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    Home > Active Ingredient News > Study of Nervous System > NBE | Wang Lihong and others develop the human brain three-dimensional panoramic fast scanning photoacoustic tomography-1K3D-fPACT

    NBE | Wang Lihong and others develop the human brain three-dimensional panoramic fast scanning photoacoustic tomography-1K3D-fPACT

    • Last Update: 2021-06-04
    • Source: Internet
    • Author: User
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    Editor-in-Chief | Brain science is the most challenging major scientific problem in the 21st century.
    Its significance is to promote human understanding of the mechanism of cognition, thinking, consciousness and language, and to help diagnose and treat brain diseases.
    It is regarded as a new economic growth point in the future.
    The potential engine leading the new technological revolution.

    The development of brain science research is inseparable from advanced brain functional imaging and detection technology.
    Among them, blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) is used as the mainstream technology of non-invasive brain functional imaging in scientific research and clinical applications.

    However, its high cost, large area, lack of molecular specificity, incompatibility with ferromagnetic implants, and the need to place the subject in a confined space with high noise limit its wide application.

    In recent years, photoacoustic imaging, as a new composite imaging technology, has been used in angiography, tumor diagnosis, and animal neuroimaging because of its molecular specificity of optical imaging and the depth and resolution of ultrasound imaging.
    Rapid development.

    At the same time, photoacoustic computed tomography (PACT) can quantify blood oxygen saturation by measuring the concentration of deoxyhemoglobin (HbR) and oxyhemoglobin (HbO2), thereby providing a safe, efficient, and low-cost functional imaging method.

    However, the early PACT system was limited by factors such as imaging speed, sensitivity, field of view and penetration depth, and its application in the field of clinical brain imaging was still blank.

    On May 31, 2021, the research team of Lihong V.
    Wang from California Institute of Technology (Caltech) and Charles Y.
    Liu and Danny J.
    Wang from the University of Southern California (USC) collaborated on Nature Biomedical Engineering.
    Published an article Massively parallel functional photoacoustic computed tomography of the human brain, applying photoacoustic imaging theory to human brain functional imaging, designed a dual-wavelength laser irradiation system and ultrasound transducer array, and developed an ultra-low noise front-end signal amplifier circuit, Integrating a real-time full-channel signal acquisition system, using a panoramic scanning strategy, developed a segmented heterogeneous acoustic medium adaptive reconstruction algorithm, and designed an ergonomic head stabilization device, and successfully developed a human brain three-dimensional panoramic fast scanning light Acoustic tomography (1K3D-fPACT).

    The researchers performed functional brain imaging on several hemicranial postoperative patients (who underwent hemicranial craniectomy) and achieved an angiogram of 11 mm below the cerebral cortex in a 10 cm diameter field of view, and measured HbR and Functional changes in HbO2 concentration can be used to observe brain function responses to cognitive stimulus tasks such as exercise, hearing, and language.

    The imaging spatial resolution and temporal resolution reached 350 microns and 2 seconds, respectively, the spatial specificity corresponding to 83% sensitivity was 85% to 93%, and the area under the receiver operating characteristic curve (ROC) (AUC) was 0.

    These characteristic parameters are highly consistent with the results obtained by the same subjects using 7T MRI imaging, and the functional response delay detected by photoacoustic tomography is about 2 seconds shorter than that of 7T MRI imaging, so it can more accurately reflect the characteristics of neuronal activity.
    It is expected to improve the accuracy of clinical brain function detection.

    In terms of hardware design, the imaging system uses pulsed lasers of two wavelengths (corresponding to the dominant absorption bands of HbR and HbO2, respectively) to achieve wide-field illumination.

    In terms of ultrasonic detection, the system consists of 4 1/4 arc ultrasonic transducer arrays.
    Each array evenly distributes 256 transducers with a center frequency of 2.
    25 MHz, which are connected to the preamplifier and On the data acquisition card.

    The four annular arrays can be rotated and scanned coaxially around the center of the sphere, thereby forming a hemispherical detection surface.

    According to different imaging applications, the system can scan in reference mode (to achieve an isotropic spatial resolution of 350 microns) and functional mode (to achieve a time resolution of 2 seconds).

    In the experimental design, in order to compare the imaging quality of 1K3D-fPACT and 7T BOLD fMRI, the researchers performed brain scans on several patients.

    In the benchmark mode, 1K3D-fPACT can obtain clear three-dimensional angiography.
    After image registration, the result has a high degree of spatial similarity with the gold standard magnetic resonance angiography (MRA) imaging, and can obtain more abundant Blood vessel details.

    Using functional mode to scan, the 1K3D-fPACT system can achieve functional imaging of brain functional areas at a frame rate of 0.
    5 Hz.

    Aiming at the motor area of ​​the cerebral cortex, the researchers designed three motor function tasks (respectively, continuous finger tapping, lip wrinkling, and tongue tapping) for the subjects to complete.

    During the execution of each action, the researchers used 1K3D-fPAC and 7T fMRI to image the subjects’ brains, and recorded the changes in signal intensity in various areas of the cerebral cortex during the process.

    Based on this time series, the researchers used statistical methods to extract the more violent areas of the cerebral cortex and compared them with BOLD fMRI.

    The comparison results show that the cerebral cortex response areas detected by the two imaging methods are highly similar, which proves the feasibility of using 1K3D-fPACT for functional brain imaging.

    Furthermore, the researchers designed passive auditory tasks and silent word generation tasks to image the central response of the subjects’ language functions, and the results are still highly similar to BOLD fMRI.

    In summary, this research combines high-density ultrasound detection, high-quality hardware architecture, and high-stability algorithm design to achieve high-quality brain function imaging of patients undergoing hemicranial resection.

    This research result has laid a solid foundation for more extensive and universal clinical brain function photoacoustic imaging.

    It is reported that the first author of this article is Dr.
    Na Shuai from California Institute of Technology, and the other three co-first authors are Assistant Professor and Director of Cerebrovascular Surgery Russin J.
    Johnathan from USC, Dr.
    Lin Li from California Institute of Technology, and Dr.
    Yuan Xiaoyun is now a postdoctoral fellow at Tsinghua University.

    The corresponding authors of this article are Professor Charles Y.
    Liu from USC and Professor Lihong V.
    Wang from California Institute of Technology.

    Original link: https://doi.
    1038/s41551-021-00735-8 Plate maker: Notes for reprinting on the 11th [Non-original article] The copyright of this article belongs to the author of the article.
    Personal forwarding and sharing are welcome.
    Reprinting without permission is prohibited.
    The author has all legal rights, and offenders must be investigated.
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