鼻咽癌动态调强放疗计划的剂量学验证

目的建立鼻咽癌动态调强放疗计划的剂量学验证方法。方法对80例鼻咽癌动态调强放疗计划分别进行3个项目的剂量验证一是用电离室在人体等效模体中测量靶区参考点的绝对剂量,二是使用二维电离室矩阵测量调强计划每个射野的剂量强度分布,三是使用慢感光胶片竖插在模体内,测量调强计划横断面的剂量分布。结果92.5%计划靶区参考点的绝对剂量误差小于5%,在改用体积较小的电离室和调整机架角度避开固定装置重新制定计划后,所有计划靶区参考点的绝对剂量误差也都小于5%。有88.1%的照射野剂量分布误差小于3%。结论为了得到更加真实的测量结果,建议所有测量,尤其是绝对剂量测量都在计划实际机架角度下进行。利用二维电离室矩阵可定量分析照射野剂量分布误差,并且省时省力,有利于验证工作的常规化。胶片法验证由于费时费力且误差较大已趋于淘汰。对于动态调强计划,模体计划各个射野的机器跳数(MU)应与实际计划相同,这样才能得到更加真实的测量结果。     

ADAC逆向调强放射治疗计划的验证

目的：验证ADAC逆向调强治疗计划系统的物理精度。方法：用胶片和电离室，检测IMRT的MLC形状、空间点的绝对吸收剂量和等剂量曲线。结果：IMRT的MLC形状符合度误差1mm,空间点绝对吸收剂量与计划计算的误差3．6％，等剂量曲线分布的胶片测量结果与计划计算的很接近。结论：ADAC逆向治疗计划系统符合临床要求。     

调强放射治疗计划

调强放射治疗（IMRT）作为一种新近发展起来的先进放射治疗技术。在一些发达国家已经应用于临床,其优势在于肿瘤靶区三维剂量分布的适形程度及其均匀性较标准的适形放疗更好,从而在减少或不增加正常组受高剂量照射的前提下增加肿瘤组织的受照剂量,这样就可以提高肿瘤的局部控制率,降低正常组织并发症的发生率,本文对调强放疗的计划过程、剂量计算及优化方式等进行了综述。     

ADAC逆向调强放射治疗计划的验证

目的验证ADAC逆向调强治疗计划系统的物理精度.方法用胶片和电离室,检测IMRT 的MLC形状、空间点的绝对吸收剂量和等剂量曲线.结果IMRT的 MLC形状符合度误差1 mm,空间点绝对吸收剂量与计划计算的误差3.6%,等剂量曲线分布的胶片测量结果与计划计算的很接近.结论ADAC逆向治疗计划系统符合临床要求.     

调强适形放射治疗剂量学验证体系的建立

模体内剂量实测为基础的验证是调强适形放射治疗计划的主要剂量验证方法.该文将胶片剂量仪和针点电离室作为主要测量工具,介绍了剂量测量系统的建立方法:并选择1例鼻咽癌患者,介绍模体内剂量实测为基础的调强适形放射治疗计划剂量验证方法.     

调强适形放射治疗的剂量学验证

理论上 ,调强适形放射治疗 (ｉｎｔｅｎｓｉｔｙｍｏｄｕｌａｔｅｄｒａｄｉａｔｉｏｎｔｈｅｒａｐｙ,ＩＭＲＴ)与常规放射治疗相比较的优势 ,一是提高了靶区的剂量 ,二是减少了周围正常组织或关键器官的照射剂量。ＩＭＲＴ技术与常规放射治疗技术相比远为复杂 ,逆向计划的优化算法在某些方面还不成熟 ,放射治疗中还存在众多不确定因素 ,ＩＭＲＴ实施后的剂量准确与否直接关系到治疗的最终结果。虽然远期的治疗结果是检验ＩＭＲＴ计划乃至剂量准确性的金标准 ,但遗憾的是 ,至今还没有关于该技术治疗恶性肿瘤长期结果的报道。因此 ,治疗前的…     

调强放射治疗的物理剂量验证

目的：检测调强适形放射治疗（Intensity modulatet radiation therapy,IMRT)的剂量误差,探索IMRT的质量控制和质量保证的措施和方法。方法：（1）用体模治疗计划移植的方法对43例IMRT治疗计划的照射区以电离室作实际物理剂量测量,以验证治疗计划系统剂量计算的准确性,照射设备的可靠性和稳定性,修正IMRT治疗剂量误差和确定其剂量精度范围。（2）选取计划照射区内剂量梯度变化较大处进行重复摆位测量剂量,推算和验证由于摆位误差可能造成的剂量误差。结果：（1）与计划剂量比较,实际测量剂量的相对误差范围为-0.74%-4.98%并近似正态分布,平均误差为2.38%。标准差为1.39%,标准误为0.21%。全部43例的剂量误差均在5%以内。（2）实际测量的剂量梯度变化与计划剂量梯度一致,全部计划中的最大梯度值为15%/mm。在该处重复摆位测量的最在与最小值的相对差别为1.97%。结论：用体模计划移植测量方法能有效检验IMRT计划计算和执行的误差,可作为每个病人治疗前的剂量验证常规方法;IMRT治疗精度的保证需要优于1mm的额外精确摆位。     

食管癌调强放疗计划剂量学验证研究

目的 对比分析食管癌调强放疗(IMRT)计划的三种剂量验证方法.方法 使用Pinnacle 8.0 h计划系统完成7例食管癌IMRT计划,选用二、三维剂量验证设备MATRIXX和Delta4完成测量验证.IMRT原计划和Delta4移植计划使用蒙特卡罗方法重新计算.评价MATRIXX和Delta4测量的gamma通过率;Pinnacle计算,Delta4测量与蒙特卡罗模拟结果分别比较gamma图,中心层面剂量分布,剂量曲线和剂量体积直方图.结果 gamma误差设定为3%/3 mm,MATRIXX测量通过率＞98%,Delta4测量通过率为94.4%,其中有4个射野＜90%.Delta4测量和蒙特卡罗模拟比较,误差限定为2 mm/2%和3 mm/3%时,gamma通过率分别为97.6%和99.8%.Pinnacle计划系统计算的中心层面剂量分布、剂量曲线与蒙特卡罗模拟计算结果、Delta4测量结果比较一致.Delta4测量与蒙特卡罗模拟计算的剂量体积直方图一致性很好,均与Pinnacle计划系统计算略有差异.结论 3种方法均能完成食管癌IMRT计划的验证,蒙特卡罗和Delta4方法在验证过程中无数据丢失.Delta4实现了三维的剂量验证,蒙特卡罗能够在每个患者的实际CT图像上进行模拟计算.

Abstract：

Objective To compare the results of three dose verification solutions of esophageal carcinoma IMRT plans. Methods Seven esophageal carcinoma cases were planned with Pinnacle 8.0 h.The MATRIXX and Delta4 were chosen as the two-dimensional dosimetry and three-dimensional dosimetry.IMRT plans and Delta4 phantom plans were also recalculated by Monte Carlo. Gamma values were evaluated for MATRIXX and Delta4 with 3 mm/3% gamma criteria. For the comparison of Pinnacle, Delta4 and Monte gamma maps, the dose distribution in central plane, dose profiles and dose-volume histograms were used to evaluate the agreement. Results The gamma maps comparison show that with 3 mm/3% gamma criteria an over 98% pass ratio was obtained by MATRIXX measurement. A 94. 4% gamma pass ratio whicl.contains 4 fields gamma pass ratio lower than 90%, was obtained by Delta4 measurement. A 97.6% and 99. 8% gamma pass ratio was obtained between the Delta4 measurement and Monte Carlo simulation with 2 mm/2% and 3 mm/3% gamma criteria. The dose distribution in central plane and dose profiles from Pinnacle calculation were almost in agreement with both the Monte Carlo simulation and Delta4 measurement. The DVH plot have slightly differences between Pinnacle and Delta4 measurement as well as Pinnacle and Monte Carlo simulation, but have excellent agreement between Delta4 measurement and Monte Carlo simulation. Conclusions It was shown that all the three methods can be used very efficiently to verify esophageal carcinoma IMRT delivery, Delta4 and Monte Carlo simulation no data missed. The primary advantage of Delta4 is the fact it can measure true 3D dosimetry while Monte Carlo can simulate in patients CT images but not in phantom.     

逆向计划调强适形放射治疗的质量保证

目的：通过一系列调强验证方法的研究，探讨逆向计划调强适形放射治疗（IMRT）的质量保证方法是否可行。方法：用Varian Cadplan三维治疗计划系统中Helios逆向计划系统对前列腺癌、鼻咽癌、脑瘤、胰腺癌、椎骨转移癌等设计并进行IMRT。为验证计划系统生成的各个照射野注量图与实际注量图的一致性，将剂量胶片放在平板有机玻璃体模下，使计划中的各个照射野始终垂直于体模表面；调用患者治疗数据分别单独照射，冲洗胶片后与计划得出的注量图进行比较。将剂量胶片夹在仿真体模适当的部位，调用患者治疗数据对体模进行模拟照射，由此得出轴向截面上的等剂量分布，与计划的等剂量曲线拟合比对。用电离室和水箱验证等中心和偏离点的绝对剂量。在模拟机或加速器上拍正侧位照射野验证片，与CT模拟数字重建的射线影像片比较，验证等中心位置。结果：各射线束轴垂直方向测得的注量图与计划系统计算的一致；等中心点绝对剂量测量的结果与计划计算的误差在3％以内，偏离点绝对剂量误差较大；轴向截面等剂量曲线分布的胶片测量结果与计划计算的很接近；等中心位置误差在3mm以内。结论：近一年的实践证明在IMRT中所采用的上述质量保证措施是切实可行的。     

调强放疗剂量验证实践指南

调强放疗剂量验证是放疗质量保证的重要组成部分,对保证调强放疗的安全和质量非常重要。我国尚无调强放疗剂量验证的系统指南和验证工具方法的具体推荐,验证结果的解读及其临床意义、验证不通过的原因分析及处理措施,不同机构使用的工具方法和实施细节差异很大。在国家肿瘤诊疗质控中心放疗质控专家委员会的组织领导下,经过现状调查、多中心测试、专家研讨、咨询、审定等方式完成了该指南。指南规定了开展调强放疗剂量验证的机构、组织、人员、设备、技术流程,及文档记录等方面的要求,以期改进调强放疗剂量验证工作的规范化开展。     

Practice guideline of patient-specific dosimetric verification for intensity-modulated radiotherapy

Patient-specific dosimetric verification is an important component of quality assurance processes for intensity-modulated radiotherapy (IMRT), which plays a critical role in ensuring the safety and quality of IMRT. There has been no national practice guideline or explicit recommendations for tools and methods for patient-specific IMRT dosimetric verification in China. Interpretation and clinical significance of verification results, causes and management interventions for IMRT dosimetric verification failure, tools and methods and implementation details significantly differ among different institutions. Under the guidance and organization of Radiation Oncology Quality Control Committee, National Quality Control Center of Cancer Theranostics, this guideline was formulated based on the results of national survey, multi-center validation test, expert discussion, consultation and review. This guideline specifies the requirement of institution, organization, personnel, tools and device, technical workflow, and documentation,aiming to improve the standardized implementation of IMRT dosimetric verification procedures.     

用放射性铬胶片进行调强放疗剂量验证的研究

目的研究新型放射性铬胶片(RCF)的剂量响应特性,探讨其用于个体化调强放疗(IMRT)平面剂量验证的临床应用方法和剂量精度,简化传统胶片剂量测量系统的质控过程,建立更可靠易行的调强放疗剂量分布验证系统。方法采用阶梯式剂量-光密度刻度方法校正RCF和传统胶片(EDR2),比较两者剂量学特性与测量精度差别及过程的质控要求。采用模体内剂量实测方法,以RCF和EDR2胶片分别测量验证IMRT计划在同一平面的剂量分布,并与治疗计划系统计算的剂量注量分布、离轴剂量分布曲线、等剂量曲线等进行比较,评价RCF用于IMRT剂量分布验证的效果。结果在0～500 cGy外照射剂量范围内,RCF/VXR-16和EDR2/VXR-16胶片剂量系统的测量离散度均不超过0.70%,平均不确定度分别为0.37%和0.68%。IMRT剂量分布验证的RCF测量和严格执行冲片质控的EDR2胶片测量结果十分相近,两者在模体内同一平面与计划计算的最大离轴剂量偏差分别为3.1%和3.6%,相同DTA与△D设定值的γ像素符合率分别为94.28%和92.92%。结论RCF的剂量系统应用于临床个体化IMRT平面剂量验证,有较高可靠性和可信度,且操作和质控过程与传统剂量胶片相比大大简化,可以在临床推广应用。     

调强放疗计划设计参数对剂量验证结果影响的初步研究

目的 通过分析调强放疗计划设计参数与验证时γ分析通过率的关系,探讨各参数对调强验证通过率的影响。方法 取不同参数水平下生成的调强照射野共457个,将γ分析(3%/3 mm)通过率作为观测变量,将优化设置的最小子野面积、子野序列中最小MU数、单一射野中子野数、子野转化模式以及计划系统生成平面剂量图的像素间距作为控制变量。结果 在不同最小子野面积设置值、子野转化模式及计划系统生成的平面剂量图像素间距分组中,γ分析通过率差异有统计学意义(P<0.05),子野数及序列中的最小MU数对验证结果的影响均较小(P>0.05)。结论 应根据设备实际情况,在调强优化时选取合适的最小子野面积,尽可能地采用直接机器参数优化模式,并根据验证设备的最小探头间距选则合适的平面剂量图分辨率。     

调强放射治疗自动计划技术的研究进展

逆向调强放疗（intensity-modulated radiation therapy,IMRT）技术在保证靶区接收足够照射剂量的同时极大地降低了正常组织的受照剂量。在IMRT治疗计划的设计过程中,需要进行多次尝试与优化才能在提高靶区覆盖率与减少正常组织受照剂量的矛盾中找到平衡点。这种常规的计划设计过程十分繁杂,而且很大程度上依赖于设计者自身的经验,缺乏统一的规范和评判标准。因此,如果可以在复杂的优化过程之前就利用某些方法（例如自动计划算法）预测出最终的计划结果,将会提高计划的设计效率和质量。该研究将对放射治疗中自动计划技术的研究进展做一综述。     

IMRT不同剂量验证技术差异性分析

目的 比对瓦里安Portal dosimetry与Matrixx剂量验证结果,分析两种验证技术差异,评估EPID剂量验证临床应用的可靠性。方法 瓦里安Truebeam加速器,配置120片MLC和非晶硅EPID系统。IBA公司Matrixx矩阵及分析软件。配置EPID 算法、进行剂量校准和使用前测试。采用sliding-window计划设计,77个病种涉及头颈部(主要是鼻咽癌)、纵隔、腹部、盆腔肿瘤。创建剂量验证计划,SDD=100 cm,机架角与治疗计划一致,获剂量图像。在加速器上执行验证计划,比对分析EPID测量与TPS计算图像,比对分析EPID与Matrixx验证结果,采用3%/3 mm标准γ分析评估。配对t检验差异。结果 对77个不同部位肿瘤调强计划EPID和Matrixx验证结果显示两者验证γ通过率均在97%以上,除头颈部癌P=1.018外余均P> 0.05)。结论 EPID与Matrixx验证结果具有较好的一致性。可以用EPID进行验证,仅对结果通过率低者用电离室矩阵复验,确保治疗安全。     

Applicator-guided intensity-modulated radiation therapy

: We are introducing a novel method for delivering highly conformal dose distributions to cervical cancer tumors using external beam intensity-modulated radiation therapy. The method, termed applicator-guided intensity-modulated radiation therapy (AGIMRT), will use an applicator substitute placed in the vagina and uterus to provide spatial registration and immobilization of the gynecologic organs. The main reason for the applicator substitute will be to localize the fornices, cervix, and uterus with the expectation that the other nearby organs will also be reproducibly positioned with respect to the applicator substitute. Intensity-modulated radiation therapy (IMRT) dose distributions will be used as a substitute for high-dose-rate intracavitary brachytherapy procedures. The flexibility of IMRT will enable customized dose distributions that have the potential to reduce complications and improve local control, especially for locally advanced disease.

: To test the advantages of IMRT over intracavitary brachytherapy, volumetric scans of three cervical cancer patients were obtained with implanted CT-compatible applicators. IMRT dose distribution simulations using tomotherapy, were compared against intracavitary brachytherapy using cesium tubes to investigate the dosimetric differences of the two modalities. Because these tumor volumes do not image well on CT, the target volumes were defined as the isodose surface containing the traditional point A, defined as 2 cm superior to the vaginal fornices and 2 cm lateral to the intrauterine canal. One patient had a uterus that wrapped superior and anterior to the bladder. For this case, the cervix and uterus were selected as the target volume. To determine the potential for using an applicator substitute to localize internal organs, the posterior bladder and anterior rectal surfaces were localized relative to the colpostats. Comparisons of the colpostat-localized surfaces were conducted for two scan studies for 3 patients.

: The IMRT distributions covered the point-A isodose surfaces while reducing doses to the bladder and rectum. Brachytherapy showed extensive underdose regions in the target volume for the wrapped-around target. Spatial positioning was better than 0.7 and 1.3 cm in the rectum and bladder, respectively, indicating the potential that an applicator substitute may be able to localize these structures.

: AGIMRT has the potential for improving critical structure avoidance while maintaining highly reproducible and accurate internal organ registration found with brachytherapy.     

Update report of nasopharyngeal carcinoma treated with reduced-volume intensity-modulated radiation therapy and hypothesis of the optimal margin

Background and purpose

To establish the minimally required margins in different directions measured from GTV in the definitive treatment of nasopharyngeal carcinoma (NPC) using IMRT based on the 5-year results.

Methods and materials

Between November 2003 and May 2007, 414 patients with non-metastatic NPC were treated with IMRT according to our institutional protocol. Treatment outcomes at 5 years were analyzed. Distances from GTV-T to CTV2 (i.e., CTV 59.4 Gy) in 6 directions (anterior, posterior, superior, inferior, and bilateral) were measured and analyzed.

Results

The 5-year estimated overall survival (OS), disease free survival (DFS), local control (LC) were 80%, 77% and 95%, respectively. For the margins measured from GTV-T to CTV2, margins used with T4 disease were significantly and uniformly smaller than the whole group in all the 6 directions (P = 0.000, 0.000, 0.000, 0.000 and 0.046, respectively). However, no increase of local recurrence was associated to this limited margins used.

Conclusions

Our 5-years’ experience showed a very high LC rate. The strategy we used for CTV delineation was safe and reliable. Determined CTV through GTV expansion to a minimally required margin, using GTV + margin (used in our T4 patients) + the whole nasopharyngeal mucosa, especially for the patients with early T disease, might be feasible.     

Fatal pneumonitis associated with intensity-modulated radiation therapy for mesothelioma

PURPOSE: To describe the initial experience at Dana-Farber Cancer Institute/Brigham and Women's Hospital with intensity-modulated radiation therapy (IMRT) as adjuvant therapy after extrapleural pneumonectomy (EPP) and adjuvant chemotherapy. METHODS AND MATERIALS: The medical records of patients treated with IMRT after EPP and adjuvant chemotherapy were retrospectively reviewed. IMRT was given to a dose of 54 Gy to the clinical target volume in 1.8 Gy daily fractions. Treatment was delivered with a dynamic multileaf collimator using a sliding window technique. Eleven of 13 patients received heated intraoperative cisplatin chemotherapy (225 mg/m(2)). Two patients received neoadjuvant intravenous cisplatin/pemetrexed, and 10 patients received adjuvant cisplatin/pemetrexed chemotherapy after EPP but before radiation therapy. All patients received at least 2 cycles of intravenous chemotherapy. The contralateral lung was limited to a V20 (volume of lung receiving 20 Gy or more) of 20% and a mean lung dose (MLD) of 15 Gy. All patients underwent fluorodeoxyglucose positron emission tomography (FDG-PET) for staging, and any FDG-avid areas in the hemithorax were given a simultaneous boost of radiotherapy to 60 Gy. Statistical comparisons were done using two-sided t test. RESULTS: Thirteen patients were treated with IMRT from December 2004 to September 2005. Six patients developed fatal pneumonitis after treatment. The median time from completion of IMRT to the onset of radiation pneumonitis was 30 days (range 5-57 days). Thirty percent of patients (4 of 13) developed acute Grade 3 nausea and vomiting. One patient developed acute Grade 3 thrombocytopenia. The median V20, MLD, and V5 (volume of lung receiving 5 Gy or more) for the patients who developed pneumonitis was 17.6% (range, 15.3-22.3%), 15.2 Gy (range, 13.3-17 Gy), and 98.6% (range, 81-100%), respectively, as compared with 10.9% (range, 5.5-24.7%) (p = 0.08), 12.9 Gy (range, 8.7-16.9 Gy) (p = 0.07), and 90% (range, 66-98.3%) (p = 0.20), respectively, for the patients who did not develop pneumonitis. CONCLUSIONS: Intensity-modulated RT treatment for mesothelioma after EPP and adjuvant chemotherapy resulted in a high rate of fatal pneumonitis when standard dose parameters were used. We therefore recommend caution in the utilization of this technique. Our data suggest that with IMRT, metrics such as V5 and MLD should be considered in addition to V20 to determine tolerance levels in future patients.