宫颈癌二维近距离后装治疗中危及器官参考点剂量与三维体积剂量的相关性研究

目的 利用宫颈癌二维近距离后装治疗中危及器官（OARs）点剂量预测其三维体积剂量,评估在特定条件下,二维计划OARs体积剂量能否满足三维后装剂量限值要求。方法 回顾性分析基于CT图像的10例宫颈癌患者近距离后装治疗计划,将处方参考点剂量定为600 cGy,膀胱和直肠参考点剂量<360 cGy,设计并优化得到二维后装治疗计划。采用Pearson相关分析法对膀胱、直肠参考点剂量及OARs体积受量做相关性分析,利用线性回归方法得出膀胱、直肠参考点与其体积剂量的线性方程。结果 膀胱、直肠参考点剂量分别与其D_{1 cm³}、D_{2 cm³}、D_{5 cm³}和平均剂量显著正相关（r=0.559~0.668,P<0.05）;膀胱、直肠参考点剂量分别是其D_{2 cm³}的1.404和1.181倍;内外照射完成后膀胱、直肠D_{2 cm³}的相当于200 cGy分次等效生物剂量（EQD2）分别为8 410.0和6 827.0 cGy,均低于二者体积剂量限值。结论 利用膀胱、直肠参考点剂量能在一定程度上预测其体积剂量,对于满足膀胱、直肠参考点剂量低于处方剂量60%二维近距离后装计划,可将膀胱、直肠体积受量控制在相对安全的剂量范围内。而由于缺乏对小肠、乙状结肠剂量检测,二维后装计划在临床使用上仍然具有很大局限性。     

基于3D U-net的宫颈癌近距离治疗剂量分布预测

目的 基于三维（3D） U-net深度学习模型,建立预测CT引导下宫颈癌近距离治疗计划的3D空间剂量分布。方法 2021年4-9月收集114例宫颈癌患者三维近距离放疗计划（处方剂量6 Gy）组成数据集,按84 ∶11 ∶19划分为训练集、验证集、测试集。利用3D U-net模型进行500次（epoch）训练,分别评估测试集病例体素级的平均剂量偏差（MDD）与绝对剂量偏差（MADD）、等剂量面包围体积的戴斯系数（DSC）、处方剂量适形度指数（CI）、高危临床靶区（HRCTV）的D₉₀和平均剂量D_mean、膀胱、直肠、小肠、结肠的D_{1 cm³}与D_{2 cm³}剂量学参数。结果 测试集中19例患者的3D剂量矩阵MDD与MADD分别为-0.01±0.03和（0.04±0.01） Gy。50%到150%处方剂量的DSC在0.89到0.94之间,处方剂量CI为0.70±0.04。HRCTV的D₉₀的平均偏差为2.22%,D_mean的偏差为-4.30%。膀胱、直肠、小肠、结肠的D_{1 cm³}与D_{2 cm³}最大偏差分别为2.46%和2.58%。模型预测平均耗时2.5 s。结论 本研究实现了一种基于3D U-net的预测宫颈癌3D剂量分布的深度学习模型,为宫颈癌近距离治疗自动化设计奠定基础。     

宫颈癌后装放疗时膀胱直肠小肠受照剂量探讨

目的 探讨宫颈癌腔内放疗时不同体积的膀胱、直肠与危及器官受照剂量的关系。方法 选取宫颈癌患者共47例,给予剂量点处方剂量600 cGy的高剂量率腔内后装治疗,用剂量体积直方图(DVH)评价标准计划下不同体积的膀胱、直肠和小肠对相应受照剂量的影响。将膀胱按体积大小分成<80 cm³组、80~120 cm³组和>120 cm³组,直肠按体积大小分成>60 cm³ 组和≤60 cm³组,分析其体积与剂量分布的关系。采用方差分析和t检验方法分析D_{1 cm³}、D_{2 cm³}、D_30%和D_50%。结果 与膀胱体积<80 cm³组相比,80~120 cm³组和>120 cm³组的膀胱D_30%、D_50%受照剂量增高(F=5.074、5.088,P<0.05),小肠D_{1 cm³}和D_{2 cm³}值差异无统计学意义(P>0.05);与直肠体积>60 cm³ 组相比,≤60 cm³组的直肠D_{1 cm³}受照剂量减小(t=-2.045,P<0.05)。结论 宫颈癌近距离放疗时,保持膀胱的适当充盈,直肠体积的减少,可使直肠、膀胱和小肠的受照射剂量均相对降低,从而减少放疗的不良反应。     

宫颈癌外照射急性放射性直肠炎剂量-体积-时间关系研究

目的 回顾性分析宫颈癌调强放射治疗（intensity-modulated radiation therapy,IMRT）中急性放射性直肠炎的发生与直肠受照剂量、体积以及受照时间关系。方法 收集本院2011年1月至2013年12月行IMRT照射的51例宫颈癌病例,根据RTOG/EORTC毒性分级标准分为1~4级。用剂量体积直方图（DVH）评价标准计划下不同放射性直肠炎分级组的患者直肠受照剂量体积。分析直肠D_max、D_mean、D_{1 cm³}、D_{2 cm³}、D₄₀、V₄₀和出现症状时直肠受照剂量。结果 急性放射性直肠炎发生的平均时间为放疗后（23.06±12.01）d。与发生放射性直肠炎3~4级组相比,放射性直肠炎2级组的直肠D_max值更低,差异有统计学意义（F=5.268,P<0.05）;与发生放射性直肠炎3~4级组相比,放射性直肠炎1级、2级组的直肠D_{1 cm³}、D_{2 cm³}值均低于放射性直肠炎3~4级组（F=4.893、4.406,P<0.05）,而直肠D₄₀和V₄₀值的差异无统计学意义（P>0.05）。结论 宫颈癌患者IMRT放疗20 d左右较易发生急性放射性直肠炎,且较多发生轻度到中度急性放射性直肠炎,重度急性放射性直肠炎的发生率低。在宫颈癌IMRT放疗时,尽量减小直肠D_max、D_{1 cm³}、D_{2 cm³}的值,对降低重度急性放射性直肠炎的发生率有意义。     

宫颈癌腔内联合组织间插植近距离后装治疗中IPSA和HIPO逆向优化算法的比较分析

目的 比较宫颈癌腔内联合组织间插植三维后装计划中模拟退火逆向优化（IPSA）和混合逆向优化（HIPO）剂量分布的差异,为宫颈癌腔内联合组织间插植后装治疗逆向计划优化方法的选择提供依据。方法 选取2016年12月至2017年5月于河北省沧州中西医结合医院43例宫颈癌患者资料,所有患者原后装治疗计划采用IPSA优化,基于原图像信息,给定同样的初始约束条件,不进行手动优化,直接计算IPSA和HIPO计划,对高危靶区（HR-CTV）剂量体积参数D₉₀、D₁₀₀、V_100%,以及均匀性指数（HI）、适形指数（CI）、危及器官（OAR）（膀胱、直肠和乙状结肠）D_{2 cm³}的数据进行评价。结果 两组间HR-CTV的D₉₀、D₁₀₀以及CI剂量差异无统计学意义（P>0.05）,但HIPO组HR-CTV的V_100%为（87.72±0.49）%;HI为（0.51±0.08）,明显高于IPSA组的（85.01±0.55）%,HI（0.42±0.06）,差异具有统计学意义（t=2.54、3.02,P<0.05）。对于OAR,与IPSA计划相比,HIPO计划中膀胱的D_{2 cm³}（3.42±0.17）Gy,直肠的D_{2 cm³}（3.04±0.37）Gy,明显低于IPSA计划膀胱的D_{2 cm³}（3.57±0.28）Gy,直肠的D_{2 cm³}（3.21±0.48）Gy,差异具有统计学意义（t=0.27、0.19,P<0.05）。乙状结肠D_{2 cm³}剂量两者差异无统计学意义。结论 在宫颈癌腔内联合组织间插植后装治疗中,采用HIPO优化比IPSA优化可以获得更好的靶区HI以及减少膀胱和直肠的受照剂量。     

三种不同优化方法在局部晚期宫颈癌腔内联合组织间插植近距离治疗计划中的剂量学比较

目的 比较分析局部晚期宫颈癌腔内联合组织间插植近距离治疗计划3种优化方法的剂量学差异。方法 回顾性选取局部晚期宫颈癌患者20例,对每例患者根据不同优化方法,分别制定3种计划,分别为手动计划组,基于图形优化;逆向1计划组,基于模拟退火优化算法;逆向2计划组,在逆向1组基础上增加了靶区（CTV）最大剂量限定。比较计划中CTV的体积剂量参数V₂₀₀、V₁₅₀、V₁₀₀、D₁₀₀、D₉₀、均匀性指数（HI）,以及直肠、膀胱、乙状结肠的剂量参数D_{0.1 cm³}、D_{1 cm³}、D_{2 cm³}。结果 CTV方面,手动组和2个逆向组的D₁₀₀参数差异无统计学意义（P>0.05）,但2个逆向组的V₂₀₀、V₁₅₀、V₁₀₀、HI参数明显优于手动组（t=-3.422~9.910,P<0.05）。逆向1组的V₁₀₀和D₁₀₀优于逆向2组（t=7.238、5.032,P<0.05）。危及器官（OARs）方面,与手动组相比,2个逆向组中直肠、膀胱、乙状结肠的D_{0.1 cm3}、D_{1 cm³}和D_{2 cm³}明显降低（t=2.235~5.819,P<0.05）。结论 对于局部晚期宫颈癌腔内联合组织间插植技术,基于3组优化方法的计划均能满足临床需求,且使用逆向优化方法保证了靶区剂量覆盖,同时减少直肠、膀胱、乙状结肠的最大受量。     

3D打印共面坐标模板辅助125I放射性粒子植入治疗盆壁复发宫颈癌的剂量学研究

目的 探讨放疗后盆壁复发宫颈癌患者采用3D打印共面坐标模板（3D-PCT）辅助¹²⁵I放射性粒子植入治疗剂量精确性实施的可行性。方法 本研究为单中心的回顾性研究,选取2016年4月至2017年12月北京大学第三医院应用3D-PCT辅助¹²⁵I放射性粒子植入治疗的放疗后盆壁复发宫颈癌患者资料10例。患者年龄37~71岁,中位年龄53.5岁,KPS评分≥ 70分。所有患者均接受过盆腔放疗。病灶体积为3.5~58.0 cm³（中位31.9 cm³）,处方剂量120~180 Gy,粒子活度0.55~0.67 mCi（1 Ci=3.7×10¹⁰Bq）,术前计划植入粒子数目为50（12~81）颗。根据术前计划在3D-PCT引导下行放射性粒子植入术。术后实际植入粒子数目为53（10~82）颗。评估剂量学参数包括D₉₀、D₁₀₀、V₁₀₀、V₁₅₀、V₂₀₀、靶区外体积指数（EI）、适形指数（CI）和均匀性指数（HI）,以及危及器官剂量D_{2 cm³}、D_{1 cm³}和D_{0.1 cm³}。术前计划与术后计划参数的比较采用相关样本非参数检验。结果 术后实际植入粒子数目多于术前计划设计,差异有统计学意义（Z=-2.255,P<0.05）。术后计划与术前计划的靶区剂量学参数D₉₀、D₁₀₀、V₁₀₀、V₁₅₀、V₂₀₀、EI、CI和HI比较,差异均无统计学意义（P>0.05）。膀胱、肠道的D_{2 cm³}、D_{1 cm³}和D_{0.1 cm³}、直肠D_{0.1 cm³}的术后计划与术前计划剂量差异均无统计学意义（P>0.05）。直肠D_{2 cm³}和D_{1 cm³}术后计划剂量低于术前计划,差异均有统计学意义（Z=-2.100、-2.240,P<0.05）。结论 3D-PCT辅助¹²⁵I放射性粒子植入治疗盆壁复发宫颈癌,通过术中剂量优化,术后实际剂量达到术前计划设计,可以保证¹²⁵I放射性粒子植入盆壁复发宫颈癌的剂量精确实施。     

局部晚期宫颈癌同步放化疗中尿道受照剂量与泌尿系统并发症相关性研究

目的 探讨局部晚期宫颈癌患者盆腔外照射时泌尿系统不良反应与膀胱及尿道剂量的相关性。方法 回顾性收集贵州医科大学附属医院肿瘤科诊治的局部晚期宫颈癌患者行盆腔外照射计划中膀胱及尿道最大剂量点(D_max)、最小剂量(D_min)、平均剂量(D_mean)、计划靶区周围0.1、1、2 cm³接受的平均剂量(D_{0.1 cm³}、D_{1 cm³}、D_{2 cm³})及接受5、10、15、20、25、30、35、40、45、50 Gy受照体积占整个器官体积百分比(V_{5 Gy}、V_{10 Gy}、V_{15 Gy}、V_{20 Gy}、V_{25 Gy}、V_{30 Gy}、V_{35 Gy}、V_{40 Gy}、V_{45 Gy}、V_{50 Gy})等相关剂量学参数及患者出现的尿频、尿急、尿痛等泌尿系症状。采用独立样本t检验及Logistic回归模型分析泌尿系症状与剂量学参数相关性。结果 膀胱及尿道的中位体积分别为294.8、4.71 cm³,以尿道各个参数的中位值为界分成两组,行单因素分析发现尿道D_max、D_min、D_mean、V_{5 Gy}、V_{10 Gy}、V_{15 Gy}、V_{20 Gy}、V_{25 Gy}、V_{30 Gy}、V_{35 Gy}、V_{40 Gy}、V_{45 Gy}、V_{50 Gy}与发生泌尿系并发症相关(t=14.30、21.65、32.19、33.36、16.62、17.91、21.52、20.11、12.27、37.25、30.18、36.24、21.98,P＜0.05),进一步行多因素分析显示,尿道D_{2 cm³}、V₂₀、V₄₀及膀胱V₄₀、D_{1 cm³}、D_{2 cm³}是预测泌尿系发生2级不良反应的独立因素(P＜0.05)。结论 建议限制尿道的D_{2 cm³}、V₂₀、V₄₀以尽量减少2级泌尿系统并发症的风险。     

组织非均匀性对宫颈癌近距离治疗剂量评估影响研究

目的 比较近距离治疗两种临床常用的剂量计算方法和基于CT影像的蒙特卡罗程序计算的剂量差异,探讨组织非均匀性对宫颈癌近距离治疗剂量评估的影响。方法 回顾性选取2018年1月至2020年6月在安徽省肿瘤医院接受三维近距离治疗的宫颈癌患者11例,分别采用美国医学物理师协会（AAPM） TG43号报告的纯水剂量计算方法（TG43-BT）、快速非均质剂量计算算法Acuros BV （BV-BT）和基于治疗CT影像的EGSnrc蒙特卡罗程序（MC-BT）计算各计划的剂量分布,分析比较3种算法的靶区剂量（D₉₈、D₉₀和D₅₀）、剂量区体积（V_{3 Gy}、V_{6 Gy}、V_{9 Gy}和V_{12 Gy}）和危及器官（OARs）D_{2 cm³}剂量差异。结果 TG43-BT中HRCTV D₉₀为6.274 Gy,比MC-BT高出了近5%,且TG43-BT对靶区体积剂量和各剂量区体积均存在过高评估;除靶区D₅₀和高剂量区V_{12 Gy}外,BV-BT和MC-BT对于靶区剂量计算差异无统计学意义（P>0.05）。此外,BV-BT和MC-BT在直肠、小肠和乙状结肠的D_{2 cm³}评估上差异无统计学意义（P>0.05）,而MC-BT膀胱D_{2 cm³}为4.609 Gy,比TG43-BT、BV-BT明显偏高。结论 TG43-BT未考虑组织非均匀性影响,普遍高估了靶区和多数OARs受量;BV-BT计算效率高,且在多数靶区和OARs评估参数上与MC-BT计算基本一致,但在近源位置和被充盈膀胱的剂量计算上存在不足,临床评估时仍需谨慎。     

宫颈癌后装治疗中图形优化与逆向模拟退火优化剂量学分析

目的 比较宫颈癌三维后装计划中图形优化（GO）和模拟退火逆向优化（IPSA）剂量分布的差异,为宫颈癌后装治疗计划优化方法的选择提供依据。方法 利用Excel 2007产生的随机数,从已完成治疗的根治性宫颈癌患者中选取21例,原后装治疗计划采用图形优化,基于原图像信息,制定IPSA计划,统计临床靶区（CTV）剂量体积参数V_100%、V_150%,以及均匀性指数（HI）、适形指数（CI）、膀胱和直肠的D_{1 cm³}、D_{2 cm³},对比两种优化方法的剂量特点。结果 两个计划的靶区剂量均能满足处方要求,所有靶区剂量参数的均值接近,差异无统计学意义（P>0.05）。与GO计划相比,IPSA计划中膀胱D_{1 cm³}、D_{2 cm³}的剂量明显降低（t=3.596、3.490,P<0.05）;直肠剂量参数的差异无统计学意义（P>0.05）。结论 在宫颈癌三管后装治疗中,采用GO和IPSA对靶区无影响,但IPSA可以减小膀胱的最大受量。     

Characterization of combined intracavitary/interstitial brachytherapy including oblique needles in locally advanced cervix cancer

PURPOSETo characterize and report on dosimetric outcomes of image guided adaptive brachytherapy (IGABT) using intracavitary and interstitial (IC/IS) applicators including oblique needles (O-needles) in locally advanced cervical cancer (LACC).METHODS AND MATERIALSTwenty LACC patients treated with radio-chemotherapy and offered IC/IS-IGABT including O-needles were analyzed. An in-house 3D-printed vaginal template was used to steer the needles parallel and obliquely in relation to the tandem, supplemented with free-hand needles if needed. Implant characteristics and loading patterns were analyzed. Using the equivalent dose in 2Gy-fractions (EQD2) concept, cumulative (EBRT+BT) V85, V75, V60Gy, targets/OARs doses and high dose volumes (150%, 200% and 300% (100% = 85 Gy EQD2₁₀)) were evaluated.RESULTSMedian(range) tumor width at diagnosis was 5.5(3.6; 7.5)cm; CTV_HR volume was 45(23; 136)cm³ with maximum distance from tandem to CTV_HR border of 3.4(2.5; 4.8)cm. T-stage distribution was IIB/III/IVA in 6(30%)/9(45%)/5(25%) of patients. At BT, 13(65%) patients had distal parametrial/pelvic wall infiltration. Median(range) number of needles per patient was 11(8–18). Average distribution of intrauterine, vaginal and interstitial dwell times were 31%, 25% and 44%, respectively. Median(range) dwell-time per dwell position was 11(2–127)% of average point-A based standard loading. Median V_85Gy/V_150%/V_200%/V_300% were 85(38; 171)/41(21; 93)/22(12; 41)/7(4; 19) cm³; CTV_HR D_90% was 93(83; 97)Gy EQD2₁₀; bladder/rectum/sigmoid/bowel D_2cm3 were 78(64; 104)/65(52; 76)/59(53; 69)/61(47; 76)Gy EQD2₃.CONCLUSIONSThe use of O-needles in patients with large and/or unfavorable tumors resulted in excellent target coverage and OARs sparing. Intrauterine and vaginal loadings were reduced compared to standard loading and almost half of the loading was shifted into IS needles. This was achieved with gentle loading in the majority of dwell positions.     

The equivalent dose contribution from high-dose-rate brachytherapy to positive pelvic lymph nodes in locally advanced cervical cancer

PurposeDefinitive radiation therapy for locally advanced cervical cancer involves external beam radiation therapy (EBRT) and high-dose-rate (HDR) brachytherapy. There remains controversy and practice pattern variation regarding the optimal radiation dose to metastatic pelvic lymph nodes (LNs). This study investigates the contribution of the pelvic LN dose from HDR brachytherapy.Methods and MaterialsFor 17 patients with 36 positive pelvic LNs, each LN was contoured on a computed tomography (CT) plan for EBRT and on brachytherapy planning CTs using positron emission tomographic images obtained before chemoradiation. The mean delivered dose from each plan was recorded, and an equivalent dose in 2-Gy fractions (EQD2) was calculated. A Student's t test was performed to determine if the mean delivered dose is significantly different from the mean prescribed dose and EQD2.ResultsThe average prescribed dose from the total EBRT was 54.09 Gy. The average prescribed HDR dose to International Commission on Radiation Units point A was 26.81 Gy. The average doses delivered to the involved LNs from EBRT and brachytherapy were 54.25 and 4.31 Gy, respectively, with the corresponding EQD2 of 53.45 and 4.00 Gy. There was no statistically significant difference (p < 0.05) between the mean delivered and the prescribed doses for EBRT and between the delivered dose and the EQD2 for EBRT and brachytherapy.ConclusionsOur study shows that the HDR contribution is 7% (4.00 Gy) of the total EQD2 (57.45 Gy). The HDR contribution should be accounted for when prescribing the EBRT boost dose to pelvic LNs for the optimal therapeutic dose.     

3D打印模板辅助CT引导192Ir组织间插植治疗复发妇科肿瘤的可行性分析

目的通过比较3D打印个体化模板(3D-PIT)辅助CT引导后装组织间插植治疗中央型复发妇科肿瘤的术前计划与术中实际物理剂量学参数,评价3D打印个体化模板辅助下CT引导的组织间插植治疗的剂量准确性。方法纳入分析2018年1月至2019年12月北京大学第三医院肿瘤放疗科中央型复发妇科肿瘤患者38例,均行3D打印个体化模板辅助CT引导¹⁹²Ir后装组织间插植治疗。大体肿瘤靶区(GTV)处方剂量10~36 Gy,2~6分次,5~6 Gy/次。比较患者治疗前、治疗时计划的90%靶区体积剂量(D₉₀)、100%靶区体积剂量(D₁₀₀)和100%处方剂量体积百分比(V₁₀₀)。危及器官膀胱、直肠和结肠2 cm^3体积接受的剂量(D_(2 cm^3))。近距离治疗质量参数包括适形指数(CI)、均匀性指数(HI)、靶区外体积指数(EI)。同时观察围手术期并发症。结果研究共纳入治疗194例次,单次中位插植针6(5~13)根,单次处方剂量5~6 Gy。术前和术中的GTV D90、D100、V100、CI、HI、EI差异均无统计学意义(P>0.05)。术前和术中危及器官膀胱和结肠D2 cm3差异无统计学意义(P>0.05),术中直肠D_(2 cm^3)剂量略高于术前计划,差异有统计学意义(t=-0.335,P=0.027)。结论3D打印模板辅助CT引导下高剂量率¹⁹²Ir后装组织间插植治疗计划完成质量良好,达到术前剂量设计要求。     

Radiobiological optimization comparison between pulse-dose-rate and high-dose-rate brachytherapy in patients with locally advanced cervical cancer

PurposeOnly scarce data are available on the possibility to include radiobiological optimization as part of the dosimetric process in cervical cancer treated with brachytherapy (BT). We compared dosimetric outcomes of pulse-dose-rate (PDR) and high-dose-rate (HDR)-BT, according to linear-quadratic model.Methods and MaterialsThree-dimensional dosimetric data of 10 consecutive patients with cervical cancer undergoing intracavitary image-guided adaptive PDR-BT after external beam radiation therapy were examined. A new HDR plan was generated for each patient using the same method as for the PDR plan. The procedure was intended to achieve the same D₉₀ high-risk clinical target volume with HDR as with PDR planning after conversion into dose equivalent per 2 Gy fractions (EQD2) following linear-quadratic model. Plans were compared for dosimetric variables.ResultsAs per study's methodology, the D₉₀ high-risk clinical target volume was strictly identical between PDR and HDR plans: 91.0 Gy (interquartile: 86.0–94.6 Gy). The median D₉₈ intermediate-risk clinical target volume was 62.9 Gy_EQD2 with HDR vs. 65.0 Gy_EQD2 with PDR (p < 0.001). The median bladder D_2cc was 65.6 Gy_EQD2 with HDR, vs. 62 Gy_EQD2 with PDR (p = 0.004). Doses to the rectum, sigmoid, and small bowel were higher with HDR plans with a median D_2cc of 55.6 Gy_EQD2 (vs. 55.1 Gy_EQD2, p = 0.027), 67.2 Gy_EQD2 (vs. S 64.7 Gy_EQD2, p = 0.002), and 69.4 Gy_EQD2 (vs. 66.8 Gy_EQD2, p = 0.014), respectively. For organs at risk (OARs), the effect of radiobiological weighting depended on the dose delivered. When OARs BT contribution to D_2cc doses was <20 Gy_EQD2, both BT modalities were equivalent. OARs EQD2 doses were all higher with HDR when BT contribution to D_2cc was ≥20 Gy_EQD2.ConclusionBoth BT modalities provided satisfactory target volume coverage with a slightly higher value with the HDR technique for OARs D2_cc while intermediate-risk clinical target volume received higher dose in the PDR plan. The radiobiological benefit of PDR over HDR was predominant when BT contribution dose to OARs was >20 Gy.     

Dose planning variations related to delineation variations in MRI-guided brachytherapy for locally advanced cervical cancer

PurposeTo examine the variability in prescribed dose due to contouring variations in intracavitary image-guided adaptive brachytherapy for cervical cancer. To identify correlations between dosimetric outcomes and delineation uncertainty metrics.Methods and MaterialsA data set from an EMBRACE sub-study on contouring uncertainties was used, consisting of magnetic resonance images of six patients with cervical cancer delineated by 10 experienced observers (target volumes and organs at risk). Two gold standard contours were generated, an expert consensus and the simultaneous truth and performance level estimation. Plans were individually optimised to all of the contour sets (12 in total). Plans were applied to the gold standard contour sets, and dose volume histogram parameters including D₉₀, D₉₈ and D_2cm³ were determined. The variability between plans was assessed. Dose volume histogram parameters and delineation uncertainty metrics were correlated using the Spearman's non-parametric rank correlation.ResultsThere is a dosimetric variability between observers, patients and the gold standard contour used for analysis. Approximately 3 Gy D₉₀ EQD2₁₀ variability (SD) was observed for the CTVHR and 1.2-3.6 Gy D_2cm³ EQD2₃ for the organs at risk. The maximum geometric dimensions of the delineations are most commonly correlated with dosimetry changes. Although the correlations are similar across gold standards, the direction of these correlations differs, indicating that the dosimetric outcomes are dependent on the contour that the plan is optimised to.ConclusionThis study highlights the dosimetric differences interobserver uncertainty in contouring can have for cervical cancer brachytherapy. The importance of carefully choosing a gold standard from which to benchmark is reiterated.     

形变配准在宫颈癌近距离放疗分次间剂量评估中的可行性研究

目的:比较近距离放疗分次间靶区和正常组织在形变配准(DIR)和简单累加剂量体积直方图(DVH)情况下,累积剂量的剂量学差异,分析在宫颈癌三维近距离放疗计划中,形变配准技术应用于靶区和正常组织剂量评估的可行性。方法:回顾性选取13例宫颈癌近距离放疗病例,每个病例均进行了4次CT定位的近距离放疗。对每个病例的4次CT进行形...     

Variable impact of intracavitary brachytherapy fractionation schedule on biologically effective dose to organs at risk in patients with cervical cancer

PurposeTo determine the effect of intracavitary brachytherapy (ICBT) fractionation schedule on biologically effective dose to organs at risk.Methods and MaterialsWe reviewed records from 26 patients who had CT imaging during ICBT for International Federation of Gynecology and Obstetrics stage IB2-IVA cervical cancer. Using α/β = 10, we calculated hypothetical nominal doses to achieve a biologically effective dose at 2 Gy per fraction (EQD2_α/β=10) of 40 Gy to Point A for high-dose-rate ICBT with 1–15 fractions. Corresponding minimum EQD2_α/β=3s to the maximally irradiated 2 cc of rectum, bladder, and sigmoid were calculated for each fractionation scheme and added to EQD2_α/β=3 from external beam radiotherapy. Total EQD2_α/β=3s were compared with American Brachytherapy Society suggested dose constraints (rectum/sigmoid, ≤75 Gy; bladder, ≤90 Gy).ResultsExcept for rectal EQD2_α/β=3 in three patients, the rectal, bladder, and sigmoid EQD2_α/β=3s decreased with increasing fractionation in all patients. Although the total rectal EQD2_α/β=3s were less than the American Brachytherapy Society rectal dose constraint in all patients at all fractionation schedules, the total bladder EQD2_α/β=3s routinely exceeded the bladder dose constraint, even at maximum fractionation. By contrast, increasing fractionation decreased the number of patients with doses exceeding the sigmoid dose constraint by 48%.ConclusionsThe relationship between ICBT fractionation schedule and relative EQD2_α/β=3s to rectum, bladder, and sigmoid depends on individual anatomy. Fractionation optimization can improve therapeutic ratios by minimizing the risk or severity of toxic effects. For patients in whom many fractions optimize the therapeutic ratio, low-dose-rate or pulsed-dose-rate brachytherapy may be preferred.