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Kirchner T, Villringer C, Laufer J. Evaluation of ultrasound sensors for transcranial photoacoustic sensing and imaging. PHOTOACOUSTICS 2023; 33:100556. [PMID: 38021292 PMCID: PMC10658602 DOI: 10.1016/j.pacs.2023.100556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 09/11/2023] [Accepted: 09/11/2023] [Indexed: 12/01/2023]
Abstract
Photoacoustic imaging through skull bone causes strong attenuation and distortion of the acoustic wavefront, which diminishes image contrast and resolution. As a result, transcranial photoacoustic measurements in humans have been challenging to demonstrate. In this study, we investigated the acoustic transmission through the human skull to design an ultrasound sensor suitable for transcranial PA imaging and sensing. We measured the frequency dependent losses of human cranial bones ex vivo, compared the performance of a range of piezoelectric and optical ultrasound sensors, and imaged skull phantoms using a PA tomograph based on a planar Fabry-Perot sensor. All transcranial photoacoustic measurements show the typical effects of frequency and thickness dependent attenuation and aberration associated with acoustic propagation through bone. The performance of plano-concave optical resonator ultrasound sensors was found to be highly suitable for transcranial photoacoustic measurements.
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Affiliation(s)
- Thomas Kirchner
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), Germany
| | - Claus Villringer
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), Germany
- Technische Hochschule Wildau, Hochschulring 1, 15745 Wildau, Germany
| | - Jan Laufer
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), Germany
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2
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Gu Y, Sun Y, Wang X, Li H, Qiu J, Lu W. Application of photoacoustic computed tomography in biomedical imaging: A literature review. Bioeng Transl Med 2023; 8:e10419. [PMID: 36925681 PMCID: PMC10013779 DOI: 10.1002/btm2.10419] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 09/11/2022] [Accepted: 09/18/2022] [Indexed: 11/06/2022] Open
Abstract
Photoacoustic computed tomography (PACT) is a hybrid imaging modality that combines optical excitation and acoustic detection techniques. It obtains high-resolution deep-tissue images based on the deep penetration of light, the anisotropy of light absorption in objects, and the photoacoustic effect. Hence, PACT shows great potential in biomedical sample imaging. Recently, due to its advantages of high sensitivity to optical absorption and wide scalability of spatial resolution with the desired imaging depth, PACT has received increasing attention in preclinical and clinical practice. To date, there has been a proliferation of PACT systems designed for specific biomedical imaging applications, from small animals to human organs, from ex vivo to in vivo real-time imaging, and from simple structural imaging to functional and molecular imaging with external contrast agents. Therefore, it is of great importance to summarize the previous applications of PACT systems in biomedical imaging and clinical practice. In this review, we searched for studies related to PACT imaging of biomedical tissues and samples over the past two decades; divided the studies into two categories, PACT imaging of preclinical animals and PACT imaging of human organs and body parts; and discussed the significance of the studies. Finally, we pointed out the future directions of PACT in biomedical applications. With the development of exogenous contrast agents and advances of imaging technique, in the future, PACT will enable biomedical imaging from organs to whole bodies, from superficial vasculature to internal organs, from anatomy to functions, and will play an increasingly important role in biomedical research and clinical practice.
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Affiliation(s)
- Yanru Gu
- Department of Radiology The Second Affiliated Hospital of Shandong First Medical University Taian China.,Department of Radiology Shandong First Medical University and Shandong Academy of Medical Sciences Taian China
| | - Yuanyuan Sun
- Department of Radiology Shandong First Medical University and Shandong Academy of Medical Sciences Taian China
| | - Xiao Wang
- College of Ocean Science and Engineering Shandong University of Science and Technology Qingdao China
| | - Hongyu Li
- College of Ocean Science and Engineering Shandong University of Science and Technology Qingdao China
| | - Jianfeng Qiu
- Department of Radiology Shandong First Medical University and Shandong Academy of Medical Sciences Taian China
| | - Weizhao Lu
- Department of Radiology The Second Affiliated Hospital of Shandong First Medical University Taian China.,Department of Radiology Shandong First Medical University and Shandong Academy of Medical Sciences Taian China
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3
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Menozzi L, del Águila Á, Vu T, Ma C, Yang W, Yao J. Three-dimensional non-invasive brain imaging of ischemic stroke by integrated photoacoustic, ultrasound and angiographic tomography (PAUSAT). PHOTOACOUSTICS 2023; 29:100444. [PMID: 36620854 PMCID: PMC9813577 DOI: 10.1016/j.pacs.2022.100444] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 10/09/2022] [Accepted: 12/23/2022] [Indexed: 06/17/2023]
Abstract
We present an ischemic stroke study using our newly-developed PAUSAT system that integrates photoacoustic computed tomography (PACT), high-frequency ultrasound imaging, and acoustic angiographic tomography. PAUSAT is capable of three-dimensional (3D) imaging of the brain morphology, blood perfusion, and blood oxygenation. Using PAUSAT, we studied the hemodynamic changes in the whole mouse brain induced by two common ischemic stroke models: the permanent middle cerebral artery occlusion (pMCAO) model and the photothrombotic (PT) model. We imaged the same mouse brains before and after stroke, and quantitatively compared the two stroke models. We observed clear hemodynamic changes after ischemic stroke, including reduced blood perfusion and oxygenation. Such changes were spatially heterogenous. We also quantified the tissue infarct volume in both stroke models. The PAUSAT measurements were validated by laser speckle imaging and histology. Our results have collectively demonstrated that PAUSAT can be a valuable tool for non-invasive longitudinal studies of neurological diseases at the whole-brain scale.
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Affiliation(s)
- Luca Menozzi
- Department of Biomedical Engineering, Duke University, Durham 27708, NC, USA
| | - Ángela del Águila
- Multidisciplinary Brain Protection Program, Department of Anesthesiology, Duke University School of Medicine, Durham 27710, NC, USA
| | - Tri Vu
- Department of Biomedical Engineering, Duke University, Durham 27708, NC, USA
| | - Chenshuo Ma
- Department of Biomedical Engineering, Duke University, Durham 27708, NC, USA
| | - Wei Yang
- Multidisciplinary Brain Protection Program, Department of Anesthesiology, Duke University School of Medicine, Durham 27710, NC, USA
| | - Junjie Yao
- Department of Biomedical Engineering, Duke University, Durham 27708, NC, USA
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4
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Discovering Glioma Tissue through Its Biomarkers' Detection in Blood by Raman Spectroscopy and Machine Learning. Pharmaceutics 2023; 15:pharmaceutics15010203. [PMID: 36678833 PMCID: PMC9862809 DOI: 10.3390/pharmaceutics15010203] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 12/27/2022] [Accepted: 12/29/2022] [Indexed: 01/11/2023] Open
Abstract
The most commonly occurring malignant brain tumors are gliomas, and among them is glioblastoma multiforme. The main idea of the paper is to estimate dependency between glioma tissue and blood serum biomarkers using Raman spectroscopy. We used the most common model of human glioma when continuous cell lines, such as U87, derived from primary human tumor cells, are transplanted intracranially into the mouse brain. We studied the separability of the experimental and control groups by machine learning methods and discovered the most informative Raman spectral bands. During the glioblastoma development, an increase in the contribution of lactate, tryptophan, fatty acids, and lipids in dried blood serum Raman spectra were observed. This overlaps with analogous results of glioma tissues from direct Raman spectroscopy studies. A non-linear relationship between specific Raman spectral lines and tumor size was discovered. Therefore, the analysis of blood serum can track the change in the state of brain tissues during the glioma development.
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Menozzi L, Yang W, Feng W, Yao J. Sound out the impaired perfusion: Photoacoustic imaging in preclinical ischemic stroke. Front Neurosci 2022; 16:1055552. [PMID: 36532279 PMCID: PMC9751426 DOI: 10.3389/fnins.2022.1055552] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 11/17/2022] [Indexed: 09/19/2023] Open
Abstract
Acoustically detecting the optical absorption contrast, photoacoustic imaging (PAI) is a highly versatile imaging modality that can provide anatomical, functional, molecular, and metabolic information of biological tissues. PAI is highly scalable and can probe the same biological process at various length scales ranging from single cells (microscopic) to the whole organ (macroscopic). Using hemoglobin as the endogenous contrast, PAI is capable of label-free imaging of blood vessels in the brain and mapping hemodynamic functions such as blood oxygenation and blood flow. These imaging merits make PAI a great tool for studying ischemic stroke, particularly for probing into hemodynamic changes and impaired cerebral blood perfusion as a consequence of stroke. In this narrative review, we aim to summarize the scientific progresses in the past decade by using PAI to monitor cerebral blood vessel impairment and restoration after ischemic stroke, mostly in the preclinical setting. We also outline and discuss the major technological barriers and challenges that need to be overcome so that PAI can play a more significant role in preclinical stroke research, and more importantly, accelerate its translation to be a useful clinical diagnosis and management tool for human strokes.
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Affiliation(s)
- Luca Menozzi
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Wei Yang
- Multidisciplinary Brain Protection Program, Department of Anesthesiology, Duke University, Durham, NC, United States
| | - Wuwei Feng
- Department of Neurology, Duke University School of Medicine, Durham, NC, United States
| | - Junjie Yao
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
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6
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Mirg S, Turner KL, Chen H, Drew PJ, Kothapalli SR. Photoacoustic imaging for microcirculation. Microcirculation 2022; 29:e12776. [PMID: 35793421 PMCID: PMC9870710 DOI: 10.1111/micc.12776] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 06/13/2022] [Accepted: 06/28/2022] [Indexed: 01/26/2023]
Abstract
Microcirculation facilitates the blood-tissue exchange of nutrients and regulates blood perfusion. It is, therefore, essential in maintaining tissue health. Aberrations in microcirculation are potentially indicative of underlying cardiovascular and metabolic pathologies. Thus, quantitative information about it is of great clinical relevance. Photoacoustic imaging (PAI) is a capable technique that relies on the generation of imaging contrast via the absorption of light and can image at micron-scale resolution. PAI is especially desirable to map microvasculature as hemoglobin strongly absorbs light and can generate a photoacoustic signal. This paper reviews the current state of the art for imaging microvascular networks using photoacoustic imaging. We further describe how quantitative information about blood dynamics such as the total hemoglobin concentration, oxygen saturation, and blood flow rate is obtained using PAI. We also discuss its importance in understanding key pathophysiological processes in neurovascular, cardiovascular, ophthalmic, and cancer research fields. We then discuss the current challenges and limitations of PAI and the approaches that can help overcome these limitations. Finally, we provide the reader with an overview of future trends in the field of PAI for imaging microcirculation.
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Affiliation(s)
- Shubham Mirg
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - Kevin L. Turner
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - Haoyang Chen
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA,Center for Neural Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - Patrick J. Drew
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA,Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802, USA,Department of Neurosurgery, Pennsylvania State University, University Park, PA 16802, USA,Center for Neural Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - Sri-Rajasekhar Kothapalli
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA 16802, USA,Penn State Cancer Institute, Pennsylvania State University, Hershey, PA 17033, USA,Graduate Program in Acoustics, Pennsylvania State University, University Park, PA 16802, USA,Center for Neural Engineering, Pennsylvania State University, University Park, PA 16802, USA,Corresponding author: Sri-Rajasekhar Kothapalli, 325 CBE Building, State College, PA, 16802, USA,
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7
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Recent Technical Progression in Photoacoustic Imaging—Towards Using Contrast Agents and Multimodal Techniques. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11219804] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
For combining optical and ultrasonic imaging methodologies, photoacoustic imaging (PAI) is the most important and successful hybrid technique, which has greatly contributed to biomedical research and applications. Its theoretical background is based on the photoacoustic effect, whereby a modulated or pulsed light is emitted into tissue, which selectively absorbs the optical energy of the light at optical wavelengths. This energy produces a fast thermal expansion in the illuminated tissue, generating pressure waves (or photoacoustic waves) that can be detected by ultrasonic transducers. Research has shown that optical absorption spectroscopy offers high optical sensitivity and contrast for ingredient determination, for example, while ultrasound has demonstrated good spatial resolution in biomedical imaging. Photoacoustic imaging combines these advantages, i.e., high contrast through optical absorption and high spatial resolution due to the low scattering of ultrasound in tissue. In this review, we focus on advances made in PAI in the last five years and present categories and key devices used in PAI techniques. In particular, we highlight the continuously increasing imaging depth achieved by PAI, particularly when using exogenous reagents. Finally, we discuss the potential of combining PAI with other imaging techniques.
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8
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Shi XF, Ji B, Kong Y, Guan Y, Ni R. Multimodal Contrast Agents for Optoacoustic Brain Imaging in Small Animals. Front Bioeng Biotechnol 2021; 9:746815. [PMID: 34650961 PMCID: PMC8505530 DOI: 10.3389/fbioe.2021.746815] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 08/12/2021] [Indexed: 12/19/2022] Open
Abstract
Optoacoustic (photoacoustic) imaging has demonstrated versatile applications in biomedical research, visualizing the disease pathophysiology and monitoring the treatment effect in an animal model, as well as toward applications in the clinical setting. Given the complex disease mechanism, multimodal imaging provides important etiological insights with different molecular, structural, and functional readouts in vivo. Various multimodal optoacoustic molecular imaging approaches have been applied in preclinical brain imaging studies, including optoacoustic/fluorescence imaging, optoacoustic imaging/magnetic resonance imaging (MRI), optoacoustic imaging/MRI/Raman, optoacoustic imaging/positron emission tomography, and optoacoustic/computed tomography. There is a rapid development in molecular imaging contrast agents employing a multimodal imaging strategy for pathological targets involved in brain diseases. Many chemical dyes for optoacoustic imaging have fluorescence properties and have been applied in hybrid optoacoustic/fluorescence imaging. Nanoparticles are widely used as hybrid contrast agents for their capability to incorporate different imaging components, tunable spectrum, and photostability. In this review, we summarize contrast agents including chemical dyes and nanoparticles applied in multimodal optoacoustic brain imaging integrated with other modalities in small animals, and provide outlook for further research.
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Affiliation(s)
- Xue-feng Shi
- Department of Respiratory Medicine, Qinghai Provincial People’s Hospital, Xining, China
| | - Bin Ji
- Department of Radiopharmacy and Molecular Imaging, School of Pharmacy, Fudan University, Shanghai, China
| | - Yanyan Kong
- PET Center, Huashan Hospital, Fudan University, Shanghai, China
| | - Yihui Guan
- PET Center, Huashan Hospital, Fudan University, Shanghai, China
| | - Ruiqing Ni
- Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
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Wang X, Luo Y, Chen Y, Chen C, Yin L, Yu T, He W, Ma C. A Skull-Removed Chronic Cranial Window for Ultrasound and Photoacoustic Imaging of the Rodent Brain. Front Neurosci 2021; 15:673740. [PMID: 34135729 PMCID: PMC8200560 DOI: 10.3389/fnins.2021.673740] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 05/06/2021] [Indexed: 11/13/2022] Open
Abstract
Ultrasound and photoacoustic imaging are emerging as powerful tools to study brain structures and functions. The skull introduces significant distortion and attenuation of the ultrasound signals deteriorating image quality. For biological studies employing rodents, craniotomy is often times performed to enhance image qualities. However, craniotomy is unsuitable for longitudinal studies, where a long-term cranial window is needed to prevent repeated surgeries. Here, we propose a mouse model to eliminate sound blockage by the top portion of the skull, while minimum physiological perturbation to the imaged object is incurred. With the new mouse model, no craniotomy is needed before each imaging experiment. The effectiveness of our method was confirmed by three imaging systems: photoacoustic computed tomography, ultrasound imaging, and photoacoustic mesoscopy. Functional photoacoustic imaging of the mouse brain hemodynamics was also conducted. We expect new applications to be enabled by the new mouse model for photoacoustic and ultrasound imaging.
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Affiliation(s)
- Xuanhao Wang
- Department of Electronic Engineering, Tsinghua University, Beijing, China
| | - Yan Luo
- Department of Electronic Engineering, Tsinghua University, Beijing, China
| | - Yuwen Chen
- Department of Electronic Engineering, Tsinghua University, Beijing, China
| | - Chaoyi Chen
- Department of Electronic Engineering, Tsinghua University, Beijing, China
| | - Lu Yin
- Department of Ultrasound, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Tengfei Yu
- Department of Ultrasound, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Wen He
- Department of Ultrasound, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Cheng Ma
- Department of Electronic Engineering, Tsinghua University, Beijing, China
- Beijing National Research Center for Information Science and Technology, Beijing, China
- Beijing Innovation Center for Future Chip, Beijing, China
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Liang B, Wang S, Shen F, Liu QH, Gong Y, Yao J. Acoustic impact of the human skull on transcranial photoacoustic imaging. BIOMEDICAL OPTICS EXPRESS 2021; 12:1512-1528. [PMID: 33796369 PMCID: PMC7984784 DOI: 10.1364/boe.420084] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/10/2021] [Accepted: 02/12/2021] [Indexed: 05/03/2023]
Abstract
With balanced spatial resolution, imaging depth, and functional sensitivity, photoacoustic tomography (PAT) hold great promise for human brain imaging. However, the strong acoustic attenuation and aberration of the human skull (∼8 mm thick) are longstanding technical challenges for PAT of the human brain. In this work, we numerically investigated the impacts of the stratified human skull on photoacoustic wave propagation (i.e., the forward model) and PAT image formation (i.e., the inverse model). We simulated two representative transcranial PAT implementations: photoacoustic computed tomography (PACT) and photoacoustic macroscopy (PAMac). In the forward model, we simulated the detailed photoacoustic wave propagation from a point or line source through a digital human skull. The wave attenuation, refraction, mode conversation, and reverberation were thoroughly investigated. In the inverse model, we reconstructed the transcranial PACT and PAMac images of a point or line target enclosed by the human skull. Our results demonstrate that transcranial PAMac suffers mainly from wave reverberation within the skull, leading to prolonged signal duration and reduced axial resolution. Transcranial PACT is more susceptible to the skull's acoustic distortion, mode conversion, and reverberation, which collectively lead to strong image artifacts and deteriorated spatial resolutions. We also found that PACT with a ring-shaped transducer array shows more tolerance of the skull's adverse impacts and can provide more accurate image reconstruction. Our results suggest that incorporating the skull's geometry and acoustic properties can improve transcranial PAT image reconstruction. We expect that our results have provided a more comprehensive understanding of the acoustic impact of the human skull on transcranial PAT.
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Affiliation(s)
- Bingyang Liang
- School of Electrical Engineering and Intelligentization, Dongguan University of Technology, Dongguan 523808, China
- National Key Laboratory on Vacuum Electronics, University of Electronic Science and Technology of China (UESTC), Chengdu 610054, China
| | - Shaomeng Wang
- National Key Laboratory on Vacuum Electronics, University of Electronic Science and Technology of China (UESTC), Chengdu 610054, China
| | - Fei Shen
- School of Electrical Engineering and Intelligentization, Dongguan University of Technology, Dongguan 523808, China
| | - Qing Huo Liu
- Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, USA
| | - Yubin Gong
- School of Electrical Engineering and Intelligentization, Dongguan University of Technology, Dongguan 523808, China
- National Key Laboratory on Vacuum Electronics, University of Electronic Science and Technology of China (UESTC), Chengdu 610054, China
| | - Junjie Yao
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
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Abstract
This review considers glioma molecular markers in brain tissues and body fluids, shows the pathways of their formation, and describes traditional methods of analysis. The most important optical properties of glioma markers in the terahertz (THz) frequency range are also presented. New metamaterial-based technologies for molecular marker detection at THz frequencies are discussed. A variety of machine learning methods, which allow the marker detection sensitivity and differentiation of healthy and tumor tissues to be improved with the aid of THz tools, are considered. The actual results on the application of THz techniques in the intraoperative diagnosis of brain gliomas are shown. THz technologies’ potential in molecular marker detection and defining the boundaries of the glioma’s tissue is discussed.
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12
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Tang Y, Yao J. 3D Monte Carlo simulation of light distribution in mouse brain in quantitative photoacoustic computed tomography. Quant Imaging Med Surg 2020; 11:1046-1059. [PMID: 33654676 DOI: 10.21037/qims-20-815] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Background Photoacoustic computed tomography (PACT) detects light-induced ultrasound (US) waves to reconstruct the optical absorption contrast of the biological tissues. Due to its relatively deep penetration (several centimeters in soft tissue), high spatial resolution, and inherent functional sensitivity, PACT has great potential for imaging mouse brains with endogenous and exogenous contrasts, which is of immense interest to the neuroscience community. However, conventional PACT either assumes homogenous optical fluence within the brain or uses a simplified attenuation model for optical fluence estimation. Both approaches underestimate the complexity of the fluence heterogeneity and can result in poor quantitative imaging accuracy. Methods To optimize the quantitative performance of PACT, we explore for the first time 3D Monte Carlo (MC) simulation to study the optical fluence distribution in a complete mouse brain model. We apply the MCX MC simulation package on a digital mouse (Digimouse) brain atlas that has complete anatomy information. To evaluate the impact of the brain vasculature on light delivery, we also incorporate the whole-brain vasculature in the Digimouse atlas. k-wave toolbox was used to investigate the effect of inhomogeneous illumination on the reconstructed images and chromophore concentration estimation. Results The simulation results clearly show that the optical fluence in the mouse brain is heterogeneous at the global level and can decrease by a factor of five with increasing depth. Moreover, the strong absorption and scattering of the brain vasculature also induce the fluence disturbance at the local level. Conclusions Both global and local fluence heterogeneity contributes to the reduced quantitative accuracy of the reconstructed PACT images of mouse brain. Correcting the optical fluence distribution can improve the quantitative accuracy of PACT.
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Affiliation(s)
- Yuqi Tang
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Junjie Yao
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
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