调强放疗保护N_0鼻咽癌患者颌下腺的研究

目的：探讨调强放疗保护N0鼻咽癌患者颌下腺的可行性。方法：选择N0鼻咽癌患者10例,对每个病例分别制定保护颌下腺的调强放疗计划（计划A）和不保护颌下腺的调强放疗计划（计划B）,比较两种计划的颌下腺、靶区和正常组织/危及器官的剂量分布、剂量体积直方图（DVH）等指标。结果：计划A和计划B相比,前者明显降低了颌下腺的照射剂量：左侧颌下腺D50分别为50.88Gy和30.96Gy,降低了19.92Gy（39.15%）,D平均分别为50.27Gy和31.16Gy,降低了19.11Gy（38.01%）;右侧颌下腺D50分别为50.71Gy和31.27Gy,降低了19.44Gy（38.34%）,D平均分别为49.79Gy和31.73Gy,降低了18.06Gy（36.27%）。两种计划中靶区剂量无明显差别：GTV的D99分别为67.29Gy和67.62Gy,GTV的D95分别为69.59Gy和69.22Gy,GTV的D1分别为73.64Gy和73.64Gy,GTV的Daverage分别为71.21Gy和70.92Gy,GTV的Dmin分别为66.95Gy和66.79Gy;CTV1的D95分别为63.12Gy和63.32Gy,CTV1的Daverage分别为67.62Gy和67.29Gy,CTV1的Dmin分别为56.94Gy和56.45Gy;CTV2的D95分别为54.35Gy和54.65Gy,CTV2的Daverage分别为61.03Gy和60.83Gy,CTV2的Dmin分别为42.62Gy和42.72Gy。脑干的D1和D5、脊髓的D1、颞叶D5、颞颌关节的D50、腮腺的D50及D平均剂量两种计划比较差别不明显。结论：利用调强放疗可以安全有效地保护N0鼻咽癌患者的颌下腺,从而有可能进一步降低患者的口干症状。     

子宫颈癌术后盆腔不同体外照射方法的剂量学研究

目的 比较常规放疗(CRT)、三维适形放疗(3DCRT)及调强放疗(IMRT)方法在子宫颈癌靶体积剂量覆盖及危及器官(OAR)保护方面的差异,探讨子宫颈癌患者术后盆腔体外照射的合理方法.方法 对10例子宫颈癌术后患者进行模拟CT增强扫描,在计划系统内勾画临床靶体积(CTV),CTV均匀外扩1.0 cm生成计划靶体积(PTV),同时勾画小肠、直肠、膀胱、骨髓、卵巢及股骨头作为OAR.进而设计出CRT、3DCRT及IMRT的3种治疗计划,对CRT要求参考点达到处方剂量45 Gy,对3DCRT及IMRT要求95%的PTV达45 Gy.应用等剂量曲线及剂量体积直方图对3种计划的CTV及OAR的剂量分布进行比较.结果 CRT计划中CTV达45 Gy的平均体积显著低于3DCRT、IMRT计划(Q=8.27、8.37,P值均＜0.01),而3DCRT和IMRT计划之间相似(Q=0.10,P＞0.05).3DCRT和IMRT计划中小肠达30、45 Gy的体积明显低于CRT.IMRT计划中直肠、膀胱达30、45 Gy的体积均显著低于CRT,而3DCRT中仅直肠、膀胱达45 Gy的体积显著低于CRT.3DCRT和IMRT使骨髓达30、45 Gy剂量的体积明显低于CRT.4例卵巢移位者中2例在3DCRT及IMRT计划中,另2例在3种计划中卵巢平均受量全部超过300 cGy.结论 IMRT和3DCRT在提高靶体积内剂量及其均匀度,以及保护小肠、直肠和膀胱方面较CRT具备明显优势,以IMRT为最佳.在高剂量范围内,IMRT和3DCRT对骨髓的保护优势确定.对于移位悬吊的卵巢,IMRT、3DCRT及CRT均不能对其形成有效保护.     

Dose Planning Study of Target Volume Coverage with Intensity-Modulated Radiotherapy for Nasopharyngeal Carcinoma: Penang General Hospital Experience

Background: To compare the dosimetric coverage of target volumes and organs at risk in the radicaltreatment of nasopharyngeal carcinoma (NPC) between intensity-modulated radiotherapy (IMRT) and threedimensionalconformal radiotherapy (3DCRT). Materials and Methods: Data from 10 consecutive patientstreated with IMRT from June-October 2011 in Penang General Hospital were collected retrospectively foranalysis. For each patient, dose volume histograms were generated for both the IMRT and 3DCRT plans usinga total dose of 70Gy. Comparison of the plans was accomplished by comparing the target volume coverage (5measures) and sparing of organs at risk (17 organs) for each patient using both IMRT and 3DCRT. The meansof each comparison target volume coverage measures and organs at risk measures were obtained and testedfor statistical significance using the paired Student t-test. Results: All 5 measures for target volume coverageshowed marked dosimetric superiority of IMRT over 3DCRT. V70 and V66.5 for PTV70 showed an absoluteimprovement of 39.3% and 24.1% respectively. V59.4 and V56.4 for PTV59.4 showed advantages of 18.4% and16.4%. Moreover, the mean PTV70 dose revealed a 5.1 Gy higher dose with IMRT. Only 4 out of 17 organsat risk showed statistically significant difference in their means which were clinically meaningful between theIMRT and 3DCRT techniques. IMRT was superior in sparing the spinal cord (less 5.8Gy), V30 of right parotid(less 14.3%) and V30 of the left parotid (less 13.1%). The V55 of the left cochlea was lower with 3DCRT (less44.3%). Conclusions: IMRT is superior to 3DCRT due to its dosimetric advantage in target volume coveragewhile delivering acceptable doses to organs at risk. A total dose of 70Gy with IMRT should be considered as astandard of care for radical treatment of NPC.     

Four-dimensional computed tomography-based treatment planning for intensity-modulated radiation therapy and proton therapy for distal esophageal cancer

PURPOSE: To compare three-dimensional (3D) and four-dimensional (4D) computed tomography (CT)-based treatment plans for proton therapy or intensity-modulated radiation therapy (IMRT) for esophageal cancer in terms of doses to the lung, heart, and spinal cord and variations in target coverage and normal tissue sparing. METHODS AND MATERIALS: The IMRT and proton plans for 15 patients with distal esophageal cancer were designed from the 3D average CT scans and then recalculated on 10 4D CT data sets. Dosimetric data were compared for tumor coverage and normal tissue sparing. RESULTS: Compared with IMRT, median lung volumes exposed to 5, 10, and 20 Gy and mean lung dose were reduced by 35.6%, 20.5%, 5.8%, and 5.1 Gy for a two-beam proton plan and by 17.4%, 8.4%, 5%, and 2.9 Gy for a three-beam proton plan. The greater lung sparing in the two-beam proton plan was achieved at the expense of less conformity to the target (conformity index [CI], 1.99) and greater irradiation of the heart (heart-V40, 41.8%) compared with the IMRT plan(CI, 1.55, heart-V40, 35.7%) or the three-beam proton plan (CI, 1.46, heart-V40, 27.7%). Target coverage differed by more than 2% between the 3D and 4D plans for patients with substantial diaphragm motion in the three-beam proton and IMRT plans. The difference in spinal cord maximum dose between 3D and 4D plans could exceed 5 Gy for the proton plans partly owing to variations in stomach gas filling. CONCLUSIONS: Proton therapy provided significantly better sparing of lung than did IMRT. Diaphragm motion and stomach gas-filling must be considered in evaluating target coverage and cord doses.     

A prospective trial of volumetric intensity-modulated arc therapy vs conventional intensity modulated radiation therapy in advanced head and neck cancer

AIM: To prospectively compare volumetric intensity-modulated arc therapy (VMAT) and conventional intensity-modulated radiation therapy (IMRT) in coverage of planning target volumes and avoidance of multiple organs at risk (OARs) in patients undergoing definitive chemoradiotherapy for advanced (stage III or IV) squamous cell cancer of the head and neck.METHODS: Computed tomography scans of 20 patients with advanced tumors of the larynx, naso-, oro- and hypopharynx were prospectively planned using IMRT (7 field) and VMAT using two arcs. Calculated doses to planning target volume (PTV) and OAR were compared between IMRT and VMAT plans. Dose-volume histograms (DVH) were utilized to obtain calculated doses to PTV and OAR, including parotids, cochlea, spinal cord, brainstem, anterior tongue, pituitary and brachial plexus. DVH’s for all structures were compared between IMRT and VMAT plans. In addition the plans were compared for dose conformity and homogeneity. The final treatment plan was chosen by the treating radiation oncologist.RESULTS: VMAT was chosen as the ultimate plan in 18 of 20 patients (90%) because the plans were thought to be otherwise clinically equivalent. The IMRT plan was chosen in 2 of 20 patients because the VMAT plan produced concentric irradiation of the cord which was not overcome even with an avoidance structure. For all patients, VMAT plans had a lower number of average monitor units on average (MU = 542.85) than IMRT plans (MU = 1612.58) (P < 0.001). Using the conformity index (CI), defined as the 95% isodose volume divided by the PTV, the IMRT plan was more conformal with a lower conformity index (CI = 1.61) than the VMAT plan (CI = 2.00) (P = 0.003). Dose homogeneity, as measured by average standard deviation of dose distribution over the PTV, was not different with VMAT (1.45 Gy) or IMRT (1.73 Gy) (P = 0.069). There were no differences in sparing organs at risk.CONCLUSION: In this prospective study, VMAT plans were chosen over IMRT 90% of the time. Compared to IMRT, VMAT plans used only one third of the MUs, had shorter treatment times, and similar sparing of OAR. Overall, VMAT provided similar dose homogeneity but less conformity in PTV irradiation compared to IMRT. This difference in conformity was not clinically significant.     

Intensity-modulated radiotherapy in nasopharyngeal carcinoma: dosimetric advantage over conventional plans and feasibility of dose escalation

PURPOSE: To compare intensity-modulated radiotherapy (IMRT) with two-dimensional RT (2D-RT) and three-dimensional conformal radiotherapy (3D-CRT) treatment plans in different stages of nasopharyngeal carcinoma and to explore the feasibility of dose escalation in locally advanced disease. MATERIALS AND METHODS: Three patients with different stages (T1N0M0, T2bN2M0 with retrostyloid extension, and T4N2M0) were selected, and 2D-RT, 3D-CRT, and IMRT treatment plans (66 Gy) were made for each of them and compared with respect to target coverage, normal tissue sparing, and tumor control probability/normal tissue complication probability values. In the Stage T2b and T4 patients, the IMRT 66-Gy plan was combined with a 3D-CRT 14-Gy boost plan using a 3-mm micromultileaf collimator, and the dose-volume histograms of the summed plans were compared with their corresponding 66-Gy 2D-RT plans. RESULTS: In the dosimetric comparison of 2D-RT, 3D-CRT, and IMRT treatment plans, the T1N0M0 patient had better sparing of the parotid glands and temporomandibular joints with IMRT (dose to 50% parotid volume, 57 Gy, 50 Gy, and 31 Gy, respectively). In the T2bN2M0 patient, the dose to 95% volume of the planning target volume improved from 57.5 Gy in 2D-RT to 64.8 Gy in 3D-CRT and 68 Gy in IMRT. In the T4N2M0 patient, improvement in both target coverage and brainstem/temporal lobe sparing was seen with IMRT planning. In the dose-escalation study for locally advanced disease, IMRT 66 Gy plus 14 Gy 3D-CRT boost achieved an improvement in the therapeutic ratio by delivering a higher dose to the target while keeping the normal organs below the maximal tolerance dose. CONCLUSIONS: IMRT is useful in treating all stages of nonmetastatic nasopharyngeal carcinoma because of its dosimetric advantages. In early-stage disease, it provides better parotid gland sparing. In locally advanced disease, IMRT offers better tumor coverage and normal organ sparing and allows room for dose escalation.     

整合呼吸因素后三维适形及调强放疗计划在胃癌术后放疗中的剂量学研究

目的 比较整合呼吸移动因素后胃癌术后三维适形、调强放疗计划的靶区及部分正常组织剂量学差异,为临床计划设计时参考.方法 10例胃癌术后患者在平静自由呼吸状态下进行常规CT定位,设计三维适形(3DCRT)及调强放疗(IMRT)计划.根据患者呼吸时相情况生成概率分布函数(PDF),将所得PDF与三维静态剂量进行三维剂量卷积计算,得到自由呼吸状态下整合后的3DCRT与IMRT计划.比较呼吸移动因素整合后3DCRT与IMRT计划在靶区剂量分布和部分正常组织受量差异,如CTV接受100%处方剂量45 Gy的体积占靶体积百分比(V45)、肝脏接受40 Gy的体积(V40)和双侧肾脏V15、V18等.结果 整合呼吸移动因素后靶区剂量覆盖率和均匀性的IMRT计划优于3DCRT计划,其中V45为98%:87%(t=-3.35,P=0.010)、平均剂量为(46.81±0.75)Gy:(45.99±1.12)Gy(t=-0.31,P=0.030).正常组织中肝脏V40的IMRT计划明显低于3DCRT计划(12%:16%;t=3.75,P=0.010),左肾脏V15和V18的IMRT计划也明显低于3DCRT计划[34%∶50%(t=2.17,P=0.050)和27%∶46%(t=3.11,P=0.020)],右肾V15和V18的3DCRT计划略优于IMRT计划[15%∶21%(t=-2.42,P=0.040)和11%∶15%(t=-2.71,P=0.030)].结论 整合呼吸移动因素后,IMRT较3DCRT计划有更好靶区覆盖率和较低肝脏及左侧肾脏受量.     

食管癌多原发肿瘤调强放疗与三维适型放疗的剂量学对比研究

  目的  在食管多原发癌中比较三维适型、静态调强、容积调强放疗计划的剂量分布。  方法  中山大学肿瘤防治中心放疗科收治的7例食管多原发癌患者, 利用CT模拟定位勾画靶区, 临床靶区包括全食管及全纵隔淋巴结引流区, 计划靶区为临床靶区外扩5 mm, 同时设计3DCRT、7野IMRT和单弧VMAT计划, 比较各个放疗计划靶区及危及器官受照射剂量体积。  结果  靶区内最低剂量IMRT与VMAT明显高于3DCRT[D99:(49.4±0.8)Gy, (49.2±0.7)Gy, (43.9±2.8)Gy, P < 0.001];IMRT、VMAT与3DCRT计划比较, 双肺V30稍低、V5明显升高(V30:11.8%±2.5%, 10.5%±2.1%, 13.2%±2.1%, P=0.096;V5:92.5%±3.2%, 93.6%±5.6%, 68.5%±2.1%, P < 0.001);心脏V30明显减少, 脊髓最高剂量明显降低。VMAT与IMRT计划在靶区均匀性、危及器官照射剂量体积无明显差异, VMAT较IMRT治疗时间明显缩短[(3.0±0.6)min, (6.2±0.2)min, P < 0.001]。  结论  调强设计明显改善处方剂量95%以上剂量覆盖的靶区体积, 降低心脏的V30及脊髓最高剂量, 但同时明显增加全肺V5体积。由于V5体积高于目前的推荐限制剂量, 调强设计全食管/全纵隔放射治疗需要谨慎。另外单弧VMAT与IMRT计划剂量分布无明显区别, 可使治疗时间缩短52%。      

Evaluation of larynx-sparing techniques with IMRT when treating the head and neck

PURPOSE: Concern exists that widespread implementation of whole-field intensity-modulated radiotherapy (IMRT) for the treatment of head-and-neck cancer has resulted in increased levels of dysphagia relative to those seen with conventional planning. Other investigators have suggested an alternative junctioned-IMRT (J-IMRT) method, which matches an IMRT plan to a centrally blocked neck field to restrict the laryngeal dose and reduce dysphagia. The effect on target coverage and sparing of organs at risk, including laryngeal sparing, in the optimization was evaluated and compared with that achieved using a J-IMRT technique. METHODS AND MATERIALS: A total of 13 oropharyngeal cancer whole-field IMRT plans were planned with and without including laryngeal sparing in the optimization. A comparison of the target coverage and sparing of organs at risk was made using the resulting dose-volume histograms and dose distribution. The nine plans with disease located superior to the level of the larynx were replanned using a series of J-IMRT techniques to compare the two laryngeal-sparing techniques. RESULTS: An average mean larynx dose of 29.1 Gy was achieved if disease did not extend to the level of the larynx, with 38.8 Gy for disease extending inferiorly and close to the larynx (reduced from 46.2 and 47.7 Gy, respectively, without laryngeal sparing). Additional laryngeal sparing could be achieved with J-IMRT (mean dose 24.4 Gy), although often at the expense of significantly reduced coverage of the target volume and with no improvement to other areas of the IMRT plan. CONCLUSION: The benefits of J-IMRT can be achieved with whole-field IMRT if laryngeal sparing is incorporated into the class solution. Inclusion of laryngeal sparing had no effect on other parameters in the plan.     

Dosimetric Comparison between Intensity Modulated Radiotherapy and 3 Dimensional Conformal Radiotherapy in the Treatment of Rectal Cancer

Objective: To compare dosimetric parameters of 3 dimensional conformal radiotherapy (3 DCRT) and intensity modulated radiotherapy (IMRT) in terms of target coverage and doses to organs at risk (OAR) in the management of rectal carcinoma. Methods: In this prospective study, conducted between August 2014 and March 2016, all patients underwent CT simulation along with a bladder protocol and target contouring according to the Radiation Therapy Oncology Group (RTOG) guidelines. Two plans were made for each patient (3 DCRT and IMRT) for comparison of target coverage and OAR. Result: A total of 43 patients were recruited into this study. While there were no significant differences in mean Planning Target Volume (PTV) D95% and mean PTV D98% between 3 DCRT and IMRT, mean PTV D2% and mean PTV D50% were significantly higher in 3 DCRT plans. Compared to IMRT, 3 DCRT resulted in significantly higher volumes of hot spots, lower volumes of cold spots, and higher doses to the entire OAR. Conclusion: This study demonstrated that IMRT achieves superior normal tissue avoidance (bladder and bowel) compared to 3 DCRT, with comparable target dose coverage.     

Optimising the dosimetric quality and efficiency of post-prostatectomy radiotherapy: a planning study comparing the performance of volumetric-modulated arc therapy (VMAT) with an optimised seven-field intensity-modulated radiotherapy (IMRT) technique

Purpose: The purpose of this study was to compare and evaluate radiotherapy treatment plans using volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) for post‐prostatectomy radiotherapy. Methods and Materials: The quality of radiotherapy plans for 10 patients planned and treated with a seven‐field IMRT technique for biochemical failure post‐prostatectomy were subsequently compared with 10 prospectively planned single‐arc VMAT plans using the same computed tomography data set and treatment planning software. Plans were analysed using parameters to assess for target volume coverage, dose to organs at risk (OAR), biological outcomes, dose conformity and homogeneity, as well as the total monitor units (MU), planning and treatment efficiency. Results: The mean results for the study population are reported for the purpose of comparison. For IMRT, the median dose to the planning target volume, V_95% and D_95% was 71.1 Gy, 98.9% and 68.3 Gy compared with 71.2 Gy, 99.2% and 68.6 Gy for VMAT. There was no significant difference in the conformity index or homogeneity index. The VMAT plans achieved better sparing of the rectum and the left and right femora with a reduction in the median dose by 7.9, 6.3 and 3.6 Gy, respectively. The total number of monitor units (MU) was reduced by 24% and treatment delivery time by an estimated 3 min per fraction without a significant increase in planning requirements. Conclusions: VMAT can achieve post‐prostatectomy radiotherapy plans of comparable quality to IMRT with the potential to reduce dose to OAR and improve the efficiency of treatment delivery.     

食管癌螺旋断层放疗及三维适形调强放疗计划剂量学研究

目的 近年来放射治疗设备不断更新,放疗技术持续发展,肿瘤放疗方式有了更多的选择.本研究通过评估食管癌的螺旋断层放疗(tomotherapy, TOMO)及三维适形调强放疗(intensity modulation radiation therapy, IMRT)的剂量学特性,为临床上食管癌放疗方式的选择提供依据.方法 选取2014-07-13-2015-02-25浙江省肿瘤医院胸部肿瘤放疗科10例食管癌患者,勾画靶区及正常器官后,分别传输至Raystation及TOMO计划系统,给予肿瘤原发灶(PGTV)61.6 Gy/28次,计划靶区(PTV)56.0 Gy/28次,根据RTOG 1106标准限制危及器官(organs at risk, OAR)剂量.分别对靶区的剂量体积直方图(dose volume histogram, DVH)、均匀性指数(homogeneity index, HI)、适形性指数(conformal index CI)和OAR(肺、心脏、脊髓)受照最大剂量及平均剂量进行评估.结果 两种计划都能满足处方剂量要求和危及器官受量限制.TOMO计划中PGTV的中位均匀性指数(HI)为0.057 5,优于IMRT计划的0.073 5, P=0.047.TOMO计划中PTV的中位适形性指数(CI)为0.785,优于IMRT计划的0.682 5, P=0.009.TOMO计划中PGTV的中位最大剂量Dmax为64.9 Gy,明显低于IMRT计划的66.5 Gy, P=0.005;TOMO计划中PTV的中位最大剂量Dmax为64.1 Gy,明显低于IMRT计划的64.9 Gy, P=0.028. TOMO计划的中位总的肺剂量为10.8 Gy,低于IMRT计划的11.9 Gy, P=0.005.TOMO计划的中位总的心脏剂量为22.6 Gy,明显低于IMRT计划的24.3 Gy, P=0.028. TOMO计划的中位脊髓最大剂量为40.2 Gy,明显低于IMRT计划的41.7 Gy, P=0.007.结论 食管癌放疗中TOMO放疗计划对比IMRT放疗计划,具有更好的靶区覆盖适形性及剂量分布均匀性,同时明显减少双肺、心脏及脊髓的受照剂量.     

Potential role of intensity-modulated photons and protons in the treatment of the breast and regional nodes

PURPOSE: To investigate, using comparative treatment planning, the potential improvements that could result through the use of intensity-modulated photons (intensity-modulated radiation therapy [IMRT]) and protons for the locoregional treatment of complex-target breast cancer. METHODS AND MATERIALS: Using CT data from a breast cancer patient, treatment plans were computed using "standard" photon/electron, IMRT, and forward-planned proton techniques. A dose of 50 Gy was prescribed to the target volume consisting of the involved breast, internal mammary, supraclavicular, and axillary nodes. The standard plan was designed using 6-MV X-ray beams to the breast, axillary, and supraclavicular areas and a mixture of 6-MV X-rays and 12-MeV electrons for the internal mammary nodes. Two IMRT (IMX1 and IMX2) plans were calculated for nine evenly spaced beams using dose-volume constraints to the organs at risk. For plan IMX1, precedence was given to optimizing the reduction in lung and heart dose while preserving target dose homogeneity. For plan IMX2, an increased precedence was given to the lungs, heart, and contralateral breast to further reduce doses to these organs and to study the effect on target coverage. The proton plan consisted of two oblique, energy-modulated fields. Target dose homogeneity and the doses to neighboring organs were both considered when comparing the different plans. RESULTS: For the standard plan, dose-volume histograms (DVHs) of the target volumes showed severe dose heterogeneity, whereas target coverage for the IMRT and proton plans was comparable. Lung DVHs for the standard and IMRT plans were also comparable, while the proton plan showed the best sparing over all dose levels. Mean doses to the ipsilateral lung for the three plans were found to be 17 Gy, 15 Gy, and 13 Gy for the standard, IMRT, and proton plans, respectively. For the heart, the IMRT plan delivered the highest mean dose (16 Gy), reflecting the extra dose delivered through this organ to spare the lungs. This was reduced somewhat by the standard plan (15 Gy), with the best sparing being provided by the proton plan (6 Gy). When the IMRT plan was reoptimized with an increased precedence to the normal tissues, the mean doses to all neighboring organs at risk could be reduced, but only at the cost of substantial target dose heterogeneity. CONCLUSIONS: In comparison with the standard plan, IMRT photons have the potential to greatly improve the target dose homogeneity with only a small increase in the doses delivered to the neighboring critical structures. However, when attempting to further reduce doses to the critical structures, substantial loss of target dose homogeneity was found. In conclusion, only the two-field, energy-modulated proton plan had the potential to preserve target dose homogeneity while simultaneously minimizing the dose delivered to both lungs, heart, and the contralateral breast.     

Intensity-modulated radiotherapy (IMRT) and conventional three-dimensional conformal radiotherapy for high-grade gliomas: Does IMRT increase the integral dose to normal brain?

PURPOSE: To determine whether intensity-modulated radiotherapy (IMRT) treatment increases the total integral dose of nontarget tissue relative to the conventional three-dimensional conformal radiotherapy (3D-CRT) technique for high-grade gliomas. METHODS AND MATERIALS: Twenty patients treated with 3D-CRT for glioblastoma multiforme were selected for a comparative dosimetric evaluation with IMRT. Original target volumes, organs at risk (OAR), and dose-volume constraints were used for replanning with IMRT. Predicted isodose distributions, cumulative dose-volume histograms of target volumes and OAR, normal tissue integral dose, target coverage, dose conformity, and normal tissue sparing with 3D-CRT and IMRT planning were compared. Statistical analyses were performed to determine differences. RESULTS: In all 20 patients, IMRT maintained equivalent target coverage, improved target conformity (conformity index [CI] 95% 1.52 vs. 1.38, p < 0.001), and enabled dose reductions of normal tissues, including brainstem (D(mean) by 19.8% and D(max) by 10.7%), optic chiasm (D(mean) by 25.3% and D(max) by 22.6%), right optic nerve (D(mean) by 37.3% and D(max) by 28.5%), and left optic nerve (D(mean) by 40.6% and D(max) by 36.7%), p < or = 0.01. This was achieved without increasing the total nontarget integral dose by greater than 0.5%. Overall, total integral dose was reduced by 7-10% with IMRT, p < 0.001, without significantly increasing the 0.5-5 Gy low-dose volume. CONCLUSIONS: These results indicate that IMRT treatment for high-grade gliomas allows for improved target conformity, better critical tissue sparing, and importantly does so without increasing integral dose and the volume of normal tissue exposed to low doses of radiation.     

Conventional, conformal, and intensity-modulated radiation therapy treatment planning of external beam radiotherapy for cervical cancer: The impact of tumor regression

PURPOSE: Investigating the impact of tumor regression on the dose within cervical tumors and surrounding organs, comparing conventional, conformal, and intensity-modulated radiotherapy (IMRT) and the need for repeated treatment planning during irradiation. METHODS AND MATERIALS: Fourteen patients with cervical cancer underwent magnetic resonance (MR) imaging before treatment and once during treatment, after about 30 Gy. Target volumes and critical organs were delineated. First conventional, conformal, and IMRT plans were generated. To evaluate the impact of tumor regression, we calculated dose-volume histograms for these plans, using the delineations of the intratreatment MR images. Second conformal and IMRT plans were made based on the delineations of the intratreatment MR images. First and second plans were compared. RESULTS: The average volume receiving 95% of the prescribed dose (43 Gy) by the conventional, conformal, and IMRT plans was, respectively, for the bowel 626 cc, 427 cc, and 232 cc; for the rectum 101 cc, 90 cc, and 60 cc; and for the bladder 89 cc, 70 cc, and 58 cc. The volumes of critical organs at this dose level were significantly reduced using IMRT compared with conventional and conformal planning (p < 0.02 in all cases). After having delivered about 30 Gy external beam radiation therapy, the primary gross tumor volumes decreased on average by 46% (range, 6.1-100%). The target volumes on the intratreatment MR images remained sufficiently covered by the 95% isodose. Second IMRT plans significantly diminished the treated bowel volume, if the primary gross tumor volumes decreased >30 cc. CONCLUSIONS: Intensity-modulated radiation therapy is superior in sparing of critical organs compared with conventional and conformal treatment, with adequate coverage of the target volumes. Intensity-modulated radiation therapy remains superior after 30 Gy external beam radiation therapy, despite tumor regression and internal organ motion. Repeated IMRT planning can improve the sparing of the bowel and rectum in patients with substantial tumor regression.     

HT及IMRT在儿童全中枢放疗剂量学比较及二次致癌风险评估

目的 探讨HT及IMRT计划在儿童全中枢放疗中的剂量学特点,并根据EAR模型估算儿童全中枢放疗后二次致癌风险。方法 选取2012-2017年间接受全脑全脊髓照射患者CT图像15例,勾画靶区及OAR后分别完成IMRT及HT计划,t检验两种计划间靶区HI、CI和OAR的Dmax、Dmean及V10、V20并优化临床治疗方案。根据各器官DVH及EAR模型估算比较两种计划二次致癌风险。结果 两组计划在靶区覆盖度上均能达到临床要求(100%剂量≥95%靶体积),其中HT组HI优于IMRT组(P=0.000);CI上HT组并未显示优势。但HT组对于海马保护具有绝对优势,D2%和Dmean均明显低于IMRT组(P=0.000)。对OAR保护,HT在甲状腺的Dmax、Dmean、V20及心脏的Dmax、V10均小于IMRT (P=0.001、0.002、0.014及P=0.001、0.003)。在二次致癌方面,HT组相较于IMRT组对于甲状腺和肺脏的二次致癌风险更高,甲状腺和肺脏EAR分别为28.666∶26.926(P=0.010)和20.496∶18.922(P=0.003);对胃二次致癌风险似乎较高(P=0.248),对肝脏二次致癌风险相对较小(P=0.020)。结论 在儿童保护海马的全中枢放疗中HT计划优于IMRT计划。但HT对甲状腺和肺脏有较高二次致癌风险,在计划制定时应评估这些致癌风险及其他正常组织效应的平衡。     

CT及3.0T MRI在食管癌IMRT中的价值

目的 探讨CT及3.0T MRI在食管癌IMRT计划中的价值。方法 选取2013-2015年本院放疗科首次确诊并行根治性IMRT的食管癌患者35例,分别在CT及MRI T2WI与DWI融合图像上勾画靶区,以相同处方剂量和OAR限制剂量分别制定计划,比较2种计划的靶区体积、处方剂量及OAR受量差异。配对t检验差异。结果 2种计划的剂量分布及计划参数均达到了临床处方剂量要求。基于3.0T MRI计划的病灶长度、VGTV和VPTV均小于CT计划(P=0.00、0.03、0.03)。2种计划的PGTV、PTV-PGTV的D2%、D98%、D50%、HI、CI差异均无统计学意义(P均>0.05)。基于3.0T MRI计划的双肺平均剂量明显低于CT计划(P=0.00),双肺实际受量亦与CT计划相近(P均>0.05)。2种计划的脊髓最大耐受量及心脏耐受量相近(P均>0.05)。结论 基于CT及3.0T MRI计划所勾画的靶区及参数均能满足临床需求,但基于3.0T MRI计划的靶区体积更小,可能会使部分OAR潜在获益。