SignificanceEndoscopic screening for esophageal cancer (EC) may enable early cancer diagnosis and treatment. While optical microendoscopic technology has shown promise in improving specificity, the limited field of view (<1 mm) significantly reduces the ability to survey large areas efficiently in EC screening.AimTo improve the efficiency of endoscopic screening, we propose a novel concept of end-expandable endoscopic optical fiber probe for larger field of visualization and for the first time evaluate a deep-learning-based image super-resolution (DL-SR) method to overcome the issue of limited sampling capability.ApproachTo demonstrate feasibility of the end-expandable optical fiber probe, DL-SR was applied on simulated low-resolution microendoscopic images to generate super-resolved (SR) ones. Varying the degradation model of image data acquisition, we identified the optimal parameters for optical fiber probe prototyping. The proposed screening method was validated with a human pathology reading study.ResultsFor various degradation parameters considered, the DL-SR method demonstrated different levels of improvement of traditional measures of image quality. The endoscopists’ interpretations of the SR images were comparable to those performed on the high-resolution ones.ConclusionsThis work suggests avenues for development of DL-SR-enabled sparse image reconstruction to improve high-yield EC screening and similar clinical applications.
Barrett’s esophagus is the main pre-cancer risk factor for the development of esophageal adenocarcinoma. Over the last decades, the incidence rate of esophageal adenocarcinoma increases exponentially in the Western World. Endoscopic screening and minimally-invasive treatment of Barrett’s esophagus are challenging due to large surface area of the lining (1-20 cm). Current microendoscopy technologies have shown high specificity; however, its sensitivity is low due to tiny field-of-view (the probe diameter is 100-1000 μm). Therefore, we proposed a novel approach with end-expandable optical fiber brush to collect endoscopic sparse imaging data and deep learning super-resolution enhancement to provide high yield diagnostics.
The experience of research on the analysis of industrial and atmospheric aerosols by atomic emission spectroscopy is summarized. Various methods of Petryanov filters preparation for spectral analysis have been investigated. It has been shown that for all brands of these aerosol analytical filters, the best at the moment is a combined method of sample preparation. To optimize the conditions of atomic emission analysis, an appropriate carrier was selected. On the basis of the research conducted, a technique for the atomic emission determination of metals in atmospheric air samples, the working area and emissions has been developed.
The formation of amyloid – aggregate of misfolded proteins – is associated with more than 50 human pathologies, including Alzheimer’s disease, Parkinson’s disease, and Type 2 diabetes mellitus. Investigating protein aggregation is a critical step in drug discovery and development of therapeutics targeted to these pathologies. However, screens to identify protein aggregates are challenging due to the stochastic character of aggregate nucleation. Here we employ photoacoustics (PA) to screen thermodynamic conditions and solution components leading to formation of protein aggregates. Particularly, we study the temperature dependence of the Gruneisen parameter in optically-contrasted, undersaturated and supersaturated solutions of glycoside hydrolase (lysozyme). As nucleation of protein aggregates proceeds in two steps, where the first is liquid-liquid separation (rearrangement of solute’s density), the PA response from complex solutions and its temperature-dependence monitor nucleation and differentiate undersaturated and supersaturated protein solutions. We demonstrate that in the temperature range from 22 to 0° C the PA response of contrasted undersaturated protein solution behaves similar to water and exhibits zero thermal expansion at 4°C or below, while the response of contrasted supersaturated protein solution is nearly temperature independent, similar to the behavior of oils. These results can be used to develop a PA assay for high-throughput screening of multi-parametric conditions (pH, ionic strength, chaperone, etc.) for protein aggregation that can become a key tool in drug discovery, targeting aggregate formation for a variety of amyloids.
Noninvasive real-time temperature imaging during thermal therapies is able to significantly improve clinical outcomes. An optoacoustic (OA) temperature monitoring method is proposed for noninvasive real-time thermometry of vascularized tissue during cryotherapy. The universal temperature-dependent optoacoustic response (ThOR) of red blood cells (RBCs) is employed to convert reconstructed OA images to temperature maps. To obtain the temperature calibration curve for intensity-normalized OA images, we measured ThOR of 10 porcine blood samples in the range of temperatures from 40°C to −16°C and analyzed the data for single measurement variations. The nonlinearity (ΔTmax) and the temperature of zero OA response (T0) of the calibration curve were found equal to 11.4±0.1°C and −13.8±0.1°C, respectively. The morphology of RBCs was examined before and after the data collection confirming cellular integrity and intracellular compartmentalization of hemoglobin. For temperatures below 0°C, which are of particular interest for cryotherapy, the accuracy of a single temperature measurement was ±1°C, which is consistent with the clinical requirements. Validation of the proposed OA temperature imaging technique was performed for slow and fast cooling of blood samples embedded in tissue-mimicking phantoms.
KEYWORDS: Prostate, Tissues, Ultrasonography, Temperature metrology, Blood, In vivo imaging, Prostate cancer, Image filtering, Data acquisition, Calibration
Cryoablation of prostate cancer is an FDA approved clinical procedure, which involves repetitive rapid cooling of a lesion to lethal temperatures of -40°C and below. The major drawback of the technique is the insufficient control over the fast thermal processes that may result in severe complications (impotence, incontinence, perforation of the rectal wall) and morbidity. The developed optoacoustic imaging technique provides non-invasive real-time temperature mapping of tissue adjacent to prostate and enables more efficient control over the procedure, which is necessary to reduce side effects and accelerate the physician’s learning curve. In these studies we successfully demonstrated real-time transrectal optoacoustic imaging during prostate cryoablation in live canine model focused on optoacoustic thermography of the rectal wall within the depth of 1cm. Our method utilized previously discovered universal thermal dependence of the normalized optoacoustic response of blood. Nanosecond-pulse radiation of Ti-Sapphire laser tuned to the isosbestic point of hemoglobin (802±3 nm) was delivered via fiberoptic illuminators assembled on both sides of the linear array of the 128-channel transrectal ultrasound probe. Temperature readouts at discrete locations inside and nearby prostate were also performed using standard transperineal needle sensors. The effect of homeostasis on optoacoustic imaging in live tissue was examined during cooling and shown to be significant only within the range of ±1.5°C in respect to the body temperature. Accuracy of in vivo optoacoustic temperature measurements was determined as ±2°C for the range of temperature from +35 to -15°C, which is more than sufficient for tracking the essential isotherms in the course of clinical procedures.
We found and interpreted the universal temperature-dependent optoacoustic (photoacoustic) response (ThOR) in blood; the normalized ThOR is invariant with respect to hematocrit at the hemoglobin’s isosbestic point. The unique compartmentalization of hemoglobin, the primary optical absorber at 805 nm, inside red blood cells (RBCs) explains the effect. We studied the temperature dependence of Gruneisen parameter in blood and aqueous solutions of hemoglobin and for the first time experimentally observed transition through the zero optoacoustic response at temperature T0, which was proved to be consistent for various blood samples. On the other hand, the hemoglobin solutions demonstrated linear concentration function of the temperature T0. When this function was extrapolated to the average hemoglobin concentration inside erythrocytes, the temperature T0 was found equivalent to that measured in whole and diluted blood. The obtained universal curve of blood ThOR was validated in both transparent and light scattering media. The discovered universal optoacoustic temperature dependent blood response provides foundation for future development of non-invasive in vivo temperature monitoring in vascularized tissues and blood vessels.
Optoacoustic (photoacoustic) imaging is being adopted for monitoring tissue temperature during hypothermic and hyperthermic cancer treatments. The technique’s accuracy benefits from the knowledge of speed of sound (SoS) and acoustic coefficient of attenuation (AcA) as they change with temperature in biological tissues, blood, and acoustic lens of an ultrasound probe. In these studies we measured SoS and AcA of different ex vivo tissues and blood components (plasma and erythrocyte concentrates) in the temperature range from 5°C to 60°C. We used the technique based on measurements of time-delay and spectral amplitude of pressure pulses generated by wideband planar acoustic waves propagating through the interrogated medium. Water was used as a reference medium with known acoustic properties. In order to validate our experimental technique, we measured the temperature dependence of SoS and AcA for aqueous NaCl solution of known concentration and obtained the results in agreement with published data. Similar to NaCl solution and pure water, SoS in blood and plasma was monotonously increasing with temperature. However, SoS of erythrocyte concentrates displayed abnormalities at temperatures above 45°C, suggesting potential effects from hemoglobin denaturation and/or hemolysis of erythrocytes. On the contrary to aqueous solutions, the SoS in polyvinyl-chloride (plastisol) – a material frequently used for mimicking optical and acoustic properties of tissues – decreased with temperature. We also measured SoS and AcA in silicon material of an acoustic lens and did not observe temperature-related changes of SoS.
A new experimental approach for measurements of temperature dependence of the Grüneisen parameter in optically absorbing solutions is proposed. Two-dimensional optoacoustic (OA) imaging is used to improve accuracy of signal amplitude measurements and spatial localization of the studied samples. We estimated OA response of optically absorbing solutions measuring median intensity of OA images within the region of interest (ROI) as a function of temperature. We showed that when normalized to its value at a particular temperature, OA image intensity becomes an accurate metric reflecting temperature changes of Grüneisen parameter regardless of local optical fluence and absorbance, assuming those remain constant with temperature. Using the proposed method we studied temperature dependence of aqueous solutions of nickel and cupric sulfate in the range from 4 to 40°C. Obtained results were compared with temperature dependence for the Grüneisen parameter of DI-water, which we measured by using carbon ink colloid. We also found that Grüneisen-temperature relationship for nickel sulfate exhibits linear trend with respect to the concentration, and is independent of coupling medium and laser excitation wavelength.In the future, the developed methodology could be adopted for important applications of in vivo optoacoustic temperature monitoring.
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