T2-Weighted 4D Magnetic Resonance Imaging for Application in Magnetic Resonance-Guided Radiotherapy Treatment Planning.
T2-Weighted 4D Magnetic Resonance Imaging for Application in Magnetic Resonance-Guided Radiotherapy Treatment Planning.
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DOI：
10.1097/rli.0000000000000381
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发表时间：
2017-10
影响因子：
6.7
通讯作者：
Wetscherek A
中科院分区：
文献类型：
--
作者：
Freedman JN;Collins DJ;Bainbridge H;Rank CM;Nill S;Kachelrieß M;Oelfke U;Leach MO;Wetscherek A
补充的数字内容可在文本中找到。本研究的目的是开发和验证一种利用t1加权四维（4D- t1w） MRI的运动信息获得良好时间分辨率的t2加权四维（4D- t2w）磁共振成像（MRI）的方法，以支持MRI引导放疗的治疗计划。对10例原发性非小细胞肺癌患者进行1.5 T轴向扫描，采用呼气门控的体积t2加权涡轮旋转回波序列和自由呼吸时获得的体积t1加权叠星破坏梯度回波序列。基于k空间中心的自门控信号，利用最近开发的4D联合MoCo-HDTV算法重构了20个呼吸相。通过呼吸相之间的可变形图像配准获得描述呼吸周期的运动向量场，并将其投影到t2加权图像体积上。将得到的4D-T2w体积与4D-T1w体积进行验证：使用边缘检测方法测量隔膜位置；比较放射肿瘤学家划定的解剖标志的位置，并计算归一化互信息来评估体积图像的相似性。获得高分辨率4D-T2w MRI。在计算的4D-T2w MRI上保持呼吸运动，膈正中位置一致，所有患者均小于6.6 mm（2体素），10例患者中有9例小于3.3 mm（1体素）。4D-T1w和4D-T2w MRI的几何位置一致，所有对应解剖标志之间的欧几里得距离在7.6 mm（2体素欧几里得距离）内一致，470对解剖标志中有355对小于3.8 mm（1体素欧几里得距离）。4D-T1w和4D-T2w MRI的体积图像相似度相当，4D-T1w和4D-T2w MRI的相应呼吸期与4D-T1w和三维T2w MRI的对应呼吸期之间的归一化互信息（在所有呼吸期和患者上计算）的平均百分比差异一致为0.41%±0.37%。四维T2w MRI比相应的4D-T1w MRI更清晰地显示肿瘤的范围、结构和位置，特别是当移动肿瘤部位靠近危险器官时。开发并验证了一种获取4D-T2w MRI的方法，该方法将4D-T1w MRI的运动信息回顾性地应用于三维T2w MRI。由于肿瘤组织对比差，4D-T1w MRI可以帮助临床医生描绘难以在4D-T1w MRI上定义的可移动病变。
Supplemental digital content is available in the text. The aim of this study was to develop and verify a method to obtain good temporal resolution T2-weighted 4-dimensional (4D-T2w) magnetic resonance imaging (MRI) by using motion information from T1-weighted 4D (4D-T1w) MRI, to support treatment planning in MR-guided radiotherapy. Ten patients with primary non–small cell lung cancer were scanned at 1.5 T axially with a volumetric T2-weighted turbo spin echo sequence gated to exhalation and a volumetric T1-weighted stack-of-stars spoiled gradient echo sequence with golden angle spacing acquired in free breathing. From the latter, 20 respiratory phases were reconstructed using the recently developed 4D joint MoCo-HDTV algorithm based on the self-gating signal obtained from the k-space center. Motion vector fields describing the respiratory cycle were obtained by deformable image registration between the respiratory phases and projected onto the T2-weighted image volume. The resulting 4D-T2w volumes were verified against the 4D-T1w volumes: an edge-detection method was used to measure the diaphragm positions; the locations of anatomical landmarks delineated by a radiation oncologist were compared and normalized mutual information was calculated to evaluate volumetric image similarity. High-resolution 4D-T2w MRI was obtained. Respiratory motion was preserved on calculated 4D-T2w MRI, with median diaphragm positions being consistent with less than 6.6 mm (2 voxels) for all patients and less than 3.3 mm (1 voxel) for 9 of 10 patients. Geometrical positions were coherent between 4D-T1w and 4D-T2w MRI as Euclidean distances between all corresponding anatomical landmarks agreed to within 7.6 mm (Euclidean distance of 2 voxels) and were below 3.8 mm (Euclidean distance of 1 voxel) for 355 of 470 pairs of anatomical landmarks. Volumetric image similarity was commensurate between 4D-T1w and 4D-T2w MRI, as mean percentage differences in normalized mutual information (calculated over all respiratory phases and patients), between corresponding respiratory phases of 4D-T1w and 4D-T2w MRI and the tie-phase of 4D-T1w and 3-dimensional T2w MRI, were consistent to 0.41% ± 0.37%. Four-dimensional T2w MRI displayed tumor extent, structure, and position more clearly than corresponding 4D-T1w MRI, especially when mobile tumor sites were adjacent to organs at risk. A methodology to obtain 4D-T2w MRI that retrospectively applies the motion information from 4D-T1w MRI to 3-dimensional T2w MRI was developed and verified. Four-dimensional T2w MRI can assist clinicians in delineating mobile lesions that are difficult to define on 4D-T1w MRI, because of poor tumor-tissue contrast.