Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
Med Phys. 2017 Aug;44(8):4188-4193. doi: 10.1002/mp.12363. Epub 2017 Jun 30.
Diffusion-weighted (DW) MRI, showing high contrast between tumor and background tissue, is a promising technique in radiotherapy for tumor delineation. However, its use for head-and-neck patients is hampered by poor geometric accuracy in conventional echo planar imaging (EPI) DW-MRI. An alternative turbo spin echo sequence, DW-SPLICE, is implemented and demonstrated in patients.
The DW-SPLICE sequence was implemented on a 3.0 T system and evaluated in 10 patients. The patients were scanned in treatment position, using a customized head support and immobilization mask. Image distortions were quantified at the gross tumor volume (GTV) using field map analysis. The apparent diffusion coefficient (ADC) was evaluated using an ice water phantom.
The DW images acquired by DW-SPLICE showed no image distortions. Field map analysis at the gross tumor volumes resulted in a median distortion of 0.2 mm for DW-SPLICE, whereas for the conventional method this was 7.2 mm. ADC values, measured using an ice water phantom were in accordance with literature values.
The implementation of DW-SPLICE allows for diffusion-weighted imaging of patients in treatment position with excellent geometrical accuracy. The images can be used to facilitate target volume delineation in RT treatment planning.
扩散加权（DW）MRI 能在肿瘤和背景组织之间产生高对比度，是肿瘤放疗中一种很有前途的技术。然而，由于常规 echo 平面成像（EPI）DW-MRI 的几何精度较差，其在头颈部患者中的应用受到限制。本文提出了一种替代的 turbo 自旋回波序列 DW-SPLICE，并在患者中进行了验证。
DW-SPLICE 序列在 3.0 T 系统上实现，并在 10 名患者中进行了评估。患者采用定制的头架和固定面罩在治疗位进行扫描。使用场图分析在大体肿瘤体积（GTV）处量化图像失真。使用冰水 phantom 评估表观扩散系数（ADC）。
DW-SPLICE 采集的 DW 图像没有图像失真。GTV 处的场图分析结果显示，DW-SPLICE 的平均失真度为 0.2mm，而常规方法的平均失真度为 7.2mm。使用冰水 phantom 测量的 ADC 值与文献值相符。
DW-SPLICE 的实现允许在治疗位对患者进行扩散加权成像，具有出色的几何精度。这些图像可用于辅助 RT 治疗计划中的靶区勾画。
