Diffusion-weighted imaging with flow-compensated diffusion encodings and tri-exponential IVIM imaging

具有流量补偿扩散编码和三指数 IVIM 成像的扩散加权成像

• 批准号: 437119659
• 负责人: Professor Dr. Frederik B. Laun
• 金额: --
• 依托单位: Radiologisches Institut
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/437119659?language=en
• 关键词: Diffusion; weighted; imaging; flow; compensated

The intravoxel incoherent motion (IVIM) by Denis le Bihan et al. attributes the observed strong signal decay in magnetic resonance diffusion-weighted imaging at low b-values to the presence of a compartment containing blood as a flowing fluid, which is separated from a tissue compartment that only experiences diffusive motion. The IVIM model is attractive because it allows assessment of perfusion parameters in native exams. Ongoing discussions about Gadolinium depositions in the human brain have further increased this attractiveness. This proposal builds on two recent research findings. First, the IVIM effect vanishes when using short flow-compensated (FloCo) diffusion encodings, but returns for FloCo diffusion encodings of longer duration. Using the IVIM model by Denis le Bihan et al. for interpreting this behavior makes possible the assessment of blood flow correlation time τ and vessel segment length l, which represent parameters that are important in the context of angiogenesis in oncology. Second, the often assumed bi-exponential signal decay model breaks down at low b-values and a tri-exponential model (tri-exp) often appears to be more appropriate. The origin of this tri-exponential behavior is currently unclear, but appealing interpretations can easily be imagined such as attributing venous and arterial compartment to the two flow-compartments of the tri-exponential model. This proposal aims at elucidating the mechanisms that generate the FloCo and tri-exp IVIM contrast. Experimentally, this shall be achieved by performing FloCo and tri-exp IVIM with varying echo time (TE) and field strength (B0). This shall help identifying the contributions of different compartments (such as venous, arterial, pre-urine in kidney) by making use of the fact that transversal relaxation times of these compartments differ and moreover depend on B0. Since these IVIM exams are experimentally challenging, one part of the proposal is focused on optimized data acquisition strategies. The experiments will be conducted measuring healthy volunteers.

Denis le Bihan等人的体素内非相干运动（IVIM）将在低b值下磁共振扩散加权成像中观察到的强信号衰减归因于存在包含血液作为流动流体的隔室，其与仅经历扩散运动的组织隔室分离。IVIM模型是有吸引力的，因为它允许在本地检查中评估灌注参数。正在进行的关于钆在人脑中沉积的讨论进一步增加了这种吸引力。这一建议建立在两项最新研究成果的基础上。首先，当使用短流量补偿（FloCo）扩散编码时，IVIM效应消失，但是对于较长持续时间的FloCo扩散编码返回。使用Denis le Bihan等人的IVIM模型来解释这种行为，可以评估血流相关时间τ和血管段长度l，这两个参数在肿瘤血管生成的背景下非常重要。其次，通常假设的双指数信号衰减模型在低b值处失效，并且三指数模型（tri-exp）通常看起来更合适。这种三指数行为的起源目前尚不清楚，但可以很容易地想象出吸引人的解释，例如将静脉和动脉室归因于三指数模型的两个流动室。该提案旨在阐明产生FloCo和tri-exp IVIM造影剂的机制。在实验上，这应通过使用不同回波时间（TE）和场强（B 0）执行FloCo和tri-exp IVIM来实现。这将有助于通过利用这些隔室的横向弛豫时间不同并且还取决于B 0的事实来识别不同隔室（诸如肾中的静脉、动脉、前尿）的贡献。由于这些IVIM考试在实验上具有挑战性，因此该提案的一部分集中在优化的数据采集策略上。实验将测量健康志愿者。