血流抑制磁化准备梯度回波识别颅内斑块内出血的关键技术和临床应用研究

In China, ischemic stroke is mostly caused by the rupture of atherosclerotic plaques. Presence of intraplaque hemorrhage (IPH) indicates that the plaque has high risk of rupture. Detection of intracranial IPH is therefore important in the diagnosis of ischemic stroke. IPH consists of a component called methemoglobin which has a short T1 relaxation rate. Methemoglobin has a very high signal in MPRAGE, and is a very good biomarker for plaque instability. However, in the brain, the blood signal in MPRAGE can also be high, interfering with the depiction of IPH. This project proposes to develop dark blood MPRAGE by inserting an appropriate blood suppression module between the magnetization preparation part and acquisition part of the sequence. The blood suppression module would interfere with the inversion recovery process and lead to a reduction in signal-to-noise ratio and spatial resolution. These negative side effects will be compensated through appropriate design of the k-space trajectory and use of variable flip angle during acquisition. Use of fast imaging for scan time reduction will also be incorporated in the sequence. The new sequence will be tested on phantoms and healthy volunteers for its properties. It will then be combined with a T1 weighted three dimensional imaging technique (T1w-SPACE) to study how IPH and other plaque characteristics identified using T1w-SPACE correlate with symptoms among patients with ischemic stroke. The project outcome will help the image based diagnosis of intracranial atherosclerotic diseases.

缺血性脑卒中多由颅内斑块破裂引起。斑块内出血（intraplaque hemorrhage,IPH）反映斑块具有破裂风险，因此识别颅内斑块IPH可以帮助预警缺血性脑卒中。磁化准备快速梯度回波（MPRAGE）磁共振成像技术是用于鉴别IPH的一项关键技术，但在检查颅内血管时，现有的MPRAGE会受到血流伪影的干扰，令识别IPH十分困难，严重妨碍其临床应用。本项目拟研发具有抑制血流功能的MPRAGE解决此难题，序列将选用合适的血流抑制模块配合MPRAGE达到黑血效果，再配以合适的k-空间轨迹和重建方法来增加图像信噪比和提高图像的采集速度，以满足临床应用的需求。新序列还将配合三维T1加权快速自旋回波成像技术，多角度了解颅内斑块的性质，相对全面地了解颅内斑块的成分与临床症状之间的联系。项目成果将提升影像评估颅内斑块破裂风险的能力，对脑血管疾病的早期诊断，早期治疗有推动作用。

项目背景：脑卒中已成为我国致死率和致残率最高的疾病，其中缺血性卒中占80%。缺血性卒中多由颅内斑块破裂所致。斑块内出血（Intraplaque hemorrhage, IPH）反应斑块具有破裂的风险，因此识别颅内斑块内出血能帮助预警缺血性脑卒中。磁化准备快速梯度回波（MPRAGE）是用于鉴别斑块内出血的一个关键技术，但在用于颅内血管壁成像时，现有的MPRAGE 会受到血流伪影的干扰，令识别斑块内出血非常困难，严重妨碍其临床应用。.主要研究内容：（1）利用MATLAB对DANTE进行数值仿真，研究DANTE对磁化矢量的影响。并在西门子序列开发平台上将DANTE开发出来，添加到MPRAGE序列中，开发出新序列DANTE-MPRAGE；（2）开发基于卷积特征的快速磁共振重建方法，用于加速磁共振成像；（3）将新序列DANTE-MPRAGE和T1加权，T2加权SPACE结合起来，组成一套高分辨颅内血管壁扫描方案，用此扫描方案扫描30例脑卒中患者，发现新序列DANTE-MPRAGE能有效识别斑块内出血和夹层中的血栓信号。.重要结果和关键数据：（1）新序列DANTE-MPRAGE，能有效抑制血液信号，覆盖范围180x144x112mm3,能完全覆盖颅内主要大动脉，包括大脑中动脉，颈内动脉，基底动脉，大脑前动脉。分辨率为0.7mm各向同性，扫描时间为6分钟；（2）新序列DANTE-MPRAGE和T1加权和T2加权SPACE相结合，组成一套颅内高分辨动脉斑块的临床检查方案。新方案能清楚识别颅内斑块及其成分，例如斑块内出血和夹层内血栓，提升影像评估颅内斑块破裂风险的能力；（3）发表SCI文章5篇，国际会议摘要6篇，其中口头报告3个，申请PCT专利2个，培养硕士研究生2名，在职博士研究生一名。.科学意义：新血管壁成像技术能对引起动脉血管狭窄的斑块进行直接观测，并对斑块的成分和稳定性进行评估，极大提高对缺血性脑卒中的病因认识，早期预防和精准治疗。