Ultrasound Imaging of Breast by Use of a Hemispheric Array and Inverse Scattering

描述（由申请人提供）：该项目的目标是通过使用半球换能器阵列进行测量和逆散射进行图像重建，在体内形成整个乳房体积的高分辨率无斑点定量超声图像。这一目标的实现将表明在不使用电离x射线的情况下使用非电离超声成像筛查乳腺癌的临床可行性，并将为乳腺癌检测的无风险检查奠定基础。所提出的方法将克服x线乳房摄影的局限性，如致密乳房的对比度分辨率低，压迫引起的解剖变形和患者的不适，以及植入乳房的成像效果差。这项技术的成功将最终改变乳腺癌筛查的方式，并显著改善乳腺癌的检测、诊断和复发监测以及对乳腺癌治疗的反应。在提出的系统中，超声波被传输到乳房，接收乳房散射的波，并存储散射波的测量值，用于随后的离线图像重建。所设想的与每个换能器元件相关联的发射和接收通道的并行结构允许在短时间内（例如，大约两秒钟）收集来自体内乳房的散射，以避免图像退化的运动伪影。计划利用可用的计算资源进行脱机处理以进行图像重建，从而避免了获取和配置计算机设备的需要。该半球阵列由多个平面组成，因此可以使用传统的平面晶圆制造技术来实现该阵列。该系统具有发送电子设备、接收电子设备和与每个元件相关联的发送-接收开关。控制单元与电子设备通信。图像重建首先使用测量的脉冲波形来估计乳房的总体特性（即轮廓，平均声速和平均衰减斜率）。根据这些特性，确定背景散射并从测量的散射中减去，得到与组织变化线性相关的残余散射。散射测量是在近场，但散射信号的时间傅里叶变换系数模拟了局部区域的远场测量，这些局部区域用局部组织变化的空间傅里叶变换分量填充了傅里叶空间频率空间的一个半球。这些测量被外推，以获得在相反半球的傅里叶空间频率分量的值。基于乳房特征的初始估计，利用整个空间频率分量形成场的加权乘积，然后进行迭代细化。所得到的图像显示整个乳房体积的声速和衰减斜率。

DESCRIPTION (provided by applicant): The objective of this project is to form high-resolution speckle-free quantitative ultrasound images throughout the volume of the breast in vivo by using a hemispheric transducer array for measurements and inverse scattering for image reconstruction. Achievement of this objective will show the clinical feasibility of using non-- ionizing ultrasound imaging to screen for breast cancer without the use of ionizing x-rays and will provide a foundation for risk-free examination of the breast for cancer detection. The proposed methods will overcome x- ray mammography limitations such as low resolution of contrast in dense breasts, compression-induced deformation of anatomy and discomfort in patients, and poor imaging of breasts with implants. Success would ultimately change the way screening for breast cancer is performed and significantly improve detection, diagnosis, and monitoring for recurrence or response to treatment of breast cancer. In the proposed system, ultrasound waves are transmitted into the breast, waves scattered by the breast are received, and the measurements of the scattered waves are stored for subsequent off-line reconstruction of images. The envisioned parallel architecture of the transmit and receive channels associated with each transducer element permits the collection of scattering from the in vivo breast during a short time, e.g., about two seconds, to avoid image-degrading motion artifacts. The planned use of off-line processing by available computing resources for image reconstruction circumvents the need to acquire and configure computer facilities. The hemispheric array is comprised of multiple planar facets so that conventional flat-wafer fabrication technology can be used to implement the array. The system has transmit electronics, receive electronics, and a transmit-receive switch associated with each element. A control unit communicates with the electronics. Image reconstruction begins by using measured pulse waveforms to estimate the gross properties (i.e., contour, average speed of sound, and average slope of attenuation) of the breast. From these properties, background scattering is determined and subtracted from the measured scattering to obtain residual scattering linearly related to tissue variations. The scattering measurements are in the near field but the coefficients of the temporal Fourier transform of the scattered signals emulate far field measurements in local regions that fill a hemisphere of Fourier spatial-- frequency space with components of the spatial Fourier transform of the local tissue variations. These measurements are extrapolated to obtain values of the Fourier spatial-frequency components in the opposite hemisphere. The entire sphere of spatial-frequency components is used to form weighted products of fields that are based on the initial estimate of breast characteristics and are then iteratively refined. The resulting images show sound speed and attenuation slope throughout the breast volume. PUBLIC HEALTH RELEVANCE: The objective of this project is to form significantly improved ultrasonic images throughout the volume of the breast in vivo by using a novel imaging system. Achievement of this objective will show the clinical feasibility of using non-ionizing ultrasound imaging to screen for breast cancer without the use of ionizing x-rays, provide a foundation for risk-free examination of the breast for cancer detection, and overcome x-ray mammography limitations such as low resolution of contrast in dense breast, compression induced deformation of anatomy and discomfort in patients, and poor imaging of breasts with implants. Success would ultimately change the way screening for breast cancer is performed and significantly improve detection, diagnosis, and monitoring for recurrence or response to treatment of breast cancer.