MRI-Based Elasticity Imaging

乳腺癌是导致妇女死亡的第二大原因，尽管存在一些问题，但人们普遍认为，及早发现恶性肿瘤可以提高成功治疗的机会。越来越多的证据表明，组织弹性可能是检测和分类乳腺病变的一种手段，因为硬度是一种与癌症密切相关的特性。在乳腺癌筛查中，身体检查已经并将继续占据重要地位，这一理论基础得到了强调。支撑项目一的主要假设是乳房组织弹性特性是病理的敏感和特定的预测因素。我们将解决五个具体目标：1)改进我们的数据采集技术，以(i)在更多质量的组织中诱导更大的位移，（ii）通过改进脉冲序列设计减少图像采集时间，以及（iii）使用连续振动操作模式获取数据。2)与Computational Core合作，推进我们基于模型的图像重建方法，包括(i)组织阻尼，（ii）多值属性恢复，（iii）瞬态效应和（iv）重叠区域优化，首先在二维，然后在三维。3)进行瞬态效应和（iv）重叠区域优化，先二维，再三维。3)在受控条件下进行广泛的模拟和模拟成像实验，以确定目标#1和#2中所研究的最佳机械刺激、图像采集和属性估计选项。4)开发一套临床系统，在合理的时间内评估双乳的力学性能，在有限数量的志愿者中论证其可行性并完善手术方案。5)恢复正常和异常乳房x光检查患者的乳腺组织力学特性，首先通过评估的测试阶段，然后与临床核心合作进行前瞻性验证研究。项目一综合了现有的和新颖的想法，将解决许多与乳房弹性成像相关的当前问题。首先，将开发产生压缩或膨胀位移的谐波机械刺激。谐波位移的相位对比测量也将有助于减少患者运动伪影，而多光谱振动刺激的使用将提供解释耗散效应的机会。其次，采用基于模型的属性重建方法，开发可在三维空间精确测量的多维位移场梯度；此外，拟议的MR系统提供的体积地下位移数据提供了比基于模型的图像重建环境中通常可用的组织响应观测更广泛的组织响应观测，这可能转化为相对于迄今为止弹性成像所获得的空间和对比度分辨率的改进。

Breast cancer is the second leading cause of death in women and, despite some questions, it is generally agreed that early detection of malignancies improves the chances of successful treatment. There is mounting evidence to suggests that tissue elasticity might be a means to detect and classify breast lesions because hardness is a property strongly associated with cancer. This rationale is underscore by the prominent place that physical examination has and continues to hold in breast cancer screening. The principle hypotheses which underpins Project I is that breast tissue elastic properties are sensitive and specific predictors of pathology. We will address five specific aims: 1) Advance our data acquisition techniques to (i) induce larger displacements in more mass of tissue, (ii) decrease the image acquisition time through improved pulse sequence designs, and (iii) acquire data using a continuous vibration mode of operation. 2) Advance our model-based image reconstruction methodology in collaboration with the Computational Core to include (i) tissue dampening, (ii) multi-valued property recovery, (iii) transient effects and (iv) overlapping zone optimization, first in two and then in three dimensions. 3) Conduct transient effects and (iv) overlapping zone optimization, first in two and then in three-dimensions. 3) Conduct extensive simulations and phantom imaging experiments under controlled conditions to identify optimal mechanical stimulation, image acquisition and property estimation options from those investigated in Aims #1 and #2. 4) Develop a clinical system to estimate the mechanical properties of both breasts in reasonable times, demonstrate its feasibility and refine procedural protocols on a limited number of volunteers. 5) Recover the mechanical properties of breast tissue on patients with normal and abnormal mammograms, first through a test phase of evaluation followed by a prospective validation study executed in collaboration with the Clinical Core. Project I pursues a synthesis of existing and novel ideas which will address many of the current problems associated with breast elasticity imaging. First, harmonic mechanical stimuli which produce compressional or dilatational displacements will be developed. Phase contrast measurements of harmonic displacement will also serve to reduce patient motion artifacts while the use of multi-spectral vibrational stimuli will afford the opportunity to account for dissipational effects. Second, model-based property reconstruction methods will be deployed to exploit the multi-dimensional displacement field gradients which can be accurately measured in three dimensions. Further, the volumetric subsurface displacement data provided by the proposed MR system provides tissue response observations that are more extensive than those typically available in the model-based image reconstruction context which is likely to translate into improved spatial and contrast resolutions relative to those which have been achieved with elasticity imaging to date.