三维实时磁共振温度成像方法研究

Noninvasive core body thermometry is an enabling technology for the core body temperature related basic medical research, such as metabolism, immunology and neuroscience, as well as MRI guided thermotherapy such as hyperthermia-mediated drug delivery and focus ultrasound ablation. Magnetic resonance thermometry is the only proven technique to measure temperature distribution noninvasively. However, the current magnetic resonace thermometry is limited by measurement precision, temporal resolution and imaging coverage. Based on our preliminary research work, the project is proposed to address these problems by innovatively developing a three dimensional referenceless thermometry based on multi-shot echo planar imaging sequence. The project will reveal the impact mechanism of the imaging parameters to measurement precision, temporal resolution and imaging coverage. The project will develop a novel referenceless method to improve the measurement accuracy while maintaining the three dimensional imaging coverage and temporal resolution requirements. The project will clarify the intrinsic relationship between susceptibility and temperature accuracy, and develop a method to correct susceptibility induced error for PRFS thermometry. The project will finally realize the real-time visualization of the temperature distribution in whole three dimensional targeted area during magnetic resonance imaging guided ablation therapy (2-3seconds/frame, error ≤ 1.5℃). The implementation of the proposed project will promte the core body temperature related medical research and improve the effectiveness and safety of the image guided ablation therapy and temperature sensitive drug delivery, and thus facilitate the rising technique to other new applications.

无创性精确测量深部组织温度对医学基础研究和热治疗前沿技术突破有重要推动作用。但现有磁共振温度成像技术的测量精度、时间分辨率和成像覆盖范围不能完全满足相关科学研究的迫切需求。本项目在前期研究的基础上，以高精度、三维、实时温度测量为目标，提出一种基于多次激发平面回波序列的三维实时磁共振温度成像方法，研究成像参数对温度成像精度的影响机制；针对磁化率不均和运动伪影等主要影响因素，阐明磁化率分布与温度成像精度的内在联系，并由此建立磁化率伪影的校正方法。同时，提出一种可用于三维数据采集的无参考快速温度重建算法，进一步提高温度成像的测量精度和速度(2-3秒/帧，精度1.5℃)，并最终实现高精度三维实时磁共振温度成像和空间温度分布的可视化。本项目的成功实施对进一步推进相关的医学基础研究以及温敏药物释放和聚焦超声治疗监控等关键问题研究具有重要意义。

基于已有的磁共振成像系统，完成了一套磁共振图像引导的聚焦超声实验平台，能够更好地与磁共振成像系统配合扫描；.结合并行成像技术，完成三维多重激发GRE-EPI序列，进一步提高温度成像的时间分辨率和空间覆盖度，同时优化了成像序列参数，该序列成像范围为240mm*240mm*60mm，分辨率达到1.25mm*1.25mm*3.0mm，采集时间为2.7s。离体温度测量精度达到0.5°左右，在体（人体头部，有运动情况下）温度测量精度在1.1°左右。.提出一种基于相位差分的无参考温度成像方法，该方法不依赖于多维相位解卷绕，并且适用于三维数据，同时将该方法与已有方法在离体组织和在体器官内做了详细对比，为在特定场合下选择合适的算法提供依据；此外还开发了一种算法，避免磁化率伪影对无参考温度成像算法的影响。.完成温度三维可视化，完成三维温度实时监控系统。.发表SCI论文4篇，授权专利7项，参加国际学术会议交流2次，培养学生3名，达到预期指标。.项目实施总体满足预期指标。