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目的:探讨螺旋断层放射治疗系统图像引导技术在鼻咽癌精确放疗中的应用。方法:选择本院螺旋断层放疗中心2013年5月至2013年7月30例接受螺旋断层放疗的鼻咽癌患者,每例患者在每次治疗前均采用兆伏级CT(MVCT)扫描获得治疗体位图像,将该图像与定位CT图像进行配准,分别获得X轴(左右方向)、Y轴(头脚方向)、Z轴(腹背方向)3个方向的偏移数据,并根据van-Herk推荐外扩边界估计值公式计算得出靶区外扩边界的估计值。使用该估计值进行边界外扩,重新勾画靶区,在计划系统中重新计算剂量,得到调整前后的正常组织平均剂量对比。结果:30例鼻咽癌患者的摆位误差(系统误差±随机误差)在X、Y、Z方向上分别为(0.96±0.88)mm、(1.55±1.13)mm、(1.03±0.78)mm,根据van-Herk推荐外扩边界估计值公式计算得出:X方向为1.74 mm,Y方向2.14 mm,Z方向1.65 mm。使用不同外扩边界值前后,腮腺、内耳、颞颌关节、喉(食道)、下颌骨的平均剂量降低比例分别为12%、9.5%、11.9%、14.7%、22.4%。结论:TomoTherapy图像引导技术保证了精确放疗的实施,降低了正常组织的平均照射剂量,可为临床医生勾画靶区提供依据。
Objective: To investigate the application of spiral CT guided radiotherapy in radiotherapy of nasopharyngeal carcinoma. Methods: Thirty patients with nasopharyngeal carcinoma treated with helical CT were selected from our hospital from May 2013 to July 2013. Each patient was treated with MVCT scan before each treatment The position images are registered with the positioning CT images to obtain the offset data in three directions of X-axis (left-right direction), Y-axis (head-and-tail direction) and Z-axis It is recommended to calculate the estimated value of the extended boundary of the target area to obtain the estimated value of the extended boundary of the target area. Using this estimate to extrapolate the boundary, the target area was redrawn and the dose was recalculated in the planning system to obtain the average dose comparison of the normal tissue before and after adjustment. Results: The setup error (systematic error ± random error) of 30 nasopharyngeal carcinoma patients was (0.96 ± 0.88) mm, (1.55 ± 1.13) mm and (1.03 ± 0.78) mm in X, According to van-Herk’s estimation of extended boundary estimation formula: 1.74 mm in X direction, 2.14 mm in Y direction and 1.65 mm in Z direction. The average dose reduction of parotid gland, internal ear, temporomandibular joint, larynx (esophagus) and mandible before and after different extended boundary values were 12%, 9.5%, 11.9%, 14.7% and 22.4% respectively. Conclusion: TomoTherapy image guidance technology to ensure the implementation of accurate radiotherapy, reducing the average dose of normal tissue dose, clinicians can provide the basis for the target outlined.