基于EPID在体三维剂量验证系统的物理模型测试及初步临床探索

目的 使用模体验证基于电子射野影像装置(EPID)在体三维剂量验证建模的准确性,并进行临床应用的初步研究。方法 通过方野和调强计划在均匀和非均匀模体上检测EPID在体三维剂量验证系统应用于不同介质中的剂量计算精度和重建精度,比较不同剂量/距离一致性标准下的γ通过率。对临床病例进行靶区和危及器官剂量体积分析。结果 方野在均匀模体中3%/3mm标准平均γ通过率为(97.49±1.11)%,在非均匀模体中为(94.06±5.11)%(P>0.05)。不同出束方式的调强计划之间也相近(P>0.05)。临床病例疗前剂量验证3%/2mm标准γ通过率为(97.96±1.84)%,在体三维剂量验证3%/3mm标准为(90.51±6.96)%。临床病例中小体积和体积变化较大的危及器官有较大剂量偏差。结论 基于EPID建立的在体三维剂量验证模型,经初步测试可应用于临床提供更全面的质量保证,为以后自适应放疗工作提供了技术保障。     

非共面照射技术对鼻咽癌筛窦侵犯的剂量分析

目的 探讨鼻咽癌筛窦侵犯调强放疗中非共面射野对正常组织的保护和提高肿瘤区的剂量.方法 收集鼻咽癌筛窦侵犯患者15例,每一例患者设计2种射野方案,Ⅰ方案采用9野共面照射技术,Ⅱ方案采用9野和1野非共面照射技术.结果 2种方案比较发现:加设非共面射野能够有效改善正常组织的剂量,腮腺30Gy的照射体积减少10％以上.靶区剂量明显提高,适形性指数CI平均提高8％,均匀性指数HI平均提高6％.结论 非共面照射技术在鼻咽癌筛窦调强放疗中对正常组织有保护作用并可提高肿瘤区剂量.     

利用非晶硅电子射野影像系统对多叶准直器叶片到位精度作质量控制

背景与目的：加速器的多叶准直器叶片到位精度误差会对调强放射治疗产生剂量分布偏差。剂量偏差将导致治疗失败或者是严重的器官损伤。本研究将通过简单的方法实现多叶准直器叶片到位精度的质量控制和质量保证。方法：使用医科达加速器和医科达iViewGT非晶硅平板电子射野影像系统（electronic portal imaging devices,EPIDs）,使用8MV光子线,获得计划系统设计好的射野图形．利用软件测量叶片的实际到位坐标,同DicomRT文件中的坐标作比较,获得他们之间的误差,根据误差的方向和大小调整叶片的到位精度。结果：可以控制叶片的到位精度在1mm之内。结论：利用EPIDs做叶片到位精度的质量控制,方法简单快速可靠。     

胸段食管癌三维适形放疗摆位误差研究

Objective To study the setup errors in three-dimensional conformal radiotherapy (3DCRT) for thoracic esophageal carcinoma using electronic portal imaging device(EPID) and calculate the margins from CTV to PTV. Methods Forty-one patients with thoracic esophageal carcinoma who received 3DCRT were continuously enrolled into this study. The anterior and lateral electronic portal images (EPI) were aquired by EPID once a week. The setup errors were obtained through comparing the difference between EPI and digitally reconstructed radiographs(DRR). Then the setup margins from CTV to PTV were calculat-ed. By using self paired design,22 patients received definitive radiotherapy with different margins. Group A: the margins were 10 mm in all the three axes;Group B: the margins were aquired in this study. The differ-ence were compared by Paired t-test or Wilcoxon signed-rank test. Results The margins from CTV to PTV in x,y and z axes were 8.72 mm, 10.50 mm and 5.62 mm, respectively. Between the group A and group B, the difference of the maximum dose of the spinal cord was significant(4638.7 cGy±1449.6 cGy vs. 4310.2 cGy±1528.7 cGy; t=5.48, P=0.000), and the difference of NTCP for the spinal cord was also significant (4.82%±5.99% vs. 3.64%±4.70%;Z=-2.70,P=0.007). Conclusions For patients with tho-racic esophageal carcinoma who receive 3DCRT in author's department,the margins from CTV to PTV in x, y and z axes were 8.72 mm, 10.50 mm and 5.62 mm, respectively. The spinal cord could be better protected by using these setup margins than using 10 mm in each axis.     

拍片验证在腹部肿瘤放射治疗的可行性分析

目的:探讨拍片验证在腹部肿瘤放射治疗的可行性和意义.方法:运用OPTIVUETM(平板电子射野验证成像设备)对第一次放射治疗或每周位置精度验证的病人进行拍片.结果:在113个腹部肿瘤的病人进行的放射治疗期间所拍的500张的验证片与RTT图象(CT扫描合成的参考图象)对比,在200张的调强放射治疗验证片中误差＞3mm占7%(14/200);在300张的适型放射治疗验证片中误差＞5mm占9%(27/300);在113个腹部肿瘤的病人中因肿瘤部位不同造成的摆位误差:上腹部肿瘤39个病人摆位误差的平均值2.15mm;中腹部肿瘤27个病人摆位误差的平均值 2.89mm;下腹部肿瘤40个病人摆位误差的平均值 1.42mm.结论:验证拍片在腹部肿瘤放射治疗中有帮助.