全脑高分辨伪连续动脉自旋标记技术的优化与应用

发布时间：2018-05-26 22:15

本文选题：脑血流 + 动脉自旋标记　；参考：《浙江大学》2017年硕士论文

【摘要】：定量测量脑血流(CBF)作为测量灌注的方式之一,对血管性或神经退行性疾病的病理机制的理解和诊断具有重要意义。动脉自旋标记技术(ASL)是目前唯一一种无创、无外加造影剂的定量检测CBF的方法。但ASL存在一些误差来源和不确定性,包括组织T1效应、传输时间效应、信噪比(SNR)低、时空分辨率低等,其鲁棒性有待提高。近几年发展起来的3DGRASEpCASL序列极大地提高了 ASL的SNR,multi-shot的读出方式也有利于分辨率的提高,但其参数和采样策略仍有待于进一步优化。颞叶癫痫伴海马硬化(TLE-HS)与发作间期海马区域的低灌注有重要关系。以往TLE-HS的CBF偏侧性都是在忽略组织T1效应的情况下得出的,但实际上海马硬化的同时T1也升高,将会影响CBF偏侧性。许多病变与白质的异常灌注有关,但白质的灌注测量一直面临SNR低和传输时间效应的问题,使得ASL在白质中的应用受到限制。针对以上相关问题,本论文进行了以下两项主要工作:(1)本文通过仿真,并用multi-shot 3D GRASE pCASL序列采集21个高分辨的病人数据,来研究组织T1对于CBF偏侧化的影响。由于ASL的模型有很多种,本文选择其中常见的三种模型:Buxton模型,ParkesI模型和ParkesS模型,并进行比较。经研究,使用T1成像后,偏侧性中值从-2.56最多变为-6.96,诊出率从61.9%最多变为81.0%。TLE-HS的CBF偏侧性提高了,使得更容易区分病人和正常人,从而提高诊断准确性。与病情严重程度的相关性提高,使CBF偏侧性可以作为病情严重程度的参考参数。(2)本文采用多延时(multi-PLD)采样策略来测量白质的CBF,以克服低SNR和传输时间效应。对multi-PLD采样策略进行优化,寻找有效信噪比最优时的标记时长,从而最大化白质CBF估计的可靠性。并采用目前信噪比最高的multi-shot 3D GRASE pCASL序列采集2个健康人的数据以进行验证,发现白质的相关性和p值显著的体素百分比均得到了一定的改善,CBF估计的可靠性得到了提高。
[Abstract]:Quantitative measurement of cerebral blood flow (CBF), as one of the methods of measuring perfusion, is of great significance in understanding and diagnosing the pathological mechanism of vascular or neurodegenerative diseases. Arterial spin labeling (ASL) is the only non-invasive, non-contrast agent quantitative detection method for CBF. However, there are some error sources and uncertainties in ASL, including tissue T1 effect, transmission time effect, low signal-to-noise ratio (SNR), low spatial and temporal resolution, etc. Its robustness needs to be improved. The 3DGRASEpCASL sequences developed in recent years greatly improve the SNR multi-shot readout method of ASL, but its parameters and sampling strategies still need to be further optimized. Temporal lobe epilepsy with hippocampal sclerosis (TLE-HSN) is associated with hypoperfusion in the hippocampal region during interictal period. In the past, the CBF laterality of TLE-HS was obtained by ignoring the tissue T1 effect, but in fact, the hippocampal sclerosis was accompanied by the increase of T1, which would affect the CBF laterality. Many lesions are related to abnormal perfusion of white matter, but the measurement of white matter perfusion has been faced with the problem of low SNR and transmission time effect, which limits the application of ASL in white matter. Aiming at the above problems, the following two main tasks were carried out in this paper: 1) in this paper, 21 high-resolution patient data were collected by multi-shot 3D GRASE pCASL sequence through simulation to study the effect of tissue T1 on CBF lateralization. Because there are many kinds of ASL models, this paper selects and compares three common models: 1: Buxton model (1) Parkes I model and (2) ParkesS model. After the use of T1 imaging, the median value of hemiplegia changed from -2.56 to -6.96, and the diagnostic rate from 61.9% to 81.0%.TLE-HS increased, which made it easier to distinguish patients from normal people and improve the diagnostic accuracy. In order to overcome the low SNR and transmission time effect, we use multi-delay multi-PLD sampling strategy to measure the white matter CBFs. In order to maximize the reliability of white matter CBF estimation, the multi-PLD sampling strategy is optimized to find the best marking time when the effective signal-to-noise ratio (SNR) is optimal. The multi-shot 3D GRASE pCASL sequences with the highest signal-to-noise ratio (SNR) were used to collect data from two healthy subjects for verification. It was found that both the correlativity of white matter and the percentage of voxels with significant p value improved the reliability of CBF estimation to some extent.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R445.9

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