Introduction: Intensity Modulated Radiation Therapy (IMRT) planning dose calculation process depends on IMRT dose constraints. So, if there was any structure along the treatment beam path not delineated, it would not ...Introduction: Intensity Modulated Radiation Therapy (IMRT) planning dose calculation process depends on IMRT dose constraints. So, if there was any structure along the treatment beam path not delineated, it would not be taken into account during that calculation process. During IMRT routine practical work, it is noticed that there are some non-delineated normal tissue volumes that received un-aimed dose. Aim: The purpose of this study was to study the effect of unusually delineated normal volumes in IMRT treatment for left sided breast cancer. Method: Ten left sided breast cancer patients were planned with IMRT inverse planning system. The unusually delineated normal volumes were delineated and taken into account in IMRT dose constraints as an Organ at Risk. Doses received by that volume were compared in the two methods quantitatively from Dose Volume Histograms (DVHs) and qualitatively from (axial cuts). Results: The results showed that doses received by the unusually delineated volume when they were delineated and taken into account in IMRT dose constraints were significantly higher than when they were not. Conclusions: The results showed that for IMRT planning technique used for treating left-sided breast cancer, all of the normal tissues/structures that are closed to the treatment targets must be delineated and taken into account in the IMRT planning dose constraints.展开更多
Introduction: Field-in-Field (FIF) and Intensity Modulated Radiation Therapy (IMRT) are two advanced radiation therapy planning techniques. Both of them are being used to achieve the same two related aims which are, t...Introduction: Field-in-Field (FIF) and Intensity Modulated Radiation Therapy (IMRT) are two advanced radiation therapy planning techniques. Both of them are being used to achieve the same two related aims which are, to expose the targeted tumor to the full radiation dose and to spare the nearby normal tissues (or organs) from being exposed to high amounts of radiation more than its tolerance dose limits. FIF is a forward planning while IMRT is an inverse planning and FIF is a forward IMRT. Aim: The purpose of this study was to compare between Field-in-Field and IMRT techniques in prostate cancer radiotherapy. Method: A treatment planning system supporting both inverse and forward planning facilities is used. Ten prostate cancer patients were planned with both FIF and IMRT planning techniques. Doses received by the Planning Target Volume (PTV) and Organs at Risk (OARs) were compared in the two methods quantitatively from Dose Volume Histograms (DVHs) and qualitatively from (axial cuts). Results: The results showed that the IMRT planning technique achieved better dose coverage to the PTV than the FIF planning technique but, except RT and LT Femoral Heads, FIF achieved a better protection to the Rectum and the Bladder (OARs) than IMRT. Conclusions: The results showed that the inverse planning based IMRT technique is better and recommended in the prostate cancer radiotherapy than the FIF technique.展开更多
The inverse planning for a step-and-shoot plan in intensity-modulated radiotherapy (IMRT) is usually a multiple step process. Before being converted into the MLC segments, the optimum intensity profiles of beams, whic...The inverse planning for a step-and-shoot plan in intensity-modulated radiotherapy (IMRT) is usually a multiple step process. Before being converted into the MLC segments, the optimum intensity profiles of beams, which are generated by an optimization algorithm, shall be discretized into a few intensity levels. The discretization process of the optimum intensity profiles can induce deviations in the final dose distribution from the original optimum dose distribution. This paper describes a genetic algorithm for the discretization of given optimum intensity profiles. The algorithm minimizes an objective function written in terms of the intensity levels. Both the dose-based objective function, which is defined by the deviation between the dose distributions before and after the discretization, and the intensity-based objective function, which is defined by the deviation between the optimum intensity profiles and the discretization intensity profiles, have been adopted. To evaluate this algorithm, a series of simulation calculations had been carried out using the present algorithm, the even-spaced discretization and the k-means clustering algorithm respectively. By comparing the resultant discretization-induced deviations (DIDs) in intensity profiles and in dose distributions, we have found that the genetic algorithm induced less DIDs in comparison with that induced in the even-spaced discretization or the k-means clustering algorithm. Additionally, it has been found that the DIDs created in the genetic algorithm correlate with the complexity of the intensity profiles that is measured by the "fluence map complexity".展开更多
目的研究比较商用计划系统蒙特卡洛算法（XVMC）和解析算法的差异,为肺癌临床剂量计算算法选择提供依据。方法在以往大量针对模体研究的基础上,选择符合RTOG 1306规程的10例临床肺癌病例,按规程用iPlan PB算法采用Sliding Windows IMRT...目的研究比较商用计划系统蒙特卡洛算法（XVMC）和解析算法的差异,为肺癌临床剂量计算算法选择提供依据。方法在以往大量针对模体研究的基础上,选择符合RTOG 1306规程的10例临床肺癌病例,按规程用iPlan PB算法采用Sliding Windows IMRT技术完成治疗计划,再分别采用PBC、AAA、XMVC算法重算,计算结果统一按照1cGy精度间隔导出DVH参数,记录临床关心的靶区和器官参数,并行成对t检验统计分析。结果照射剂量分布显示,PB、PBC算法在54~62Gy间差异有统计学意义,XVMC算法和AAA算法在〈58.2Gy和〉61.8Gy时差异有统计学意义（均P〈0.05）,且XVMC算法与AAA算法结果差异比PB算法与PBC算法间差异大;临床参数统计显示,XVMC算法和AAA算法多项剂量参数差异均有统计学意义（均P〈0.05）。结论对RTOG 1306规程病例,相对XVMC算法,AAA算法高估靶区剂量,低估了肺的剂量体积,可能影响临床医师判断,临床选用时应当注意。本组数据差异在1%左右。展开更多
文摘Introduction: Intensity Modulated Radiation Therapy (IMRT) planning dose calculation process depends on IMRT dose constraints. So, if there was any structure along the treatment beam path not delineated, it would not be taken into account during that calculation process. During IMRT routine practical work, it is noticed that there are some non-delineated normal tissue volumes that received un-aimed dose. Aim: The purpose of this study was to study the effect of unusually delineated normal volumes in IMRT treatment for left sided breast cancer. Method: Ten left sided breast cancer patients were planned with IMRT inverse planning system. The unusually delineated normal volumes were delineated and taken into account in IMRT dose constraints as an Organ at Risk. Doses received by that volume were compared in the two methods quantitatively from Dose Volume Histograms (DVHs) and qualitatively from (axial cuts). Results: The results showed that doses received by the unusually delineated volume when they were delineated and taken into account in IMRT dose constraints were significantly higher than when they were not. Conclusions: The results showed that for IMRT planning technique used for treating left-sided breast cancer, all of the normal tissues/structures that are closed to the treatment targets must be delineated and taken into account in the IMRT planning dose constraints.
文摘Introduction: Field-in-Field (FIF) and Intensity Modulated Radiation Therapy (IMRT) are two advanced radiation therapy planning techniques. Both of them are being used to achieve the same two related aims which are, to expose the targeted tumor to the full radiation dose and to spare the nearby normal tissues (or organs) from being exposed to high amounts of radiation more than its tolerance dose limits. FIF is a forward planning while IMRT is an inverse planning and FIF is a forward IMRT. Aim: The purpose of this study was to compare between Field-in-Field and IMRT techniques in prostate cancer radiotherapy. Method: A treatment planning system supporting both inverse and forward planning facilities is used. Ten prostate cancer patients were planned with both FIF and IMRT planning techniques. Doses received by the Planning Target Volume (PTV) and Organs at Risk (OARs) were compared in the two methods quantitatively from Dose Volume Histograms (DVHs) and qualitatively from (axial cuts). Results: The results showed that the IMRT planning technique achieved better dose coverage to the PTV than the FIF planning technique but, except RT and LT Femoral Heads, FIF achieved a better protection to the Rectum and the Bladder (OARs) than IMRT. Conclusions: The results showed that the inverse planning based IMRT technique is better and recommended in the prostate cancer radiotherapy than the FIF technique.
文摘目的:研究基于人工智能优化引擎(IOE)的Ethos系统自带的Auto Plan计划:9野静态调强放疗(9F-IMRT)、12野静态调强放疗(12F-IMRT)以及3弧容积旋转调强放疗(3-VMAT)技术在宫颈癌放射治疗中的剂量学差异。方法:随机选取收治的宫颈癌患者20例,进行CT模拟定位,基于瓦里安Ethos系统的Auto Plan自动生成9F-IMRT、12F-IMRT以及3-VMAT计划,比较三种计划的靶区剂量适形度、均匀性和危及器官的剂量学差异,以及机器跳数(MU)。结果:9F-IMRT、12F-IMRT以及3-VMAT计划的靶区剂量均能够满足剂量学要求,12F-IMRT和3-VMAT计划靶区适形度的差异无统计学意义(P>0.05),9F-IMRT计划靶区适形度略差;9F-IMRT、12F-IMRT计划靶区均匀性更优,且与3-VMAT相比差异具有统计学意义(P<0.05)。危及器官保护方面,三种计划在膀胱、直肠、小肠、结肠、股骨头中最大剂量D_(max)具有显著性差异(P<0.05)。3-VMAT计划的MU低于9F-IMRT计划和12F-IMRT计划,差异具有统计学意义(P<0.05)。结论:对于宫颈癌患者,Ethos Auto Plan生成的9F-IMRT、12F-IMRT以及3-VMAT技术均可达到临床靶区剂量和危及器官的保护要求,但9F-IMRT、12F-IMRT计划在靶区均匀性方面优于3-VMAT计划;VMAT计划机器跳数明显低于IMRT计划,表明其治疗更高效。
基金Supported by the National Natural Science Foundation of China (Grant No. 10275045)the Excellent Young Teachers Program of China.
文摘The inverse planning for a step-and-shoot plan in intensity-modulated radiotherapy (IMRT) is usually a multiple step process. Before being converted into the MLC segments, the optimum intensity profiles of beams, which are generated by an optimization algorithm, shall be discretized into a few intensity levels. The discretization process of the optimum intensity profiles can induce deviations in the final dose distribution from the original optimum dose distribution. This paper describes a genetic algorithm for the discretization of given optimum intensity profiles. The algorithm minimizes an objective function written in terms of the intensity levels. Both the dose-based objective function, which is defined by the deviation between the dose distributions before and after the discretization, and the intensity-based objective function, which is defined by the deviation between the optimum intensity profiles and the discretization intensity profiles, have been adopted. To evaluate this algorithm, a series of simulation calculations had been carried out using the present algorithm, the even-spaced discretization and the k-means clustering algorithm respectively. By comparing the resultant discretization-induced deviations (DIDs) in intensity profiles and in dose distributions, we have found that the genetic algorithm induced less DIDs in comparison with that induced in the even-spaced discretization or the k-means clustering algorithm. Additionally, it has been found that the DIDs created in the genetic algorithm correlate with the complexity of the intensity profiles that is measured by the "fluence map complexity".
