Plan evaluation and dosimetric comparison of IMRT using AAPM TG119 test suites and recommendations

In order to verify intensity modulated radiotherapy quality assurance procedure and to establish the practical base line commissioning, American Association of Physicists in Medicine-Task Group 119 test suite DICOM-RT images and structure were downloaded for planning and dosimetric comparison. The square slab phantom of water equivalent plastic was used for the measurement. This phantom can permit point dose measurement with ionization chamber by placing the chamber at 7.5 cm depth in the slab phantom. The planar dose measurements were carried out by positioning the Matrixx detector at 10 cm depth. The planning and measurements were performed as per AAPM TG119 guidelines. The test suite includes AP:PA field, band test, multitarget, prostate, head and neck and C-shape. The ion chamber measurements were within 3% of the planned dose for target and avoidance structure region. The ion chamber measurement results are in good agreement with the TG119 recommendation of ±3% for all the test suites. The planar dose measurements were performed with Matrixx for individual fields at the planned gantry angle. The results show that the pass criteria for γ ≤ 1 were between 93 to 97% for all the test cases. Our results are in good agreement with the TG119 recommendation. The present study aimed to compare the measured dose with the planned dose using computer planning system. The test suites were used to assess the planning and delivery systems so as to provide the basis for IMRT commissioning and QA.     

200例SBRT计划验证结果的通过率分析

目的 总结分析200例SBRT放疗计划验证结果，分析SBRT计划验证的γ通过率及其影响因素。方法 采用二维和三维探测器矩阵（Mapcheck、瑞典Delta4）对SBRT放疗计划进行治疗前的计划验证。分析不同治疗技术IMRT和VMAT对计划验证通过率的影响。研究不同验证标准（2%/2 mm、3%/3 mm、5%/3 mm标准，阈值10%）并比较验证计划与治疗计划验证结果之间的差异，并行独立样本t检验。研究并分析不同肿瘤类型对计划通过率的影响。结果 200例SBRT计划γ通过率均能满足临床治疗的要求：IMRT计划的γ通过率在2%/2 mm、3%/3 mm标准下依次为（95.95±7.39）%、（99.76±1.94）%；VMAT计划使用Delta4验证结果显示：γ通过率在2%/2 mm、3%/3 mm标准下依次为（97.02±3.86）%、（99.51±1.41）%；不同肿瘤类型计划验证的γ通过率不同，IMRT和VMAT计划验证γ通过率差异无统计学意义。结论 200例SBRT计划的验证结果均能达到临床治疗的要求，IMRT和VMAT计划验证通过率不同，无统计学意义；不同肿瘤和治疗技术（IMRT和VMAT）的SBRT计划验证通过率不同，统计学分析显示无意义。     

调强放疗计划验证γ通过率的参考范围

目的目前,我国尚无统一的关于调强放疗(IMRT&VMAT)计划验证γ通过率的参考范围,该研究通过回顾性分析,以期建立合理的可实现的γ通过率参考范围。方法回顾性分析2017年6月至2019年7月于医院行调强放疗的2487例患者的计划剂量验证结果,采用SPSS 19.0统计软件按照病种部位(因素A)、计划系统(因素B)和验证工具(因素C)对3%/3 mm、3%/2 mm和2%/2 mm评价标准下的γ通过率进行分类,并进行3×3×2析因分析,检验各因素对γ通过率的影响情况,同时参照AAPM TG-119报告提出的置信限(CL)的定义,探讨2%/2 mm、3%/2 mm和3%/3 mm评价标准对应病种部位、计划系统及验证工具下的调强放疗计划γ通过率的置信度区间。结果不同病种部位、计划系统和验证工具均是γ通过率的独立影响因素,它们之间的差异均有统计学意义(P<0.01);同时,病种部位与计划系统、病种部位与验证工具、计划系统与验证工具对γ通过率的影响均有交互作用(P<0.01)。对于头颈部、胸部和腹部肿瘤,在不考虑计划系统和验证工具的情况下,其3%/3 mm、3%/2 mm、2%/2 mm的γ通过率的平均CL分别为(5.7、9.4、16.2)、(5.1、9.6、19.3)、(5.5、9.9、20.4);对于Pinnacle、Oncentra和Monaco计划系统,在不考虑病种部位和验证工具的情况下,其3%/3 mm、3%/2 mm、2%/2 mm的γ通过率的平均CL分别为(7.2、12.1、23.0)、(4.6、9.4、18.4)、(4.4、7.4、14.5);对于ArcCheck和MapCheck验证工具,在不考虑病种部位和计划系统的情况下,其3%/3 mm、3%/2 mm、2%/2 mm的γ通过率的平均CL分别为(5.0、9.6、18.9)、(5.8、9.6、18.3)。结论病种部位、计划系统及验证工具对调强放疗计划验证的γ通过率既是独立影响的主效应因素,又存在因素之间的交互作用,即不同病种部位、计划系统和验证工具的调强放疗计划验证的γ通过率不同,CL值也不同。     

Assessment of electron density effects on dose calculation and optimisation accuracy for nasopharynx,for MRI only treatment planning

Computed tomography (CT) is the gold standard for radiotherapy simulation and treatment planning, providing spatial accuracy, bony anatomy definition and electron density information for dose calculations. Magnetic resonance imaging (MRI) has been introduced in radiotherapy to improve visualisation of anatomy for accurate target definition and contouring, however lacks electron density information required for dose calculations, with various methods used to overcome this. The aim of this work is to assess the impact on dose calculation accuracy and optimisation results of different approaches to determine electron density, as could be used in MRI only treatment planning for nasopharyngeal datasets with VMAT treatment plans. Volumetric modulated arc therapy (VMAT) plans were created for 10 retrospective head and neck (H&N) nasopharyngeal patients. The VMAT plans were generated on the gold standard dataset, the original CT scan. Data sets with no density correction (water equivalent) and two different sets of bulk density correction for bone/air/tissue applied separately were generated for these patients and the VMAT plans were recalculated for each case. Plans were also reoptimised on these data sets, and recalculated. Optimisation error was assessed through equivalent uniform dose (EUD) differences. Additionally, point dose comparison, dose volume histogram (DVH) analysis and gamma analysis of dose were used to assess dose calculation error. The dose calculation error on average was an increase in EUD whereas the optimisation error on average was a reduction in EUD compared to the original plan for all datasets aside from the bone only override dataset where bone was set to 1.61 g/cm³. For the optimisation error, the largest mean absolute error (MAE) was 1.88 Gy EUD for the PTV, and 2.21 Gy EUD for the brainstem, for the reoptimisation completed on the air only overridden dataset, and recalculated on the original. Bulk density corrections for bone and air provide dose calculations within 3% of the original treatment plans. Optimisation errors have the potential to be greater than dose calculation errors if incorrect density corrections are utilized. Electron density correction using a bulk density approach achieves dose calculation uncertainties within 3%, however more advanced approaches, such as a voxel based approach, may improve accuracy and should be considered.     

基于VMAT的混合调强技术在乳腺癌保乳术后放疗中的应用研究

目的 评估3DCRT+VMAT的混合调强技术在乳腺癌保乳术后瘤床同步加量放疗中的剂量学优势及临床实用性。方法 选择10例乳腺癌保乳术后患者,在同一优化条件下,分别设计基于VMAT的混合调强计划（3DCRT+VMAT）和基于IMRT的混合调强计划（3DCRT+IMRT）,比较两组计划的靶区适形度指数（CI）、均匀性指数（HI）、危及器官的受照剂量体积。结果 3DCRT+VMAT组中PTV的D₉₅为50.29±0.25,优于3DCRT+IMRT组的50.69±0.20（P<0.05）,两组计划PGTV的D₉₅、PTV和PGTV的CI、HI无统计学差异（P>0.05）;3DCRT+VMAT组心脏的D_mean、V₃₀较3DCRT+IMRT组有所降低,且具有统计学意义（P<0.05）;在3DCRT+VMAT组健侧乳腺的D_mean为1.31±0.44低于3DCRT+IMRT组的1.88±0.28（P<0.05）,两组计划患侧肺V₅、V₁₀、V₂₀、D_mean、健侧肺的D_mean无统计学差异（P>0.05）;3DCRT+VMAT组较3DCRT+IMRT组机器跳数减少了31%（P<0.05）,平均治疗时间节省了38%（P<0.05）。结论 基于VMAT的混合调强方式与基于IMRT的混合调强方式相比,在保证靶区的适形度和均匀性前提下,更好的保护了心脏和健侧乳腺,同时显著缩短了计划执行时间,具有较高的临床应用潜力。     

容积旋转调强与固定野调强在宫颈癌根治性放疗中的剂量学比较

目的 比较容积旋转调强(VMAT)与7野固定野调强(dIMRT)两种放射治疗技术在中晚期宫颈癌放射治疗中的剂量学差异。方法 选取10例不适合行腔内照射的中晚期宫颈癌患者,分别制定7野调强放疗计划和容积旋转调强放疗计划。利用剂量体积直方图来统计GTV和PTV的相关参数、适行指数(CI)、均匀性指数(HI),小肠、直肠、膀胱、股骨头正常组织的剂量体积参数,以及机器跳数(MU)及治疗时间。结果 VMAT技术GTV的平均剂量略高于7IMRT且具有统计学意义,GTV的D₂、D₉₈、CI、HI差异无统计学意义,PTV中的D₂、D₉₈、D_mean、CI、HI差异均无统计学意义,VMAT技术直肠的V₄₀、V₄₆、D_mean优于7IMRT且差异有统计学意义,V₁₀、V₂₀、V₃₀差异无统计学意义,两种计划在小肠、膀胱、股骨头的剂量分布差异无统计学差异。VMAT技术机器跳数较7IMRT减少35.68%,平均治疗时间减少61.5%。结论 VMAT技术在剂量分布上与7IMRT相当或略优,但机器跳数和治疗时间明显减少。     

左乳癌保乳术后4种放疗计划的剂量学比较

目的 比较左侧乳腺癌保乳术后行全乳放射治疗时4种放射治疗计划的靶区及危机器官剂量学差异,探讨保乳术后较优的放疗治疗方式.方法 随机选取23例左侧乳腺癌术后行全乳放射放疗患者,给予PTV 25分·次、50 Gy处方剂量;分别设计适形混合调强计划(Hybrid_IMRT)、限制铅门多野调强计划(restricted jaw...     

两种鼻咽癌调强放疗计划的剂量学比较与分析

目的 比较分析鼻咽癌固定射野调强(IMRT)和容积旋转调强(VMAT)计划的靶区和危及器官(OAR)的剂量差异及分次治疗时间和机器跳数的差异。方法 选择在我院接受放疗的15例鼻咽癌患者,对其进行IMRT和VMAT计划设计的比较。结果 靶区:VMAT的大部分参数的HI和CI及D_1%和D_means优于IMRT计划的结果。OAR:虽然脑干的D_means、左右视神经的D_1%及右晶体的D_1%的差异无统计学意义,但其余指标差异均有统计学意义,且VMAT的结果优于IMRT。分次治疗时间:VMAT (4.1 min)要少于IMRT (8.8 min)。分次治疗跳数:VMAT (597.7 MUs)要比IM-RT (823.5 MUs)少约37.8%。结论 鼻咽癌的IMRT和VMAT计划在靶区剂量和OAR保护上都可以达到临床要求,但VMAT的大部分指标要优于IMRT。不过,VMAT在对视神经及晶体等小体积OAR的保护上没有太大优势。VMAT的分次治疗时间和机器跳数都要小于IMRT。     

食管癌固定野调强和旋转容积调强计划的剂量学比较

目的 比较固定5野调强和旋转容积调强在中上段食管癌放疗中的剂量学差异。方法 选取2018年10—12月在我科治疗的中上段食管癌病患20例，用Monaco5.11计划系统分别设计固定5野调强IMRT、单弧VMAT1和双弧VMAT2，在靶区剂量覆盖率都为95%的情况下在剂量体积直方图（DVH）上比较3组计划靶区和危及器官的剂量学差异。结果 VMAT1计划靶区剂量分布均匀性指数（HI）和IMRT计划适形性指数（CI）较其他两种要好（P < 0.05），IMRT计划的靶区最大量和平均受量最小。危及器官方面：IMRT计划对降低脊髓最大受量D_max和心脏平均受量D_mean要优于其他两种；VMAT1计划对双肺的保护最好，VMAT2计划在心脏V₃₀、V₄₀的保护中有优势。机器跳数方面：IMRT计划机器总跳数最少，VMAT1计划次之，VMAT2计划机器总跳数最多。结论 对于胸中上段食管癌，5野调强计划具有脊髓最大受量和心脏平均受量低，靶区适形性好，单次机器跳数低等优点，可以满足临床剂量学要求。     

晚期胸腺瘤精确放疗计划的剂量学对比研究

目的 放疗是不可手术切除的晚期胸腺瘤重要的姑息性治疗手段。本研究拟对比不可手术切除胸腺瘤三维适形调强放疗（IMRT）、容积旋转调强放疗（VMAT）及螺旋断层放射治疗（TOMO）的剂量学参数，为晚期胸腺瘤放疗技术的选择提供理论依据。方法 选取本院9例接受姑息性放疗的晚期不可手术切除胸腺瘤患者，勾画放疗靶区及危及器官，传输至Raystation及TOMO计划系统，分别评估三组计划的等剂量曲线分布图、剂量体积直方图、均匀性指数、适形性指数以及危及器官受照剂量。结果 三组计划均能够满足处方剂量要求及危及器官限量。PGTV，TOMO组等剂量曲线覆盖体积的适形性及剂量均匀性优于IMRT及VMAT组，TOMO组的中位V₅为41.858%，小于IMRT组的45.9%，同时小于VMAT组的48.86%，TOMO组的中位V₂₀为20.25%，小于IMRT组的23.78%。TOMO组心脏的中位V₄₀为23.576%，明显小于VMAT组的27.81%。脊髓中位D_max相比，TOMO组为37.65 Gy，小于IMRT组的38.39 Gy及VMAT组的39.6 Gy。结论 不可手术切除的晚期胸腺瘤，与IMRT及VMAT相比，TOMO放疗计划具有更优的靶区适形性及剂量分布均匀性，并可减少双肺、心脏及脊髓的受照剂量。     

3种全脑放疗技术对中耳剂量学研究

目的 比较脑转移瘤全脑放射治疗(WBRT)3种放疗技术对中耳的剂量学差异,对比3种放疗技术在改善靶区剂量和保护中耳腔和咽鼓管峡部的优劣势.方法 选取2018年7月1日-2019年8月1日我院收治的30例脑转移瘤患者,分别设计固定野调强放疗(ff-IMRT)计划、容积旋转调强放疗(VMAT)和三维适形放疗(3DCRT)计...     

Octavius 4D剂量验证系统应用及误差因素分析

本文首先阐述了Octavius 4D剂量验证系统原理及应用,对其用于VMAT放疗计划进行剂量验证的实施方法、验证方式等进行了分析,探讨了剂量验证误差的影响因素.     

Feasibility of single-isocenter,multi-arc non-coplanar volumetric modulated arc therapy for multiple brain tumors using a linear accelerator with a 160-leaf multileaf collimator: a phantom study

The feasibility of single isocenter, multi-arc non-coplanar volumetric modulated arc therapy (VMAT) for multiple brain tumors was studied using an Elekta Synergy linear accelerator with an Agility multileaf collimator and a Monaco treatment planning system. Two VMAT radiosurgery plans consisting of a full arc and three half arcs were created with a prescribed dose of 20 Gy in a single fraction. After dose delivery to a phantom, ionization chambers and radiochromic films were used for dose measurement. The first VMAT radiosurgery plan had nine targets inside the phantom, and the doses were measured by the chambers at two different points and by the films on three sagittal and three coronal planes. The differences between the calculated dose and the dose measured by a Farmer ionization chamber and a pinpoint ionization chamber were <1.00% and <2.30%, respectively, and the average pass rates of gamma indices among the six planes under each of 3%/3 mm and 2%/2 mm criteria were 98.6% and 92.6%, respectively. The second VMAT radiosurgery plan was based on a clinical 14 brain metastases. Differences between calculated and film-measured doses were evaluated on two sagittal planes. The average pass rates of the gamma indices on the planes under each of 3%/3 mm and 2%/2 mm criteria were 97.8% and 88.8%, respectively. It was confirmed that single-isocenter, non-coplanar multi-arc VMAT radiosurgery for multiple brain metastases was feasible using Elekta Synergy with Agility and Monaco treatment planning systems. It was further shown that film dosimetry was accurately performed for a dose of up to nearly 25 Gy.     

EBT2 radiochromic film for quality assurance of complex IMRT treatments of the prostate: micro-collimated IMRT,RapidArc, and TomoTherapy

In response to the clinical need for a dosimetry system with both high resolution and minimal angular dependence, this study demonstrates the utility of Gafchromic EBT2 radiochromic dosimetry film for the quality assurance of micro-collimated IMRT, RapidArc and TomoTherapy treatments. Firstly, preliminary measurements indicated that the dose response of EBT2 film does not appreciably vary with either the angle of incidence of the radiation beam or the depth in water at which the film is placed. Secondly, prostate treatment plans designed for delivery using static-beam IMRT (collimated using the BrainLab m3 microMLC), RapidArc and TomoTherapy were investigated by comparing dose planes obtained from treatment planning calculations with EBT2 film measurements. For all treatment plans, the proportion of dose points agreeing with the film measurements to within γ (3%,3 mm) was found to be above 95%, with all points agreeing within 5%. The film images provided sufficient information to verify that the treatments could be delivered with an acceptable level of accuracy, while also providing additional information on low-level dose variations that were not predicted by the treatment planning systems. This information included: the location and extent of dose from inter-leaf leakage (in the RapidArc plan) and helical field junctioning (in the TomoTherapy plan), as well as the existence of small regions where the treatment planning system under-predicted the dose from very small treatment segments (in the micro-collimated IMRT plan).     

动态适形弧放射治疗与容积旋转调强放射治疗在非小细胞肺癌立体定向放射治疗中的剂量学差异

目的 比较动态适形弧放射治疗(DCAT)与容积旋转调强放射治疗(VMAT)在非小细胞肺癌立体定向放射治疗(SBRT)中的剂量学差异.方法 选取2016年1月至2020年1月于济宁医学院附属医院接受放射治疗的15例非小细胞肺癌患者,用Monaco5.11.03治疗计划系统以相同的目标优化模板和治疗计划参数分别设计DCAT...     

Pre-treatment verification of intensity modulated radiation therapy plans using a commercial electronic portal dosimetry system

We commissioned a commercially available portal dosimetry system for quality assurance of intensity modulated radiation therapy (IMRT) treatment plans. The system included gamma analysis software to compare the measured and predicted fluence maps from individual IMRT fields. The portal dosimetry system was tested using six head and neck IMRT patient plans, and we demonstrated that the accuracy of the alignment of measured and predicted images improved by retracting and repositioning the electronic portal imaging device (EPID) at each new gantry angle. The mean gamma score (fraction of pixels passing the gamma criteria) for the six test plans (after initial testing and using the EPID retracting and repositioning method) was 0.987 (2SD = 0.018), using gamma criteria of a dose difference of 2% of the maximum field dose and 2 mm distance to agreement. The mean gamma score was 0.989 (2SD = 0.017) for 24 head and neck IMRT patient plans carried out with portal dosimetry. Using gamma criteria of 2% maximum field dose and 2 mm distance to agreement, a gamma score tolerance of 0.980 is a useful way of highlighting only those fields requiring further analysis. Portal dosimetry is a quick way of assessing individual field fluence distributions and can be integrated into an IMRT quality assurance programme.     

An open source solution for an in-house built dynamic platform for the validation of stereotactic ablative body radiotherapy for VMAT and IMRT

An in-house solution for the verification of dose delivered to a moving phantom as required for the clinical implementation of lung stereotactic ablative body radiation therapy was developed. The superior–inferior movement required to simulate tumour motion during a normal breathing cycle was achieved via the novel use of an Arduino Uno?, a low-cost open-source microcontroller board connected to a high torque servo motor. Slow CT imaging was used to acquire the image set and a 4D cone beam CT (4D-CBCT) verified the efficacy of contoured margins before treatment on the moving phantom. Treatment fields were delivered to a section of a CIRS? anthropomorphic phantom. Dose verification to the dynamic phantom with Gafchromic EBT3 film using 3 %-1 mm gamma analysis acceptance criteria registered an absolute dose pass rate for IMRT and VMAT of 98 and 96.6 %, respectively. It was verified that 100 % of the PTV received the prescribed dose of 12 Gy per fraction using the dynamic phantom, and no major discrepancy between planned and measured results due to interplay between multileaf collimator sequences and target motion was observed. This study confirmed that the use of an in-house solution using open source hardware and software with existing quality assurance equipment was appropriate in validating a new treatment technique.