基于柔性线圈的下肢和足部磁共振无创灌注成像研究

In recent years, the lower extremity arterial occlusive disease (LEAOD) has been becoming more and more common. Meanwhile, the lower limb amputation rate and death rate caused by the LEAOD has also been increasing. In this study, we will firstly design the multi-channel flexible radio-frequency (RF) coil for lower limb and foot imaging with high signal to noise ratio (SNR) and large field of view (FOV). Furthermore, we will explore the noninvasive magnetic resonance perfusion imaging of lower limb and foot by utilizing the technique of artery spin labeling (ASL). Specifically, the vessel encoded ASL (VEASL) method will be applied to obtain the corresponding perfusion territory of the anterior tibial artery, posterior tibial artery and peroneal artery in lower limb. Then the velocity selective ASL (VSASL) approach will be used for the precise quantification of the muscle blood flow (MBF). Moreover, we will introduce the three-dimensional parallel spatially selective excitation RF pulse design to the ASL technique for specific perfusion imaging of the anterior tibial artery and posterior tibial artery in the lower limb and foot with high labeling efficiency. For clinical application, we will explore the relationship between the pathological process of the lower limb and foot arterial occlusive disease and the corresponding tissue perfusion change and collateral circulation development, by comparing the perfusion imaging results of the patients with varying severity of the lower limb and foot arterial occlusive diseases. It is believed that by using the proposed strategy, it will provide a more efficient noninvasive perfusion quantification tool for the preoperative and postoperative evaluation of endovascular surgery and amputated position determination for partial diabetic foot amputation.

近年来，下肢动脉缺血性疾病越来越常见，由其造成的截肢率以及死亡率也逐渐升高。本项目通过设计下肢和足部专用的高信噪比和大成像视野的多通道柔性射频成像线圈，探索将动脉自旋标记这种磁共振无创定量灌注功能成像方法引入到下肢和足部动脉缺血性疾病的临床评价中。利用血管编码技术获得下肢胫前、胫后以及腓动脉的不同血供区域的灌注分布；采用流速选择技术获得下肢血流灌注的精确定量；进一步将高空间选择性的射频脉冲设计引入动脉自旋标记技术中，实现膝下尤其是踝足部胫前和胫后动脉血管的高标记效率灌注成像。在临床应用上，通过比较不同严重程度的典型下肢和足部动脉缺血性疾病患者的组织灌注结果，探索下肢和足部缺血性疾病的病理发展过程与相应的组织灌注变化以及侧枝循环重建之间的变化规律，为下肢球囊支架等血管介入治疗的术前评估和术后疗效评价，以及糖尿病足截肢术前截肢平面确定提供重要的无创组织灌注定量评价手段。

众多动脉退行性病变的临床表现是与下肢和足部的血供不足密切相关，而且下肢缺血再灌注损伤还可引起肢体局部及肾脏损伤和功能下降。有效评价下肢动脉灌注和氧代谢功能，对指导治疗及评估预后均具有重要的临床意义。..通过本课题的研究，提出和发展了一系列适用于下肢、足部以及肾脏动脉缺血的氧摄取率和氧代谢无创定量动态功能成像新技术， 以及基于血流伪影充分抑制的高清血管壁成像新方法，并利用组织磁化率模型分析得到了稳定的氧代谢功能参数；提出并验证了气体刺激任务下氧摄取率成像新策略，为动脉缺血的早期诊断提供了有价值的影像学工具。同时，基于时谐目标场理论设计实现了适用于人体各个关节的开放式射频线圈，以及磁共振足底机械力刺激仪，为下肢和足部成像提供了任务态辅助成像工具。除此之外，发展了压缩感知和小视野成像技术，验证了在缺血组织的灌注成像以及高分辨成像中的潜在临床价值；最后，提出并验证了一系列基于机器学习的运动伪影去除和配准方法，为功能成像的定量分析提供了可行的新工具。.本项目的研究为下肢动脉缺血的定量灌注和氧代谢功能成像提供了重要的可行性验证，具有突出的方法学贡献和明确的学术价值。相关的系列成果能够为下肢、足部以及肾脏等腹部脏器的早期氧代谢异常甄别、下肢缺血的水肿甄别以及术后康复评价提供有潜在临床应用价值的成像工具；同时也为将来从氧代谢视角深入理解下肢、足部和肾脏动脉缺血的病理发展过程奠定了坚实的实验基础。