Optoacoustic (OA) imaging is a promising modality for quantifying blood oxygen saturation (sO$_2$) in various biomedical applications - in diagnosis, monitoring of organ function or even tumor treatment planning. We present an accurate and practically feasible real-time capable method for quantitative imaging of sO$_2$ based on combining multispectral (MS) and multiple illumination (MI) OA imaging with learned spectral decoloring (LSD). For this purpose we developed a hybrid real-time MI MS OA imaging setup with ultrasound (US) imaging capability; we trained gradient boosting machines on MI spectrally colored absorbed energy spectra generated by generic Monte Carlo simulations, and used the trained models to estimate sO$_2$ on real OA measurements. We validated MI-LSD in silico and on in vivo image sequences of radial arteries and accompanying veins of five healthy human volunteers. We compared the performance of the method to prior LSD work and conventional linear unmixing. MI-LSD provided highly accurate results in silico and consistently plausible results in vivo. This preliminary study shows a potentially high applicability of quantitative OA oximetry imaging, using our method.
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…
Results of an experiment are presented whose aim is to explore the relationship between respiration and cerebral oxygenation. Measurements of end tidal CO2 (EtCO2) were taken simultaneously with cerebral oxygen saturation (rSO2) using the INVOS Cerebral Oximeter of Somanetics. Due to the device limitations we could explore only subjects who could perform with a breathing rate of around 2/min or less. Six subjects were used who were experienced in yoga breathing techniques. They performed an identical periodic breathing exercise including periodicity of about 2/min. The results of all six subje…
Multispectral photoacoustic (PA) imaging is a prime modality to monitor hemodynamics and changes in blood oxygenation (sO2). Although sO2 changes can be an indicator of brain activity both in normal and in pathological conditions, PA imaging of the brain has mainly focused on small animal models with lissencephalic brains. Therefore, the purpose of this work was to investigate the usefulness of multispectral PA imaging in assessing sO2 in a gyrencephalic brain. To this end, we continuously imaged a porcine brain as part of an open neurosurgical intervention with a handheld PA and ultrasonic (U…
Spherical matrix arrays arguably represent an advantageous tomographic detection geometry for non-invasive deep tissue mapping of vascular networks and oxygenation with volumetric optoacoustic tomography (VOT). Hybridization of VOT with ultrasound (US) imaging remains difficult with this configuration due to the relatively large inter-element pitch of spherical arrays. We suggest a new approach for combining VOT and US contrast-enhanced imaging employing injection of clinically-approved microbubbles. Power Doppler (PD) and US localization imaging were enabled with a sparse US acquisition seque…
We tested the hypothesis that simple exercises may significantly increase cerebral blood flow (CBF) and/or cerebral oxygenation. Eighteen subjects ranging in age from nineteen to thirty nine participated in a four-stage study during which measurements of end tidal CO_2 (EtCO2 - by capnometer) and local brain oxygenation (by near-infrared spectroscopy (NIRS) sensor) were taken. The four stages were 1) baseline, 2) breathing exercises, 3) solving an arithmetic problem, and 4) biofeedback. During the breathing exercises there was a significant increase in EtCO2 indicating a significant increase i…
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…
The fundamentals of near infrared spectroscopy (NIRS) are reviewed. Among the major factors controlling the cerebral blood flow (CBF), the effect of PaCO2 is peculiar in that it violates autoregulatory CBF mechanisms and allows to explore the full range of the CBF. A simple physical model, with a four parameter formula, relating the CBF to PaCO2 is presented. It can be used to transform the fits of one animal to the fits of another one. It enable the use of rats data as monkeys data simply by rescaling the PaCO2 values and the CBF data. Controlled breathing can change the PaCO2. Experiments on…
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…
Crises like COVID-19 can create a massive unmet demand for rare blood oxygenation membrane machines for impaired lungs: Extracorporeal Membrane Oxygenation (ECMO) machines. Meanwhile, Hemodialysis (HD) machines, which use membranes to supplement failing kidneys, are extremely common and widespread, with orders of magnitude more available than for ECMO machines. This short study examines whether the membranes for HD can be modified for use in blood oxygenation (ECMO). To do so, it considers mass transfer at the micro-scale level, and calculations for the macro-scale level such as blood pumping …
Conditioning Deep Anatomical Prior Knowledge for Reconstruction of Multispectral Optoacoustic Tomography Images
Technical University of Munich（慕尼黑工业大学）；Central Institute for Translational Cancer Research (TranslaTUM)（转化癌症研究中心 (TranslaTUM)）；School of Computation, Information and Technology, Technical University of Munich（慕尼黑工业大学计算、信息与技术学院）；Institute of Computational Biology, Helmholtz Zentrum München（赫尔姆霍兹中心慕尼黑计算生物学研究所）；Institute of AI for Health, Helmholtz Zentrum München（赫尔姆霍兹中心慕尼黑健康人工智能研究所）；Ludwig-Maximilians-Universität München（慕尼黑大学）
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…
Simultaneous 3D co-registered perfusion and oxygenation with ULM, photoacoustic imaging, and a planar matrix array
Sorbonne Université（索邦大学）；CNRS（法国国家科学研究中心）；Inserm（法国国家健康与医学研究院）；Laboratoire d’Imagerie Biomédicale, LIB（生物医学成像实验室）；Université Paris Cité（巴黎西岱大学）；Centre de Recherche des Cordeliers（科尔德洛耶研究中心）；Institut Cochin（科尚研究所）；Department of Nuclear Medicine, Hôpital Pitié Salpêtrière, APHP（皮蒂埃-萨尔佩特里埃医院核医学科）；PARCC（PARCC研究中心）；Service de Radiologie, AP-HP, Hôpital européen Georges Pompidou（乔治·蓬皮杜欧洲医院放射科）
Photoacoustic (PA) imaging systems based on clinical linear ultrasound arrays have become increasingly popular in translational PA research. Such systems can be more easily integrated in a clinical workflow due to the simultaneous access to ultrasonic imaging and their familiarity of use to clinicians. In contrast to more complex setups, hand held linear probes can be applied to a large variety of clinical use cases. However, most translational work with such scanners is based on proprietary development and as such not accessible to the community. In this contribution, we present a custom-buil…
In many clinical conditions, such as head trauma, stroke, and low cardiac output states, the brain is at risk for hypoxic-ischemic injury. The metabolic rate and oxygen consumption of the brain are reflected in internal jugular venous oxygen saturation (sijvO2). The current gold standard for monitoring brain oxygenation is invasive; it requires jugular vein catheterization under fluoroscopic guidance and therefore is rarely used. Photoacoustic (PA) measurement, on the other hand, can estimate the oxygen consumption of the brain non-invasively in real time. Such a convenient method can potentia…
German Cancer Research Center（德国癌症研究中心）；Heidelberg University（海德堡大学）；University of Bern（伯尔尼大学）
Multispectral photoacoustic imaging (PAI) is an emerging imaging modality which enables the recovery of functional tissue parameters such as blood oxygenation. However, the underlying inverse problems are potentially ill-posed, meaning that radically different tissue properties may - in theory - yield comparable measurements. In this work, we present a new approach for handling this specific type of uncertainty by leveraging the concept of conditional invertible neural networks (cINNs). Specifically, we propose going beyond commonly used point estimates for tissue oxygenation and converting si…
German Cancer Research Center (DKFZ)（德国癌症研究中心）；Heidelberg University（海德堡大学）
Real-time monitoring of functional tissue parameters, such as local blood oxygenation, based on optical imaging could provide groundbreaking advances in the diagnosis and interventional therapy of various diseases. While photoacoustic (PA) imaging is a novel modality with great potential to measure optical absorption deep inside tissue, quantification of the measurements remains a major challenge. In this paper, we introduce the first machine learning based approach to quantitative PA imaging (qPAI), which relies on learning the fluence in a voxel to deduce the corresponding optical absorption…
