA images were obtained before and after treatment. The possibilities of the method for detecting changes in the vascular bed in dynamics are demonstrated. Compared with the initial data, after therapy an increase in the density of visualized vessels was shown.

Publications

1. Li W., Hofmann U.A.T., Rebling Jo., Zhou Q., Chen Zh., Ozbek A.,Gong Yu., Subochev P..V., Razansky D., Deán-Ben X.L. Broadband Model-Based Optoacoustic Mesoscopy Enables Deep-Tissue Imaging beyond the Acoustic Diffraction Limit Laser and Photonics Reviews, Number 2100381, paper. 1-11 (year - 2022) https://doi.org/10.1002/lpor.202100381

2. Turchin I.V., Bano Sh., Kirillin M.Yu.,Orlova A.G., Perekatova V.V., Plekhanov V.I., Sergeeva E.A., Kurakina D.A., Khilov A.V., Kurnikov A.A., Subochev P.V., Shirmanova M.V., Komarova A.D., Yuzhakova D.V., Gavrina A.I., Mallidi S., Hasan T. Combined Fluorescence and Optoacoustic Imaging for Monitoring Treatments against CT26 Tumors with Photoactivatable Liposomes Cancers MDPI, Cancers 2022, 14 (1), 197, paper 1-22 (year - 2021) https://doi.org/10.3390/cancers14010197

3. Perekatova V.V., Kirillin M.Yu.,Turchin I.V., Khilov A.V., Nemirova S.V., Kurnikov A.A., Orlova A.G., Pavlova K.G., Kazakov V.V., Subochev P.V. Quantification of Microvasculature Parameters in Normal and Pathological Tissues Based on Three-dimensional Raster-scan Optoacoustic Angiography OSA Technical Digest (Optical Society of America, 2021), European Conferences on Biomedical Optics 2021 (ECBO), paper ETu5B.8 (year - 2021)

4. Subochev P.V., Deán-Ben X.L, Chen Zh., Orlova A.G, Razansky D. PVDF Spherical Matrix Array for High Resolution Cerebral Optoacoustic Micro-Angiography of Rodents OSA Technical Digest (Optical Society of America, 2021), European Conferences on Biomedical Optics 2021 (ECBO), paper ETu4D.6 (year - 2021)

5. - Invited presentation of Pavel Subochev at ECBO-2021 (The World of Photonics Congress ) Ютюб канал photoacoustics.ru, - (year - )

Annotation of the results obtained in 2019
A theoretical model has been developed for a compact optoacoustic (OA) probe, designed for pulsed OA angiography of human superficial tissues and consisting of a fiber and a spherical ultrasonic antenna. The calculations of the spatial distribution of fluence and the initial distribution of pressure were carried out for point-like blood vessels contained in diffusion-scattering half-space. As optical parameters, the averaged values of the optical coefficients for human skin were used under normal conditions and for various pathologies. The calculation of model OA signals (A-scans and B-scans) detected by a focused antenna from blood vessels was carried out using a software package http://k-wave.org/. As the acoustic parameters of the skin (density, speed of sound, frequency-dependent attenuation coefficient of ultrasound), literary values were used. Based on the results of numerical simulation, a compact OA probe was developed, consisting of a broadband PVDF antenna with a high numerical aperture (0.71), a broadband (0.3-80 MHz) matching amplifier, and a multimode optical fiber. To ensure smooth adjustment of the antenna focus relative to the surface of the medium under study, a spring-screw drive was built into the OA probe. The developed device for two-dimensional OA scanning consists of a fast (400 mm / s) piezoelectric scanner and a load-lifting (25 N) step-screw mechanism. To enable scanning at an arbitrary position, the OA probe was placed in an immersion chamber with a light / sound-transparent window. To increase the functional value of the OA scanner, the option of wavelength selection (532 or 1064 nm) for OA sensing was ensured. Phantom experiments were conducted with a developed OA probe. Using a two-component phantom as a model of human superficial tissues with blood vessels, an experimental validation of the numerical model of the OA probe was carried out. The spatial resolution of the developed OA scanner was measured, amounting to 31-33 microns. Using the calibrated flat emitter at 10 and 30 MHz and a flat PVDF detector of equivalent area, the noise equivalent pressure of the ultrasonic antenna was estimated, amounting to NEP ~ 12 Pa. To experimentally test the possibility of OA imaging of blood vessels with a new OA probe, an in vivo experiment was conducted with a rabbit ear. Sequential OA scanning of an object at two wavelengths of 532 and 1064 nm was provided. Along with OA A scans, at each scanning position ultrasound (US) A scans in the laser-ultrasound (LU) mode were recorded. Three-dimensional composition of OA / US images is available at https://www.youtube.com/watch?v=dKqomRljlII While a wavelength of 532 nm is an isosbestic point of optical absorption of oxy / deoxyhemoglobin, at a wavelength of 1064 nm, the optical absorption of oxygenated blood 10 times prevails over the absorption of non-oxygenated blood. The provided technical possibility of OA probing at an additional wavelength (1064 nm) can therefore help to distinguish between blood vessels with varying degrees of oxygenation in human surface tissues.

Publications

1. A.A. Anosov, M.Yu. Kirillin, A.G. Orlova, A.V. Erofeev, A.S. Sharakshane, M.I. Shcherbakov, E.A. Sergeeva, Y. Saijo and P.V. Subochev Volumetric quantification of skin microcirculation disturbance induced by local compression Laser Physics Letters, - (year - 2020)

2. A. Orlova, M. Sirotkina, I. Turchin, and P. Subochev In Vivo Raster-Scan Optoacoustic Angiography of Superficial Tissues OSA Technical Digest (Optical Society of America, 2020), Biophotonics Congress: Biomedical Optics 2020 (Translational, Microscopy, OCT, OTS, BRAIN), paper STu4D.4. (year - 2020)

3. - Youtube-канал нашей ОА группы Youtube, - (year - )

Annotation of the results obtained in 2020
A portable optoacoustic (OA) microscope has been developed, consisting of an OA scanner and medical robotic arm with built-in auxiliary equipment. The developed portable OA microscope provides the possibility of simultaneous optoacoustic and laser-ultrasound imaging of human superficial tissues with an arbitrary orientation of the OA probe. Numerical methods of OA reconstruction and computer algorithms implementing them have been developed. The developed numerical methods allow converting OA data into angiographic images. When tested on a computer based on Intel Core i9-9900KF and GPU RTX 2070 built into a portable OA microscope, the total time required for sequential application of all the developed methods to a three-dimensional OA dataset containing (200 x 200 x 200) voxels has been reduced from 11 seconds to more practical 3 seconds. In phantom experiments, the lateral and axial resolution of the developed portable OA microscope was measured, amounting to 55 μm and 29 μm, respectively. In the course of preliminary in vivo experiments on the rabbit ear, the capabilities of the OA scanner for trimodal diagnostics were demonstrated. High-contrast (44 dB) OA angiography of the microvascular bed was realized at a wavelength of 532 nm, which is the isobestic point of optical absorption for oxy- and deoxyhemoglobin. In laser-ultrasound mode, the fine internal structure of the rabbit auricle, represented by groups of cartilage cells, was visualized. By means of performing complementary OA imaging at an additional wavelength of 1064 nm, corresponding to a higher optical absorption of oxyhemoglobin, the possibility of qualitative differentiation of veins and arteries by two-wavelength 532/1064 nm OA imaging was demonstrated. Using a portable OA microscope, in vivo images of the vasculature of the skin of healthy volunteers of different age groups were obtained. Based on the obtained angiograms, parameters were selected for a qualitative and quantitative description of the state of the microvasculature of tissues. Images of the vasculature of healthy volunteers were obtained at various pressures of OA scanner to the tissue surface, and the optimal pressure values were identified. The arteriographic capabilities of the OA microscope for the dynamic study of the response of the vascular system to changing temperature were determined. Web-page of our project team: http://photoacoustics.ru/ Our Youtube-channel: https://www.youtube.com/channel/UCJmdxJAykIrxp2KeeDR4P5Q

Publications

1. Valeriya Perekatova, Svetlana Nemirova, Anna Orlova, Mikhail Kirillin, Alexey Kurnikov, Ksenia Pavlova, Aleksandr Khilov, Andrey Kovalchuk and Pavel Subochev Three-dimensional dual-wavelength optoacoustic angiography reveals arteriovenous anastomoses Laser Physics Letters, V. 18, P. 045601 (7pp) (year - 2021) https://doi.org/10.1088/1612-202X/abe7df

2. Anna G. Orlova, Ksenia G. Pavlova, Aleksey A. Kurnikov, Marina A. Sirotkina, Anna V. Maslennikova, Mikhail Yu. Kirillin, Dmitriy V. Skamnitsky, Ilya V. Turchin, Pavel V. Subochev In vivo applications of raster-scan optoacoustic angiography Proceedings of SPIE, Proc. SPIE 11642, Photons Plus Ultrasound: Imaging and Sensing 2021, 1164209 (year - 2021) https://doi.org/10.1117/12.2578206

3. Pavel Subochev, Ekaterina Sergeeva, Mikhail Kirillin, Daria Kurakina, Anna Orlova, Alexey Kurnikov, Xosé Luís Deán-Ben, Zhenyue Chen, Daniel Razansky Optimization of light and sound delivery for in vivo whole-brain optoacoustic angiography of rodents Proceedings of SPIE, Proc. SPIE 11642, Photons Plus Ultrasound: Imaging and Sensing 2021, 116422N (year - 2021) https://doi.org/10.1117/12.2579210

4. Pavel Subochev, Xosé Luís Deán-Ben, Zhenyue Chen, Anna Orlova, Daniel Razansky Polymer-based spherical matrix array for high resolution real-time volumetric optoacoustic micro-angiography Proceedings of SPIE, Proc. SPIE 11642, Photons Plus Ultrasound: Imaging and Sensing 2021, 116421V (year - 2021) https://doi.org/10.1117/12.2579204

5. - Ученые ИПФ РАН создали уникальную антенну для диагностики опасных болезней без хирургического вмешательства Нижегородская правда, выпуск 10/08/2020, первая полоса (year - )

6. - Дистанционное сканирование сосудов — российское ноу-хау Россия 1, Утро России. Эфир от 16.09.2020 (05:00). (year - )

7. - Рассмотрели капилляры тоньше волоса Российская газета, Российская газета - Неделя - Приволжье № 154(8208) (year - )