CN116942103B - Dark-field photoacoustic tomography system and method - Google Patents
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Abstract
Description
技术领域Technical field
本发明涉及生物医学影像技术,尤其涉及一种暗场光声层析成像系统及方法。The invention relates to biomedical imaging technology, and in particular to a dark field photoacoustic tomography system and method.
背景技术Background technique
作为一种新兴的生物医学影像技术,光声层析成像具备速度快、分辨率高、成像信息丰富、安全无辐射的特点,与传统医学影像技术形成了优势互补,并于近年开始向临床转化。光声层析成像技术利用脉冲光照射生物组织,对光有吸收的生物组织成分会在光声效应下产生超声信号,通过探测该超声信号即重建生物组织中吸光成分的图像。As an emerging biomedical imaging technology, photoacoustic tomography has the characteristics of fast speed, high resolution, rich imaging information, safety and no radiation. It complements the advantages of traditional medical imaging technology and has begun to be translated into clinical practice in recent years. . Photoacoustic tomography technology uses pulsed light to illuminate biological tissue. The components of biological tissue that absorb light will generate ultrasonic signals under the photoacoustic effect. By detecting the ultrasonic signals, the image of the light-absorbing components in the biological tissue is reconstructed.
光声效应的机理在于,当脉冲光照射生物体时,对该波长光照有吸收的组织成分会产生短暂的温度升高,从而引起局部压强的快速变化。该压强变化会以超声波(也称光声信号)的形式向生物体外传播,被周边的超声换能器所探测。基于超声换能器在不同位置和时间探测到的不同强度的光声信号,图像重建算法测算生物体中吸光色团的成分(如血红蛋白)、浓度、位置,提供吸光色团分布图像。因此,在光声层析成像系统中,脉冲光照与超声探测的配合从根本上决定了光声层析成像系统的成像性能。The mechanism of the photoacoustic effect is that when pulsed light irradiates an organism, tissue components that absorb light of this wavelength will produce a brief temperature increase, causing rapid changes in local pressure. This pressure change will propagate outside the body in the form of ultrasonic waves (also called photoacoustic signals) and be detected by surrounding ultrasonic transducers. Based on the photoacoustic signals of different intensities detected by the ultrasonic transducer at different positions and times, the image reconstruction algorithm measures the composition (such as hemoglobin), concentration, and location of the light-absorbing chromophore in the organism, and provides an image of the light-absorbing chromophore distribution. Therefore, in the photoacoustic tomography system, the cooperation of pulsed illumination and ultrasonic detection fundamentally determines the imaging performance of the photoacoustic tomography system.
经过了近二十年的发展,光声成像技术已经有了长足的进步。然而,现有的光声层析成像系统在设计中,特别是脉冲光照与超声探测的协同配合上,尚未进行优化与规范,常见的问题在于,现有光声层析成像系统中,脉冲光照在生物组织表面的光照分布与超声探测范围存在较大重叠,造成超声探测区域内的光通量(单位面积的光能量)分布差异较大。由于光在进入生物组织后随深度指数衰减,所以光声成像系统接收到来自组织表面的光声信号通常远强于来自深层组织的光声信号。然而,在有效成像区域内较大的光声信号幅度差异会导致在使用反投影或延时求和等图像重建算法时,在深层组织图像中易呈现无法忽略的浅表信号伪影。除此之外,组织表面较强的光通量产生的较强光声信号在声学特性不均一的生物组织中传播会经历不规则散射,该无效散射信号在被超声换能器接收后,也将在重建图像中产生伪影。After nearly two decades of development, photoacoustic imaging technology has made great progress. However, the design of existing photoacoustic tomography systems, especially the synergy between pulsed illumination and ultrasonic detection, has not been optimized and standardized. A common problem is that in existing photoacoustic tomography systems, pulsed illumination There is a large overlap between the illumination distribution on the surface of biological tissue and the ultrasonic detection range, resulting in a large difference in the distribution of light flux (light energy per unit area) within the ultrasonic detection area. Since light decays exponentially with depth after entering biological tissue, the photoacoustic signal received by the photoacoustic imaging system from the tissue surface is usually much stronger than the photoacoustic signal from the deep tissue. However, the large difference in photoacoustic signal amplitude within the effective imaging area will lead to superficial signal artifacts that cannot be ignored in deep tissue images when using image reconstruction algorithms such as back-projection or delayed summation. In addition, strong photoacoustic signals generated by strong light flux on the tissue surface will experience irregular scattering when propagating in biological tissues with non-uniform acoustic properties. After being received by the ultrasonic transducer, this invalid scattering signal will also Artifacts are produced in the reconstructed image.
发明内容Contents of the invention
针对现有光声层析成像技术的不足,本发明提供一种暗场光声层析成像系统及方法。In view of the shortcomings of existing photoacoustic tomography technology, the present invention provides a dark field photoacoustic tomography system and method.
一种暗场光声层析成像系统,包括导光模块、超声探测模块和承载塑形模块;A dark-field photoacoustic tomography system, including a light guide module, an ultrasonic detection module and a load-bearing shaping module;
所述导光模块对脉冲光束进行扩束和/或定形后形成扩束脉冲光照射待测体,待测体中对扩束脉冲光有吸收的成分吸收扩束脉冲光的能量后产生局部压强变化,局部压强变化以超声波的形式向待测体外多个方向传播超声信号;所述超声探测模块对沿多个方向传播的超声信号进行探测,并将超声信号转化为电压信号;所述承载塑形模块通过安装塑形槽,承载待测体并约束待测体表面形态与方位,从而使得扩束脉冲光在待测体表面的照射范围与入射角度稳定可控;The light guide module expands and/or shapes the pulse beam to form an expanded beam pulse light that irradiates the object to be measured. The component in the object to be measured that absorbs the expanded beam pulse light absorbs the energy of the expanded beam pulse light and generates local pressure. Changes, local pressure changes propagate ultrasonic signals in the form of ultrasonic waves in multiple directions outside the body to be measured; the ultrasonic detection module detects ultrasonic signals propagating in multiple directions, and converts the ultrasonic signals into voltage signals; the load-bearing plastic By installing a shaping groove, the shape module carries the object to be measured and constrains the surface shape and orientation of the object to be measured, thereby making the irradiation range and incident angle of the expanded beam pulse light on the surface of the object to be measured stable and controllable;
所述导光模块调节扩束脉冲光在待测体表面的照射范围,从而调节与超声探测模块对待测体的有效超声探测范围之间的相对位置和角度,使扩束脉冲光在待测体表面的照射范围与超声探测模块的有效超声探测范围在待测体表面不存在重叠区域,或者重叠区域的面积不大于扩束脉冲光在待测体表面照射范围的50%,形成暗场照明;The light guide module adjusts the irradiation range of the expanded-beam pulse light on the surface of the object to be measured, thereby adjusting the relative position and angle between the effective ultrasonic detection range of the object to be measured and the ultrasonic detection module, so that the expanded-beam pulse light can illuminate the surface of the object to be measured. There is no overlapping area between the irradiation range of the surface and the effective ultrasonic detection range of the ultrasonic detection module on the surface of the object to be measured, or the area of the overlapping area is not greater than 50% of the irradiation range of the expanded beam pulse light on the surface of the object to be measured, forming dark field illumination;
所述待测体为生物体、生物组织或者非生物体中的一种或者几种组合;The subject to be tested is one or several combinations of living organisms, biological tissues or non-living bodies;
所述超声探测模块包括多个超声换能器单元,分布于待测体周围,多个超声换能器单元形成一个或多个超声换能器阵列,超声换能器阵列在有效超声探测范围内探测扩束脉冲光在待测体中产生的沿多个方向传播的超声信号,并将超声信号转化为电压信号输出;每个换能器单元可选择自聚焦或非自聚焦的形状,每个换能器单元的有效探测范围服从超声衍射公式;每个超声换能器阵列或探测矩阵的有效超声探测范围亦服从空间采样定理;The ultrasonic detection module includes multiple ultrasonic transducer units, which are distributed around the object to be measured. The multiple ultrasonic transducer units form one or more ultrasonic transducer arrays, and the ultrasonic transducer arrays are within the effective ultrasonic detection range. Detects the ultrasonic signals propagating in multiple directions generated by the expanded beam pulse light in the object to be measured, and converts the ultrasonic signals into voltage signals for output; each transducer unit can choose a self-focusing or non-self-focusing shape. The effective detection range of the transducer unit obeys the ultrasonic diffraction formula; the effective ultrasonic detection range of each ultrasonic transducer array or detection matrix also obeys the spatial sampling theorem;
所述超声探测模块可根据不同需求设计为不同形态,具体为:The ultrasonic detection module can be designed in different forms according to different needs, specifically:
(1)超声探测模块包括一个或多个弧形超声换能器阵列,超声换能阵列的弧度范围在 10度至359度,弧形超声换能器阵列形成弧形超声换能模块;(1) The ultrasonic detection module includes one or more arc-shaped ultrasonic transducer arrays. The arc range of the ultrasonic transducer array is from 10 degrees to 359 degrees. The arc-shaped ultrasonic transducer array forms an arc-shaped ultrasonic transducer module;
(2)超声探测模块包括两个或以上线性超声换能器阵列,排列形成一个多边形或多边形的一部分;(2) The ultrasonic detection module includes two or more linear ultrasonic transducer arrays, arranged to form a polygon or a part of a polygon;
(3)超声探测模块包括多个超声换能器单元,超声换能器单元在空间排布成球面的一部分,形成球面超声换能器阵列;(3) The ultrasonic detection module includes multiple ultrasonic transducer units, which are arranged as part of a sphere in space to form a spherical ultrasonic transducer array;
(4)超声探测模块包括多个超声换能器单元,超声换能器单元在空间排布成一多面体的一部分,形成多面体超声换能器阵列;(4) The ultrasonic detection module includes multiple ultrasonic transducer units. The ultrasonic transducer units are arranged in space as part of a polyhedron to form a polyhedral ultrasonic transducer array;
所述弧形超声换能器阵列的两侧放置导光模块,形成双侧暗场照明;线性超声换能器阵列的一侧放置导光模块,形成单侧暗场照明;球面超声换能器阵列的边缘放置导光模块,形成环形暗场照明;多面体超声换能器阵列的超声换能器单元间隙放置导光模块,形成多边形暗场照明;Light guide modules are placed on both sides of the arc-shaped ultrasonic transducer array to form double-sided dark field illumination; light guide modules are placed on one side of the linear ultrasonic transducer array to form single-sided dark field illumination; spherical ultrasonic transducers Light guide modules are placed at the edge of the array to form annular dark field illumination; light guide modules are placed in the gaps between the ultrasonic transducer units of the polyhedral ultrasonic transducer array to form polygonal dark field illumination;
所述承载塑形模块通过在成像窗口附近安装塑形槽对待测体进行承载与塑形,塑形槽采用坚固或不易形变的材料;承载塑形模块在有效成像区域附近留出供扩束脉冲光和超声信号穿过的成像窗口,窗口采用光和超声易穿过的材料覆盖,在保证约束待测体表面形状的同时,保证不遮挡扩束脉冲光对待测体的照射,也不遮挡超声探测模块对超声信号的探测;The load-bearing shaping module carries and shapes the object to be measured by installing a shaping slot near the imaging window. The shaping slot is made of solid or non-deformable material; the load-bearing shaping module leaves room for beam expansion pulses near the effective imaging area. The imaging window through which light and ultrasonic signals pass through is covered with a material that light and ultrasound can easily pass through. It ensures that the surface shape of the object to be measured is constrained while ensuring that it does not block the irradiation of the expanded beam pulse light on the object to be measured, nor does it block ultrasound. The detection module detects ultrasonic signals;
所述有效成像区域为超声探测模块的有效超声探测范围在待测体内覆盖区域,为待测体一定厚度的截面或者待测体的立体空间;有效成像区域包括表面区域和深层区域,表面区域靠近承载塑形模块,深层区域远离承载塑形模块;有效成像区域的表面区域距离靠近承载塑形模块的承载待测体表面垂直距离0至1 mm,有效成像区域的深层区域距离靠近承载塑形模块的待测体表面垂直距离大于1 mm并小于100 mm;The effective imaging area is the area covered by the effective ultrasonic detection range of the ultrasonic detection module in the body to be measured, which is a section of a certain thickness of the body to be measured or the three-dimensional space of the body to be measured; the effective imaging area includes a surface area and a deep area, and the surface area is close to Bearing the shaping module, the deep area is far away from the bearing shaping module; the surface area of the effective imaging area is 0 to 1 mm away from the surface of the body under test close to the bearing shaping module, and the deep area of the effective imaging area is close to the bearing shaping module The vertical distance on the surface of the object to be measured is greater than 1 mm and less than 100 mm;
扩束脉冲光的照射方向指向或近似指向有效成像区域的中心位置,从待测体表面的照射区域到有效成像区域的中心位置直线距离不超过5 cm,扩束脉冲光在待测体中传播并衰减后,成像区域的深层区域的光通量分布强度至少高于待测体表面最强光通量的1/1000;The irradiation direction of the expanded-beam pulse light points or approximately points to the center of the effective imaging area. The straight-line distance from the irradiation area on the surface of the object to be measured to the center of the effective imaging area does not exceed 5 cm. The expanded-beam pulse light propagates in the object to be measured. After attenuation, the luminous flux distribution intensity in the deep area of the imaging area is at least 1/1000 higher than the strongest luminous flux on the surface of the object to be measured;
扩束脉冲光在待测体表面的照射范围和角度与有效成像区域的尺寸和形状匹配,从而使扩束脉冲光在待测体中传播并散射后在待测体内的光通量分布涵盖有效成像区域的深层区域和表面区域,有效成像区域内的最强光通量与有效成像区域内的最弱光通量的关系为:最强光通量与最弱光通量之比小于等于200;The irradiation range and angle of the expanded beam pulse light on the surface of the object to be measured match the size and shape of the effective imaging area, so that the luminous flux distribution in the object to be measured after the expanded beam pulse light propagates and scatters in the object to be measured covers the effective imaging area In the deep area and surface area, the relationship between the strongest luminous flux in the effective imaging area and the weakest luminous flux in the effective imaging area is: the ratio of the strongest luminous flux to the weakest luminous flux is less than or equal to 200;
所述一种暗场光声层析成像系统还包括:脉冲生成模块、空间扫描模块、数据采集模块以及图像重建模块:The dark-field photoacoustic tomography system also includes: a pulse generation module, a spatial scanning module, a data acquisition module and an image reconstruction module:
所述脉冲光生成模块包括一个或多个光源,用于生成单波长或多波长脉冲光光束;所述空间扫描模块调整待测体与光声成像系统主体的相对位置;所述数据采集模块对超声探测模块输出的电压信号进行处理输出信号数据;所述图像重建模块根据信号数据计算待测体中各吸光色团浓度的分布,生成待测体的图像;The pulse light generation module includes one or more light sources for generating single-wavelength or multi-wavelength pulse light beams; the spatial scanning module adjusts the relative position of the object to be measured and the main body of the photoacoustic imaging system; the data acquisition module The voltage signal output by the ultrasonic detection module is processed to output signal data; the image reconstruction module calculates the distribution of the concentration of each light-absorbing chromophore in the object to be tested based on the signal data, and generates an image of the object to be tested;
所述空间扫描模块调节待测体有效成像区域至与操作者期望观测的区域重叠,同时增大光声层析成像系统成像范围;具体通过定位镜头或标记定位点反馈待测体与光声层析成像系统主体的相对位置或角度;根据待测体的安放位置,手动、自动、自适应中的任意一种或几种方式移动或转动光声成像系统主体与待测体的相对位置;所述光声成像系统主体包括:脉冲生成模块、导光模块、超声探测模块和数据采集模块;The spatial scanning module adjusts the effective imaging area of the object to be measured to overlap with the area that the operator expects to observe, and at the same time increases the imaging range of the photoacoustic tomography system; specifically, it feeds back the object to be tested and the photoacoustic layer through positioning lenses or marking positioning points. Analyze the relative position or angle of the main body of the imaging system; according to the placement position of the object to be measured, move or rotate the relative position of the main body of the photoacoustic imaging system and the object to be measured by any one or more of manual, automatic, and adaptive methods; The main body of the photoacoustic imaging system includes: pulse generation module, light guide module, ultrasonic detection module and data acquisition module;
所述数据采集模块对超声探测模块输出的电压信号进行、采集、处理、传输和存储,并输出信号数据,输出的信号数据幅度正比于与待测体种类有关的超声信号幅度,亦正比于待测体中局部压强变化幅度;The data acquisition module collects, processes, transmits and stores the voltage signal output by the ultrasonic detection module, and outputs signal data. The amplitude of the output signal data is proportional to the amplitude of the ultrasonic signal related to the type of object to be measured, and is also proportional to the amplitude of the ultrasonic signal to be measured. The local pressure change amplitude in the measuring body;
所述图像重建模块根据数据采集模块的信号数据所包含的时间信息和幅度信息进行待测体的图像重建,计算有效成像区域中局部压强变化幅度的分布,进而计算待测体中各吸光色团浓度的分布,生成待测体的图像;The image reconstruction module reconstructs the image of the object to be measured based on the time information and amplitude information contained in the signal data of the data acquisition module, and calculates the local pressure change amplitude in the effective imaging area. distribution, and then calculate the distribution of the concentration of each light-absorbing chromophore in the object to be tested, and generate an image of the object to be tested;
所述局部压强变化幅度正比于吸光成分的光学吸收系数和局部光通量F的乘积,吸光成分的光学吸收系数/>能够表征待测体中各吸光色团浓度,为了基于局部压强变化幅度/>最终获得待测体中吸光成分的光学吸收系数/>,需要根据脉冲光生成模块、导光模块及待测体种类对有效成像区域提供相对均匀或可控的光通量F分布。The local pressure change amplitude is proportional to the optical absorption coefficient of the light-absorbing component The product of the local luminous flux F, the optical absorption coefficient of the light-absorbing component/> It can characterize the concentration of each light-absorbing chromophore in the object to be measured, in order to based on the local pressure change amplitude/> Finally, the optical absorption coefficient of the light-absorbing component in the object to be measured is obtained/> , it is necessary to provide a relatively uniform or controllable light flux F distribution in the effective imaging area according to the pulse light generation module, light guide module and type of object to be measured.
一种暗场光声层析成像方法,基于上述一种暗场光声层析成像系统实现,包括如下步骤:A dark-field photoacoustic tomography method, implemented based on the above-mentioned dark field photoacoustic tomography system, includes the following steps:
步骤1:设计并测试超声探测模块的有效超声探测范围;Step 1: Design and test the effective ultrasonic detection range of the ultrasonic detection module;
步骤2:根据超声探测模块的有效超声探测范围安装承载塑形模块,固定承载塑形模块位置,从而进一步标定脉冲光照区域与承载塑形模块的位置关系;Step 2: Install the load-bearing shaping module according to the effective ultrasonic detection range of the ultrasonic detection module, and fix the position of the load-bearing shaping module, thereby further calibrating the positional relationship between the pulse illumination area and the load-bearing shaping module;
步骤3:确定导光模块的初步安装位置及角度,安装导光模块,引导脉冲光生成模块发出的光束在定形、扩束后照射拟照明区域;通过调节导光模块的光学器件,调整光照范围与角度,与步骤2中标定的脉冲光照区域重叠,以实现光声层析暗场照明;Step 3: Determine the preliminary installation position and angle of the light guide module, install the light guide module, and guide the beam emitted by the pulse light generation module to illuminate the intended illumination area after shaping and expanding it; adjust the illumination range by adjusting the optical devices of the light guide module and angle, overlapping with the pulse illumination area calibrated in step 2 to achieve photoacoustic tomography dark field illumination;
步骤4:在待测体承载塑形模块中放置与人体声学特性相近仿生假体测试其成像效果,通过微调光照的范围与角度,优化成像质量;在优化完成后,判断在拟成像区域内的光学能量密度和功率密度是否服从美国国家激光安全标准;如符合,脉冲光束、超声探测模块、承载塑形模块三者的相对位置与角度得以优化并相对稳定;不符合则继续调节;Step 4: Place a bionic prosthesis with acoustic characteristics similar to that of the human body in the body-to-be-tested body-bearing shaping module to test its imaging effect. Optimize the imaging quality by fine-tuning the range and angle of illumination; after the optimization is completed, determine the area within the intended imaging area. Whether the optical energy density and power density comply with the US national laser safety standards; if they comply, the relative positions and angles of the pulse beam, ultrasonic detection module, and load-bearing shaping module can be optimized and relatively stable; if they do not comply, continue to adjust;
步骤5:根据承载塑形模块所反馈待测体的安放位置,利用空间扫描模块手动、自动或自适应调节待测体与光声层析成像系统主体的相对位置,使得待测体目标成像区域与有效成像区域重叠;Step 5: According to the placement position of the object under test fed back by the load-bearing shaping module, use the spatial scanning module to manually, automatically or adaptively adjust the relative position of the object under test and the main body of the photoacoustic tomography system so that the target imaging area of the object under test is Overlap with the effective imaging area;
步骤6:测试完成后放置待测样品,基于暗场光声层析成像系统完成光照激发、超声探测、空间扫描、数据采集,与图像重建,得到待测体图像。Step 6: After the test is completed, place the sample to be tested. Based on the dark-field photoacoustic tomography system, the illumination excitation, ultrasonic detection, spatial scanning, data acquisition, and image reconstruction are completed to obtain an image of the body to be tested.
本发明有益技术效果:Beneficial technical effects of the present invention:
在光声层析成像中,由于脉冲光在进入待测体后光通量一般随穿透深度的增加呈指数衰减,传统光声层析成像系统接收到来自待测体浅表区域的超声信号通常远强于来自深层区域的超声信号。然而,在成像区域内若存在较大的超声信号幅度差异将会导致在使用反投影或延时求和等图像重建算法时,在待测体深层区域图像中呈现无法忽略的来自浅表区域信号的伪影。除此之外,组织表面区域较强的光通量产生的较强超声信号在声学特性不均一的组织中传播会经历不规则散射,该无效散射信号经超声换能器接收后,也将在待测体深层区域的图像中产生伪影。由于对待测体表面的形状和位置通常缺乏约束或限制,通常导致对待测体表面的光照分布区域可控性较差,降低了光声层析成像系统的成像质量稳定性。为此本发明提出一种暗场光声层析成像系统及方法,采用光声层析暗场照明,解决现有技术的不足。In photoacoustic tomography, since the luminous flux of pulsed light generally attenuates exponentially with the increase of penetration depth after entering the object to be measured, the ultrasonic signal received by the traditional photoacoustic tomography system from the superficial area of the object to be measured is usually far away. Stronger than ultrasound signals from deeper areas. However, if there is a large difference in ultrasound signal amplitude within the imaging area, when using image reconstruction algorithms such as back-projection or delayed summation, signals from the superficial area will not be ignored in the deep area image of the object to be measured. artifacts. In addition, the strong ultrasonic signal generated by the strong light flux in the tissue surface area will experience irregular scattering when propagating in the tissue with non-uniform acoustic properties. After the invalid scattering signal is received by the ultrasonic transducer, it will also be measured in the Artifacts are produced in images of deep areas of the body. Due to the lack of constraints or restrictions on the shape and position of the surface of the object to be measured, the illumination distribution area on the surface of the object to be measured is usually less controllable, reducing the imaging quality stability of the photoacoustic tomography system. To this end, the present invention proposes a dark-field photoacoustic tomography imaging system and method, which uses photoacoustic tomography dark-field illumination to solve the shortcomings of the existing technology.
在本发明中,待测体由承载塑形模块对其进行承载和表面形态的约束;扩束脉冲光在待测体表面的照射范围与超声探测模块的有效超声探测范围在待测体表面不存在重叠区域,或者扩束脉冲光在待测体表面的照射范围与超声探测模块的有效超声探测范围在待测体表面的重叠区域的面积不大于扩束脉冲光在待测体表面照射范围的50%;待测体的有效成像区域为超声探测模块的有效超声探测范围在待测体内覆盖区域,有效成像区域包括表面区域和深层区域,表面区域靠近承载塑形模块,深层区域远离承载塑形模块。调节扩束脉冲光在待测体表面的照射范围与待测体的有效成像区域之间的相对位置和角度,扩束脉冲光不直接照射有效成像区域中的表面区域,在有效成像区域的表面区域实现光声层析暗场照明,使扩束脉冲光在待测体中传播并衰减后,在有效成像区域内提供比传统光声层析成像系统更均匀的光通量分布。In the present invention, the object to be measured is supported and the surface shape is constrained by the load-bearing shaping module; the irradiation range of the expanded-beam pulse light on the surface of the object to be measured is different from the effective ultrasonic detection range of the ultrasonic detection module on the surface of the object to be measured. There is an overlapping area, or the area of the overlapping area between the irradiation range of the expanded beam pulse light on the surface of the object to be measured and the effective ultrasonic detection range of the ultrasonic detection module on the surface of the object to be measured is not larger than the irradiation range of the expanded beam pulse light on the surface of the object to be measured. 50%; the effective imaging area of the object to be measured is the area covered by the effective ultrasonic detection range of the ultrasonic detection module within the body to be measured. The effective imaging area includes the surface area and the deep area. The surface area is close to the load-bearing shaping module, and the deep area is far away from the load-bearing shaping module. module. Adjust the relative position and angle between the illumination range of the expanded beam pulse light on the surface of the object to be measured and the effective imaging area of the object to be measured. The expanded beam pulse light does not directly illuminate the surface area in the effective imaging area. The area realizes photoacoustic tomography dark field illumination, so that after the expanded beam pulse light propagates and attenuates in the object to be measured, it provides a more uniform light flux distribution in the effective imaging area than the traditional photoacoustic tomography system.
本发明方法可以降低表面区域较强的光声信号在图像中的伪影,同时也有助于降低成像系统对数据采集模块中数据采样深度即数位分辨率的要求。通过优化光照区域与超声探测范围,规范待测物体的位置和形态,大幅度降低待测体浅表区域产生的超声信号在深层区域的伪影,提升光声层析成像系统的图像清晰度和图像质量稳定性。The method of the present invention can reduce the artifacts of strong photoacoustic signals in the surface area in the image, and also helps to reduce the requirements of the imaging system for the data sampling depth, that is, the digital resolution, in the data acquisition module. By optimizing the illumination area and ultrasonic detection range, standardizing the position and shape of the object to be measured, the artifacts of ultrasonic signals generated in the superficial area of the object to be measured in the deep area are greatly reduced, and the image clarity and image clarity of the photoacoustic tomography system are improved. Image quality stability.
附图说明Description of the drawings
图1为本发明光声层析成像系统结构示意图。Figure 1 is a schematic structural diagram of the photoacoustic tomography system of the present invention.
图2为本发明光声层析成像系统暗场照明示意图。Figure 2 is a schematic diagram of dark field illumination of the photoacoustic tomography system of the present invention.
图3为本发明成像女性乳腺内部血管例图。Figure 3 is an example of imaging the internal blood vessels of the female breast according to the present invention.
图4为本发明弧形超声换能器阵列的两侧放置导光模块,形成双侧暗场照明示意图。Figure 4 is a schematic diagram of placing light guide modules on both sides of the arc-shaped ultrasonic transducer array of the present invention to form double-sided dark field illumination.
图5为本发明多边形超声换能器阵列一侧放置导光模块,形成单侧暗场照明示意图。Figure 5 is a schematic diagram of placing a light guide module on one side of the polygonal ultrasonic transducer array of the present invention to form single-sided dark field illumination.
图6为本发明承载塑形模块示意图。Figure 6 is a schematic diagram of the bearing shaping module of the present invention.
图7为本发明半球面超声换能器阵列结合环形暗场照明的结构示意图。Figure 7 is a schematic structural diagram of a hemispherical ultrasonic transducer array combined with annular dark field illumination according to the present invention.
图8为本发明多面体超声换能器阵列结合多边形暗场照明的结构示意图。Figure 8 is a schematic structural diagram of a polyhedral ultrasonic transducer array combined with polygonal dark field illumination of the present invention.
具体实施方式Detailed ways
本发明为了改进光声层析系统的成像性能与图像质量,提出了一种暗场光声层析成像系统;下面结合说明书附图和具体实施方式来进一步说明本发明的技术方案。In order to improve the imaging performance and image quality of the photoacoustic tomography system, the present invention proposes a dark-field photoacoustic tomography system; the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments of the description.
本发明提供的一种暗场光声层析成像系统如图1所示,该系统包括脉冲光生成模块1、导光模块2、超声探测模块3、承载塑形模块4、空间扫描模块5、数据采集模块6和图像重建模块7。A dark-field photoacoustic tomography system provided by the present invention is shown in Figure 1. The system includes a pulse light generation module 1, a light guide module 2, an ultrasonic detection module 3, a load-bearing shaping module 4, and a spatial scanning module 5. Data acquisition module 6 and image reconstruction module 7.
所述脉冲光生成模块1包括一个或多个光源,用于生成单波长或多波长脉冲光光束;脉冲光为单波长光束或多波长光束,波长范围为0.3μm–3μm。脉冲光生成模块1为现有技术,例如Nd:YAG纳秒脉冲激光器。The pulse light generation module 1 includes one or more light sources for generating a single-wavelength or multi-wavelength pulse light beam; the pulse light is a single-wavelength light beam or a multi-wavelength light beam, with a wavelength range of 0.3 μm-3 μm. The pulsed light generation module 1 is an existing technology, such as Nd:YAG nanosecond pulse laser.
所述导光模块2,包括反射镜、棱镜、散射片、透镜、光纤和/或光导臂,用于对脉冲光生成模块1发出的脉冲光束进行扩束和/或定形后形成扩束脉冲光,扩束脉冲光照射至待测体,待测体中的吸光成分吸收扩束脉冲光能量后发生局部压强变化,以超声波的形式向待测体外多个方向传播超声信号;待测体可选为生物体、生物组织、非生物体中的一种或者几种组合。The light guide module 2 includes a reflector, a prism, a scattering sheet, a lens, an optical fiber and/or a light guide arm, and is used to expand and/or shape the pulse beam emitted by the pulse light generation module 1 to form an expanded pulse light. , the expanded beam pulse light is irradiated to the object to be measured, and the light-absorbing component in the object to be measured absorbs the energy of the expanded beam pulse light and undergoes local pressure changes, and propagates ultrasonic signals in the form of ultrasonic waves in multiple directions outside the body to be measured; the object to be measured is optional It is one or several combinations of living organisms, biological tissues, and non-living entities.
扩束脉冲光在待测体内衰减,其衰减特性服从Beer-Lambert定律,即待测体内距离体表距离z处的光通量 ,其中/>为待测体表面的光通量,待测体在脉冲光波长下的有效衰减系数 /> ,其中/>为待测体在脉冲光波长下的光学吸收系数,/>为待测体在脉冲光波长下的光学约化散射系数。The expanded beam pulse light attenuates in the body to be measured, and its attenuation characteristics obey the Beer-Lambert law, that is, the luminous flux in the body to be measured at a distance z from the body surface , of which/> is the luminous flux on the surface of the object to be measured, and the effective attenuation coefficient of the object to be measured at the pulse light wavelength/> , of which/> is the optical absorption coefficient of the object under test at the pulse light wavelength,/> is the optically reduced scattering coefficient of the object under test at the pulse light wavelength.
所述超声探测模块3,包括多个超声换能器单元,分布于待测体周围,多个超声换能器单元形成一个或多个超声换能器阵列,超声换能器阵列在有效超声探测范围内探测扩束脉冲光在待测体中产生的沿多个方向传播的超声信号,并将超声信号转化为电压信号输出;每个换能器单元可选择自聚焦或非自聚焦的形状,每个换能器单元的有效探测范围服从超声衍射公式;每个超声换能器阵列或者探测矩阵的有效超声探测范围亦需服从空间采样定理。The ultrasonic detection module 3 includes multiple ultrasonic transducer units distributed around the object to be measured. The multiple ultrasonic transducer units form one or more ultrasonic transducer arrays. The ultrasonic transducer arrays are used in effective ultrasonic detection. It detects the ultrasonic signals propagating in multiple directions generated by the expanded beam pulse light in the object to be measured, and converts the ultrasonic signals into voltage signals for output; each transducer unit can choose the shape of self-focusing or non-self-focusing, The effective detection range of each transducer unit obeys the ultrasonic diffraction formula; the effective ultrasonic detection range of each ultrasonic transducer array or detection matrix also needs to obey the spatial sampling theorem.
超声探测模块3的有效超声探测范围与超声换能器阵列的超声换能器单元的分布范围、相邻间距、探测超声信号波长有关。超声探测模块3的超声换能器阵列在有效探测范围内的空间采样间距短于超声信号波长的一半。The effective ultrasonic detection range of the ultrasonic detection module 3 is related to the distribution range, adjacent spacing, and detection ultrasonic signal wavelength of the ultrasonic transducer units of the ultrasonic transducer array. The spatial sampling spacing of the ultrasonic transducer array of the ultrasonic detection module 3 within the effective detection range is shorter than half the wavelength of the ultrasonic signal.
如图4所示,超声探测模块3包括一个或多个弧形超声换能器阵列,超声换能阵列的弧度范围在10度至359度,弧形超声换能器阵列组合形成超声探测模块3。弧形超声换能器阵列的两侧放置导光模块2,形成双侧暗场照明。As shown in Figure 4, the ultrasonic detection module 3 includes one or more arc-shaped ultrasonic transducer arrays. The arc range of the ultrasonic transducer array is from 10 degrees to 359 degrees. The arc-shaped ultrasonic transducer arrays are combined to form the ultrasonic detection module 3. . Light guide modules 2 are placed on both sides of the arc-shaped ultrasonic transducer array to form bilateral dark field illumination.
如图5所示,超声探测模块3包括两个或以上线性超声换能器阵列,排列形成一个多边形或多边形的一部分。线性超声换能器阵列的一侧放置导光模块2,形成单侧暗场照明。As shown in Figure 5, the ultrasonic detection module 3 includes two or more linear ultrasonic transducer arrays, arranged to form a polygon or a part of a polygon. The light guide module 2 is placed on one side of the linear ultrasonic transducer array to form single-sided dark field illumination.
如图7所示,超声探测模块3包括多个超声换能器单元,超声换能器单元在空间排布成球面的一部分,形成球面超声换能器阵列。球面超声换能器阵列的边缘放置导光模块2,形成环形暗场照明。As shown in FIG. 7 , the ultrasonic detection module 3 includes multiple ultrasonic transducer units. The ultrasonic transducer units are arranged as part of a sphere in space to form a spherical ultrasonic transducer array. The light guide module 2 is placed on the edge of the spherical ultrasonic transducer array to form annular dark field illumination.
如图8所示,超声探测模块3包括多个超声换能器单元,超声换能器单元在空间排布成一多面体的一部分,形成多面体超声换能器阵列。多面体超声换能器阵列的超声换能器单元间隙放置导光模块,形成多边形暗场照明。As shown in FIG. 8 , the ultrasonic detection module 3 includes multiple ultrasonic transducer units. The ultrasonic transducer units are arranged as part of a polyhedron in space, forming a polyhedral ultrasonic transducer array. A light guide module is placed in the gap between the ultrasonic transducer units of the polyhedral ultrasonic transducer array to form polygonal dark field illumination.
承载塑形模块4,通过安装塑形槽承载待测体并约束待测体表面10形态与方位与预期相同或近似,从而使得扩束脉冲光在待测体表面10的照射范围与入射角度稳定可控,如图6所示。承载塑形模块4通过在成像窗口附近安装塑形槽401对待测体进行承载与塑形,塑形槽401采用坚固或不易形变的材料,包括环氧树脂、塑料、硅胶、橡胶等。承载塑形模块4在有效成像区域9附近留出供扩束脉冲光和/或超声信号穿过的窗口402,窗口采用光和/或超声易穿过的材料覆盖,包括玻璃、亚克力、透明树脂、透明塑料等材料,在保证约束待测体表面10形状的同时,保证不遮挡扩束脉冲光对待测体的照射,也不遮挡超声探测模块3对超声信号的探测。The carrying shaping module 4 carries the object to be measured by installing the shaping groove and constrains the shape and orientation of the surface 10 of the object to be tested to be the same or similar to expected, thereby making the irradiation range and incident angle of the expanded beam pulse light on the surface of the object to be measured 10 stable. Controllable, as shown in Figure 6. The load-bearing shaping module 4 carries and shapes the object to be measured by installing a shaping groove 401 near the imaging window. The shaping groove 401 is made of solid or non-deformable materials, including epoxy resin, plastic, silicone, rubber, etc. The load-bearing shaping module 4 leaves a window 402 near the effective imaging area 9 for the expanded pulse light and/or ultrasound signals to pass through. The window is covered with a material that light and/or ultrasound can easily pass through, including glass, acrylic, and transparent resin. , transparent plastic and other materials, while ensuring to constrain the shape of the surface 10 of the object to be measured, it also ensures that it does not block the illumination of the expanded beam pulse light on the object to be measured, nor does it block the detection of ultrasonic signals by the ultrasonic detection module 3 .
待测体的有效成像区域9为超声探测模块3的有效超声探测范围在待测体内覆盖的区域,为待测体一定厚度的截面或者待测体的立体空间。有效成像区域9包括表面区域和深层区域,表面区域靠近承载塑形模块4,深层区域远离承载塑形模块4。有效成像区域9的表面区域距离待测体表面10的垂直距离为0至1 mm,有效成像区域9的深层区域距离待测体表面10的垂直距离大于1 mm且小于100 mm。The effective imaging area 9 of the object to be measured is the area covered by the effective ultrasonic detection range of the ultrasonic detection module 3 within the object to be measured, and is a section with a certain thickness of the object to be measured or the three-dimensional space of the object to be measured. The effective imaging area 9 includes a surface area and a deep area. The surface area is close to the bearing shaping module 4 and the deep area is far away from the bearing shaping module 4 . The vertical distance between the surface area of the effective imaging area 9 and the surface 10 of the object to be measured is 0 to 1 mm, and the vertical distance between the deep area of the effective imaging area 9 and the surface 10 of the object to be measured is greater than 1 mm and less than 100 mm.
通过导光模块2调节扩束脉冲光在待测体表面10的照射范围与待测体的有效成像区域9之间的相对位置和角度,使扩束脉冲光在待测体表面10上的照射范围与超声探测模块3的有效超声探测范围在待测体表面10上不存在重叠区域,或者重叠区域的面积不大于扩束脉冲光在待测体表面10照射范围的50%,从而在有效成像区域9的表面区域实现光声层析暗场照明。 如附图2所示;The relative position and angle between the illumination range of the expanded-beam pulse light on the surface of the object to be measured 10 and the effective imaging area 9 of the object to be measured are adjusted by the light guide module 2, so that the expanded-beam pulse light is illuminated on the surface of the object to be measured 10. There is no overlapping area between the range and the effective ultrasonic detection range of the ultrasonic detection module 3 on the surface of the object to be measured 10, or the area of the overlapping area is not greater than 50% of the irradiation range of the expanded beam pulse light on the surface of the object to be measured 10, so that effective imaging is achieved The surface area of area 9 realizes photoacoustic tomography dark field illumination. As shown in Figure 2;
扩束脉冲光的照射方向指向或近似指向有效成像区域9的中心位置,从待测体表面10的照射区域到有效成像区域9的中心位置直线距离不超过5 cm,扩束脉冲光在待测体中传播并衰减后,有效成像区域的光通量分布强度至少高于待测体表面10上最强光通量的1/1000。The irradiation direction of the expanded-beam pulse light points or approximately points to the center of the effective imaging area 9. The straight-line distance from the irradiation area of the surface 10 of the object to be measured to the center of the effective imaging area 9 does not exceed 5 cm. After propagating and attenuating in the body, the intensity of the light flux distribution in the effective imaging area is at least higher than 1/1000 of the strongest light flux on the surface 10 of the body to be measured.
扩束脉冲光在待测体表面10的的照射范围与有效成像区域9的尺寸和形状匹配,使扩束脉冲光在待测体中传播并经过待测体散射后在待测体内的光通量分布覆盖有效成像区域9的深层区域和表面区域,在有效成像区域9内的最强光通量与有效成像区域9内的最弱光通量的关系为:最强光通量与最弱光通量之比小于等于200。The irradiation range of the expanded beam pulse light on the surface 10 of the object to be measured matches the size and shape of the effective imaging area 9, so that the expanded beam pulse light propagates in the object to be measured and is scattered by the object to be measured. The light flux distribution in the object to be measured is Covering the deep area and surface area of the effective imaging area 9, the relationship between the strongest luminous flux in the effective imaging area 9 and the weakest luminous flux in the effective imaging area 9 is: the ratio of the strongest luminous flux to the weakest luminous flux is less than or equal to 200.
空间扫描模块5包括运动模组和导轨,用于调整待测体与超声探测模块3的相对位置,从而将待测体中有效成像区域9与操作者希望期望观测的区域重叠,同时增大光声层析成像系统成像范围。待测体与光声层析成像系统的相对位置或角度通过定位镜头或标记定位点反馈。The spatial scanning module 5 includes a motion module and a guide rail, which are used to adjust the relative position of the object to be measured and the ultrasonic detection module 3, so that the effective imaging area 9 in the object to be measured overlaps the area that the operator wishes to observe, and at the same time, the light is increased. Acoustic tomography system imaging range. The relative position or angle of the object to be measured and the photoacoustic tomography system is fed back through the positioning lens or marked positioning points.
数据采集模块6对超声探测模块3输出的电压信号进行放大、采集、处理、传输和存储,并输出信号数据,信号数据的幅度正比于超声信号幅度,亦正比于待测体中局部压强变化幅度。数据采集模块6为现有技术,例如PST的LEGION ADC。The data acquisition module 6 amplifies, collects, processes, transmits and stores the voltage signal output by the ultrasonic detection module 3, and outputs signal data. The amplitude of the signal data is proportional to the ultrasonic signal amplitude and also proportional to the local pressure change amplitude in the body to be measured. . The data acquisition module 6 is an existing technology, such as PST's LEGION ADC.
图像重建模块7根据数据采集模块6的信号数据所包含的时间信息和幅度信息进行待测体的图像重建,计算有效成像区域9中局部压强变化幅度的分布,进而计算待测体中各吸光色团浓度的分布,生成待测体的图像。The image reconstruction module 7 performs image reconstruction of the object to be measured based on the time information and amplitude information contained in the signal data of the data acquisition module 6, and calculates the local pressure change amplitude in the effective imaging area 9 distribution, and then calculate the distribution of the concentration of each light-absorbing chromophore in the object to be tested, and generate an image of the object to be tested.
如图3所示是女性乳腺内部血管成像例图,图像反映接近4cm的深度处依然有一定的血管信号未被体表的信号干扰,形成了较为清晰的血管图像;而常规的光声层析成像设备在4cm深度处会被体表的强信号严重干扰,无法肯定该位置超声信号的确切来源。Figure 3 shows an example of imaging of internal blood vessels in the female breast. The image reflects that there are still certain blood vessel signals at a depth of nearly 4cm that are not interfered by signals from the body surface, forming a clearer blood vessel image; while conventional photoacoustic tomography The imaging equipment will be severely interfered by strong signals from the body surface at a depth of 4cm, making it impossible to determine the exact source of the ultrasound signal at this location.
局部压强变化幅度正比于吸光成分的光学吸收系数和局部光通量F的乘积,吸光成分的光学吸收系数/>能够表征待测体中各吸光色团浓度,为了基于局部压强变化幅度最终获得待测体中吸光成分的光学吸收系数/>,需要对有效成像区域9提供相对均匀或可控的光通量F分布。The local pressure change amplitude is proportional to the optical absorption coefficient of the light-absorbing component The product of the local luminous flux F, the optical absorption coefficient of the light-absorbing component/> Able to characterize the concentration of each light-absorbing chromophore in the object to be measured, in order to based on the local pressure change amplitude Finally, the optical absorption coefficient of the light-absorbing component in the object to be measured is obtained/> , it is necessary to provide a relatively uniform or controllable light flux F distribution for the effective imaging area 9 .
在本实施例中,数据采集模块6的各数据采集通道与超声换能器阵列8的各超声换能器单元一一对应,因此,每个光照脉冲后都能够完成对待测体中一个二维截面的成像。空间扫描模块5可根据定位镜头或标记定位点所反馈待测体的安放位置,手动、自动、或自适应移动或转动待测体或光声层析成像设备,进而在三维空间内提供更大的成像范围。In this embodiment, each data acquisition channel of the data acquisition module 6 corresponds to each ultrasonic transducer unit of the ultrasonic transducer array 8 one-to-one. Therefore, a two-dimensional image of the object to be measured can be completed after each illumination pulse. Cross-sectional imaging. The spatial scanning module 5 can manually, automatically, or adaptively move or rotate the object under test or the photoacoustic tomography device according to the position of the object under test fed back by the positioning lens or the marked positioning point, thereby providing a larger view in the three-dimensional space. imaging range.
具体地,半球面超声换能器阵列8在空间扫描模块5的作用下,可以对待测体在三维空间内提供密集的空间采样,在三维有效成像区域9内实现各向均一的空间分辨率,同时该阵列也可接收在三维空间内沿多个方向传播的超声信号。Specifically, the hemispherical ultrasonic transducer array 8, under the action of the spatial scanning module 5, can provide dense spatial sampling of the object to be measured in the three-dimensional space, and achieve uniform spatial resolution in all directions within the three-dimensional effective imaging area 9. At the same time, the array can also receive ultrasonic signals propagating in multiple directions in three-dimensional space.
本实施例所述一种暗场光声层析成像方法,基于上述一种暗场光声层析成像系统实现,包括如下步骤:The dark-field photoacoustic tomography method described in this embodiment is implemented based on the above-mentioned dark-field photoacoustic tomography system and includes the following steps:
步骤1:设计并测试所述超声探测模块3的有效超声探测范围。在设计过程中如果是在模拟条件下,可借助理论计算、声场仿真软件或有限元分析对超声换能器阵列8的声学特性进行计算和模拟,分析其声场分布等参数,从而确定其有效超声探测范围;如果在实验条件下,可利用单通道超声换能器、超声麦克风等测试工具,测量超声换能器阵列8的声场特性,确定其有效超声探测范围;Step 1: Design and test the effective ultrasonic detection range of the ultrasonic detection module 3. If the design process is under simulation conditions, the acoustic characteristics of the ultrasonic transducer array 8 can be calculated and simulated with the help of theoretical calculations, sound field simulation software or finite element analysis, and its sound field distribution and other parameters can be analyzed to determine its effective ultrasonic Detection range; if under experimental conditions, single-channel ultrasonic transducers, ultrasonic microphones and other testing tools can be used to measure the sound field characteristics of the ultrasonic transducer array 8 to determine its effective ultrasonic detection range;
步骤2:根据超声探测模块3的有效超声探测范围安装承载塑形模块4,并进一步标定拟实施的脉冲光照区域与待测体承载塑形模块4的位置关系;Step 2: Install the load-bearing shaping module 4 according to the effective ultrasonic detection range of the ultrasonic detection module 3, and further calibrate the positional relationship between the pulse illumination area to be implemented and the body-to-be-tested load-bearing shaping module 4;
步骤3:根据待测体种类和有效成像区域9的大小确定拟实施的脉冲光照区域光斑的位置及尺寸;Step 3: Determine the position and size of the light spot in the pulse illumination area to be implemented according to the type of object to be measured and the size of the effective imaging area 9;
根据需求选择不同特性的扩散片,具体为:根据脉冲光生成模块1发出脉冲光束的光斑大小选择扩散片大小,根据导光模块2的安装方式选择扩散片形状,根据重建图像幅度选择扩散片的扩散角大小,初步计算扩散片到承载塑形模块4上成像窗口402的大致空间距离;Select diffusers with different characteristics according to needs, specifically: select the size of the diffuser according to the spot size of the pulse beam emitted by the pulse light generation module 1, select the shape of the diffuser according to the installation method of the light guide module 2, and select the size of the diffuser according to the amplitude of the reconstructed image. The size of the diffusion angle, preliminary calculation of the approximate spatial distance from the diffusion sheet to the imaging window 402 on the load-bearing shaping module 4;
运用折射定律计算扩束脉冲光进入成像窗口402时的入射角,使扩束脉冲光的光照区域在超声探测模块3的有效成像区域9内,且照射方向指向或近似指向有效成像区域9的中心位置;Apply the law of refraction Calculate the incident angle when the expanded beam pulse light enters the imaging window 402, so that the illumination area of the expanded beam pulse light is within the effective imaging area 9 of the ultrasonic detection module 3, and the illumination direction points to or approximately points to the center of the effective imaging area 9;
依据上述理论计算的空间距离和入射角,安装导光模块2,引导脉冲光生成模块1发出的光束在定形、扩束后照射拟照明区域。进一步地,通过调节导光模块2的光学器件,调整光照范围与角度,与理论计算中标定的脉冲光照区域重叠,以实现光声层析暗场照明。在该步骤中,可在拟照明的区域处放置激光显影纸、能量/功率计,或光斑测量仪等光学测量装置,确定实际光照的范围、角度,及能量均匀性等参数;Based on the spatial distance and incident angle calculated by the above theory, the light guide module 2 is installed to guide the light beam emitted by the pulse light generation module 1 to illuminate the intended illumination area after shaping and expanding. Further, by adjusting the optical device of the light guide module 2, the illumination range and angle are adjusted to overlap with the pulse illumination area calibrated in the theoretical calculation, so as to realize photoacoustic tomography dark field illumination. In this step, optical measurement devices such as laser developing paper, energy/power meter, or spot measuring instrument can be placed in the area to be illuminated to determine the actual illumination range, angle, energy uniformity and other parameters;
步骤4:在待测体承载塑形模块4中放置与人体声学特性相近仿生假体(如琼脂)并测试其成像效果,通过微调光照的范围与角度,优化成像质量。在优化完成后,确认在拟成像区域内的光学能量密度和功率密度服从美国国家激光安全标准(ANSI,z136.131–2014)。自此,脉冲光束、超声探测模块3、承载塑形模块4三者的相对位置与角度得以优化并相对稳定;Step 4: Place a bionic prosthesis (such as agar) with acoustic characteristics similar to the human body in the body-to-be-tested body-bearing shaping module 4 and test its imaging effect. Optimize the imaging quality by fine-tuning the range and angle of illumination. After the optimization is completed, confirm that the optical energy density and power density in the intended imaging area comply with the American National Laser Safety Standard (ANSI, z136.131–2014). Since then, the relative positions and angles of the pulse beam, the ultrasonic detection module 3, and the load-bearing shaping module 4 have been optimized and relatively stable;
步骤5:安装并调节空间扫描模块5,可根据承载塑形模块4所反馈待测体的安放位置,手动、自动、或自适应调节待测体与光声层析成像系统的相对位置,使得待测体中的目标成像区域与超声成像探测区域重叠;Step 5: Install and adjust the spatial scanning module 5. The relative position of the object to be measured and the photoacoustic tomography system can be adjusted manually, automatically, or adaptively according to the placement position of the object to be tested as fed back by the shaping module 4, so that The target imaging area in the object to be measured overlaps with the ultrasonic imaging detection area;
步骤6:安放待测样品,完成光照激发、超声探测、空间扫描、数据采集,与图像重建。Step 6: Place the sample to be tested and complete illumination excitation, ultrasonic detection, spatial scanning, data collection, and image reconstruction.
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