ⅣA期胸腺瘤IMRT疗效及安全性初步分析

目的 初步评估IMRT对无法手术ⅣA期胸腺瘤的疗效及安全性。方法 回顾分析2010-2017年间15例无法手术接受IMRT的ⅣA期胸腺瘤患者,其中男9例、女6例,中位数59岁。PTV、CTV、GTV放疗剂量分别为50、60、70Gy分15~20次,分析近期疗效、总生存率及不良反应。结果 中位随访时间48个月,近期部分缓解率93%(14/15),1、3、5年总生存率分别为100%、75%、75%,仅1例出现3级血液系统反应。4例死亡患者均为肿瘤相关死亡。结论 初步证明ⅣA期胸腺瘤IMRT疗效较好、安全性高,可作为无法手术治疗的胸腺瘤患者安全、有效的治疗手段。     

模拟调强技术照射鼻咽低分化鳞癌细胞的生物效应机制研究

Objective To study the altered radiobiological effect of simulative intensity-modulated radiotherapy (SIMR) in cultured human nasopharyngeal carcinoma (NPC) cells and the related mechanism. Methods Single cell suspension of exponentially growing CNE-2 cells, a poor differentiated NPC cell line, was seeded and cultured for 12 hours, then the cells were irradiated in two different models by 6 MV X-ray beams at 3 Gy/min. In single fraction irradiation (SFR) model, cells were irradiated a single fraction of 0, 2, 4, 6 or 8 Gy within 0 to 3 minutes. In S1MR model, cells were irradiated 0, 2, 4, 6 or 8 Gy in 5 frac-tions with interval of 8.0-8.5 minutes between. Clonogenic assay was performed to determine the radiosen-sitivity. Cellular apoptosis was measured by flow cytometry. RT-PCR was used to detect mRNA expressions of Bax and Bcl-2, Respectively. Results Compared with SFR group, the survival fraction in SIMR group was higher at all the dose levels. The values of α, β, D0 and Dq were higher in SIMR group than in SFR group. At dose levels of 2 Gy, 4 Gy and 6 Gy, The early and late apoptotic cells in SIMR group were lower than in SFR group (21.20%: 15.89%, F=18.51, P=0.020;13.00%: 10.20, F=15.67, P=0.040).The mRNA expression of Bax was upregulated in a dose-dependent manner in the both groups. Compared with SFR group, the mRNA expression of Bax in SIMR group was lower at all the dose levels (Mean value of 76.75% : 62.50%, F =36.57, P =0.000). Bcl-2 mRNA expression at every dose level had no significant difference between the two groups (Mean value of 29.25% : 29.75%, F=0.74, P=0.800). Conclusions Prolonged delivery time in SIMR model can decrease the radiobiological effects.     

脑转移瘤同期加量混合调强放疗与调强放疗的剂量学比较

目的:探讨同时运用三维适形与调强的混合调强放疗（Hybrid-IMRT）与调强放疗（IMRT）用于脑转移瘤同期加量的剂量学差异。方法:选取20例进行头颅放疗的患者，分别设计Hybrid-IMRT计划和IMRT计划。Hybrid-IMRT计划包括全脑行三维适形（两野对穿）3 600 cGy/20 F、脑转移灶行IMRT同期加量至5 000 cGy/20 F；IMRT计划全程运用IMRT给予全脑照射3 600 cGy/20 F、脑转移灶5 000 cGy/20 F。在满足临床要求的前提下，比较两组计划靶区的均匀性指数、适形度指数、平均剂量和机器跳数，危及器官脑干、视神经、晶体、视交叉、眼球的最大剂量和平均剂量。结果:两种计划均能满足临床要求。Hybrid-IMRT计划的PGTV均匀性优于IMRT计划（P<0.001）；Hybrid-IMRT计划的脑干、视交叉、左右晶体的最大剂量与平均剂量，左右眼球的平均剂量以及左右视神经的最大剂量均低于IMRT计划（P<0.05）；Hybrid-IMRT计划的机器跳数比IMRT计划减少了约70%（P<0.001）。结论:两种计划均能满足临床要求，Hybrid-IMRT计划相较IMRT计划靶区剂量更加均匀，治疗时间缩短，也能更好地保护危及器官。     

新型TiGRT IVS系统引导肺癌调强放射治疗摆位研究

目的:以锥形束CT(cone beam CT,CBCT)配准结果为参考,验证TiGRT IVS系统的在线校位精度,从而验证其临床有效性及可行性。方法:选择2019年10月至2020年2月在陆军军医大学第二附属医院全军肿瘤研究所放疗中心接受调强放射治疗的30例肺癌患者。首次摆位时行TiGRT IVS系统和CBCT位置验证,常规剂量分割患者每周行1次位置验证,大剂量分割患者每次治疗时均行位置验证,并与数字重建放射影像(digitally reconstructured radiograph,DRR)图像进行配准。其中TiGRT IVS系统配准方法分为IVS-A和IVS-B 2种,IVS-A根据椎体、肋骨等进行骨性配准;IVS-B在IVS-A的基础上,正位片采用气管作为特征结构进行配准。将IVS-A和IVS-B配准的结果与CBCT进行比较,观察TiGRT IVS系统对肺癌调强放射治疗摆位误差的分析与控制结果。结果:IVS-A、IVS-B、CBCT配准所需时间分别为(69±12)、(54±8)、(112±14)s,TiGRT IVS系统配准时间少于CBCT,而且IVS-B配准时间少于IVS-A。TiGRT IVS系统的摆位误差主要集中在0~5 mm,8 mm以上的摆位误差很少,且TiGRT IVS系统与CBCT得到的摆位误差只有在患者Vrt(前后)方向上具有统计学差异,但在临床标准范围内。对于1例大剂量分割患者在Lng(头脚)方向前1~7治疗分次的摆位误差,TiGRT IVS系统配准结果与CBCT相比有统计学差异。结论:TiGRT IVS系统能够有效测出肺癌患者调强放射治疗的摆位误差,正位片中可选气管作为配准的特征结构,大剂量分割患者图像引导时可结合CBCT观察靶区位置。     

调强放疗射野复杂度对剂量验证的影响

目的:探究针对射野的几何特征提出复杂度的量化方式，分析各个复杂度对γ通过率的影响和ROC曲线，并与其它研究提出的复杂度进行比较。方法:本文提出小子野占比、子野偏离等中心程度、形状不规则度的量化公式。通过放疗计划系统导出临床放疗计划中157个射野的子野MLC位置、跳数等数据，并编写MATLAB程序，代入公式计算相关的复杂度。以各复杂度为自变量，γ通过率为因变量进行线性回归分析。并作出复杂度的ROC曲线以研究复杂度的识别能力。与其它研究提出的跳数利用率（MU/Gy）、小子野评分、以等中心为圆心特定半径圆外面积占比进行比较。结果:线性回归结果显示， x方向偏离度（P<0.001）、y方向偏离度（P<0.001）、形状不规则度（P<0.001）、小子野占比（P=0.026）对γ通过率有显著的影响，ROC曲线下面积较大，识别效果较好。对比以等中心为圆心特定半径圆外面积占比、跳数利用率（Mu/Gy）、小子野评分的量化方式，本研究提出的量化方法与通过率的相关性更高,识别能力更强。结论:基于射野几何复杂度的新的量化方式，其中形状不规则度、偏离等中心程度与通过率的相关性最强，并且前三者对低通过率射野具有一定的识别能力。对计划选择及优化方向提供一定的参考。     

T4N (+)Ⅲ期食管胸中下段癌3DRT长期生存分析

目的 观察T₄N (+)Ⅲ期食管胸中下段癌IMRT长期生存情况及不良反应。方法 2004-2010年间300例T₄N (+)Ⅲ期食管中下段癌患者采用3DCRT 202例、IMRT 98例,常规分割照射剂量60 Gy。比较两种不同治疗方式的长期生存情况及不良反应。Kaplan Meier法计算生存率并Logrank法检验。结果 5、7年样本量分别为239、120例。3DCRT和IMRT组1、3、5、7年LC率分别为64.4%、40.6%、38.3%、34.2%和68.3%、55.3%、51.9%、51.9%(P=0.048),OS率分别为54.5%、19.8%、14.7%、10.9%和63.3%、34.7%、24.4%、20.3%(P=0.013)。分层分析显示年龄>65岁、放疗前食管造影长度>8.0 cm、CT最大横径>4.6 cm、GTV>60 cm³、邻近组织或器官受累、非手术 N₂期、未行化疗者,IMRT组OS率高于3DCRT组(P=0.022、0.003、0.022、0.034、0.016、0.044、0.047)。IMRT组GTVD_min、GTVD₁₀₀高于3DCRT组(P=0.000、0.000),脊髓D_max低于3DCRT组(P=0.000)。IMRT组急性放射性食管炎发生率明显高于3DCRT组,以轻度(1-2级)食管炎为著(P=0.000)。3DCRT组死于肿瘤局部因素的比率明显高于IMRT组(P=0.039)。结论 局部晚期食管胸中下段癌IMRT安全有效,LC率明显提高,正常组织保护良好,长期生存获益显著。基于回顾分析结果还有待前瞻性随机对照研究的证实。     

调强放射治疗在不可切除老年胃癌患者姑息治疗中的临床价值

目的:探讨调强放射治疗（intensity-modulated radiotherapy，IMRT）在老年不可切除胃癌患者中姑息减症治疗的临床价值。方法:回顾性分析23例老年病理确诊胃癌患者，手术无法切除，伴有出血(78.3%)、梗阻(52.2%)及疼痛(69.6%)症状；采用调强放射治疗为主的姑息治疗。观察治疗后症状缓解率、症状缓解时间以及中位生存时间（median overall survival，mOS）。结果: 全组患者男性16例，女性7例，年龄60~89岁(平均74岁)；Ⅲ期9例，Ⅳ期14例。全部采用6MV X线IMRT，常规分割，1.8~2.2 Gy/次，5次/周，总剂量35~50 Gy；同步放化5例，序贯化疗9例。出血、梗阻及疼痛症状缓解率分别为77.8%(14例)、58.3%(7例)和56.2%(9例)；中位症状缓解时间分别为101天、87天和99天。全组中位生存时间114天，症状缓解者中位生存时间较症状未缓解者明显延长(129天 vs 73天，P=0.01)。治疗期间出现Ⅲ级毒副反应者2例。结论:IMRT是一个有效的、可耐受的并能够缓解老年不可切除胃癌患者临床症状的治疗手段，可以改善患者生活质量，延长生存期。     

The Effect of Dose Grid Resolution on Dose Volume Histograms for Slender Organs at Risk during Pelvic Intensity-modulated Radiotherapy

PurposeThere are enduring uncertainties regarding the optimal dose grid resolution for use with pelvic intensity-modulated radiotherapy (IMRT) plans in which the adjacent organs at risk are slender and transect the field edge. Therefore, this study evaluated the effect of dose grid resolution on bladder wall dose-volume histogram (DVH) calculations for prostate IMRT plans.Materials and MethodsThe planning computed tomography scans and clinical plans from 15 prostate cancer patients were included in this analysis. For each study computed tomography, the entire inner and outer bladder surfaces were delineated. Nine versions of the clinical plan were created, varying interval between the dose grid calculation points uniformly in three dimensions, whereas all other plan parameters were kept constant. The dose grid increments tested were 1–10 mm. The plans were recalculated and the bladder wall DVH compared against the study benchmark (1 mm grid).ResultsAll the dose grid increments evaluated resulted in a systematic overestimation of the bladder wall volume receiving low doses and an underestimation of the volume receiving high doses. Grid increments <2.5 mm all resulted in mean volume differences less than 1 cm³ across the whole DVH. Grid increments >5.0 mm resulted in mean volume differences greater than 2 cm³. Individual patient analysis revealed that only the 1.5 mm increment resulted in maximum volume differences ≤1 cm³ for every patient across the full length of the DVH curve. Bladder wall thickness ranged from 1.7 to 4.4 mm and displayed no correlation with the magnitude of the dose grid effect.ConclusionsFor an accurate DVH calculation for bladder wall during IMRT planning for prostate cancer, a 1.5 mm dose grid increment is recommended. This finding was unaffected by a normal range in bladder wall thickness. It is suggested that the application of any new treatment planning technique or organ delineation method be accompanied with an evaluation of optimal dose grid resolution.     

Dosimetric benefits of placing dose constraints on the brachial plexus in patients with nasopharyngeal carcinoma receiving intensity-modulated radiation therapy: a comparative study

This study aimed to evaluate whether placing dose constraints on the brachial plexus (BP) could provide dosimetric benefits in patients with nasopharyngeal carcinoma (NPC) undergoing intensity-modulated radiation therapy (IMRT). Planning CT images for 30 patients with NPC treated with definitive IMRT were retrospectively reviewed. Target volumes, the BP and other critical structures were delineated; two separate IMRT plans were designed for each patient: one set no restrictions for the BP; the other considered the BP as a critical structure for which a maximum dose limit of ≤66 Gy was set. No significant differences between the two plans were observed in the conformity index, homogeneity index, maximum dose to the planning target volumes (PTVs), minimum dose to the PTVs, percentages of the volume of the PTVnx and PTVnd receiving more than 110% of the prescribed dose, or percentages of the volume of the PTVs receiving 95% and > 93% of the prescribed dose. Dose constraints significantly reduced the maximum dose, mean dose, V45, V50, V54, V60, V66 and V70 to the BP. Dose constraints significantly reduced the maximum dose to the BP, V45, V60 and V66 in both N0–1 and N2–3 disease; however, the magnitude of the dosimetric gain for each parameter between N0–1 and N2–3 disease was not significantly different, except for the V60 and V66. In conclusion, placing dose constraints on the BP can significantly decrease the irradiated volume and dose, without compromising adequate dose delivery to the target volume.