改良头颈肩热塑体膜固定下乳腺癌改良根治术后调强放疗中的摆位误差分析

目的 应用锥形束CT分析改良头颈肩热塑体膜和乳腺托架在乳腺癌改良根治术后调强放疗中的摆位精度差异。方法 回顾性分析天津医科大学肿瘤医院2015年8月至2018年12月68例接受调强放疗（IMRT）的乳腺癌改良根治术后患者资料。根据体位固定方式的不同,将患者分为改良头颈肩热塑体膜组（体膜组,42例）和乳腺托架组（托架组,26例）。在患者的第1、6、11、16、21次治疗摆位后行锥形束CT（CBCT）扫描,获得两组患者在左右（RL）、腹背（AP）、头脚（SI）方向的摆位误差,同时记录放疗摆位的时间。比较两组的摆位误差、分布比例、摆位时间,计算出各自的M_PTV外放值,并分析多种因素对体膜组患者摆位误差的影响。结果 42例体膜组扫描210次,26例托架组扫描130次。体膜组和托架组在RL、AP、SI方向的摆位误差分别为（2.12±2.01）和（2.38±1.92）mm、（3.29±2.46）和（3.88±2.76）mm、（3.47±2.29）和（4.11±3.15）mm,其中两组在AP和SI方向的摆位误差比较,差异均有统计学意义（t=-2.05、-2.16,P<0.05）;SI方向体膜组摆位误差≤ 3 mm的次数占总扫描次数的比例较高,优于托架组差异有统计学意义（χ²=4.97,P<0.05）;当AP和SI方向体膜组摆位误差>5 mm的次数占总扫描次数的比例较低,优于托架组差异有统计学意义（χ²=5.21、9.29,P<0.05）。体膜组的摆位时间较短,优于托架组差异有统计学意义（t=-2.16,P<0.05）。RL、AP、SI方向体膜组计算的M_PTV值均小于托架组。改良头颈肩热塑体膜体位固定方式对高龄（≥ 60岁）、体质量指数（BMI）≥ 24 kg/m²和对放疗过程相对不熟悉（治疗时间≤ 2周）的患者会造成AP和（或）SI方向的摆位误差偏大。其中,SI方向<60岁的患者摆位误差较小,优于高龄患者（≥ 60岁）差异有统计学意义（t=-2.43,P<0.05）;AP和SI方向BMI<24 kg/m²的患者摆位误差较小,优于BMI ≥ 24 kg/m²的患者,差异有统计学意义（t=-2.21、-2.04,P<0.05）;AP方向治疗时间>2周的患者摆位误差较小,优于对放疗过程相对不熟悉的患者（治疗时间≤ 2周）差异有统计学意义（t=2.23,P<0.05）。结论 在乳腺癌改良根治术后IMRT放疗时应用改良头颈肩热塑体膜可以降低腹背和头脚方向的摆位误差,同时缩短摆位时间。对于≥ 60岁、BMI ≥ 24 kg/m²和对放疗过程相对不熟悉（治疗时间≤ 2周）的患者,要关注腹背和头脚方向的摆位,以保证放疗的效果。     

腹盆腔充盈度对膈肌位置的影响

目的 研究腹盆腔充盈度对膈肌位置的影响。方法 回顾性查阅2018年3月至2020年9月,苏州大学附属第一医院影像存储和传输系统(PACS)存储具有4~7次CT图像患者,共搜集25例、137次CT影像。勾画自膈顶至耻骨联合上缘每横断面腹盆腔轮廓,分别计算腹、盆腔及整体充盈体积。同一患者多次影像,两两排列组合共379组进行比较,计算腹盆腔体积变化率(△VR)、膈顶高度差值(△H);腹盆腔整体充盈度增大且膈顶升高为一致组,而膈顶降低为不一致组。统计一致组在所有样本占比,不一致组中过度深吸气占总样本比例;一致组和不一致组的△VR、△H行组间比较,一致组中腹、盆腔的△VR进行比较,均采用Mann-Whitney检验;一致组中腹、盆腔△VR与膈顶升高高度的相关性采用Spearman相关性分析;模拟计算腹盆腔充盈增加500 ml,所有样本、一致组的膈顶平均升高高度。结果 一致组占比为67.28%;不一致组中深吸气在总样本占比为26.39%;一致组较不一致组,腹盆腔整体△VR、△H差异具有统计学意义(Z=-4.95、-5.49,P＜0.05);一致组中,腹腔与盆腔△VR比较,差异有统计学意义(Z=-7.53,P＜0.05);膈顶升高高度与腹腔△VR相关(r_s=0.43,P＜0.05);模拟计算腹盆腔平均充盈增加500 ml可导致所有样本、一致组膈顶平均分别升高4.54、8.43 mm。结论 腹盆腔充盈度可能是影响膈肌位置及相关器官放疗精准性的主要因素之一,其中腹腔充盈度对其影响较大,建议尽可能在放疗疗程中重复CT定位扫描时充盈程度。     

呼吸运动对部分乳腺外照射靶区剂量学的影响

目的 探讨呼吸运动对部分乳腺外照射（EB-PBI）靶区和危及器官（OAR）剂量学的影响。方法 选取保乳术后符合EB-PBI条件的20例患者,在四维CT（4D-CT）10个时相上,由同一勾画者基于术腔边界金属夹结合术腔血清肿勾画靶区（TB）。以0时相为参考时相,制定三维适形放疗计划（3D-CRT）,并将0时相的3D-CRT复制到其余9个时相上。观察呼吸周期中呼吸运动导致的靶区及OAR剂量学变化,其中相关剂量学参数如下：平均剂量（D_mean）、均匀性指数（HI）、适形度指数（CI）以及接受x Gy照射的百分体积（V_x）。结果 自由呼吸状态下TB在左右、前后、头脚方向上的位移中位数分别为0.90、0.75和0.80 mm,三维位移矢量中位数为0.95 mm。在头脚方向上,TB位移与靶区D_mean、HI和CI具有相关性（r=-0.458、-0.451和0.462,P < 0.05）,尤其与靶区D_mean呈负相关,并且TB位移在头脚方向上与患侧正常乳腺的D_mean、V₂₀和V₃₀呈正相关（r=0.527、0.488和0.526,P < 0.05）。在三维运动矢量上,TB位移与患侧肺的D_mean、V₅、V₁₀和V₂₀呈正相关（r=0.416、0.503、0.522和0.498,P < 0.05）。心脏的D_mean、V₅和V₁₀仅与心脏体积变化相关（r=0.727、0.704和0.695,P < 0.05）。 结论 自由呼吸状态下呼吸运动引起EB-PBI靶区小幅度的位移能引起靶区剂量学的变化,从而有可能造成照射过程中靶区剂量脱靶或漏照。肺脏受照剂量体积参数的变化受靶区位移及胸廓扩张的双重影响,但心脏受照剂量受呼吸运动的影响并不显著。     

新型真空垫在盆腔肿瘤放疗体位固定中的应用评估

目的 对一种新型定制真空垫在盆腔肿瘤放疗体位固定中的应用进行评估,并与传统体位固定方式进行对照研究,以提高盆腔肿瘤摆位精度。方法 66名盆腔肿瘤患者接受放射治疗,将患者按照随机数表法分为3组,每组22名,采用3种不同固定方式：平板固定（N组）、传统真空垫（V组）和定制真空垫（New-V组）。固定效果用三维方向及矢状位轴向旋转的摆位误差测量结果进行评估。结果 New-V组摆位误差在前后（x）、头脚（y）、左右（z）及矢状位轴向旋转角度（r）依次为（0.35±0.37）、（0.21±0.22）、（0.29±0.28） cm和（0.70±0.65）°;N组相应摆位误差依次为（0.44±0.43）、（0.31±0.62）、（0.45±0.60） cm和（1.25±1.00）°;V组依次为（0.38±0.36）、（0.27±0.25）、（0.32±0.29）和（1.09±0.77）°。其中,r值各组比较,差异有统计学意义（F=7.859,P<0.05）。New-V组的r值误差比其他两组小。分次间误差波动性分析显示,z和r方向各组比较,差异有统计学意义（F=3.166,P<0.05）,New-V组在4个方向上波动性较小。根据摆位误差分布,对误差引起中心偏移量进行估计,其引起计划靶区（PTV）的剂量分布差异统计显示,New-V组在最小剂量和平均剂量上差异较小,且最小剂量差异有统计学意义（F=8.018,P<0.05）。结论 New-V组的固定方式较平板（N组）和普通真空垫（V组）固定方式摆位误差、照射分次间误差波动性较小,相对位置误差引起潜在PTV剂量变化较小。因此,新型定制真空垫可优化摆位精度,改善治疗效果。     

胸部DR摄影中管电压对影像质量和辐射剂量影响的模体研究

目的 研究胸部数字X射线摄影(DR)中,不同管电压对影像质量以及受检者辐射剂量的影响。方法 管电压在80~130 kV范围内间隔10 kV变化,每种管电压设置下自动曝光控制(AEC)范围在-4~4对成人胸部模体进行曝光。测量模体表面的皮肤入射剂量,计算相对噪声值和对比度噪声比(CNR),并估算每次曝光时受检者的有效剂量。结果 皮肤入射剂量为(0.062 9±0.027 4)mGy,有效剂量为(0.012 7±0.004 5)mSv,有效剂量随着皮肤入射剂量的增加而呈线性增加,两者呈正相关关系(r=0.912,P<0.01)。随着有效剂量的增加,相同管电压下,相对噪声与有效剂量呈负相关关系(r=-0.967、-0.969、-0.968、-0.969、-0.968、-0.970, P<0.01);CNR与有效剂量呈正相关关系(r=0.987、0.987、0.986、0.987、0.988、0.989,P<0.01)。AEC不变时,随着kV值增加,皮肤入射剂量和有效剂量均降低,最大可降低50%和20%;相对噪声值降低,最大可降低23%;CNR增加,最大可增加8%。结论 胸部DR摄影中,在满足影像质量要求的前提下,高kV值可有效降低受检者辐射剂量。     

鼻咽癌同期放化疗中急性皮肤黏膜反应的临床观察及其相关因素分析

目的 探讨鼻咽癌患者同期放化疗中急性皮肤及黏膜反应的影响因素,对主要相关因素进行分析。方法 对85例接受同期放化疗的鼻咽癌患者进行研究,观察并记录BMI、每周放疗剂量、口腔黏膜及颈部皮肤反应情况、血常规等15项临床指标及实验室指标,并进行单因素分析和多因素分析,筛选决定性影响因素。结果 与急性放射性口腔黏膜反应发生密切相关的危险因素,有吸烟史（OR=3.467,P<0.05）和原发灶GTV单次量>2.15Gy（OR=3.393,P<0.05）;与急性放射性皮肤反应发生密切相关的危险因素,有糖尿病史（OR=87.859,P<0.05）,放疗前1周血红蛋白值>130g/L（OR=21.404,P<0.05）。结论 对于同期放化疗的鼻咽癌患者,吸烟史和原发灶GTV单次量为急性放射性口腔黏膜反应的独立影响因素,糖尿病史和放疗前1周的血红蛋白值为急性放射性皮肤反应的独立影响因素。     

腹盆腔放疗诱发肠道微生态失调与肠源性感染的实验研究

目的 探索腹盆腔放疗照射对肠道微生态的影响及其与肠源性感染的关系。方法 模拟腹盆腔放疗照射BALB/c小鼠,2.0 Gy/d,连续照射5 d/周,分别于照射3周、5周和6周后停照1周的时间点收集回肠组织及其内容物样本。用实时定量RT-PCR检测抗菌肽和促炎性因子的表达;用PCR检测细菌在小鼠体内的移位情况;用变性梯度凝胶电泳技术检测分析肠道微生态的特征。结果 腹盆腔照射诱发了肠道潘氏细胞隐窝素-1和-4表达紊乱,照射3周或照射6周后停照1周,小鼠回肠隐窝素-1和-4均呈现显著性降低(t=-7.43、-3.54、-4.72、-4.27,P<0.05);而照射5周小鼠回肠隐窝素-1和-4表达明显升高(t=6.15、5.75,P<0.05)。放疗模拟照射3和5周时小鼠肠道微生物区系多样性指数和丰富度显著降低(t=-3.49、-4.19、-3.44、-4.97,P<0.05),呈现以乳酸杆菌等益生菌减少,大肠杆菌和弗氏志贺氏菌等条件致病菌增多为特征的微生态失调。受照小鼠肠系膜淋巴结和血液中的细菌DNA阳性率明显增高。照射3和5周后回肠组织IL-1β、IL-6和TNF-α显著性高表达(t=4.85、6.16、7.71、4.60、4.86、5.97,P<0.05);照射6周后停照1周时,肠道促炎性因子的表达量有所回落,但IL-1β和TNF-α的表达量仍显著性高表达(t=3.67、5.88,P<0.05)。结论 腹盆腔放疗可诱发肠道抗菌肽表达紊乱,引起肠道微生态失调,进而导致肠源性细菌移位及感染性炎症的发生。微生态可能成为减轻放疗患者消化道不良反应的有效干预靶点。     

前列腺癌放疗定位中膀胱体积的变化对摆位重复性的影响

目的 研究前列腺癌放疗定位膀胱体积对放疗中膀胱体积的一致性和摆位精度的影响,为临床实践提供参考。方法 回顾性选取2015年8月至2020年11月在中山大学肿瘤防治中心进行调强放疗的66例前列腺癌患者,患者在CT定位及治疗前自主憋尿后进行定位扫描或执行放疗,每次放疗前行锥形束计算机体层(CBCT)扫描获得左右、头脚和前后平移方向误差。在CT模拟定位影像和CBCT影像上勾画膀胱轮廓并计算体积,根据CT定位影像上膀胱体积进行分组,200~300 ml组18例、300~400 ml组24例、>400 ml组24例,分析CT定位膀胱体积对放疗过程中CBCT膀胱体积相对计划体积的变化百分比和摆位误差的影响。结果 200~300 ml组放疗中膀胱体积减少15%,300~400 ml组放疗中膀胱体积减少26%,>400 ml组放疗中膀胱体积减少32%,3组膀胱体积变化百分比两两比较差异均有统计学意义(Z=3.43、7.97、4.83,P<0.05)。三维平移方向摆位误差比较:头脚方向差异有统计学意义(H=26.72,P<0.05),左右、前后方向无统计学意义(P>0.05)。头脚方向摆位误差分别为200~300 ml组:0.00(-0.20,0.20)cm; 300~400 ml组:0.00(-0.20,0.30)cm;>400 ml组: -0.10(-0.30,0.20)cm。>400 ml组在头脚方向摆位误差大于其余两组,差异有统计学意义(Z=4.17、4.66,P<0.05),其余差异无统计学意义(P>0.05)。结论 模拟定位时膀胱充盈容积控制在200~300 ml,有利于患者在放疗中保持膀胱体积一致性及减少放疗时的摆位误差。     

皮肤温度监测在女性乳腺癌术后放疗期间放射性皮炎风险预警中的应用

目的 分析放射区皮肤温度变化与乳腺癌术后放疗期间放射性皮炎发生的相关性,探讨皮肤温度监测在放射性皮炎风险预警中的应用价值。方法 连续收集2022年5月至11月河北医科大学第四医院接受三维适形放疗的乳腺癌根治术后患者103例,每周记录放射区皮肤温度及放射性皮炎情况。比较皮肤相对温差和不同级别放射性皮炎的关系。计算发生2级及以上放射性皮炎的最佳截断值,采用受试者工作特征曲线(ROC)评价其预测效果。应用二元logistic回归比较不同皮肤温度与放射性皮炎发生的风险。结果 放射野区皮肤温度与放射性皮炎级别呈正相关。胸壁平均值(40 Gy/20次)、胸壁最大值(40 Gy/20次)、锁上值(30 Gy/15次)的最佳截断值分别为0.45、0.55、0.15℃。分别用最佳截断值将受试者分为低、高危风险组,高危风险组发生2级及以上放射性皮炎的风险分别是低危风险组的5.71、4.29、5.15倍(OR=5.71,95％CI 1.81~17.99,P=0.003;OR=4.29,95％CI 1.65~11.12,P=0.003;OR=5.15,95％CI 2.16~12.31,P＜0.001)。结论 皮肤温度监测能够较好地预测2级及以上放射性皮炎的发生,应密切观察放疗区域皮肤温度,放疗40 Gy/20次时胸壁的平均值、最大值相对温差分别升高0.45、0.55℃或者放疗30 Gy/15次锁上相对温差升高0.15℃时,2级及以上放射性皮炎发生风险增加。     

直肠癌新辅助同步加量调强放疗对侧方淋巴结转移的影响

目的 在侧方淋巴结转移的直肠癌中,评估侧方淋巴结加量放疗的疗效及安全性。方法 2016年1月至2022年12月入组103例合并侧方淋巴结转移的直肠癌患者,按随机数表法分为加量放疗组52例和常规放疗组51例。加量放疗组在盆腔放疗50 Gy的基础上,侧方淋巴结同步加量放疗至60 Gy。常规放疗仅盆腔放疗剂量50 Gy。研究首要终点为侧方复发率,比较两组的疗效及不良反应。结果 加量放疗组和常规放疗组新辅助放疗的不良反应及手术并发症相仿,侧方淋巴结治疗有效率分别为76.9%和56.9%(χ²=4.69,P=0.03),局部复发率分别为7.7%和25.5%(χ²= 5.92,P = 0.015),侧方复发率分别为3.8%和23.5%(χ²= 8.49,P = 0.004)。单因素分析显示,同步加量放疗、放疗后侧方淋巴结短径< 5 mm以及术后淋巴结病理阴性为侧方复发相关因素;多因素回归分析显示,加量放疗(HR=6.42, 95% CI: 1.40~29.49)及放疗后侧方淋巴结短径<5 mm(HR=0.17, 95%CI: 0.04~0.66)为侧方复发的独立相关因素。两组3年无病生存率(DFS)分别为73.25%和62.6%(P＞0.05),3年总生存率(OS)分别为87%和82.5%(P＞0.05)。结论 侧方淋巴结转移直肠癌同步加量放疗安全有效,加量放疗和新辅助治疗后侧方淋巴结短径<5 mm是侧方复发的独立影响因素。     

Accuracy of set-up of thoracic radiotherapy: prospective analysis of 24 patients treated with radiotherapy for lung cancer

In thoracic radiotherapy, a number of factors hinder the use of portal films and electronic portal imaging devices for measuring field placement errors (FPEs). The aim of this study was to assess the accuracy of treatment set-up using simulator check films (SCFs) in radiotherapy for lung cancer. Prospective evaluation was performed on 24 patients. During their radiotherapy, patients returned to the simulator weekly for a minimum of four SCFs, for which the parameters from the original simulator planning film were set, positioning being achieved without fluoroscopy. A total of 96 SCFs were taken. FPEs in left-right (L-R) and superior-inferior (S-I) direction, as well as coronal rotational errors, were measured. The mean absolute FPE was 0.35 cm in the L-R axis and 0.43 cm in the S-I axis. Statistically, the FPEs in the S-I direction were greater than those in the L-R direction (p<0.001). A margin of 0.93 cm between the clinical target volume and the planning target volume would cover 95% of FPEs in the L-R direction, whilst a margin of 1.13 cm is needed for this degree of certainty in the S-I direction. Mean coronal rotational error was 1.6 degrees. Systematic errors were greater than random errors. This study demonstrated that the FPEs were within clinical tolerance (< or = 0.7 cm) in 84.9% of the measurements. The planning margins used in our clinical practice compare favourably with the FPEs in this study.     

A strategy for the use of image-guided radiotherapy (IGRT) on linear accelerators and its impact on treatment margins for prostate cancer patients

Background and Purpose

In external beam radiotherapy of prostate cancer, the consideration of various systematic error types leads to wide treatment margins compromising normal tissue tolerance. We investigated if systematic set-up errors can be reduced by a set of initial image-guided radiotherapy (IGRT) sessions.

Patients and Methods

27 patients received daily IGRT resulting in a set of 882 cone-beam computed tomographies (CBCTs). After matching to bony structures, we analyzed the dimensions of remaining systematic errors from zero up to six initial IGRT sessions and aimed at a restriction of daily IGRT for 10% of all patients. For threshold definition, we determined the standard deviations (SD) of the shift corrections and selected patients out of this range for daily image guidance. To calculate total treatment margins, we demanded for a cumulative clinical target volume (CTV) coverage of at least 95% of the specified dose in 90% of all patients.

Results

The gain of accuracy was largest during the first three IGRTs. In order to match precision and workload criteria, thresholds for the SD of the corrections of 3.5 mm, 2.0 mm and 4.5 mm in the left-right (L-R), cranial-caudal (C-C), and anterior-posterior (A-P) direction, respectively, were identified. Including all other error types, the total margins added to the CTV amounted to 8.6 mm in L-R, 10.4 mm in C-C, and 14.4 mm in A-P direction.

Conclusion

Only initially performed IGRT might be helpful for eliminating gross systematic errors especially after virtual simulation. However, even with daily IGRT performance, a substantial PTV margin reduction is only achievable by matching internal markers instead of bony anatomical structures.     

光学引导跟踪系统在放疗应用中的准确性研究

目的初步探究体表光学引导跟踪系统(OGTS)在肿瘤放射治疗应用中的追踪精度。方法分为模体验证及临床验证, 模体验证采用专用设备, 利用OGTS记录光学标记点在反光球平台上从指定位置移动到目标位置的位移值, 将该位移值与模体中固定距离比较, 以计算系统的准确性与重复性。临床验证通过选取45例放疗患者进行OGTS跟踪准确性和重复性研究, 其中头部、乳腺、直肠肿瘤患者各15例。每例患者均获取随机3个治疗分次下图像引导校正摆位前后图像引导定位系统(IGPS)和OGTS的值, 分别记录每次误差校正的平移值。治疗前用IGPS修正患者摆位误差并获取相关数据, 以IGPS校正平移误差的结果为金标准验证OGTS监测患者位置平移的准确性, 计算综合平移偏差。结果模体测量结果显示, 跟踪准确性的综合平移偏差最大值为0.18 mm, 跟踪重复性综合平移偏差的标准差为0.03 mm。临床试验结果统计显示, IGPS与OGTS追踪精度仅在头部z方向上差异有统计学意义(t=2.21, P<0.05), 而在头部其他方向及乳腺、直肠的3个平移方向差异均无统计学意义(P>0.05)。综合平移偏差分析表明, ...     

Pilot study on interfractional and intrafractional movements using surface infrared markers and EPID for patients with rectal cancer treated in the prone position

Objective:

To evaluate interfractional and intrafractional movement of patients with rectal cancer during radiotherapy with electronic portal imaging device (EPID) and surface infrared (IR) markers.

Methods:

20 patients undergoing radiotherapy for rectal cancer with body mass index ranging from 18.5 to 30 were enrolled. Patients were placed in the prone position on a couch with a leg pillow. Three IR markers were put on the surface of each patient and traced by two stereo cameras during radiotherapy on a twice-weekly basis. Interfractional isocentre movement was obtained with EPID images on a weekly basis. Movement of the IR markers was analysed in correlation with the isocentre movement obtained from the EPID images.

Results:

The maximum right-to-left (R-L) movement of the laterally located markers in the horizontal isocentre plane was correlated with isocentre translocation with statistical significance (p = 0.018 and 0.015, respectively). Movement of the surface markers was cyclical. For centrally located markers, the 95% confidence intervals for the average amplitude in the R-L, cranial-to-caudal (C-C) and anterior-to-posterior (A-P) directions were 0.86, 2.25 and 3.48 mm, respectively. In 10 patients, intrafractional movement exceeding 5 mm in at least one direction was observed. Time-dependent systematic movement of surface markers during treatment, which consisted of continuous movement towards the cranial direction and a sail back motion in the A-P direction, was also observed.

Conclusion:

Intrafractional movement of surface markers has both cyclic components and time-dependent systematic components. Marker deviations exceeding 5 mm were mainly seen in the A-P direction. Pre- or post-treatment EPID images may not provide adequate information regarding intrafractional movement because of systematic movement in the A-P direction during radiotherapy.

Advances in knowledge:

This work uncovered a sail back motion of patients in the A-P direction during radiotherapy. Pre- or post-treatment EPID images may not provide accurate positioning of patients in the A-P direction because of this time-dependent intrafractional motion.Patients treated in the prone position are reported to be more susceptible to positioning errors during radiotherapy.^1–3 Set-up errors in relation to patient position have been frequently reported in patients treated for prostate cancer. Bayley et al¹ showed that for patients with prostate cancer treated in the prone position, isocentre positioning errors were 0.0 ± 3.7 and 0.1 ± 4.3 mm in the anterior-to-posterior (A-P) and cranial-to-caudal (C-C) directions, respectively. Isocentre positioning errors ranged from −7.6 to 8.8 mm in the A-P direction. However, for errors in the C-C direction, there was no significant difference between the supine and prone positions. Weber et al² also reported that the prone position was more unstable than the supine position with a greater distribution of isocentre translocation (prone 4.7 mm vs supine 4.2 mm) in the A-P direction. In addition, systematic set-up variation was larger in the prone position than in the supine position (2.7 vs 1.9 mm). Griffiths et al³ demonstrated that the probability of set-up errors exceeding 5 mm was 12% in the right-to-left (R-L) direction and 33% in the C-C direction. These findings suggest that efforts should be made to reduce set-up uncertainties for patients, especially those treated in the prone position, for more accurate treatment delivery, specifically in an era of intensity-modulated radiotherapy and image-guided radiotherapy. Unlike prostate cancer, patients with rectal cancer are advised to be treated in the prone position to minimize the radiation exposure to the small bowel. But set-up instabilities for patients with rectal cancer have not been studied as much as those for patients with prostate cancer, as described above.As one of the methods of monitoring patient motion, a non-invasive infrared (IR) monitoring system within the radiotherapy treatment room has been established at the Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea, and the reliability of the system has previously been reported.⁴ An IR monitoring system as a tool for measuring patient motion can be easily set up using IR cameras and IR markers that are placed on the surface of the patient. This system is not only non-invasive but is also capable of detecting surface motion in real time.The primary goals of this pilot study were to monitor and analyse patterns in patient motion, which may consist of systematic and/or random components, during radiotherapy using the IR monitoring system. The secondary goal was to validate the applicability of the IR monitoring system by correlation with electronic portal imaging device (EPID) images.     

基于4D-CT测定的保乳术后全乳调强放疗靶区位移的相关性研究

目的 探讨基于4D-CT的乳腺癌保乳术后全乳靶区在自由呼吸状态下随呼吸运动位移变化及与术腔中选定银夹、乳头及体表金属标记位移的相关性。方法 13例保乳术后拟行全乳调强放疗的患者,在自由呼吸状态下行大孔径CT模拟定位并获4D-CT图像。在瓦里安Eclipse治疗计划系统中,由同一放疗医师在每例患者10个呼吸时相CT图像上分别行全乳靶区、乳头、最上层银夹、体中线体表标记勾画,获各中心点在三维方向上的位移,分析靶区位移及与银夹、乳头和体表标记相关性。分析各呼吸时相CT图像上肺体积变化及与靶区位移的相关性。结果 全乳靶区x、y、z轴最大位移分别为0.71、0.76、1.29 mm (F=5.755,P<0.05);全乳靶区中心点三维方向位移与靶体积及同侧肺体积变化均不存在相关性;吸气末2个连续时相与呼气末3个连续时相靶区x、y、z轴平均位移相似,全乳靶体积大小相似;在x、z轴上全乳靶区位移与乳头、体中线体表标记、最上层银夹位移均无相关性,在y轴上全乳靶区位移则与乳头、正中体表标记针、最上层银夹位移有相关性的比例分别为8/13、7/11、9/13,但群体性分析显示全乳靶区位移仅与最上层银夹有相关性(r=0.657,P<0.05)。结论 乳腺体积大小和肺体积改变对全乳靶区位移无明显影响;术腔中选定银夹可用以监测靶区活动度,其用以靶区位移测量和校正可靠性优于乳头及体中线处体表标记。     

Retrospective audit of inter-fraction motion for pelvic node radiotherapy in prostate cancer patients

IntroductionPelvic lymph nodes move independently to the prostate. When delivering radiotherapy to prostate and pelvic lymph nodes, daily inter- and intra-fraction anatomical changes need to be accounted for. Planning target volume (PTV) margins, grown from the pelvic lymph node clinical target volume need to be determined, to account for this variation in position.MethodsTwenty patients who had daily online image guided radiotherapy to prostate and pelvic lymph nodes between April and December 2018 were selected. Ten pre-treatment verification images using cone beam CT from each patient were registered to pelvic bone anatomy, prostate soft tissue or fiducial markers and pelvic lymph node soft tissue to assess the accuracy of treatment delivery. Population systematic and random errors and PTV margins were calculated.ResultsPTV margins of 0.4 cm, 0.4 cm and 0.7 cm left–right (LR), superior–inferior (SI) and anterior–posterior (AP) respectively were derived for the pelvic lymph nodes when registering to prostate. PTV margins of 0.3 cm, 0.2 cm and 0.4 cm LR, SI and AP respectively were derived for the pelvic lymph nodes when registering to bone. There was a posterior systematic shift of the prostate during the treatment course.ConclusionThere is differential motion of pelvic lymph nodes to prostate and in the era of prostate and pelvic radiotherapy for patients with node positive prostate cancer; there is increasing importance in the accuracy of dose delivery to the involved lymph node. Hence, this group of patients may benefit from personalised radiotherapy PTV margins, especially if the involved pelvic lymph node is within the anterior part of the clinical target volume.Implications for practiceOptimisation of dose delivery to the pelvic lymph nodes when prioritising the prostate in prostate and pelvic lymph node image guided radiotherapy.     

Multifield optimization intensity-modulated proton therapy (MFO-IMPT) for prostate cancer: Robustness analysis through simulation of rotational and translational alignment errors

To evaluate the dosimetric consequences of rotational and translational alignment errors in patients receiving intensity-modulated proton therapy with multifield optimization (MFO-IMPT) for prostate cancer. Ten control patients with localized prostate cancer underwent treatment planning for MFO-IMPT. Rotational and translation errors were simulated along each of 3 axes: anterior-posterior (A-P), superior-inferior (S-I), and left-right. Clinical target-volume (CTV) coverage remained high with all alignment errors simulated. Rotational errors did not result in significant rectum or bladder dose perturbations. Translational errors resulted in larger dose perturbations to the bladder and rectum. Perturbations in rectum and bladder doses were minimal for rotational errors and larger for translational errors. Rectum V45 and V70 increased most with A-P misalignment, whereas bladder V45 and V70 changed most with S-I misalignment. The bladder and rectum V45 and V70 remained acceptable even with extreme alignment errors. Even with S-I and A-P translational errors of up to 5 mm, the dosimetric profile of MFO-IMPT remained favorable. MFO-IMPT for localized prostate cancer results in robust coverage of the CTV without clinically meaningful dose perturbations to normal tissue despite extreme rotational and translational alignment errors.     

Acute skin toxicity in Korean breast cancer patients carrying BRCA mutations

Abstract

Purpose: In contrast to in vitro studies, most clinical trials testing the radiosensitivity of BRCA (Breast cancer susceptibility gene) mutations do not find a correlation between BRCA status and enhanced radiosensitivity. These trials include different ethnicities, and there is a lack of clinical data on BRCA1/2 mutation carriers and radiosensitivity in non-Caucasian patients. The goal of this study was to investigate acute skin toxicity, as a part of radiosensitivity, in breast cancer patients with BRCA1/2 mutations.

Material and methods: BRCA mutation analysis was performed for 213 patients who underwent breast-conserving therapy using radiotherapy. Skin toxicity was scored according to the Radiation Therapy Oncology Group (RTOG) criteria during treatment and during one-month follow-up after radiation therapy.

Results: Forty-six patients had BRCA1/2 mutations and 57 patients showed higher than grade 2 (RTOG) skin toxicity. In multivariate analysis, significant associations were found between mean breast volume and acute skin toxicity. BRCA mutation status, however, failed to show a significant correlation.

Conclusions: Our results indicate that carriers of BRCA1/2 mutations among non-Caucasian breast cancer patients showed no enhancement in radiation sensitivity. Multiple genetic markers may be correlated with normal tissue responses after radiotherapy. Further studies are needed to identify genetic predispositions to normal tissue responses after radiotherapy.