TISSUE CHARACTERIZATION WITH SLAB SCAN DIFFUSIION MRI

在医学影像中，组织表征是评估脑肿瘤病理和形态的基础。在没有造影剂的情况下获得的T1或T2加权MR图像。因此，病理组织与正常组织的区别往往是有限的。然而，在急性脑卒中的情况下，弥散加权磁共振成像结果非常好。此外，张量扩散加权的范围比通常使用的要宽得多，已经证明用两个扩散成分更好地描述脑组织中的扩散。这一发现被称为多组分扩散，可能是由于不同的水室，如细胞外和细胞内的水池，或者是由于微结构特征，脑肿瘤的线扫描扩散成像（LSDI）获得的初步数据表明，两种表观扩散系数（ADC）及其各自的振幅允许肿瘤，周围水肿和正常组织之间的明确区分。基于这些参数的图像，以及通过弥散张量成像对纤维束的详细映射，提供了非常适合评估脑肿瘤病理和形态的组织特征。本文提出的主要研究目标是实现一种快速扩散成像技术，称为平板扫描扩散成像（SSDI），用于在几分钟的扫描时间内对整个脑体积进行张量和多分量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。使用SSDI，与单次回波平面扩散加权成像相反，在磁化率变化较大的区域失真伪影最小。收集正常志愿者和不同脑肿瘤患者的弥散张量和多分量ADC数据。正常组织值及其各自的方向变异性（各向异性）将根据正常受试者的ADC数据建立。使用弥散张量数据和多分量ADC参数的组织分离可以与使用造影剂和传统t1加权MR成像建立的肿瘤边缘进行比较。我们的计划是将扩散张量数据和多分量ADC参数与特定的肿瘤病理、恶性导向以及肿瘤的不同组成部分（坏死部分、边缘、浸润周围组织）联系起来。因此，该研究建议将基础研究直接应用于临床情况，对其他治疗决策的侵入性治疗要求尽可能高的敏感性和特异性。

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.