Dynamic MRM: Source of Specificity Errors and Solutions

描述（由申请人提供）： 磁共振乳腺摄影（MRM）是一种正在开发的成像技术，以克服X射线乳腺摄影的局限性。一种方法使用从动态对比增强（DCE）数据得到的渗透率-表面积（PS）乘积来提高特异性。通过这种技术获得的特异性（37 - 97%）存在争议。DCE需要高的时间分辨率来收集动力学信息，但牺牲了空间分辨率。没有人报道过部分容积效应引起的PS产品的平均值是否限制了使用PS产品区分和分级肿瘤的有效性。我们正在测试的假设，即在人类DCE MRM中使用的空间分辨率导致部分体积平均值，显着减少了预后信息与PS产品计算从DCE-MRM数据，并减少编码方法，重建图像的基础上，一个参考图像产生PS产品与部分体积平均值。然后，我们展示了一种技术，以获得高的时间和空间分辨率的图像。我们将通过研究Gd（III）-DTPA在N-乙基-N-亚硝基脲诱导的大鼠乳腺肿瘤中感兴趣的肿瘤区域中的PS产物作为平面分辨率和切片厚度的函数来实现这些目标。使用两室模型计算PS值，平面内分辨率包括临床上使用的分辨率6.25 mm 2，以及用于体外分析血管密度的“显微镜视野”尺寸0.74和0.152 mm 2。PS值与肿瘤分级、血管密度和血管通透性因子相关。我们应用减少编码方法获得DCE MRM数据具有高的时间和空间分辨率，并表明，从这些图像计算的PS产品是准确的相对于那些与标准的高空间分辨率技术。该算法使用了一个广义的系列方法与前和后对比度增强的参考图像，TRIGR。利用TRIGR技术将低平面分辨率的动态数据重建到高空间分辨率。这保持了高的时间分辨率。该协议，然后使用DCE MRM和树枝状聚合物为基础的造影剂，以区分良性和恶性肿瘤，并与组织学方法进行比较。

DESCRIPTION (provided by applicant): Magnetic resonance mammography (MRM) is an imaging technique under development to overcome the limitations of X-ray mammography. One method uses permeability-surface area (PS) products derived from dynamic contrast enhancement (DCE) data to improve specificity. The specificity, 37 to 97%, obtained by this technique is controversial. DCE requires high temporal resolution to collect the kinetic information at the expense of spatial resolution. No one has reported if the averaging of the PS product, induced by partial volume effects, limits the effectiveness in using PS products to differentiate and grade tumors. We are testing the hypothesis that the spatial resolution used in human DCE MRM results in partial volume averaging that significantly reduces the prognostic information obtainable with PS products calculated from DCE-MRM data, and that reduced encoding methods that reconstruct images based on one reference image produce PS-products with partial volume averaging. We then demonstrate a technique to obtain images with both high temporal and spatial resolutions. We will accomplish these goals by studying the PS product of Gd(III)-DTPA in tumor region of interests in N-ethyI-N-nitrosourea induced rat mammary tumors as a function of both the in plane resolution and slice thickness. The PS values are calculated with a two compartment model at in plane resolutions that include those used clinically, 6.25 mm2, and at the "microscopic field" sizes used to analyze vascular density, 0.74 and 0.152 mm2, in vitro. PS values are correlated to tumor grade, vascular density, and vascular permeability factor obtained by in vitro histochemical methods. We apply a reduced encoding method to obtain DCE MRM data with both high temporal and spatial resolutions, and show that the PS product calculated from these images are accurate relative to those obtained with standard high spatial resolution techniques. The algorithm uses a generalized series method with both pre and post contrast enhanced reference images, TRIGR. The dynamic data obtained with low in plane resolution is reconstructed to high spatial resolution with TRIGR. This maintains the high temporal resolution. The protocol is then used with DCE MRM and a dendrimer based contrast agent to differentiate benign from malignant tumors and compared against histological methods.