Mohandass P, Khanna D, Kumar T Manoj, Thiyagaraj T, Saravanan C, Bhalla Narendra Kumar, Puri Abhishek
Department of Physics, Karunya Institute of Technology and Sciences, Coimbatore, Tamil Nadu, India.
Department of Radiation Oncology, Fortis Cancer Institute, Fortis Hospital, Mohali, Punjab, India.
J Med Phys. 2018 Oct-Dec;43(4):207-213. doi: 10.4103/jmp.JMP_67_18.
This study compared three different methods used in registering cone-beam computed tomography (CBCT) image set with planning CT image set for determining patient setup uncertainties during volumetric modulated arc therapy (VMAT) for breast cancer patients.
Seven breast cancer patients treated with 50 Gy in 25 fractions using VMAT technique were chosen for this study. A total of 105 CBCT scans were acquired by image guidance protocol for patient setup verification. Approved plans' CT images were used as the reference image sets for registration with their corresponding CBCT image sets. Setup errors in mediolateral, craniocaudal, and anteroposterior direction were determined using gray-scale matching between the reference CT images and onboard CBCT images. Patient setup verification was performed using clip-box registration (CBR) method during online imaging. Considering the CBR method as the reference, two more registrations were performed using mask registration (MR) method and dual registration (DR) (CBR + MR) method in the offline mode. For comparison, systematic error (∑), random error (σ), mean displacement vector (), mean setup error (), and registration time ( ) were analyzed. Tukey's honest significant difference test was performed for multiple comparisons.
Systematic and random errors were less in CBR as compared to MR and DR ( > 0.05). The mean displacement error and mean setup errors were less in CBR as compared to MR and DR ( > 0.05). Increased was observed in DR as compared to CBR and MR ( < 0.05). In addition, multiple comparisons did not show any significant difference in patient setup error ( > 0.05).
For breast VMAT plan delivery, all three registration methods show insignificant variation in patient setup error. One can use any of the three registration methods for patient setup verification.
本研究比较了三种不同的方法，这些方法用于将锥形束计算机断层扫描（CBCT）图像集与计划CT图像集进行配准，以确定乳腺癌患者容积调强弧形放疗（VMAT）期间的患者摆位不确定性。
本研究选取了7例采用VMAT技术、25次分割给予50 Gy治疗的乳腺癌患者。通过图像引导方案获取了总共105次CBCT扫描，用于患者摆位验证。将批准计划的CT图像用作参考图像集，与相应的CBCT图像集进行配准。使用参考CT图像与机载CBCT图像之间的灰度匹配来确定内外侧、头脚方向和前后方向的摆位误差。在在线成像期间，使用夹盒配准（CBR）方法进行患者摆位验证。将CBR方法作为参考，在离线模式下使用蒙版配准（MR）方法和双重配准（DR）（CBR + MR）方法进行另外两次配准。为了进行比较，分析了系统误差（∑）、随机误差（σ）、平均位移向量（）、平均摆位误差（）和配准时间（）。进行了Tukey的诚实显著差异检验以进行多重比较。
与MR和DR相比，CBR中的系统误差和随机误差较小（> 0.05）。与MR和DR相比，CBR中的平均位移误差和平均摆位误差较小（> 0.05）。与CBR和MR相比，DR中的增加（< 0.05）。此外，多重比较在患者摆位误差方面未显示任何显著差异（> 0.05）。
对于乳腺癌VMAT计划的实施，所有三种配准方法在患者摆位误差方面显示出不显著的差异。可以使用这三种配准方法中的任何一种进行患者摆位验证。
