Endoscopic iso-pathlength self-calibration for direction-resolved retrieval of tissue optical properties.

The ultrasound-assisted transport of drugs or fluorophore-loaded nanoagents plays an important role in the desirable drug delivery and imaging contrasts. Unlike conventional ultrasound techniques that rely on thermal or cavitation effects, this study aims to conduct an experimental investigation into the dynamics of interstitial fluid streaming and tissue recovery in ex vivo chicken breast and porcine loin muscle tissues during and after ultrasound exposures, which has not been experimentally investigated in the literature. Biological tissues consist of both a fluid and a solid matrix, and an ultrasound beam compresses the tissues within a small focal volume from all directions, which generates macroscopic streaming of interstitial fluid and compression of the tissue's solid matrix. After the ultrasonic exposure, the solid matrix undergoes recovery, leading to a backflow of the fluid matrix. Temperature-insensitive sulforhodamine-101 encapsulated poly(lactic-co-glycolic acid) nanoparticles with an average diameter size of 175 nm were locally injected into ex vivo chicken breast and porcine loin muscle tissues to study the ultrasound-induced dynamics in the tissues during and after ultrasound exposure by analyzing the distribution of fluorescence. The changes in fluorescence over time caused by the streaming and backflow of interstitial fluid were studied with two ex vivo tissue models, and a faster recovery was observed in porcine tissues compared with chicken tissues. The ultrasound-induced transportability of the nanoagent in porcine muscle tissues was much higher (∼8.75 times) than in chicken breast tissue likely due to structural differences. The study reveals a promising, non-invasive strategy for enhancing drug delivery in dense tissues by leveraging mechanical ultrasound effects, potentially advancing therapeutic and diagnostic applications.

<p><strong>Purpose:</strong></p> <p>The aims of this study are: (a) to investigate the capability of photoacoustic (PA) method in detecting high-intensity focused ultrasound (HIFU) treatments in muscle tissues<em>in vitro</em>; and (b) to determine the optical properties of HIFU-treated and native tissues in order to assist in the interpretation of the observed contrast in PA detection of HIFU treatments.</p> <p><strong>Methods:</strong></p> <p>A single-element, spherically concaved HIFU transducer with a centre frequency of 1 MHz was utilized to create thermal lesions in chicken breast tissues<em>in vitro</em>. To investigate the detectability of HIFU treatments photoacoustically, PA detection was performed at 720 and 845 nm on seven HIFU-treated tissue samples. Within each tissue sample, PA signals were acquired from 22 locations equally divided between two regions of interest within two volumes in tissue – a HIFU-treated volume and an untreated volume. Optical spectroscopy was then carried out on 10 HIFU-treated chicken breast specimens in the wavelength range of 500–900 nm, in 1-nm increments, using a spectrophotometer with an integrating sphere attachment. The authors’ optical spectroscopy raw data (total transmittance and diffuse reflectance) were used to obtain the optical absorption and reduced scattering coefficients of HIFU-induced thermal lesions and native tissues by employing the inverse adding-doubling method. The aforementioned interaction coefficients were subsequently used to calculate the effective attenuation coefficient and light penetration depth of HIFU-treated and native tissues in the wavelength range of 500–900 nm.</p> <p><strong>Results:</strong></p> <p>HIFU-treated tissues produced greater PA signals than native tissues at 720 and 845 nm. At 720 nm, the averaged ratio of the peak-to-peak PA signal amplitude of HIFU-treated tissue to that of native tissue was 3.68 ± 0.25 (mean ± standard error of the mean). At 845 nm, the averaged ratio of the peak-to-peak PA signal amplitude of HIFU-treated tissue to that of native tissue was 3.75 ± 0.26 (mean ± standard error of the mean). The authors’ spectroscopic investigation has shown that HIFU-treated tissues have a greater optical absorption and reduced scattering coefficients than native tissues in the wavelength range of 500–900 nm. In fact, at 720 and 845 nm, the ratio of the optical absorption coefficient of HIFU-treated tissues to that of native tissues was 1.13 and 1.17, respectively; on the other hand, the ratio of the reduced scattering coefficient of HIFU-treated tissues to that of native tissues was 13.22 and 14.67 at 720 and 845 nm, respectively. Consequently, HIFU-treated tissues have a higher effective attenuation coefficient and a lower light penetration depth than native tissues in the wavelength range 500–900 nm.</p> <p><strong>Conclusions:</strong></p> <p>Using a PA approach, HIFU-treated tissues interrogated at 720 and 845 nm optical wavelengths can be differentiated from untreated tissues. Based on the authors’ spectroscopic investigation, the authors conclude that the observed PA contrast between HIFU-induced thermal lesions and untreated tissue is due, in part, to the increase in the optical absorption coefficient, the reduced scattering coefficient and, therefore, the deposited laser energy fluence in HIFU-treated tissues.</p>

The aims of this study are: (a) to investigate the capability of photoacoustic (PA) method in detecting high-intensity focused ultrasound (HIFU) treatments in muscle tissues in vitro; and (b) to determine the optical properties of HIFU-treated and native tissues in order to assist in the interpretation of the observed contrast in PA detection of HIFU treatments. A single-element, spherically concaved HIFU transducer with a centre frequency of 1 MHz was utilized to create thermal lesions in chicken breast tissues in vitro. To investigate the detectability of HIFU treatments photoacoustically, PA detection was performed at 720 and 845 nm on seven HIFU-treated tissue samples. Within each tissue sample, PA signals were acquired from 22 locations equally divided between two regions of interest within two volumes in tissue - a HIFU-treated volume and an untreated volume. Optical spectroscopy was then carried out on 10 HIFU-treated chicken breast specimens in the wavelength range of 500-900 nm, in 1-nm increments, using a spectrophotometer with an integrating sphere attachment. The authors' optical spectroscopy raw data (total transmittance and diffuse reflectance) were used to obtain the optical absorption and reduced scattering coefficients of HIFU-induced thermal lesions and native tissues by employing the inverse adding-doubling method. The aforementioned interaction coefficients were subsequently used to calculate the effective attenuation coefficient and light penetration depth of HIFU-treated and native tissues in the wavelength range of 500-900 nm. HIFU-treated tissues produced greater PA signals than native tissues at 720 and 845 nm. At 720 nm, the averaged ratio of the peak-to-peak PA signal amplitude of HIFU-treated tissue to that of native tissue was 3.68 ± 0.25 (mean ± standard error of the mean). At 845 nm, the averaged ratio of the peak-to-peak PA signal amplitude of HIFU-treated tissue to that of native tissue was 3.75 ± 0.26 (mean ± standard error of the mean). The authors' spectroscopic investigation has shown that HIFU-treated tissues have a greater optical absorption and reduced scattering coefficients than native tissues in the wavelength range of 500-900 nm. In fact, at 720 and 845 nm, the ratio of the optical absorption coefficient of HIFU-treated tissues to that of native tissues was 1.13 and 1.17, respectively; on the other hand, the ratio of the reduced scattering coefficient of HIFU-treated tissues to that of native tissues was 13.22 and 14.67 at 720 and 845 nm, respectively. Consequently, HIFU-treated tissues have a higher effective attenuation coefficient and a lower light penetration depth than native tissues in the wavelength range 500-900 nm. Using a PA approach, HIFU-treated tissues interrogated at 720 and 845 nm optical wavelengths can be differentiated from untreated tissues. Based on the authors' spectroscopic investigation, the authors conclude that the observed PA contrast between HIFU-induced thermal lesions and untreated tissue is due, in part, to the increase in the optical absorption coefficient, the reduced scattering coefficient and, therefore, the deposited laser energy fluence in HIFU-treated tissues.

<p><strong>Purpose:</strong></p> <p>The aims of this study are: (a) to investigate the capability of photoacoustic (PA) method in detecting high-intensity focused ultrasound (HIFU) treatments in muscle tissues<em>in vitro</em>; and (b) to determine the optical properties of HIFU-treated and native tissues in order to assist in the interpretation of the observed contrast in PA detection of HIFU treatments.</p> <p><strong>Methods:</strong></p> <p>A single-element, spherically concaved HIFU transducer with a centre frequency of 1 MHz was utilized to create thermal lesions in chicken breast tissues<em>in vitro</em>. To investigate the detectability of HIFU treatments photoacoustically, PA detection was performed at 720 and 845 nm on seven HIFU-treated tissue samples. Within each tissue sample, PA signals were acquired from 22 locations equally divided between two regions of interest within two volumes in tissue – a HIFU-treated volume and an untreated volume. Optical spectroscopy was then carried out on 10 HIFU-treated chicken breast specimens in the wavelength range of 500–900 nm, in 1-nm increments, using a spectrophotometer with an integrating sphere attachment. The authors’ optical spectroscopy raw data (total transmittance and diffuse reflectance) were used to obtain the optical absorption and reduced scattering coefficients of HIFU-induced thermal lesions and native tissues by employing the inverse adding-doubling method. The aforementioned interaction coefficients were subsequently used to calculate the effective attenuation coefficient and light penetration depth of HIFU-treated and native tissues in the wavelength range of 500–900 nm.</p> <p><strong>Results:</strong></p> <p>HIFU-treated tissues produced greater PA signals than native tissues at 720 and 845 nm. At 720 nm, the averaged ratio of the peak-to-peak PA signal amplitude of HIFU-treated tissue to that of native tissue was 3.68 ± 0.25 (mean ± standard error of the mean). At 845 nm, the averaged ratio of the peak-to-peak PA signal amplitude of HIFU-treated tissue to that of native tissue was 3.75 ± 0.26 (mean ± standard error of the mean). The authors’ spectroscopic investigation has shown that HIFU-treated tissues have a greater optical absorption and reduced scattering coefficients than native tissues in the wavelength range of 500–900 nm. In fact, at 720 and 845 nm, the ratio of the optical absorption coefficient of HIFU-treated tissues to that of native tissues was 1.13 and 1.17, respectively; on the other hand, the ratio of the reduced scattering coefficient of HIFU-treated tissues to that of native tissues was 13.22 and 14.67 at 720 and 845 nm, respectively. Consequently, HIFU-treated tissues have a higher effective attenuation coefficient and a lower light penetration depth than native tissues in the wavelength range 500–900 nm.</p> <p><strong>Conclusions:</strong></p> <p>Using a PA approach, HIFU-treated tissues interrogated at 720 and 845 nm optical wavelengths can be differentiated from untreated tissues. Based on the authors’ spectroscopic investigation, the authors conclude that the observed PA contrast between HIFU-induced thermal lesions and untreated tissue is due, in part, to the increase in the optical absorption coefficient, the reduced scattering coefficient and, therefore, the deposited laser energy fluence in HIFU-treated tissues.</p>

Optical coherence tomography (OCT) is a non-invasive and non-contact imaging technique that uses the reflection of light waves for tissue imaging. Compared to all other OCT variants, the swept-source OCT (SS-OCT) configuration offers higher imaging speed, better signal-to-noise ratio, and more resolution. Despite its numerous advantages, SS-OCT greatly suffers from limited contrast and reduced penetration ability. Over the years, several nanoparticles (NPs) like AgNP, TiO2, ZnO, etc have been exploited extensively as exogenous contrast agents to enhance the image contrast. Subsequently, herein, we have presented gadolinium oxide (Gd2O3) as a potential exogenous contrast agent for 3D non-invasive depth-resolved imaging of animal (chicken breast) tissue using an in-house developed SS-OCT system with centre wavelength of 1060 nm. In this work, OCT imaging of agar filled capillary tubes (phantoms) and chicken breast tissue (in vitro) was performed both with and without the application of Gd2O3 NPs. Scattering coefficient and contrast-to-noise ratio (CNR) calculations were done to study the effect of Gd2O3 NPs on the tissue sample at different time exposures. Post analysing the OCT images, a significant increase, in contrast, observed with time, where both the scattering coefficient (0.4879 mm−1 to 1.3782 mm−1) and the CNR of OCT B-scans (12.42 dB to 42.21 dB) increased substantially.

Functional properties of bicarbonates and lactic acid on chicken breast retail display properties and cooked meat quality

The functional information, the absorption and diffusion coefficients, as well as the structural information of biological tissues can be provided by the DOT(Diffuse Optical Tomograph)/MicroCT. In this paper, we use boundary element method to calculate the forward problem of DOT based on the structure prior given by the MicroCT, and then we reconstruct the absorption and diffusion coefficients of different biological tissues by the Levenberg-Marquardt algorithm. The method only needs surface meshing, reducing the complexity of calculation; in addition, it reconstructs a single value within an organ, which reduces the ill-posedness of the inverse problem to make reconstruction results have good noise stability. This indicates that the boundary element method-based reconstruction can serve as an new scheme for getting absorption and diffusion coefficients in DOT/MicroCT multimodality imaging.

The optical properties of tissue change during thermal ablation. Multi-modal methods such as acousto-optic (AO) and photo-acoustic (PA) imaging may provide a real-time, direct measure of lesion formation. Baseline changes in optical properties have been previously measured over limited ranges of thermal dose for tissues exposed to a temperature-controlled water bath, however, there is scant data for optical properties of lesions created by HIFU. In this work, the optical scattering and absorption coefficients from 400–1300 nm of excised chicken breast exposed to HIFU were measured using an integrating sphere spectrophotometric technique. HIFU-induced spatiotemporal temperature elevations were measured using an infrared camera and used to calculate the thermal dose delivered to a localized region of tissue. Results obtained over a range of thermal dose spanning 9 orders of magnitude show that the reduced scattering coefficient increases for HIFU exposures exceeding a threshold thermal dose of CEM43 = 600 ± 81 cumulative equivalent minutes. HIFU-induced thermal damage results in changes in scattering over all optical wavelengths, with a 2.5-fold increase for thermal lesions exceeding 70 °C. The tissue absorption coefficient was also found to increase for thermally lesioned tissue, however, the magnitude was strongly dependent on the optical wavelength and there was substantial sample-to-sample variability, such that the existence of a threshold thermal dose could not be determined. Therapeutic windows, where the optical penetration depth is expected to be greatest, were identified in the near infrared regime centered near 900 nm and 1100 nm. These data motivate further research to improve the real-time AO and PA sensing of lesion formation during HIFU therapy as an alternative to thermometry.

Optoacoustic Tomography is a fast developing imaging modality, combining the high resolution and penetration depth of ultrasound detection with the high contrast available from optical absorption in tissue. The spectral profile of near infrared excitation light used in optoacoustic tomography instruments is modified by absorption and scattering as it propagates deep into biological tissue. The resulting images therefore provide only qualitative insight into the distribution of tissue chromophores. Knowledge of the spectral profile of excitation light across the mouse is needed for accurate determination of the absorption coefficient in vivo. Under the conditions of constant Grueneisen parameter and accurate knowledge of the light fluence, a linear relationship should exist between the initial optoacoustic pressure amplitude and the tissue absorption coefficient. Using data from a commercial optoacoustic tomography system, we implemented an iterative optimization based on the σ-Eddington approximation to the Radiative Transfer Equation to derive a light fluence map within a given object. We segmented the images based on the positions of phantom inclusions, or mouse organs, and used known scattering coefficients for initialization. Performing the fluence correction in simple phantoms allowed the expected linear relationship between recorded and independently measured absorption coefficients to be retrieved and spectral coloring to be compensated. For in vivo data, the correction resulted in an enhancement of signal intensities in deep tissues. This improved our ability to visualize organs at depth (> 5mm). Future work will aim to perform the optimization without data normalization and explore the need for methodology that enables routine implementation for in vivo imaging.

Mastering rhinoplasty surgical techniques requires extensive learning involving theoretical studies, internships, cadaver laboratories, simulators, nonhuman models, and hands-on practice. A novel method using chicken breast simplifies skill development, offering flexibility and accessibility. Training on chicken breast allows surgeons to refine skills through various techniques and grafts. This study focuses on preservation techniques using chicken as a model. Surgical sequences simulate nasal structures using prepared chicken breasts. Documentation through media illustrates procedures from basic to advanced, using materials akin to traditional rhinoplasty but in reduced quantities. Chicken breast tissue, especially sternal cartilage, offers a suitable substrate for practicing techniques and grafting without live human or cadaveric tissue. This method provides an efficient, safe, and cost-effective approach to learning rhinoplasty.

IntroductionOptical property retrieval in diffuse reflectance imaging, like diffuse reflectance spectroscopy (DRS) and hyperspectral imaging (HSI), often involves fitting measured spectra to analytical solutions using approximations such as Diffusion Theory (DT). This method, while accurate, is not always generalizable due to the assumptions inherent in DT and results in non-unique solutions for optical properties and physiological parameters. In addition, it is computationally intensive. Physics-inspired deep learning offers generalizable data descriptions guided by physical principles but requires extensive labelled data, which is hard to obtain, especially in medical contexts.MethodsWe propose a deep learning approach to retrieve physiological parameters from DRS and HSI spectra using DT-simulated training data. The DT-simulated data is synthesised using a range for the optical properties: Blood Volume Fraction (BVF), Saturation, water-fat ratio (WFR), average blood vessel radius (R), scattering amplitude (SA), and scattering slope (SL). The range for these parameters we have extracted from literature.ResultsOur feed-forward neural network achieved median relative errors of 4% and 2% for DRS and HSI, respectively.DiscussionResults suggest that the proposed method is robust and that retrieval of optical properties is possible with similar results to DT but also reducing operation time.

01821AbstractWe will present a thermal model for laser pulses with pulse widths small compared to thematerial's thermal time constant. This model will then be used to generate computer plotsof the zones of vaporized tissue as well as the predicted tissue temperature rise. Usingpublished values of absorption coefficients, we will predict the vaporization energythresholds for Er:YAG (2.94,y m), Ho:YAG (2.1 .ym) and CO2 (10.6,ym) laser pulses. We willalso examine the extent of the thermally denatured zone surrounding the zone ofvaporization. Using typical energies available from these lasers we will then predictmaterial removed per pulse, and per second.IntroductionRecently it has been shown (1) that delivering short pulses of infrared laser energy tobiological tissue targets allows precise vaporization of biological tissue with lowerenergy thresholds and less severe secondary thermal damage. If the pulse width is shortenough and scattering can be neglected, the mathematics that describe the interactiontransform from a second order differential equation to a simple excercise in energybookkeeping.The concept is numerically to keep track of the amount of energy deposited in a givenvolume of tissue. The deposited energy density, expressed in joules /cm3 (J /cm3)determines whether the volume is vaporized, and what increase in temperature would beexpected.Three such laser sources are the TEA CO2 laser at 10.6um, Er:YAG laser at 2.94um andHo:YAG laser at 2.lum. All three lasers have demonstrated the ability to vaporizebiological tissue with little carbonaceous char and minimal thermal damage. This is dueto their short pulsewidth and high absorption in water, one of the main constituents ofbiological tissue. Each of these lasers will leave a rim of thermally denatured materialaround the vaporized crater, whose extent will vary with incident energy and will dependon the tissue's absorption coefficient at the wavelength in question. Using the thermalmodel described below we can compare the energy per pulse needed to reach the tissue'svaporization threshold, while also predicting the extent of the denatured rim.Pulsed thermal modelingIf we are to ignore thermal diffusion out of the irradiated volume, the laser pulsewidth should be shorter than the material's thermal time constant. The axial thermal timeconstant will depend on the absorption coefficient, and is written:

Corneal reshaping using laser ablation effect is a well-known ophthalmologic operation implemented to correct many vision disorders. UV pulsed lasers are utilized in this surgery due to their high absorption in corneal tissue without affecting the other parts of the eye. Ideally ablation may not be associated with heat transport, since high temperature is the enemy of soft tissues. However, the thermal effect of this procedure can cause tissue damage if the temperature rises above the safety level without appropriate handling. In the present study, we try to find the trade-off between efficient ablation and minimal temperature rise. So the thermal effect on the corneal tissue after applying five UV wavelengths; 193, 210, 213, 223 and 248nm has been simulated and investigated by solving Penne's bio-heat transfer equation using the finite element method. A 3D model of the human cornea is constructed using COMSOL Multiphysics computer software and the temperature rise is determined at the end of the laser pulse. The same spot size and pulse duration are used for each wavelength. While the absorption coefficient of the corneal tissue is the only variable as it is a wavelength dependent. The proposed results show that, the heating effect is directly proportional to the absorption coefficient. The highest recorded temperature was 259°C at 193nm, while, the minimum value was (70.1°C) recorded at 248nm at which the cornea has the lowest absorption coefficient.

Ultrasonic attenuation and absorption in liver tissue.

• Moderate woody chicken breast (MWB) and normal chicken breast (NB) is evaluated by monofilament needles. • Contact pressure between chicken breast fillets and monofilament needles is expressed through the needle’s buckling indentation depth. • Compared to NB, monofilament needles buckle at significantly lower indentation depths in MWB. • SVM-derived buckling indentation depth decision boundary can differentiate MWB and NB with 94.1% accuracy. The poultry industry is experiencing increasing concerns over meat quality defects associated with the rapid growth of broilers, particularly woody breast myopathy, which negatively affects texture and reduces consumer acceptance. While severe woody breast conditions are often visually detectable, moderate cases remain challenging to identify reliably and objectively using existing manual palpation approaches. To address this challenge, we developed a novel detection approach inspired by the Semmes–Weinstein monofilament examination commonly used in clinical diabetic diagnostics. A programmable indentation system was constructed to apply monofilament needles to broiler breast fillets and to identify moderate woody samples based on the elastic buckling response of the needle. Six types of monofilament needles were selected through mechanical modeling to ensure sensitivity to the contact pressure between the needle and chicken breast tissue. During testing, each needle was incrementally indented into the cranial region of the fillet, and the buckling depth was visually recorded. Two of the six needle types demonstrated satisfactory classification performance, achieving 94.1% accuracy and F1-scores above 92%. These results indicate their suitability for evaluation. This study represents the first integration of beam buckling mechanics into meat quality assessment and introduces a low-cost, objective alternative to traditional woody breast detection methods.