The field of acousto-optical tomography (AOT) for medical applications began in the 1990s and has since developed multiple techniques for the detection of ultrasound-modulated light. Light becomes frequency shifted as it travels through an ultrasound beam. This “tagged” light can be detected and used for focused optical imaging. Here, we present a comprehensive overview of the techniques that have developed since around 2011 in the field of biomedical AOT. This includes how AOT has advanced by taken advantage of the research conducted in the ultrasound, as well as, the optical fields. Also, simulations and reconstruction algorithms have been formulated specifically for AOT imaging over this time period. Future progression of AOT relies on its ability to provide significant contributions to in vivoimaging for biomedical applications. We outline the challenges that AOT still faces to make in vivoimaging possible and what has been accomplished thus far, as well as possible future directions.
Biophotonics and laser medicine are very dynamic and continuously increasing fields ecologically as well as economically. Direct communication with medical doctors is necessary to identify specific requests and unmet needs. Information on innovative, new or renewed techniques is necessary to design medical devices for introduction into clinical application and finally to become established after positive clinical trials as well as medical approval. The long-term endurance in developing light based innovative clinical concepts and devices are described based on the Munich experience. Fluorescence technologies for laboratory medicine to improve non-invasive diagnosis or for online monitoring are described according with new approaches in improving photodynamic therapeutic aspects related to immunology. Regarding clinically related thermal laser applications, the introduction of new laser wavelengths and laser parameters showed potential in the treatment of varicose veins as well as in lithotripsy. Such directly linked research and development are possible when researchers and medical doctors perform their daily work in immediate vicinity, thus have the possibility to share their ideas in meetings by day.
This paper briefly reviews the operational principles and designs of portable in vivo skin imaging prototypes developed at the Biophotonics Laboratory of the Institute of Atomic Physics and Spectroscopy, University of Latvia. Four types of imaging devices are presented. Multi-spectral imagers ensure distant mapping of specific skin parameters (e.g., distribution of skin chromophores). Autofluorescence photobleaching rate imagers show potential for skin tumor assessment and margin delineation. Photoplethysmography video-imagers remotely detect cutaneous blood pulsations and provide real-time information on the human cardiovascular state. Multimodal skin imagers perform the above-mentioned functions by acquiring several spectral and video images using the same image sensor.
This paper presents the state of art of laser technologies in Poland. A list of primary laser technology development centers is included. The involvement of Polish scientists in the development of lasers and fourth generation synchrotron light sources as well as their applications is discussed. The development of laser applications in medical therapy and diagnostics, material micro- and macro-processing as well as environmental monitoring and protection, safety, and security is presented.
The presence of irrelevant and correlated data points in a Raman spectrum can lead to a decline in classifier performance. We introduce support vector machine (SVM)-based recursive feature elimination into the field of Raman spectroscopy and demonstrate its performance on a data set of spectra of clinically relevant microorganisms in urine samples, along with patient samples. As the original technique is only suitable for two-class problems, we adapt it to the multi-class setting. It is shown that a large amount of spectral points can be removed without degrading the prediction accuracy of the resulting model notably.
Hand-held implementations of recently introduced real-time volumetric tomography approaches represent a promising path toward clinical translation of the optoacoustic technology. To this end, rapid acquisition of optoacoustic image data with spherical matrix arrays has attained exquisite visualizations of three-dimensional vascular morphology and function deep in human tissues. Nevertheless, significant reconstruction inaccuracies may arise from speed of sound (SoS) mismatches between the imaged tissue and the coupling medium used to propagate the generated optoacoustic responses toward the ultrasound sensing elements. Herein, we analyze the effects of SoS variations in three-dimensional hand-held tomographic acquisition geometries. An efficient graphics processing unit (GPU)-based reconstruction framework is further proposed to mitigate the SoS-related image quality degradation without compromising the high-frame-rate volumetric imaging performance of the method, essential for real-time visualization during hand-held scans.
In this study, we investigate the effect of pulse waves on the transmission of near-infrared radiation in the outer tissue layers of the human head. This effect is important in using optical radiation to monitor brain conditions based on measuring the transmission changes in the near-infrared radiation between the source and the detector, placed on the surface of the scalp. This is because the signal related to the changes in the width of the subarachnoid space (SAS) due to the pulse wave is modified. These latter changes can be used, for instance, in detecting cerebral edema and in evaluating cerebral oxygenation. The research was performed by modeling the propagation of near-infrared radiation in the tissue layers using a Monte-Carlo method. The main objective of this study was to assess the extent to which the changes in the transmission of near-infrared radiation correspond to the changes in the optical parameters of the tissues of the head and in the width of the subarachnoid layer.
The autofluorescence spectroscopy of biological tissues is a powerful tool for non-invasive detection of tissue pathologies and evaluation of any biochemical and morphological changes arising during the lesions’ growth. To obtain a full picture of the whole set of endogenous fluorophores appearing in the gastrointestinal (GI) tumors investigated, the technique of excitation-emission matrix (EEM) development was applied in a broad spectral region, covering the ultraviolet and visible spectral ranges. We could thus address a set of diagnostically-important chromophores and their alterations during tumor development, namely, collagen, elastin, nicotinamide adenine dinucleotide (NADH), flavins, porphyrins, while hemoglobin’s absorption influence on the spectra obtained could be evaluated as well. Comparisons are presented between EEM data of normal mucosae, benign polyps and malignant carcinoma, and the origins are determined of the fluorescence signals forming these matrices.
The nail plate forms a barrier that limits the effectiveness of drug delivery in the treatment of nail diseases and prevents the outflow of fluid in the case of subungual hematoma formation. Microperforation of the nail plate through laser radiation can increase the effectiveness of drug delivery and ensure the possibility of blood outflow.
This study detected and identified the type and threshold of effects that arise from exposing the nail plate to Yb,Er:Glass (l= 1.54 µm) and Er:YLF (l= 2.81 µm) laser radiation. The rate and efficiency of nail plate ablation by the radiation of these lasers were studied. The effect of the storage time of a freshly extracted nail plate in open air on its ablation rate by Er:YLF (l=2.81 µm) laser radiation was also investigated.
The impact of the Yb,Er:Glass and Er:YLF laser pulses on the nail plate caused bleaching, carbonization, ablation with microcrater formation, and microperforation. The laser energy densities WE (thresholds) required for these effects were determined. The maximum ablation rate for Yb,Er:Glass laser radiation was 8 µm/pulse at WE= 91±2 J/cm2, whereas that for Er:YLF laser radiation was 12 µm/pulse at WE= 10.5±0.5 J/cm2. The maximum ablation efficiency for Yb,Er:Glass laser radiation was 0.1 µm/mJ at WE = 10.5±0.5 J/cm2, whereas that for Er:YLF laser radiation was 4.6 µm/mJ at WE= 5.3±0.3 J/cm2. The laser ablation rate depends on the storage time and conditions of the freshly extracted nail plate. For example, when exposed to Er:YLF laser radiation, the laser ablation rate decreased by half from the initial maximum value in 96 h of air storage and returned to the initial value after 1 h of storage in distilled water.
Mueller matrices were measured for natural (or reference) samples of human nails and samples irradiated by a 2 Gy ionizing radiation dose. The elements of the total Mueller matrix as a function of scattering angle were measured in backscattering mode at a wavelength of 632.8 nm. Several types of depolarizing Mueller matrix decompositions, namely, Ossikovsky, Williams, and Chipman, were calculated as a function of scattering angle for each nail sample. A comparative analysis of the sensitivity of the Mueller matrix decompositions in relation to the problem of emergency dose assessment in nails was performed.
Tumor oxygenation is one of the key factors influencing disease prognosis and the effectiveness of treatment. Assessment of tumor oxygenation levels facilitates the selection of optimum conditions for radiation therapy, and plays an important role in creating alternative regimes of irradiation. Treating tumors with agents capable of increasing tumor oxygenation in order to increase radiosensitivity is a promising avenue of enquiry. Diffuse optical spectroscopy (DOS) allows a noninvasive determination of tissue oxygen levels based on information about the local changes in optical parameters, and the visualization of metabolic processes in the region of interest. DOS allows reconstruction of the two-dimensional distribution of main tissue chromophores that characterize the processes of oxygen supply (oxygenated hemoglobin) and oxygen consumption (deoxygenated hemoglobin), as well as the blood oxygen saturation levels, which indirectly reflect the tissue oxygenation levels. In the present study, a hemorheologic drug, pentoxifylline, which can improve microcirculation in regions with circulatory disturbances, was used for modifying tumor tissue oxygenation. Pliss’s lymph sarcoma (PLS), which is characterized by rapid growth and early occurrence of necrotic areas, was chosen as a tumor model. Tumor oxygenation was monitored by DOS with parallel plane geometry. Pentoxifylline could improve tumor oxygenation by increasing the concentration of oxyhemoglobin. The increased blood oxygen saturation persisted from 30 to 120 min after drug administration. Normal healthy tissue (muscle) and tumor tissue responded differently to the drug. DOS can be used for testing new agents that influence tissue oxygen status and blood-filling rate.
A method for determining and correcting distortions in spectral-domain optical coherence tomography images caused by medium dispersion was developed. The method is based on analysis of the phase distribution of the interference signal recorded by an optical coherence tomography device using an iterative approach to find and compensate for the effect of a medium’s chromatic dispersion on point-spread function broadening in optical coherence tomography. This enables compensation of the impact of medium dispersion to an accuracy of a fraction of a radian (units of percent) while avoiding additional measurements and solution of the optimization problem. The robustness of the method was demonstrated experimentally using model and biological objects.
