Random matrix theory provides new insights into multiple scattering in random media. In a recent study, we demonstrated the statistical separation of single- and multiple-scattering components based on a Wishart random matrix. The first- and second-order moments were estimated through a Wishart random matrix constructed using dynamically-backscattered speckle images. In this study, this new strategy was applied to laser speckle contrast imaging (LSCI) of in-vivo blood flow. The random matrix-based method was adapted and parameterized using electric field Monte Carlo simulations and in-vitro blood flow phantom experiments. The new method was further applied in in-vivo experiments, demonstrating the benefits of separating the single- and multiple-scattering components, and was compared with the traditional temporal LASCA method. More specifically, the new method captures stimulus-induced functional changes in blood flow and tissue perfusion in the superficial and deeper layers. The new method extends the ability of LSCI to image functional and pathological changes.
Speckle contrast imaging is an established technique to obtain relative blood maps over wide field of views. Currently, its most accurate implementation relies on the acquisition of raw speckle images at different exposure times but requires modulation of a laser pulse in duration and intensity and precise synchronization with camera. This complex instrumentation has limited the use of multiple exposure speckle imaging. We evaluate here a simplified approach based on synthetic exposure images created from the sum of successive frames acquired with a 1 ms exposure time. Both methods have been a…
We present an intensity speckle simulation algorithm based on stochastic differential equations. Intensity speckles are generated with a negative exponential distribution and an exponential auto-correlation decay. The mean of the distribution is spatially varying dictated by photon diffusion to take into account of diffuse speckles. The algorithm is validated using simulation studies for both surface and deep tissue blood flow with potential applications in diffuse correlation spectroscopy.
Infrared light scattering methods have been developed and employed to non-invasively monitor human cerebral blood flow (CBF). However, the number of reflected photons that interact with the brain is low when detecting blood flow in deep tissue. To tackle this photon-starved problem, we present and demonstrate the idea of interferometric speckle visibility spectroscopy (ISVS). In ISVS, an interferometric detection scheme is used to boost the weak signal light. The blood flow dynamics are inferred from the speckle statistics of a single frame speckle pattern. We experimentally demonstrated the i…
Quantitative ultrasound imaging of bone: anatomical images, tissue structural quality, and pulsatile blood flow
Delft University of Technology（代尔夫特理工大学）；University of Angers（昂热大学）；CHU Angers（昂热大学医院）；Inserm（法国国家健康与医学研究院）；CNRS（法国国家科学研究中心）；MITOVASC（MITOVASC团队）；SFR ICAT（ICAT综合研究设施）；Vascular medicine unit, CHU Angers（昂热大学医院血管医学部）；University Jean Monnet（让·莫内大学）；Mines Saint-Etienne（圣艾蒂安国立高等矿业学院）
The speckle statistics of optical coherence tomography images of biological tissue have been studied using several historical probability density functions. A recent hypothesis implies that underlying power-law distributions in the medium structure, such as the fractal branching vasculature, will contribute to power-law probability distributions of speckle statistics. Specifically, these are the Burr type XII distribution for speckle amplitude, the Lomax distribution for intensity, and the generalized logistic distribution for log amplitude. In this study, these three distributions are fitted …
The study of the interaction between laser and brain tissue has important theoretical and practical significance for brain imaging. A two-dimensional simulation model that studies the propagation of light and heat transfer in brain tissue based on finite element has been developed by using the commercial finite element simulation software COMSOL Multiphysics. In this study, the model consists of three parts of 1) a layer of water on the surface of the brain, 2) brain tissue and 3) short pulsed laser source (the wavelength is 840nm). The laser point source is located in the middle of the layer …
Enrolling patients in clinical trials to obtain fresh tumor biopsies to profile anticancer agents can be slow and expensive. However, if flash-frozen biopsies can be thawed to produce viable living tissue with relevant biodynamic profiles, then a large reservoir of tissue-banked samples could become available for phenotypic library building. Here, we report biodynamic profiles acquired from revived flash-frozen canine B-cell lymphoma biopsies using digital speckle holography. We compared the thawed-tissue drug-response spectrograms to spectrograms from fresh tissues in a study of canine B-cell…
De Montfort University（德蒙福特大学）；University of Huddersfield（哈德斯菲尔德大学）
This paper investigates the effectiveness of an expert system based on K-nearest neighbors algorithm for laser speckle image sampling applied to the early detection of diabetes. With the latest developments in artificial intelligent guided laser speckle imaging technologies, it may be possible to optimise laser parameters, such as wavelength, energy level and image texture measures in association with a suitable AI technique to interact effectively with the subcellular properties of a skin tissue to detect early signs of diabetes. The new approach is potentially more effective than the classic…
Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this s…
Photoacoustic tomography (PAT) is intrinsically sensitive to blood oxygen saturation (sO2) in vivo. However, making accurate sO2 measurements without knowledge of tissue- and instrumentation-related correction factors is extremely challenging. We have developed a low-cost flow phantom system to facilitate validation of photoacoustic tomography systems. The phantom is composed of a flow circuit, which is partially embedded within a tissue mimicking phantom, with independent sensors providing online monitoring of the optical absorption spectrum and partial pressure of oxygen in the tube. We firs…
Objective: Realistic tissue-mimicking phantoms are essential for the development, the investigation and the calibration of medical imaging techniques and protocols. Because it requires taking both mechanical and imaging properties into account, the development of robust, calibrated phantoms is a major challenge in elastography. Soft polyvinyl chloride gels in a liquid plasticizer (plastisol or PVCP) have been proposed as soft tissue-mimicking phantoms (TMP) for elasticity imaging. PVCP phantoms are relatively low-cost and can be easily stored over long time periods without any specific require…
Recent theories examine the role of the fractal branching vasculature as a primary site of Born scattering from soft normal tissues. These derivations postulate that the first order statistics of speckle from tissue such as the liver, thyroid, and prostate will follow a Burr distribution with a power law parameter that can be related back to the underlying power law which governs the branching network. However, the issue of scatterer spacing, or the number of cylindrical vessels per sample volume of the interrogating pulse, has not been directly addressed. This is now examined with a 3D simula…
Tumor growth relies heavily on the continuous blood and nutrients supply. Theoretically, it is an ideal therapeutic way of killing tumor by only vascular embolization. However, most of the existing vascular embolic agents are still rather insufficient to fulfill the real clinical need due to the reasons like: incomplete filling of target vasculature, being easily washed away by blood or body solution, or just producing toxicity to tissues. Here from an alternative way, the body temperature liquid metal, a kind of soft and highly compliant material, was proposed for the first time as blood vess…
Institute for Biological and Medical Imaging (IBMI), Helmholtz Zentrum München（亥姆霍兹慕尼黑中心生物与医学成像研究所）；Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München（慕尼黑工业大学伊萨尔河畔医院放射肿瘤科）；Chair for Biological Imaging, Technische Universität München（慕尼黑工业大学生物成像教席）；CCG – Innate immunity in Tumor Biology, Helmholtz Zentrum München（亥姆霍兹慕尼黑中心肿瘤生物学先天免疫合作研究组）
Light propagating in tissue attains a spectrum that varies with location due to wavelength-dependent fluence attenuation by tissue optical properties, an effect that causes spectral corruption. Predictions of the spectral variations of light fluence in tissue are challenging since the spatial distribution of optical properties in tissue cannot be resolved in high resolution or with high accuracy by current methods. Spectral corruption has fundamentally limited the quantification accuracy of optical and optoacoustic methods and impeded the long sought-after goal of imaging blood oxygen saturati…
Estimation of blood oxygenation with spectroscopic photoacoustic imaging is a promising tool for several biomedical applications. For this method to be quantitative, it relies on an accurate method of the light fluence in the tissue. This is difficult deep in heterogeneous tissue, where different wavelengths of light can experience significantly different attenuation. In this work, we developed a new deep neural network to simultaneously estimate the oxygen saturation in blood vessels and segment the vessels from the surrounding background tissue. The network was trained on estimated initial p…
Significance: 2D fully convolutional neural networks have been shown capable of producing maps of sO$_2$ from 2D simulated images of simple tissue models. However, their potential to produce accurate estimates in vivo is uncertain as they are limited by the 2D nature of the training data when the problem is inherently 3D, and they have not been tested with realistic images. Aim: To demonstrate the capability of deep neural networks to process whole 3D images and output 3D maps of vascular sO$_2$ from realistic tissue models/images. Approach: Two separate fully convolutional neural networks wer…
We report on wide-field imaging of pulsatile microvascular blood flow in the exposed cerebral cortex of a mouse by holographic interferometry. We recorded interferograms of laser light backscattered by the tissue, beating against an off-axis reference beam with a 50 kHz framerate camera. Videos of local Doppler contrasts were rendered numerically by Fresnel transformation and short-time Fourier transform analysis. This approach enabled instantaneous imaging of pulsatile blood flow contrasts in superficial blood vessels over 256 x 256 pixels with a spatial resolution of 10 microns and a tempora…
Significance: Speckle has historically been considered a source of noise in coherent light imaging. However, a number of works in optical coherence tomography (OCT) imaging have shown that speckle patterns may contain relevant information regarding sub-resolution and structural properties of the tissues from which it is originated. Aim: The objective of this work is to provide a comprehensive overview of the methods developed for retrieving speckle information in biomedical OCT applications. Approach: PubMed and Scopus databases were used to perform a systematic review on studies published unt…
Non-invasive measurement of the arterial blood speed gives rise to important healthinformation such as cardio output and blood supplies to vital organs. The magnitude andchange in arterial blood speed are key indicators of the health conditions and development andprogression of diseases. We demonstrated a simple technique to directly measure the blood flowspeed in main arteries based on the diffused light model. The concept is demonstrated with aphantom that uses intralipid hydrogel to model the biological tissue and an embedded glass tubewith flowing human blood to model the blood vessel. The…
We performed non-invasive video imaging of retinal blood flow in a pigmented rat by holographic interferometry of near-infrared laser light backscattered by retinal tissue, beating against an off-axis reference beam sampled at a frame rate of 39 kHz with a high throughput camera. Local Doppler contrasts emerged from the envelopes of short-time Fourier transforms and the phase of autocorrelation functions of holograms rendered by Fresnel transformation. This approach permitted imaging of blood flow in large retinal vessels (30 microns diameter) over 400 by 400 pixels with a spatial resolution o…
Real-time diffuse correlation spectroscopy with a chip-based correlator for measuring human cerebral blood flow and brain function
University of Strathclyde（斯特拉斯克莱德大学）；Faculty of Health Sciences, University of Macau（澳门科技大学）；The University of Edinburgh（爱丁堡大学）；Zhuhai UM Science and Technology Research Institute, University of Macau（澳门大学珠海研究院）；Centre for Cognitive and Brain Sciences, University of Macau（澳门大学认知与脑科学中心）；A*STAR Skin Research Labs (A*SRL), Agency for Science, Technology and Research (A*STAR)（新加坡科技研究局皮肤研究实验室）
Imaging airway tissue, optical coherence tomography (OCT) provides cross-sectional images of tissue structures, shows cilia movement and mucus secretion, but does not provide sufficient contrast to differentiate individual cells. By using fast sequences of microscopic resolution OCT (mOCT) images, OCT can picture small signal fluctuations (dynamic) OCT and overcomes the lack in contrast caused by speckle noise. In this way, OCT visualizes airway morphology on a cellular level and allows to track the dynamic behavior of immune cells, as well as mucus transport and secretion. Here, we demonstrat…
German Cancer Research Center (DKFZ)（德国癌症研究中心）；Heidelberg University（海德堡大学）
One of the main applications of photoacoustic (PA) imaging is the recovery of functional tissue properties, such as blood oxygenation (sO2). This is typically achieved by linear spectral unmixing of relevant chromophores from multispectral photoacoustic images. Despite the progress that has been made towards quantitative PA imaging (qPAI), most sO2 estimation methods yield poor results in realistic settings. In this work, we tackle the challenge by employing learned spectral decoloring for quantitative photoacoustic imaging (LSD-qPAI) to obtain quantitative estimates for blood oxygenation. LSD…
Self-Portrait of the Focusing Process in Speckle: III. Tailoring Complex Spatio-Temporal Focusing Laws To Overcome Reverberations in Reflection Imaging
Mechanistic multiphysics modeling reveals how blood pulsation drives CSF flow, pressure, and brain deformation under physiological and injection conditions
