前列腺癌调强放疗的治疗方案比较

目的 通过对前列腺癌调强放疗的多种布野方案比较，确定符合临床要求的最佳方案。方法 对8例前列腺癌患者采用调强放疗方案，处方总剂量76Gy。共设计7个计划，其中共面布野方案5个，分别为5、6、7、9野均匀分布和7野非均匀分布；非共面布野方案2个，分别为5、7野冠状交角照射。分别比较它们的剂量分布、剂量体积直方图、适形度指数等指标。结果 所有7个共面和非共面计划的计划靶区剂量分布无明显差别，非共面计划比共面计划降低了直肠D59(50％体积所受剂量)剂量23％，但增加了股骨头剂量，膀胱的剂量大致相同；同时非共面计划还延长了治疗时间，摆位较麻烦。对于共面射野计划，当射野数目由5增至7时，增加照射野数目对靶区、直肠和膀胱剂量分布没有改善且会增加治疗时间，但能降低股骨头受量，靶区剂量均匀性、适合度指数提高，5、6野情况大致相同。当射野数由7野增加到9野时，股骨头受量和靶区剂量均匀性、适合度均无改善。结论 5～7野共面调强计划可使前列腺肿瘤获得理想的剂量分布，共面、等角度分布的照射野设计简单、治疗实施效率高。非共面计划射野从5野增加到7野，剂量分布无改善。     

应用EPID分析头颈部肿瘤调强放疗的摆位误差

目的 通过对头颈部肿瘤患者群体的射野图像回顾性分析,了解患者群体的摆位误差分布情况,为治疗计划设计设置计划靶体积(PTV)时提供依据.方法 通过配准数字重建图像(DRR)和电子射野影像装置(EPID)拍摄的正、侧位验证像的骨性解剖结构,计算平移和旋转误差.结果 平移误差左右方向为(1.40±1.27)mm,头脚方向为(1.34±1.37)mm,腹背方向为(1.34±1.30)mm;旋转误差冠状面为(0.791±0.976).,矢状面为(0.531±0.750)..结论 对于头颈部肿瘤调强放疗(IMRT),临床靶体积(cTV)到PTV的外放边界在左右方向宜为3.7 mm,头脚及腹背方向宜为3.6 mm.考虑到旋转误差,当靶区比较长时靶区两端外放要更大一些.     

Optimizing patient positioning for intensity modulated radiation therapy in hippocampal-sparing whole brain radiation therapy

PurposeSparing the hippocampus during whole brain radiation therapy (WBRT) offers potential neurocognitive benefits. However, previously reported intensity modulated radiation therapy (IMRT) plans use multiple noncoplanar beams for treatment delivery. An optimized coplanar IMRT template for hippocampal-sparing WBRT would assist in clinical workflow and minimize resource utilization. In this study, we sought to determine the optimal patient position to facilitate coplanar treatment planning and delivery of hippocampal-sparing WBRT using IMRT.Methods and materialsA variable angle, inclined board was utilized for patient positioning. An anthropomorphic phantom underwent computed tomography simulation at various head angles. The IMRT goals were designed to achieve target coverage of the brain while maintaining hippocampal dose–volume constraints designed to conform to the Radiation Therapy Oncology Group 0933 protocol. Optimal head angle was then verified using data from 8 patients comparing coplanar and noncoplanar WBRT IMRT plans.ResultsHippocampal, hippocampal avoidance region, and whole brain mean volumes were 1.1 cm³, 12.5 cm³, and 1185.1 cm³, respectively. The hippocampal avoidance region occupied 1.1% of the whole brain planning volume. For the 30-degree head angle, a 7-field coplanar IMRT plan was generated, sparing the hippocampus to a maximum dose of 14.7 Gy; D100% of the hippocampus was 7.4 Gy and mean hippocampal dose was 9.3 Gy. In comparison, for flat head positioning the hippocampal Dmax was 22.9 Gy with a D100% of 9.2 Gy and mean dose of 11.7 Gy. Target coverage and dose homogeneity was comparable with previously published noncoplanar IMRT plans.ConclusionsCompared with conventional supine positioning, an inclined head board at 30 degrees optimizes coplanar whole brain IMRT treatment planning. Clinically acceptable hippocampal-sparing WBRT dosimetry can be obtained using a simplified coplanar plan at a 30-degree head angle, thus obviating the need for complex and time consuming noncoplanar IMRT plans.     

Sensitivity of intensity modulated proton therapy plans to changes in patient weight.

PURPOSE: A retrospective study to investigate the sensitivity of intensity modulated proton therapy (IMPT) to changes in body weight occurring during the course of radiotherapy for patients treated in the sacral region. MATERIALS AND METHODS: During therapy, important weight gain and loss were observed for two patients treated to para-spinal tumors, which resulted in both patients being re-scanned and re-planned. Both patients were treated as part of their therapy, with a narrow-angle IMPT (NA-IMPT) plan delivering a 'dose hole' around the cauda equina (CE), which was mainly formed through modulation of Bragg peaks in depth. To investigate the impact of these weight changes on the proton range and delivered dose, the nominal fields were re-calculated on the new CT data sets. Results were analyzed by comparing these new plans with those originally delivered and by calculating changes in range and delivered doses in target volumes and normal tissues. RESULTS: Maximum differences in proton range in the CE region of up to +8 mm and -13 mm, respectively, for the patient who gained weight and for the patient who lost weight, increased the maximum dose to the CE by only 2%. This indicates that both IMPT plans were relatively insensitive to substantial range uncertainties. Even greater differences in range (16 mm) in the planning target volume only slightly affected its dose homogeneity (differences in V(90%) of 6% in the worst case). Nevertheless, some large undesired local dose differences were observed. CONCLUSIONS: We demonstrated, that, at least for the two analyzed cases, NA-IMPT plans are less sensitive to weight variations than one may expect. Still, we would advise to calculate new plans in case of substantial change in weight for patients treated in the sacral region, primarily due to the presence of new hot/cold area.     

三维适形放疗和调强放疗

自居里夫妇发现镭并用于肿瘤治疗以来 ,肿瘤的放疗已超过了一个世纪的历程。在这一百余年的历史中 ,放射肿瘤学有了明显的发展。目前放射治疗已是恶性肿瘤的根治手段之一。据世界卫生组织估计 ,在全部恶性肿瘤中 ,4 5 %的病人可以被目前的治疗方法治愈 ,其中 2 2 %被手术治愈 ,18%被放射治疗治愈 ,余下 5 %被药物治愈。若以全部肿瘤病人计算 ,其中的三分之二在其病程的某一阶段可接受根治性或姑息性的放疗。可见放疗已被广泛应用于肿瘤的治疗。然而 ,近 2 0多年以来 ,随着各种肿瘤治疗技术的发展 ,新的抗癌药物和生物治疗的不断出现 ,使肿瘤…     

New developments in intensity modulated radiation therapy

As intensity modulated radiation therapy (IMRT) becomes routine clinical practice, its advantages and limitations are better understood. With these new understandings, some new developments have emerged in an effort to alleviate the limitations of the current IMRT practice. This article describes a few of these efforts made at the University of Maryland, including: i) improving IMRT efficiency with direct aperture optimization; ii) broadening the scope of optimization to include the mode of delivery and beam angles; and iii) new planning methods for intensity modulated arc therapy (IMAT).     

Direct aperture optimization as a means of reducing the complexity of intensity modulated radiation therapy plans

Background

To evaluate the impact of four different rectum contouring techniques and rectal toxicities in patients with treated with 3D conformal radiotherapy (3DCRT).

Methods

Clinical and dosimetric data were evaluated for 94 patients who received a total dose 3DCRT of 70 Gy, and rectal doses were compared in four different rectal contouring techniques: the prostate-containing CT sections (method 1); 1 cm above and below the planning target volume (PTV) (method 2); 110 mm starting from the anal verge (method 3); and from the anal verge to the sigmoid flexure (method 4). The percentage of rectal volume receiving RT doses (30–70 Gy) and minimum, mean rectal doses were assessed.

Results

Median age was 69 years. Percentage of rectal volume receiving high doses (≥ 70 Gy) were higher with the techniques that contoured smaller rectal volumes. In methods 2 and 3, the percentage of rectal volume receiving ≥ 70 Gy was significantly higher in patients with than without rectal bleeding (method 2: 30.8% vs. 22.5%, respectively (p = 0.03); method 3: 26.9% vs. 18.1%, respectively (p = 0.006)). Mean rectal dose was significant predictor of rectal bleeding only in method 3 (48.8 Gy in patients with bleeding vs. 44.4 Gy in patients without bleeding; p = 0.02).

Conclusion

Different techniques of rectal contouring significantly influence the calculation of radiation doses to the rectum and the prediction of rectal toxicity. Rectal volume receiving higher doses (≥ 70 Gy) and mean rectal doses may significantly predict rectal bleeding for techniques contouring larger rectal volumes, as was in method 3.     

Preliminary experience with intensity modulated radiation therapy for abdominopelvic tumor sites: a comparison with 3D radiotherapy plans

Purpose. To report our preliminary experience using intensity modulated radiation therapy (IMRT) in abdominopelvic tumors and to compare IMRT and three-dimensional conformal radiotherapy (3D-CRT) plans for various pelvic sites. Materials and methods. Nine IMRT procedures were performed in 8 patients between June 2000 and June 2001. Tumor diagnosis was rectal carcinoma in 5 (local relapses in 4 and primary in 1), prostate cancer in 2, soft tissue sarcoma in 1, and paravertebral relapse from endometrial carcinoma in 1. Six patients received concurrent chemotherapy. Exhaustive dosimetric verification was performed in all procedures. Results. Average fraction delivery lasted 30–45 minutes. Acute tolerance was excellent in all patients, with only one case of dermatitis grade 2 observed. Planning target volume coverage was satisfactory with a median of 101% (range 97–103). Planning comparison of 3D-CRT and IMRT revealed an ICRU point dose percentage for small bowel of 64% versus 42%, for bladder 78% versus 22%, for rectum 58% versus 29% and for spinal cord 34% versus 20%. Conclusions. This preliminary experience shows that, with IMRT, the median dose received by small bowel, bladder, rectum and spinal cord is substantially less than seen with 3D-CRT and should reduce the morbidity of abdominal-pelvic irradiation, thereby allowing delivery of a higher dose to the tumor.     

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。     

Pilot study of conformal intensity modulated radiation therapy for localized prostate cancer]

PURPOSE:- To report our experience on treatment planning and acute toxicity in 16 patients suffering from clinically localized prostate cancer treated with high-dose intensity-modulated radiation therapy (IMRT). PATIENTS AND METHODS: - Between March 2001 and October 2002, 16 patients with clinically localized prostate cancer were treated with IMRT. Treatment planning included an inverse-planning approach, and the desired beam intensity profiles were delivered by dynamic multileaf collimation. All patients received the entire treatment course with IMRT to a prescribed dose of 78 Gy. All IMRT treatment plans were compared with a theoretical conventional three-dimensional conformal radiation therapy (3D-CRT). Acute lower gastro-intestinal (GI) and genito-urinary (GU) toxicity was evaluated in all patients and graded according to the Common Toxicity Criteria for Adverse Events version 3.0 (CTCAE v. 3.0). A relationship between dose volume and clinical toxicity was evaluated. RESULTS: - Ninety-five percent of the PTV2 received more than 76 Gy using IMRT or 3D-CRT with no difference between both methods. The dose-volume histogram mean obtained for the PTV2 was not different between IMRT and 3D-CRT. IMRT improved homogeneity of the delivered dose to the PTV2 as compared with 3D-CRT (7.5 vs 9%, respectively). Ninety-five percent of the PTV1 received 5 Gy more using IMRT with protection of the bladder and the rectum walls. The benefit was considered below 75 and 70 Gy for the wall of the bladder and the rectum, respectively. Grade 2 GI and GU toxicity was observed in four (25%) and five (31%) patients, respectively. No grade 3 toxicity was observed. There was a trend towards a relationship between the mean rectal dose and acute rectal toxicity but without statistical significant difference (P =0.09). CONCLUSION: - Dose escalation with IMRT is feasible with no grade 3 or higher acute GI or GU toxicity. Examination of a larger cohort and longer-term follow-up are warranted in the future.     

独立准直器调强放疗系统的验收测试

目的 建立IC_IMRT系统的验收测试方法并完成该系统的验收测试.方法 采用NE2571电离室和2570剂量仪测量加速器的启动特性和下咽、肺及宫颈癌3个病例的等中心和其他剂量特征点的绝对剂量.采用Mapcheck2二维半导体矩阵验证基本测试例和3个病例的二维平面剂量分布.基本测试例由矩形或方形射野组成,分别为2 cm×2 cm、5 cm×5 cm、10 cm×10 cm、20 cm×20 cm、2 cm×10 cm、10 cm×2 cm、5 cm×20 cm和20 cm×5 cm的对称射野,2 cm×2 cm(x1=4cm、y1=10 cm,χ2=-2 cm、y2=-8 cm)和5 cm×5 cm(x1=-2 cm、y1=-5 cm,χ2=7 cm、y2=10cm)的非对称射野及由5个20 cm ×4 cm的射野合成的20 cm×20 cm的条状叠加野.采用γ分析法比较测量和计算的剂量分布,通过率标准为3 mm/3%≥90%.结果 当加速器输出跳数达到4即可保证2%的剂量精确性;对所有测试例等中心及特征点的绝对剂量误差最大为-3.67%;在全部11个基本测试野和3个病例的24个照射野中只有条状叠加野和下咽癌病例2个野的通过率稍低于90%,分别是83.6%、88.3%和89.7%.3个计划的实施时间依次是15、14、27 min.结论 测试结果总体满足临床要求,系统可用于患者治疗.

Abstract：

Objective To perform an acceptance test for the IMRT system with independent collimator. Methods An ion chamber dosimeter were used to measure the startup characteristics of the accelerator and the absolute dose at isocenter and given characteristic points for three clinical cases ( a lower nasopharyngeal carcinoma, a lung cancer and a cervical cancer). The characteristic points represented the organs at risk or the target. A Mapeheck2 was used to measure dose maps of basic test fields and the treatment fields for the clinical cases. The basic test fields were as follows: 1 ). Symmetric fields in size of 2 cm ×2 cm, 5 cm ×5 cm, 10 cm× 10 cm, 20 cm ×20 cm, 2 cm × 10 cm, 10 cm ×2 cm, 5 cm ×20 cm and 20 cm ×5 cm;2). Asymmetric fields in size of 2 cm ×2 cm (x1 =4 cm, y1 = 10 cm;x2 = -2 cm, y2 = -8cm) and 5 cm ×5 cm (x1 = -2 cm, y1 = -5 cm;x2 =7 cm, y2 = 10 cm) ;3) A 20 cm ×20 cm composite field composed of five 20 cm× 4 cm narrow bar fields side by side. Gamma Index was used to compare calculated and corresponding measured dose distributions. When the criterion was 3% dose difference or 3 mm distance-to-agreement, the pass rate was required to be more than 90%. Results The accuracy of machine output was better than 2% when machine monitor units increased to 4. Among all basic test fields and all the treatment fields of three clinical cases, the maximal absolute dose error was -3.67%, and only the composite test field and two treatment fields of the lower nasopharyngeal carcinoma case had a pass rate slightly less than 90%, which were 83.6%, 88. 3% and 89. 7% ,respectively. For the three clinical cases the treatment delivery times were 15, 14, and 27 minutes, respectively. Conclusions The overall commissioning results are acceptable, and the system can be used in clinic.     

Treatment of recurrent malignant gliomas with stereotactic intensity modulated radiation therapy

Malignant gliomas are usually refractory to aggressive combined-modality therapy, and the incidence of recurrence and death after treatment is very high. State-of-the-art techniques such as stereotactic intensity-modulated radiation therapy (IMRT) are now available to deliver a high dose of radiation to the tumor with relative preservation of surrounding tissues to achieve optimal tumor coverage with minimal toxicity. We report 10 patients (median age 48 years) with recurrent malignant gliomas that were treated with stereotactic directed IMRT. Initial tumor histologies included one low grade glioma (upgraded to anaplastic astrocytoma at recurrence), four anaplastic astrocytomas, and four glioblastomas multiforme. One patient was originally presumed to have a brain metastasis secondary to renal cell carcinoma but was pathologically confirmed as having glioblastoma multiforme at the time of recurrence. Before recurrence, all patients had been treated with external beam radiation therapy (median 59.7 Gy). All recurrences were confirmed by a subtotal resection (5/10) or by imaging (5/10). The median Karnofsky performance score at the time of IMRT was 80. The median tumor volume was 34.69 cm. Treatment was delivered on a 10-MV linear accelerator with a mini-multileaf collimator, MIMiC, and planned with Peacock/Corvus software. Radiation was delivered in daily fractions of 5 Gy, to a total median dose of 30 Gy at the 71% to 93% median isodose line. Median overall survival time was 10.1 months from the date of stereotactic treatment, with 1- and 2-year survival rates of 50% and 33.3%, respectively. Fractionated stereotactic intensity modulated radiation therapy is a novel technique used in the treatment of recurrent malignant gliomas, which produces results comparable to other currently used stereotactic techniques.     

独立准直器调强放疗系统的验收测试

Objective To perform an acceptance test for the IMRT system with independent collimator. Methods An ion chamber dosimeter were used to measure the startup characteristics of the accelerator and the absolute dose at isocenter and given characteristic points for three clinical cases ( a lower nasopharyngeal carcinoma, a lung cancer and a cervical cancer). The characteristic points represented the organs at risk or the target. A Mapeheck2 was used to measure dose maps of basic test fields and the treatment fields for the clinical cases. The basic test fields were as follows: 1 ). Symmetric fields in size of 2 cm ×2 cm, 5 cm ×5 cm, 10 cm× 10 cm, 20 cm ×20 cm, 2 cm × 10 cm, 10 cm ×2 cm, 5 cm ×20 cm and 20 cm ×5 cm;2). Asymmetric fields in size of 2 cm ×2 cm (x1 =4 cm, y1 = 10 cm;x2 = -2 cm, y2 = -8cm) and 5 cm ×5 cm (x1 = -2 cm, y1 = -5 cm;x2 =7 cm, y2 = 10 cm) ;3) A 20 cm ×20 cm composite field composed of five 20 cm× 4 cm narrow bar fields side by side. Gamma Index was used to compare calculated and corresponding measured dose distributions. When the criterion was 3% dose difference or 3 mm distance-to-agreement, the pass rate was required to be more than 90%. Results The accuracy of machine output was better than 2% when machine monitor units increased to 4. Among all basic test fields and all the treatment fields of three clinical cases, the maximal absolute dose error was -3.67%, and only the composite test field and two treatment fields of the lower nasopharyngeal carcinoma case had a pass rate slightly less than 90%, which were 83.6%, 88. 3% and 89. 7% ,respectively. For the three clinical cases the treatment delivery times were 15, 14, and 27 minutes, respectively. Conclusions The overall commissioning results are acceptable, and the system can be used in clinic.     

胸中段食管癌三维适形放疗、调强放疗及旋转调强放疗的剂量学研究

 目的　研究胸中段食管癌三维适形放疗（3DCRT）、调强放疗（IMRT）、旋转调强放疗（IMAT）3种放疗计划的剂量差异。方法　选取胸中段食管癌患者15例,以Varian Eclipse 8.6计划系统分别设计3DCRT、IMRT、IMAT 3种放疗计划,其中3DCRT采用5～8个共面射野,IMRT采用7个共面射野,IMAT采用2个弧度。比较3种计划的剂量学差异。结果　IMRT、IMRT的靶区均匀指数（HI）、适形指数（CI）、95 % 计划靶体积（PTV）体积剂量均优于3DCRT,全肺V5、V20、V35、心脏V30受照剂量低于3DCRT（t＝2.531,P＜0.05）,而在全肺V10、V15、V25、V30、全肺平均、心脏平均、脊髓Dmax剂量之间三者的差异均无统计学意义（t＝1.325,P＞0.05）。结论　IMAT与IMRT在胸中段食管癌放疗靶区体积剂量覆盖和危及器官保护方面相似,二者均优于3DCRT。IMAT的机器跳数和照射时间均少于IMRT。     

螺旋断层放疗系统调强放疗验证

目的 通过螺旋断层放疗系统一系列调强放疗验证方法的研究,探讨其调强放疗的质量保证验证方法是否可行.方法 采用断层放疗计划系统进行调强放疗计划设计.为实现其剂量验证,笔者采用圆柱形固体水模体、0.056cm3 AISL电离室及EDR2胶片来实现对计划进行绝对剂量及相对剂量验证.将剂最胶片和电离室分别置于模体中,调用患者治疗计划束流数据对模体进行模拟照射;由此得出轴向截面上的等剂量分布和点绝对剂量,与计划模体的等剂量曲线及计算剂量结果进行比对.束流照射前,利用调强放疗兆伏特CT对摆位模体实行图像引导,与计划系统中模体千伏特CT图像进行配准比较,实现验证模体摆位准确性.结果 轴向测得注量分布与断层放疗计划系统计算结果相一致,测量点绝对剂量测量的结果与计划系统的计算误差均在±3%以内.测量模体的摆位误差基本可保持在1mm以内,但由于床从摆位虚拟中心到束流中心之间存在垂直下降2mm的系统误差,需要在模体或患者摆位中予以考虑.结论 3个月临床实践证明断层放疗的调强放疗所采用上述质量保证措施是切实可行的,建立了其质最保证体系.     

局部晚期喉癌3DCRT与IMRT放疗计划的剂量学对比

目的 利用ECLIPSE计划系统对局部晚期喉癌适形放疗(3DCRT)和逆向调强适形放疗(IMRT)计划作剂量学比较,评估不同照射方法的优缺点。方法 选择6例病理证实的局部晚期喉癌患者,用ECLIPSE对每例患者分别作出3DCRT和IMRT计划。根据靶区V95%、D5%、D95%、靶区最大值、最小值及平均值和正常组织受量D50、D33、D5、Dmax和Dmean来比较这两种计划剂量学的差异。结果 两种不同计划中的靶区分布中,GTV和GTVnd差别不大,但对于亚临床区CTV和某些正常组织有统计学差异。结论 对局部晚期喉癌原发灶及阳性淋巴结,3DCRT和IMRT计划均有较好覆盖。但在亚临床病灶方面,IMRT比3DCRT包含靶区更好一些,且IMRT减少了腮腺正常组织的照射剂量。     

Voxel-based automatic multi-criteria optimization for intensity modulated radiation therapy

Background

Automatic multi-criteria optimization is necessary for intensity modulated radiation therapy (IMRT) because of low planning efficiency and large plan quality uncertainty in current clinical practice. Most studies focused on imitating dosimetrists’ planning procedures to automate this process and ignored the fact that organ-based objective functions typically used in commercial treatment planning systems (such as dose-volume function) usually lead to sub-optimal plans. To guarantee the optimum results and to automate this process, we incorporate an improved automation strategy and a voxel-based optimization algorithm to generate a novel automatic multi-criteria optimization framework. We then evaluate it in clinical cases.

Methods

This novel automatic multi-criteria optimization framework incorporates a ranked priority-list based automatic constraints adjustment strategy and an in-house developed voxel-based optimization algorithm. Constraints are sequentially adjusted following a pre-defined priority list. Afterward, a voxel-based fluence map optimization (FMO) with an orientation to the newly updated constraints is launched to find a Pareto optimal solution. Loops of constraints adjustment are repeated until each of them could not be relaxed or tightened. The feasibility of the framework is evaluated with 10 automatic generated gynecology (GYN) cancer IMRT cases by comparing the dosimetric performance with the original.

Results

Plan quality improvement is observed for our automatic multi-criteria optimization method. Comparable DVHs are found for the planning target volume (PTV), but with better organs-at-risk (OAR) dose sparing. Among 13 evaluated dosimetric endpoints, 5 of them show significant improvements in automatically generated plans compared with the original plans. Investigation of improvement tendency during optimization exhibits gradual change as the optimization stage proceeds. An initial voxel-based optimization stage and in-low-priority dosimetric criteria tighten can significantly contribute to the optimization procedure.

Conclusions

We have successfully developed an automatic multi-criteria optimization framework that can dramatically reduce the current trial-and-error patterned planning workload while affording an efficient method to assure high plan quality consistency. This optimization framework is expected to greatly facilitate precise radiation therapy because of its advantages of planning efficiency and plan quality improvement.

     

Postmastectomy intensity modulated radiation therapy following immediate expander-implant reconstruction

Background/purpose

To evaluate radiation plans of patients undergoing mastectomy with immediate expander-implant reconstruction followed by postmastectomy radiation therapy (PMRT).

Materials/methods

We identified 41 patients from June 2004 to May 2007 who underwent mastectomy, immediate expander-implant reconstruction, and PMRT with intensity-modulated radiation therapy. We assessed chest wall (CW) coverage and volume of heart and lung irradiated.

Results

In 73% of patients, all CW borders were adequately covered, and in 22%, all but 1 border were adequately covered. The total lung V₂₀ was <20% in 39/41 patients. The mean lung V₂₀ was 13% (range, 3-23%), and the mean heart D_mean was 2.81 Gy (range, 0.53-9.60 Gy). In patients with left-sided lesions without internal mammary nodes (IMNs) treatment (n = 22), the mean lung V₂₀ was 12.6% and the mean heart D_mean was 3.90 Gy, and in the patient with IMN treatment, the lung V₂₀ was 18% and heart D_mean was 8.04 Gy. For right-sided lesions without IMN treatment (n = 12), the mean lung V₂₀ was 12.4% and the mean heart D_mean was 0.90 Gy, and in patients with IMN treatment (n = 6), these numbers were 17.8% and 1.76 Gy. At a median follow-up of 29 months, the 30-month actuarial local control was 97%.

Conclusions

In women undergoing immediate expander-implant reconstruction, PMRT can achieve excellent local control with acceptable heart and lung doses. These results can be achieved even when the IMN are being treated, although doses to the heart and lungs will be higher.     

A dosimetric comparison between 3D-conformal radiation therapy and intensity modulated radiation therapy plans in the treatment of posterior fossa boost in children with high risk medulloblastom

Objective:The work is a comparative study between two modalities of radiation therapy, the aim of which is to compare 3D conformal radiation therapy (3D-CRT) and intensity modulated radiation therapy (IMRT) in treating posterior fossa boost in children with high risk medul oblastoma;dosimetrical y evaluating and comparing both techniques as regard target coverage and doses to organs at risk (OAR). Methods:Twenty patients with high risk medul oblastoma were treated by 3D-CRT technique. A dosimetric comparison was done by performing two plans for the posterior fossa boost, 3D-CRT and IMRT plans, for the same patient using Eclipse planning system (version 8.6). Results:IMRT had a better conformity index compared to 3D-CRT plans (P value of 0.000). As for the dose homogeneity it was also better in the IMRT plans, yet it hasn’t reached the statistical significant value. Also, doses received by the cochleae, brainstem and spinal cord were significantly less in the IMRT plans than those of 3D-CRT (P value<0.05). Conclusion:IMRT technique was clearly able to improve conformity and homogeneity index, spare the cochleae, reduce dose to the brainstem and spinal cord in comparison to 3D-CRT technique.