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。     

切向双弧容积弧形调强技术对保乳术后包括内乳淋巴结区照射的心脏剂量学评价

目的 通过对左侧乳腺癌保乳术后患者内乳淋巴结局部放疗,探讨一种新的切向50°双弧容积弧形调强放射治疗（tangential volumetric modulated arc therapy,T-VMAT）技术的剂量学特点,评价T-VMAT对心脏的潜在保护作用。方法 15例左侧乳腺癌保乳术后患者,每例患者分别设计常规加楔形板切线野（W-TF）、6野调强适形放射治疗（6F-IMRT）和T-VMAT计划,靶区处方剂量50 Gy/25次,计算并比较靶区和危及器官（OAR）的剂量体积参数和适形指标。结果 与W-TF相比,T-VMAT技术不仅可降低心脏和冠状动脉前降支（LAD）最大剂量D_max、平均剂量D_mean和≥ 10 Gy剂量区体积（P<0.05）,而且有降低5 Gy剂量区体积V_{5 Gy}趋势,但差异无统计学意义（P>0.05）;与6F-IMRT相比,T-VMAT技术可明显降低心脏的D_mean、V_{5 Gy}、V_{10 Gy}和V_{20 Gy},以及LAD的D_mean、V_{5 Gy}和V_{10 Gy}（P<0.05）。与W-TF相比,T-VMAT计划中同侧肺V_{20 Gy}和健侧乳腺V_{5 Gy}均未增加,差异无统计学意义（P>0.05）,且靶区剂量覆盖和适形度均明显优于W-TF,热点体积V₁₁₀明显低于W-TF（P<0.05）。结论 在不增加同侧肺和健侧乳腺受照体积的同时,T-VMAT不仅可以降低心脏和LAD高剂量区受照体积,而且有降低心脏和LAD低剂量区受照体积的趋势。     

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。     

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。     

宫颈癌内外照射后放射性直肠损伤临床预测模型的研究

目的 探讨宫颈癌内外照射放疗不同剂量叠加方式的剂量学差异,建立宫颈癌放疗后慢性放射性直肠损伤(RLRI)的临床预测模型。方法 回顾性分析2020年1月1日至2021年11月30日于川北医学院附属医院肿瘤科接受根治性同步放化疗宫颈癌患者的临床资料,放疗采用外照射+近距离治疗方式,内外照射剂量评估采用内、外照射生物等效剂量(EQD2)参数直接叠加和内外照射三维计划图像形变配准(DIR)剂量叠加,分析两种剂量评估方式剂量学差异。RLRI分级标准采用肿瘤放射治疗协作组标准。运用两种剂量评估方式构建RLRI的预测模型,使用受试者工作特征(ROC)曲线计算曲线下面积,以评估不同剂量评估方式的预测准确性。结果 多次近距离治疗剂量叠加的EQD2参数较DIR剂量叠加高危临床靶区D_95%和D_90%分别高2.18和2.92 Gy,直肠D_{2 cm³}、D_{1 cm³}、D_{0.1 cm³}分别高1.74、2.28、2.26 Gy(t=3.82、5.21、4.58、5.17、2.05,P<0.05)。外照射与近距离治疗,直肠D_{2 cm³}、D_{1 cm³}、D_{0.1 cm³}的EQD2参数直接叠加比DIR剂量叠加高6.22、7.61、9.56 Gy(t=9.40、10.59、7.87,P<0.001)。联合预测模型ROC曲线下面积为0.788,最佳预测阈值的灵敏度为0.850,特异度为0.660,Hosmer-Lemeshow拟合优度检验显示,拟合优度较好(P>0.05)。传统预测指标DIR剂量叠加的预测模型:直肠D_{2 cm³}、D_{1 cm³}的ROC曲线下面积分别为0.784、0.763,最佳预测阈值的灵敏度分别为0.850、0.750,特异度分别为0.679、0.717。结论 内外照射EQD2参数直接叠加与三维计划图进行DIR剂量叠加评估剂量参数有剂量学差异。DIR剂量叠加直肠D_{2 cm³}、D_{1 cm³}与联合预测模型预测RLRI的价值较高,但联合预测模型预测RLRI计算复杂,建议临床上通过DIR剂量叠加直肠D_{2 cm³}、D_{1 cm³}预测RLRI。     

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。     

早期鼻咽癌螺旋断层放疗颈部皮肤受量的剂量学研究

目的 探索早期鼻咽癌螺旋断层放射治疗（Tomotherapy）计划设计过程中降低颈部皮肤受照剂量的方法。方法 采用简单随机抽样法选取17例已接受螺旋断层放射治疗的早期鼻咽癌病例，将各病例颈部外轮廓内缩3 mm生成新的组织器官即颈部皮肤组织，同时清除各靶区与颈部皮肤组织的交叉部分；针对上述处理过的病例进行两组计划设计，常规（TP）组按照常规计划方法进行螺旋断层放疗计划设计；新计划（NP）组是将颈部皮肤组织作为危及器官进行剂量限制计划设计；比较两组计划中各靶区以及危及器官的剂量参数、机器跳数以及治疗时间等参数。结果 两组计划均能满足临床处方要求，两组计划各靶区的D₉₈、D₉₅以及D₂差异均无统计学意义（P>0.05）；NP组的脑干D_max、脊髓D_{1 cm³}、右侧腮腺D_mean高于TP组接受的剂量（t=2.47、2.34、2.77，P<0.05），左颞颌关节D_max较TP组低（t=2.30，P<0.05），皮肤V₃₀、V₄₀、V₅₀、V₆₀比TP组明显降低（t=8.37、6.02、5.82、4.89，P<0.05）。NP组单次总机器跳数比TP组平均减少6.3%，单次实际执行时间比TP组平均减少8.1%。结论 早期鼻咽癌螺旋断层放射治疗应该勾画颈部皮肤，并在计划设计过程中将其作为危及器官进行剂量限制，该方法能够有效降低颈部皮肤受照剂量，减轻放射治疗过程中皮肤反应，提高患者生活质量。     

射波刀治疗前列腺癌初步临床观察

目的 探讨超大分割立体定向放射治疗（SBRT）前列腺癌的有效性和安全性。方法 回顾性分析2010年5月至2018年5月治疗的26例前列腺癌患者。中位年龄69（57~87）岁。临床分期为局限期14例,转移期12例。放疗方案：18例为35.0~37.5 Gy/5次,其中1例5年前行调强放射治疗（IMRT）72 Gy;8例为前列腺（25 Gy/5次）+盆腔（48.0~50.4 Gy/28次）。SBRT为隔日治疗,中位处方剂量线69.5%（65%~80%）。内分泌治疗：2例行去势手术,其余采用化学去势疗法。主要危及器官限量：直肠V_{35 Gy} <1 cm³、膀胱V_{35 Gy} <5 cm³。主要观察指标：放射损伤、前列腺特异性抗原（PSA）评价、局部控制、症状缓解。次要观察指标为无进展生存（PFS）和总生存（OS）。结果 中位随访时间22.44个月,26例患者均顺利完成治疗,未出现≥3级早期和晚期放射损伤,1、2级早期放射损伤发生率分别为38.4%和19.2%,1、2级晚期放射损伤发生率分别为30.8%和3.8%。放疗后效果评价症状缓解及局部控制情况良好。放疗后1、3、6、12个月,局限期患者PSA值与放疗前相比均下降明显（Z=2.900,2.794,2.510,2.090,P<0.05）,但转移期患者组差异均无统计学意义（P>0.05）。结论 超大分割立体定向放射治疗前列腺癌局部控制效果好,症状缓解率高,无严重不良反应。     

Target tailoring and proton beam therapy to reduce small bowel dose in cervical cancer radiotherapy

Purpose

The aim of the study was to investigate the potential clinical benefit from both target tailoring by excluding the tumour-free proximal part of the uterus during image-guided adaptive radiotherapy (IGART) and improved dose conformity based on intensity-modulated proton therapy (IMPT).

Methods

The study included planning CTs from 11 previously treated patients with cervical cancer with a >4-cm tumour-free part of the proximal uterus on diagnostic magnetic resonance imaging (MRI). IGART and robustly optimised IMPT plans were generated for both conventional target volumes and for MRI-based target tailoring (where the non-invaded proximal part of the uterus was excluded), yielding four treatment plans per patient. For each plan, the V_15Gy, V_30Gy, V_45Gy and D_mean for bladder, sigmoid, rectum and bowel bag were compared, and the normal tissue complication probability (NTCP) for ≥grade 2 acute small bowel toxicity was calculated.

Results

Both IMPT and MRI-based target tailoring resulted in significant reductions in V_15Gy, V_30Gy, V_45Gy and D_mean for bladder and small bowel. IMPT reduced the NTCP for small bowel toxicity from 25% to 18%; this was further reduced to 9% when combined with MRI-based target tailoring. In four of the 11 patients (36%), NTCP reductions of >10% were estimated by IMPT, and in six of the 11 patients (55%) when combined with MRI-based target tailoring. This >10% NTCP reduction was expected if the V_45Gy for bowel bag was >275?cm³ and >200?cm³, respectively, during standard IGART alone.

Conclusions

In patients with cervical cancer, both proton therapy and MRI-based target tailoring lead to a significant reduction in the dose to surrounding organs at risk and small bowel toxicity.

     

Proton beam therapy can achieve lower vertebral bone marrow dose than photon beam therapy during chemoradiation therapy of esophageal cancer

Chemoradiation therapy plays an important role in both the neoadjuvant and definitive management of esophageal cancer (EC). Prior studies have suggested that advanced planning techniques can better spare organs at risk including the heart. Although multiple toxicities can result from esophageal radiotherapy, one less studied acute toxicity is that of myelosuppression, which can result, in part, from the combination of chemotherapy and incidental radiotherapy administration to the vertebral bodies (VBs), which abut the posterior aspect of the esophagus, especially in the lower thoracic esophagus. Traditionally, VB bone marrow doses are not accounted during EC radiation therapy planning.We sought to compare the doses to VBs between proton and photon radiation therapy as part of chemoradiation therapy for EC treatment. By reducing doses to the vertebrae, radiation therapy can decrease treatment-related myelosuppression, which can avoid delays or chemotherapy dose reductions in therapy, which likely affect long-term patient survival.Dose constraints are not routinely employed for bone marrow in radiation treatment planning. In our previous work, we identified thresholds to avoid grade ≥3 leukopenia, including VB V_10Gy, VB V_20Gy, and a mean VB dose (MVD) of 18.8 Gy. Herein we perform a retrospective dosimetric planning study comparing passive- or double-scattering proton beam therapy (PS-PBT), volumetric-modulated arc therapy (VMAT) (photon-based), and intensity-modulated radiation therapy (IMRT) (photon-based) in 25 patients with locally advanced EC who were treated originally with photon RT at our institution between 2011 and 2016. The aforementioned dose constraints were included in the retrospective planning process for PS-PBT, VMAT, and IMRT to determine the feasibility of achieving these VB constraints while maintaining reasonable target coverage and planned, consistent constraints to other organs at risk including lungs, spinal cord, and stomach.PS-PBT plans were found to achieve lower doses for VB V_10Gy, V_20Gy, and MVD than VMAT and static IMRT plans while achieving the same target coverage. PS-PBT resulted in lower organs at risk dosimetric parameters than the photon plans, with p < 0.0001. Student's paired t-test p-values in favor of proton therapy's ability to spare organs were as follows: for PS-PBT vs VMAT and PS-PBT vs IMRT in mean doses for lung, liver, and VB and VB V_10Gy and VB V_20Gy were all <0.001 (Bonferroni corrected α=0.017). One-way ANOVA found that VB doses (VB V_10Gy, VB V_20Gy, and MVD) were significantly lower for proton therapy (p < 0.006) among the 3 planning techniques.     

Radiation therapy of synchronous bilateral breast carcinoma (SBBC) using multiple techniques

The purpose of this study was to establish intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) treatment plans for synchronous bilateral breast cancer (SBBC) and to compare those plans with the previous treatment plans using 3D conformal radiation therapy (3DCRT). The differences among the treatments were also statistically compared regarding dosimetry distribution and treatment efficiency. The research was conducted with 10 SBBC patients. The study established IMRT (12 fields with a single isocenter) and VMAT (2 partial arcs with a single isocenter) treatment plans for SBBC patients and then compared those plans with 3DCRT (8 fields with multiple isocenters). The plans were evaluated based on a dose-volume histogram analysis. For planning target volumes (PTVs), the mean doses and the values of V_95%, V_105%, conformity index, and homogeneity index were reported. For the organs at risk, the analysis included the mean dose, maximum dose, and V_XGy, depending on the organs (lungs, heart, and liver). To objectively evaluate the efficiency of the treatment plans, each plan's beam times, treatment times (including set-up time), and monitor units were compared. Tukey test and one-way analysis of variance were used to compare the PTV and organs at risk values of the 3 techniques. Additionally, the independent-samples t-test was used to compare the 2 techniques (IMRT and VMAT) based on the values of Rt. PTV and Lt. PTV (p?<?0.05). For PTV dose distribution, IMRT showed increases of approximately 1.2% in D_mean and of approximately 5.7% in V_95% dose distribution compared with 3DCRT. In comparison to VMAT, 3DCRT showed about 3.0% higher dose distribution in D_mean and V_95%. IMRT was the best in terms of conformity index and homogeneity index (p?<?0.05), whereas 3DCRT and VMAT did not significantly differ from each other. In terms of dose distribution on lungs, heart, and liver, the percentage of volume at high doses such as V_30Gy and V_40Gy was approximately 70% lower for IMRT and approximately 40% lower for VMAT than for 3DCRT. For distribution volumes of low doses such as V_5% and V_10%, that for 3DCRT was approximately 60% smaller than for IMRT and approximately 70% smaller than for VMAT. Comparison between IMRT and VMAT showed that the IMRT was superior in all distribution factors. VMAT showed better treatment efficiency than 3DCRT or IMRT. Among the SBBC radiotherapy treatment plans, IMRT was superior to 3DCRT and VMAT in terms of PTV dose distribution, whereas VMAT showed the most outstanding treatment efficiency.     

Stereotactic body radiation therapy planning with duodenal sparing using volumetric-modulated arc therapy vs intensity-modulated radiation therapy in locally advanced pancreatic cancer: A dosimetric analysis

Stereotactic body radiation therapy (SBRT) achieves excellent local control for locally advanced pancreatic cancer (LAPC), but may increase late duodenal toxicity. Volumetric-modulated arc therapy (VMAT) delivers intensity-modulated radiation therapy (IMRT) with a rotating gantry rather than multiple fixed beams. This study dosimetrically evaluates the feasibility of implementing duodenal constraints for SBRT using VMAT vs IMRT. Non–duodenal sparing (NS) and duodenal-sparing (DS) VMAT and IMRT plans delivering 25 Gy in 1 fraction were generated for 15 patients with LAPC. DS plans were constrained to duodenal D_max of<30 Gy at any point. VMAT used 1 360° coplanar arc with 4° spacing between control points, whereas IMRT used 9 coplanar beams with fixed gantry positions at 40° angles. Dosimetric parameters for target volumes and organs at risk were compared for DS planning vs NS planning and VMAT vs IMRT using paired-sample Wilcoxon signed rank tests. Both DS VMAT and DS IMRT achieved significantly reduced duodenal D_mean, D_max, D_1cc, D_4%, and V_20 Gy compared with NS plans (all p≤0.002). DS constraints compromised target coverage for IMRT as demonstrated by reduced V_95% (p = 0.01) and D_mean (p = 0.02), but not for VMAT. DS constraints resulted in increased dose to right kidney, spinal cord, stomach, and liver for VMAT. Direct comparison of DS VMAT and DS IMRT revealed that VMAT was superior in sparing the left kidney (p<0.001) and the spinal cord (p<0.001), whereas IMRT was superior in sparing the stomach (p = 0.05) and the liver (p = 0.003). DS VMAT required 21% fewer monitor units (p<0.001) and delivered treatment 2.4 minutes faster (p<0.001) than DS IMRT. Implementing DS constraints during SBRT planning for LAPC can significantly reduce duodenal point or volumetric dose parameters for both VMAT and IMRT. The primary consequence of implementing DS constraints for VMAT is increased dose to other organs at risk, whereas for IMRT it is compromised target coverage. These findings suggest clinical situations where each technique may be most useful if DS constraints are to be employed.     

俯卧盆腔固定装置在妇科肿瘤调强放疗计划中的剂量学影响

目的研究俯卧盆腔固定装置对妇科肿瘤调强放射治疗剂量学的影响。方法回顾性分析2020年8月至2021年6月在中山大学附属第三医院接受放疗的宫颈癌和子宫内膜癌患者共20例, 每位患者均采取两种方法勾画外轮廓, 第1种仅包含患者轮廓, 第2种包含患者轮廓和固定装置。每例患者在放疗计划系统(TPS)中分别用两组轮廓计算相同的7野调强计划, 通过剂量体积直方图(DVH)和计划相减来比较不带固定装置计划Planwithout和带固定装置计划Planwith间剂量学差异。在仿真人模体中使用EBT3胶片验证实际点剂量, 并分别比较其与上述两个计划剂量的差异。结果 Planwith的靶区100%、98%处方剂量的覆盖体积V50 Gy、V49 Gy和均值Dmean分别下降了19.75%、7.99%和2.54%(t = 8.96、10.49、22.09, P<0.01);皮肤的V40Gy、V30Gy、V20Gy、V15Gy和Dmean分别上升了51.79%、51.05%、45.72%、33.63%和10.80%(t = -2.54、-5.63、-15.57、-24.06、-13.88, P<0....     

Circumferential or sectored beam arrangements for stereotactic body radiation therapy (SBRT) of primary lung tumors: Effect on target and normal-structure dose-volume metrics

To compare 2 beam arrangements, sectored (beam entry over ipsilateral hemithorax) vs circumferential (beam entry over both ipsilateral and contralateral lungs), for static-gantry intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) delivery techniques with respect to target and organs-at-risk (OAR) dose-volume metrics, as well as treatment delivery efficiency. Data from 60 consecutive patients treated using stereotactic body radiation therapy (SBRT) for primary non–small-cell lung cancer (NSCLC) formed the basis of this study. Four treatment plans were generated per data set: IMRT/VMAT plans using sectored (-s) and circumferential (-c) configurations. The prescribed dose (PD) was 60 Gy in 5 fractions to 95% of the planning target volume (PTV) (maximum PTV dose ~ 150% PD) for a 6-MV photon beam. Plan conformality, R₅₀ (ratio of volume circumscribed by the 50% isodose line and the PTV), and D_2 cm (D_max at a distance ≥2 cm beyond the PTV) were evaluated. For lungs, mean doses (mean lung dose [MLD]) and percent V₃₀/V₂₀/V₁₀/V₅ Gy were assessed. Spinal cord and esophagus D_max and D₅/D₅₀ were computed. Chest wall (CW) D_max and absolute V₃₀/V₂₀/V₁₀/V_5 Gy were reported. Sectored SBRT planning resulted in significant decrease in contralateral MLD and V₁₀/V_5 Gy, as well as contralateral CW D_max and V₁₀/V_5 Gy (all p < 0.001). Nominal reductions of D_max and D₅/D₅₀ for the spinal cord with sectored planning did not reach statistical significance for static-gantry IMRT, although VMAT metrics did show a statistically significant decrease (all p < 0.001). The respective measures for esophageal doses were significantly lower with sectored planning (p < 0.001). Despite comparable dose conformality, irrespective of planning configuration, R₅₀ significantly improved with IMRT-s/VMAT-c (p < 0.001/p = 0.008), whereas D_2 cm significantly improved with VMAT-c (p < 0.001). Plan delivery efficiency improved with sectored technique (p < 0.001); mean monitor unit (MU)/cGy of PD decreased from 5.8 ± 1.9 vs 5.3 ± 1.7 (IMRT) and 2.7 ± 0.4 vs 2.4 ± 0.3 (VMAT). The sectored configuration achieves unambiguous dosimetric advantages over circumferential arrangement in terms of esophageal, contralateral CW, and contralateral lung sparing, in addition to being more efficient at delivery.