新型融合BEV/BPV信息的高分辨率快速磁共振成像方法研究

精准锁定肿瘤位置在放疗过程中至关重要。然而，由呼吸和胃肠蠕动等生理现象引起靶区和周围危及器官位置不确定性，实时图像引导放疗的需求日益增大。目前采用锥形束CT作为在线肿瘤位置验证手段，其应用受到扫描时间长，成像剂量大，软组织对比度差的限制。理论上磁共振引导加速器可以解决这一问题，得到无创、无辐射剂量、高组织对比度的图像。但目前用于实时图像引导的正交2D电影MRI具有局限性，一是图像分辨率低、图像延时等问题，二是提供信息有限，无法满足临床需求。本项目另辟蹊径将沿着射野的入射路径观BPV和垂直于射线方向的射野方向观BEV的信息纳入到成像过程中，巧妙地将有限信息的2D电影MRI转化为3.5D MRI，建立更符合临床需求的高分辨率快速磁共振成像方法。并将3.5D MRI成像方法应用到肝部和胃部肿瘤，探究其靶区和周围危及器官的运动轨迹，找寻肿瘤位移和形变的来源及规律，为精准个体化放疗提供客观依据。

Target accuracy is crucial in the whole course of radiotherapy. However, due to physiological phenomena such as respiration and gastrointestinal peristalsis，the uncertainty in the location of the targets and surrounding organs at risk has caused an increasing demand for real-time image-guided radiotherapy. At present, cone beam CT (CBCT) is widely used in radiotherapy as an online tumor location verification method, but its application is limited by the long scanning time, large imaging dose, and poor soft tissue contrast. Theoretically, MRI guided radiotherapy can solve this problem and obtain non-invasive, no radiation dose, and high tissue contrast images. However, the current orthogonal 2D cine MRI used for real-time image guidance has limitations：Firstly, low image resolution, latency and other issure. Secondly, the information provided is limited， which could not meet clinical requirement. This project has a unique approach to incorporate the BEV/BPV information of the Beam Path View（BPV） along the beam direction and Beam Eye View (BEV) perpendicular to the beam direction into the MRI imaging process, ingeniously transforming the limited-information 2D cine MRI into 3.5D MRI, to establish a newly high-resolution fast MRI imaging method which could more suitable for the clinical requirement. Then the 3.5D MRI imaging method is applied to liver and stomach tumors to determine the movement trajectories of the tumor and the surrounding organs at risk, to find the source and rules of their shift and deformation, and to provide objective evidences for precise individualized radiotherapy.