Chegeni Nahid, Birgani Mohamad Javad Tahmasebi, Birgani Fariba Farhadi, Fatehi Daryoush, Akbarizadeh Gholamreza, Tahmasbi Marziyeh
Department of Medical Physics, Medical Physics, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Department of Radiation Therapy and Medical Physics, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
J Med Signals Sens. 2019 Apr-Jun;9(2):123-129. doi: 10.4103/jmss.JMSS_26_18.
Recently, magnetic resonance imaging (MRI)-based radiotherapy has become a favorite science field for treatment planning purposes. In this study, a simple algorithm was introduced to create synthetic computed tomography (sCT) of the head from MRI.
A simple atlas-based method was proposed to create sCT images based on the paired T1/T2-weighted MRI and bone/brain window CT. Dataset included 10 patients with glioblastoma multiforme and 10 patients with other brain tumors. To generate a sCT image, first each MR from dataset was registered to the target-MR, the resulting transformation was applied to the corresponding CT to create the set of deformed CTs. Then, deformed-CTs were fused to generate a single sCT image. The sCT images were compared with the real CT images using geometric measures (mean absolute error [MAE] and dice similarity coefficient of bone [DSC]) and Hounsfield unit gamma-index (Г) with criteria 100 HU/2 mm.
The evaluations carried out by MAE, DSC, and Г showed a good agreement between the synthetic and real CT images. The results represented the range of 78-93 HU and 0.80-0.89 for MAE and DSC, respectively. The Г also showed that approximately 91%-93% of pixels fulfilled the criteria 100 HU/2 mm for brain tumors.
This method showed that MR sequence (T1w or T2w) should be selected depending on the type of tumor. In addition, the brain window synthetic CTs are in better agreement with real CT relative to bone window sCT images.
最近，基于磁共振成像（MRI）的放射治疗已成为治疗计划领域备受青睐的科学领域。在本研究中，引入了一种简单算法，用于从MRI创建头部的合成计算机断层扫描（sCT）。
提出了一种基于图谱的简单方法，以基于配对的T1/T2加权MRI和骨/脑窗CT创建sCT图像。数据集包括10例多形性胶质母细胞瘤患者和10例其他脑肿瘤患者。为生成sCT图像，首先将数据集中的每个MR图像配准到目标MR图像，将所得变换应用于相应的CT图像以创建一组变形的CT图像。然后，将变形的CT图像融合以生成单个sCT图像。使用几何测量（平均绝对误差[MAE]和骨的骰子相似系数[DSC]）以及Hounsfield单位伽马指数（Г）（标准为100 HU/2 mm）将sCT图像与真实CT图像进行比较。
通过MAE、DSC和Г进行的评估表明，合成CT图像与真实CT图像之间具有良好的一致性。结果显示MAE和DSC的范围分别为78-93 HU和0.80-0.89。Г还表明，对于脑肿瘤，约91%-93%的像素满足100 HU/2 mm的标准。
该方法表明，应根据肿瘤类型选择MR序列（T1w或T2w）。此外，相对于骨窗sCT图像，脑窗合成CT与真实CT的一致性更好。
