4D-MRI is becoming increasingly important for daily guidance of thoracic and abdominal radiotherapy. This study exploits the simultaneous multi-slice (SMS) technique to accelerate the acquisition of a balanced turbo field echo (bTFE) and a turbo spin echo (TSE) coronal 4D-MRI sequence performed on 1.5 T MRI scanners. SMS single-shot bTFE and TSE sequences were developed to acquire a stack of 52 coronal 2D images over 30 dynamics. Simultaneously excited slices were separated by half the field of view. Slices intersecting with the liver-lung interface were used as navigator slices. For each navigator slice location, an end-exhale dynamic was automatically identified, and used to derive the self-sorting signal by rigidly registering the remaining dynamics. Navigator slices were sorted into 10 amplitude bins, and the temporal relationship of simultaneously excited slices was used to generate sorted 4D-MRIs for 12 healthy volunteers. The self-sorting signal was validated using an in vivo peak-to-peak motion analysis. The smoothness of the liver-lung interface was quantified by comparing to sagittal cine images acquired directly after the SMS-4D-MRI sequence. To ensure compatibility with the MR-linac radiotherapy workflow, the 4D-MRIs were transformed into 3D mid-position (MidP) images using deformable image registration. Consistency of the deformable vector fields was quantified in terms of the distance discordance metric (DDM) in the body. The SMS-4D-TSE sequence was additionally acquired for 3 lung cancer patients to investigate tumor visibility. SMS-4D-MRI acquisition and processing took approximately 7 min. 4D-MRI reconstruction was possible for 26 out of 27 acquired datasets. Missing data in the sorted 4D-MRIs varied from 4%–26% for the volunteers and varied from 8%–24% for the patients. Peak-to-peak (SD) amplitudes analysis agreed within 1.8 (1.1) mm and 0.9 (0.4) mm between the sorted 4D-MRIs and the self-sorting signals of the volunteers and patients, respectively. Liver-lung interface smoothness was found to be in the range of 0.6–3.1 mm for volunteers. The percentage of DDM values smaller than 2 mm was in the range of 85%–89% and 86%–92% for the volunteers and patients, respectively. Lung tumors were clearly visibility in the SMS-4D-TSE images and MidP images. Two fast SMS-accelerated 4D-MRI sequences were developed resulting in T₂/T₁ or T₂ weighted contrast. The SMS-4D-MRIs and derived 3D MidP-MRIs yielded anatomically plausible images and good tumor visibility. SMS-4D-MRI is therefore a strong candidate to be used for treatment simulation and daily guidance of thoracic and abdominal MR-guided radiotherapy.

4D-MRI对于胸腹部放射治疗的日常指导变得越来越重要。本研究利用同步多层 (SMS) 技术来加速在 1.5 T MRI 扫描仪上执行的平衡涡轮场回波 (bTFE) 和涡轮自旋回波 (TSE) 冠状 4D-MRI 序列的采集。开发了 SMS 单次 bTFE 和 TSE 序列以获取超过 30 个动态的 52 个冠状二维图像的堆栈。同时激发的切片被视野的一半分开。与肝-肺界面相交的切片用作导航切片。对于每个导航切片位置，自动识别呼气末动态，并通过严格记录剩余动态来导出自分类信号。导航器切片被分类为 10 个振幅箱，并使用同时激发切片的时间关系为 12 名健康志愿者生成排序的 4D-MRI。自分类信号使用体内峰峰值运动分析。通过与在 SMS-4D-MRI 序列后直接获得的矢状电影图像进行比较，量化了肝-肺界面的平滑度。为确保与 MR-linac 放射治疗工作流程兼容，使用可变形图像配准将 4D-MRI 转换为 3D 中间位置 (MidP) 图像。可变形矢量场的一致性根据身体中的距离不一致度量 (DDM) 进行量化。另外还为 3 名肺癌患者获取了 SMS-4D-TSE 序列，以研究肿瘤的可见性。SMS-4D-MRI 采集和处理大约需要 7 分钟。27 个采集数据集中的 26 个可以进行 4D-MRI 重建。分类的 4D-MRI 中丢失的数据在志愿者中为 4%–2​​6%，在患者中为 8%–24%。峰峰值 (SD) 幅度分析在分类的 4D-MRI 与志愿者和患者的自分类信号之间分别在 1.8 (1.1) mm 和 0.9 (0.4) mm 内一致。志愿者的肝肺界面平滑度在 0.6-3.1 毫米范围内。志愿者和患者的 DDM 值小于 2 mm 的百分比分别在 85%–89% 和 86%–92% 范围内。肺肿瘤在 SMS-4D-TSE 图像和 MidP 图像中清晰可见。开发了两个快速 SMS 加速 4D-MRI 序列，导致 T 志愿者和患者的 DDM 值小于 2 mm 的百分比分别在 85%–89% 和 86%–92% 范围内。肺肿瘤在 SMS-4D-TSE 图像和 MidP 图像中清晰可见。开发了两个快速 SMS 加速 4D-MRI 序列，导致 T 志愿者和患者的 DDM 值小于 2 mm 的百分比分别在 85%–89% 和 86%–92% 范围内。肺肿瘤在 SMS-4D-TSE 图像和 MidP 图像中清晰可见。开发了两个快速 SMS 加速 4D-MRI 序列，导致 T₂ /T ₁或 T ₂加权对比度。SMS-4D-MRIs 和衍生的 3D MidP-MRIs 产生了解剖学上合理的图像和良好的肿瘤可见性。因此，SMS-4D-MRI 是用于胸部和腹部 MR 引导放射治疗的治疗模拟和日常指导的有力候选者。