骨转移螺旋断层调强放疗摆位误差分析

目的 分析骨转移患者在自带兆伏级CT（MVCT）影像引导的螺旋断层放疗中的摆位误差,为骨转移患者从临床靶体积（CTV）外放到计划靶体积（PTV）的距离提供临床依据.方法 对30例骨转移患者采用螺旋断层放疗,体网固定装置,每次治疗前均行MVCT扫描,将扫描所得MVCT图像与定位图像（KVCT）行靶区位置配准,分析患者左右（X）、头脚（Y）、腹背（Z）和横断面旋转（Roll）方向的误差值,根据公式Margin=2.5∑＋0.7σ计算出CTV-PTV外扩Margin值.结果 30例患者共行494次MVCT扫描,线性误差在X、Y、Z方向的误差（系统误差±随机误差）分别为（2.85±0.77）、（3.11±0.95）、（2.21±0.55）mm;在Roll方向的旋转误差为（0.55±0.24）..CTV-PTV外放边界在X、Y、Z三个方向Margin值分别为3.64、4.17、2.86 mm.结论 应用图像引导技术对骨转移的调强放疗可实时摆位纠正,减小了分次治疗的摆位误差,提高了治疗精度,对临床放疗具有指导价值.

Analysis of setup errors in helical tomotherapy for bone metastases

Objective　To analyze the setup errors of bone metastases patients by tomotherapy with megavoltage CT (MVCT) and calculate the CTV-PTV margins. Methods　30 patients with bone metastases were enrolled. All patients received tomotherapy,fixed with body net and received MVCT scanning before radiation. The MVCT images were registered with the kilovoltage CT (kVCT) images, the setup errors of X(lateral), Y (vertical), Z (longitudina) and Roll (transverse profile rotation) were obtained according to the formula M = 2.5Σ+0.7σ calculated CTV-PTV margin. Results　30 patients were received 494 MVCT images. The errors of systemic±random were (2.85±0.77) mm, (3.11±0.95) mm, (2.21±0.55) mm, and (0.55±0.24)° on X, Y, Z and Roll directions, respectively. The CTV-PTV margins were 3.64 mm, 4.17 mm, and 2.86 mm on X, Y, Z directions, respectively. Conclusion　The application of image-guided technology for bone metastases can correct positioning in time, which greatly reduces setup errors of the fractionated treatment, further improves the treat accuracy and has a positive value in guiding clinical radiotherapy.