TISSUE CHARACTERIZATION WITH SLAB SCAN DIFFUSIION MRI

在医学成像中，组织定征是评估脑肿瘤病理学和形态学的基础。在无造影剂情况下获得的T1或T2加权MR图像上，病理组织与正常组织的区别通常是有限的。然而，在急性中风的情况下，弥散加权MR成像的结果是良好的对比度。此外，张量扩散加权在一个相当宽的范围比通常使用的，它已被证明，在脑组织中的扩散更好地描述了两个扩散组件。这一发现被称为多成分扩散，可能是由于分离的水室，如细胞外和细胞内的水池，或由于显微结构特征。用线扫描扩散成像（LSDI）在脑肿瘤中获得的初步数据表明，两个表观扩散系数（ADC）及其各自的幅度允许在肿瘤、周围水肿、和正常组织。基于这些参数的图像，连同通过扩散张量成像的纤维束的详细映射，提供了非常适合于脑肿瘤病理学和形态学评估的组织表征。本文提出的研究的主要目标是实现快速扩散成像技术，称为平板扫描扩散成像（SSDI），在几分钟的扫描时间内对整个脑体积进行张量和多组分ADC组织表征。所提出的扩散成像技术不需要心脏门控或后处理来抑制运动伪影。与单次激发回波平面扩散加权成像相反，使用SSDI，在磁化率变化较大的区域中的失真伪影最小。将收集正常志愿者和不同脑肿瘤患者的弥散张量和多组分ADC数据。将使用正常受试者中获得的ADC数据确定正常组织值及其各自的方向变异性（各向异性）。利用扩散张量数据和多分量ADC参数的组织分离可以与通过使用造影剂和常规T1加权MR成像建立的肿瘤边缘进行比较。该计划是将扩散张量数据和多分量ADC参数与特定肿瘤病理、恶性程度指导和肿瘤的不同分量（即，坏死部分、边缘及周围组织浸润。因此，这项研究提出了将基础研究直接应用于要求最高灵敏度和特异性的临床情况，用于其他治疗决策的侵入性治疗。

In medical imaging, tissue characterization is fundamental for the assessment of brain tumor pathology and morphology. On T1 or T2- weighted MR images obtained without contrast agents., distinction of pathologic tissue from normal tissue often is limited. Excellent contrast, however, results from diffusion weighted MR imaging in the case of acute stroke. Moreover, tensor diffusion weighting over a considerable wider range than typically used, it has been demonstrated that diffusion in brain tissue is described better with two diffusion components. This finding, referred to as multi--component diffusion, may be due to separate water compartments, such as the extra- and intra-cellular water pools, or due to micro-structural features Preliminary data obtained with line scan diffusion imaging (LSDI) in brain tumors indicates that the two apparent diffusion co-efficients (ADC) and their respective amplitudes permit a clear differentiation among tumor, surrounding edema, and normal tissue. Images based on these parameters, together with the detailed mapping of the fiber tracts through diffusion tensor imaging, provide a tissue characterization that is very suitable for the assessment of brain tumor pathology and morphology. A principal goal of the research proposed here is to implement a fast diffusion imaging technique, referred to as slab scan diffusion imaging (SSDI), for tensor and multi-component ADC tissue characterization of the entire brain volume in a scan time of a few minutes. The proposed diffusion imaging technique does not require cardiac gating or post processing for the suppression of motion artifacts. With SSDI, contrary to single-shot echo planar diffusion-weighted imaging, distortion artifacts in areas of large susceptibility variations are minimal. Diffusion tensor and multi-component ADC data will be collected in normal volunteers and in patients with different brain tumors. Normal tissue values and their respective direction variability (anisotropy) will be established with the ADC data obtained in normal subjects. Tissue separations with diffusion tensor data and multi- component ADC parameters can be compared with tumor margins established by the use of contrast agents and conventional T1-weighted MR imaging. The plan is to correlate the diffusion tensor data and multi- component ADC parameters with the specific tumor pathologies, malignancy guide, and different components of a tumor, i.e., necrotic part, margin, and infiltrated surrounding tissue. The study, therefore, proposes direct applications of basic research to clinical situations demanding the highest possible sensitivity and specific for invasive treatment of other therapeutic decisions.