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
Objective We aimed to determine the effects of low- and high-energy intensity-modulated radiation therapy(IMRT) photon beams on the target volume planning and on the critical organs in the case of prostate cancer. Met...Objective We aimed to determine the effects of low- and high-energy intensity-modulated radiation therapy(IMRT) photon beams on the target volume planning and on the critical organs in the case of prostate cancer. Methods Thirty plans were generated by using either 6 MV or 15 MV beams separately, and a combination of both 6 and 15 MV beams. All plans were generated by using suitable planning objectives and dose constraints, which were identical across the plans, except the beam energy. The plans were analyzed in terms of their target coverage, conformity, and homogeneity, regardless of the beam energy. Results The mean percentage values of V_(70 Gy) for the rectal wall for the plans with 6 MV, 15 MV, and mixedenergy beams were 16.9%, 17.8%, and 16.4%, respectively, while the mean percentage values of V_(40 Gy) were 53.6%, 52.3%, and 50.4%. The mean dose values to the femoral heads for the 6 MV, 15 MV, and mixed-energy plans were 30.1 Gy, 25.5 Gy, and 25.4 Gy, respectively. The mean integral dose for the 6 MV plans was 10% larger than those for the 15 MV and mixed-energy plans. Conclusion These preliminary results suggest that mixed-energy IMRT plans may be advantageous with respect to the dosimetric characteristics of low- and high-energy beams. Although the reduction of dose to the organs at risk may not be clinically relevant, in this study, IMRT plans using mixed-energy beams exhibited better OAR sparing and overall higher plan quality for deep-seated tumors.展开更多
目的研究全段食管癌调强放射治疗计划设计中7野对称式布野与8野对称式布野的靶区及危及器官剂量学特点,为全段食管癌放射治疗患者的计划设计提供一定的参考。方法选择15例全段食管癌放射治疗患者,其中男性8例,女性7例;年龄45~84岁,平均...目的研究全段食管癌调强放射治疗计划设计中7野对称式布野与8野对称式布野的靶区及危及器官剂量学特点,为全段食管癌放射治疗患者的计划设计提供一定的参考。方法选择15例全段食管癌放射治疗患者,其中男性8例,女性7例;年龄45~84岁,平均年龄62.5岁;病灶直径(2.8±1.3)cm;病灶长度(14.6±3.7)cm。采用Eclipse计划系统,全组处方剂量均为50 Gy,以95%靶区体积达到100%处方剂量为基准,剂量体积直方图(DVH)比较7野对称式布野与8野对称式布野计划设计方法的主要危及器官的受量。结果靶区均匀性指数(HI),7野对称式布野与8野对称式布野差异无统计学意义(0.55±0.01 vs 0.56±0.01。t=-2.092,P>0.05)。通过比较,全段食管癌调强放射治疗8野对称式布野肺部V_(20)、V_(5)低于7野对称式布野计划[(21.56±3.26)%vs(25.72±1.65)%、(59.60±6.02)%vs(60.48±6.40)%],其他器官差异无统计学意义。结论常规全段食管癌调强放射治疗计划中使用8野对称式布野计划设计方法可有效地减少肺部高剂量区体积,从而进一步减少放射性肺炎的发生率。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.
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".
文摘Objective We aimed to determine the effects of low- and high-energy intensity-modulated radiation therapy(IMRT) photon beams on the target volume planning and on the critical organs in the case of prostate cancer. Methods Thirty plans were generated by using either 6 MV or 15 MV beams separately, and a combination of both 6 and 15 MV beams. All plans were generated by using suitable planning objectives and dose constraints, which were identical across the plans, except the beam energy. The plans were analyzed in terms of their target coverage, conformity, and homogeneity, regardless of the beam energy. Results The mean percentage values of V_(70 Gy) for the rectal wall for the plans with 6 MV, 15 MV, and mixedenergy beams were 16.9%, 17.8%, and 16.4%, respectively, while the mean percentage values of V_(40 Gy) were 53.6%, 52.3%, and 50.4%. The mean dose values to the femoral heads for the 6 MV, 15 MV, and mixed-energy plans were 30.1 Gy, 25.5 Gy, and 25.4 Gy, respectively. The mean integral dose for the 6 MV plans was 10% larger than those for the 15 MV and mixed-energy plans. Conclusion These preliminary results suggest that mixed-energy IMRT plans may be advantageous with respect to the dosimetric characteristics of low- and high-energy beams. Although the reduction of dose to the organs at risk may not be clinically relevant, in this study, IMRT plans using mixed-energy beams exhibited better OAR sparing and overall higher plan quality for deep-seated tumors.
文摘目的研究全段食管癌调强放射治疗计划设计中7野对称式布野与8野对称式布野的靶区及危及器官剂量学特点,为全段食管癌放射治疗患者的计划设计提供一定的参考。方法选择15例全段食管癌放射治疗患者,其中男性8例,女性7例;年龄45~84岁,平均年龄62.5岁;病灶直径(2.8±1.3)cm;病灶长度(14.6±3.7)cm。采用Eclipse计划系统,全组处方剂量均为50 Gy,以95%靶区体积达到100%处方剂量为基准,剂量体积直方图(DVH)比较7野对称式布野与8野对称式布野计划设计方法的主要危及器官的受量。结果靶区均匀性指数(HI),7野对称式布野与8野对称式布野差异无统计学意义(0.55±0.01 vs 0.56±0.01。t=-2.092,P>0.05)。通过比较,全段食管癌调强放射治疗8野对称式布野肺部V_(20)、V_(5)低于7野对称式布野计划[(21.56±3.26)%vs(25.72±1.65)%、(59.60±6.02)%vs(60.48±6.40)%],其他器官差异无统计学意义。结论常规全段食管癌调强放射治疗计划中使用8野对称式布野计划设计方法可有效地减少肺部高剂量区体积,从而进一步减少放射性肺炎的发生率。
