Zhou Yihang, Wong Oi Lei, Cheung Kin Yin, Yu Siu Ki, Yuan Jing
Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China.
Quant Imaging Med Surg. 2019 Jul;9(7):1255-1269. doi: 10.21037/qims.2019.06.18.
To evaluate the performance of a highly accelerated 3D MRI on inter-fractional positional measurement for MR-guided radiotherapy (MRgRT) in the head and neck (HN).
Fourteen healthy volunteers received 159 scans on a 1.5 T MR-sim to simulate MRgRT fractions. MRI acquisition included a high-resolution (HQI-MRI, voxel-size =1.05×1.05×1.05 mm, duration =5 min) and a highly-accelerated low-resolution (true-LQI-MRI, acceleration-factor =9, voxel-size =1.4×1.4×1.4 mm, duration =86 s) T1w spin-echo sequence (TR/TE =420/7.2 ms). The first session HQI-MRI was used as the reference to mimic planning MRI. Other HQI-MRI was also retrospectively down-sampled in K-space and GRAPPA reconstructed to generate pseudo-LQI-MRI. Inter-sessional positional shift calculated from HQI-MRI, true-LQI-MRI and pseudo-LQI-MRI rigidly registering to the reference were analyzed and compared in the overall HN and the sub-regions of brain, nasopharynx, oropharynx and hypopharynx.
The calculated SD of systematic errors (Σ) from HQI-MRI/pseudo-LQI-MRI/true-LQI-MRI images for overall HN were 1.11/1.14/1.08, 0.28/0.26/0.29, 0.43/0.44/0.60, and 0.77/0.79/0.74 mm for translation in LR, AP, SI and 3D, respectively; The corresponding RMS of random errors (σ) were 0.97/0.98/0.96, 0.28/0.27/0.26, 0.77/0.77/0.72, and 0.85/0.87/0.85 mm. For all sub-regions, brain showed the smallest Σ and σ in 3D. Other sub-regions showed direction-dependent error patterns, but the positioning results were consistent, independent of the datasets used for registration.
A highly-accelerated 3D-MRI could be used for MR-guided HN radiotherapy without compromising position verification accuracy.
评估高加速三维磁共振成像（MRI）在头颈部磁共振引导放射治疗（MRgRT）分次间位置测量中的性能。
14名健康志愿者在1.5T磁共振模拟机上接受了159次扫描以模拟MRgRT分次。MRI采集包括高分辨率（HQI-MRI，体素大小 = 1.05×1.05×1.05mm，持续时间 = 5分钟）和高加速低分辨率（true-LQI-MRI，加速因子 = 9，体素大小 = 1.4×1.4×1.4mm，持续时间 = 86秒）的T1加权自旋回波序列（TR/TE = 420/7.2ms）。将第一次扫描的HQI-MRI用作模拟计划MRI的参考。其他HQI-MRI也在K空间中进行回顾性下采样并进行GRAPPA重建以生成伪LQI-MRI。分析并比较从HQI-MRI、true-LQI-MRI和伪LQI-MRI与参考进行刚性配准计算得到的分次间位置偏移，包括整个头颈部以及脑、鼻咽、口咽和下咽的子区域。
对于整个头颈部，HQI-MRI/伪LQI-MRI/true-LQI-MRI图像在LR、AP、SI和3D方向上平移的系统误差（Σ）计算标准差分别为1.11/1.14/1.08、0.28/0.26/0.29、0.43/0.44/0.60和0.77/0.79/0.74mm；相应的随机误差（σ）均方根分别为0.97/0.98/0.96、0.28/0.27/0.26、0.77/0.77/0.72和0.85/0.87/0.85mm。对于所有子区域，脑在3D方向上显示出最小的Σ和σ。其他子区域显示出方向依赖性误差模式，但定位结果是一致的，与用于配准的数据集无关。
高加速三维MRI可用于头颈部MR引导放疗，而不影响位置验证的准确性。
