后装施源器Offset值验证研究

目的 研究后装治疗中多种施源器的Offset值。方法 选取插植钢针(Part#083.062)、插植塑料圆针(Part#189.608)、插植塑料尖针(Part#189.601)、多通道施源器软管(Part#110.800)、塑料宫腔管(Part#189.745)、金属宫腔管(Part#110.437)施源器。根据源在荧光胶片放射性成像,确定施源器顶端驻留点位置以及到施源器顶端的距离。在施源器顶端驻留点位置贴铅珠,将施源器置入盆腔体模中进行CT扫描。然后在计划系统中重建施源器,通过调整Offset值使铅珠与施源器顶端驻留点对准,从而得到施源器Offset值。塑料材质施源器由于密度与人体组织接近,施源器顶端难以准确重建,因此利用挡块或者假源重建施源器,得到塑料材质施源器Offset值。根据验证结果分析比较不同施源器Offset值差异。结果 不同施源器Offset值存在较大差异,其中插植钢针为-11.4 mm,插植塑料圆针为-4.1 mm,插植塑料尖针为-3.5 mm,多通道施源器软管为0 mm或-5.0 mm,塑料宫腔管为-6.5 mm,金属宫腔管为-7.5 mm。结论 为了适应精确放疗的发展趋势,有必要对后装中施源器Offset值进行测量验证。     

用新鲜子宫及阴道标本检测曼彻斯特系统剂量分布

目的：检测宫颈癌近距离放疗中曼彻斯特系统剂量分布,为质量控制及质量保证提供依据。方法：特制一双面模板,把插植针及软管放入槽内,夹入慢感光X光片,检测放射源的到位精度 ,把软管放入检测孔,电离室放在离源10cm处空气中测量放射源的活度,水箱中不放标本测量A点及其外1cm,2cm,3cm剂量,然后放入子宫及直管施源器,电离室放在A点外1cm,2cm,3cm处,执行2个后装治疗计划,测量各点的剂量,并与TPS推算值比较。结果：经检测,软管施源器的源到位误差约2-3mm,通过调整施源器的长度,源的到位精度在1mm内,源的顶端与插植针焊接点的距离约5mm,源活度实测与TPS推算值相差5.4%,各点的剂量学实测与TPS推算值关系复杂,水箱内无标本时实测偏差在6%内,放入子宫标本时测量误差最大为13.86%。A点外1cm,2cm,3cm剂量比值与理想平方反比定律比值偏差最大为8.01%。结论：TPS推算值与实测值偏差较小,说明目前临床使用的曼彻斯特系统结果可信。     

宫颈癌腔内联合组织间插植近距离放疗施源器模板的应用

目的设计适用于局部晚期宫颈癌的腔内联合组织间插植近距离放疗(IC-ISBT)施源器模板, 并评估其应用价值。方法收集2019年3月至2020年9月中山大学肿瘤防治中心收治的100例ⅡB-ⅣA期(国际妇产科协会2018分期)宫颈癌患者的外照射前后磁共振影像资料, 对宫颈原发病灶范围进行回顾性阅片分析对比。基于外照射后肿物残留情况, 勾画近距离放疗高危临床靶区(HR-CTV), 设计腔内联合组织间插植近距离放疗(IC-ISBT)的施源器模板, 并进一步评估施源器模板插植组(37例)与徒手插植组(63例)治疗宫颈癌的剂量和疗效差异。分类变量采用卡方检验或Fisher精确检验, 连续变量采用t检验或U检验。结果 100例宫颈癌患者外照射后残留肿物边缘按顺时针3、6、9、12点方向与宫颈管中心的距离中位数为16.5、14.0、17.0、13.0 mm。将对应的HR-CTV叠加重建三维图, 设计制作蘑菇头圆柱体式IC-ISBT施源器模板:头部长径为35 mm, 短径为20 mm, 中心适配宫腔管, 内圈C1-C12为表盘式排列, 两侧拓展B1-B5及A1-A4针道。在剂量方面, 模板插植组与徒手插...     

环形施源器重建偏差对宫颈癌患者剂量影响分析

目的 研究在CT引导的三维后装中环形施源器(Nucletron#090.617)重建偏差对宫颈癌患者后装受照剂量的影响。方法 选取已完成治疗的根治性宫颈癌患者20例,在计划系统中模拟宫腔施源器,环形施源器和两者同时发生重建偏差时的剂量分布,重建偏差的方向分为施源器顶端方向(+)和施源器连接方向(-),重建偏差模拟±1、±2、±3 mm。统计CTV的D₁₀₀、D₉₀、D₅₀,膀胱、直肠、小肠的D_0.1cc、D_1cc、D_2cc,分析施源器重建偏差对三维后装剂量的影响。结果 宫腔施源器重建偏差对剂量的影响高于环形施源器。对于CTV评价参数,由施源器重建偏差导致的剂量偏差随统计体积的增大而增大。对于OAR评价参数,由施源器重建偏差导致的剂量偏差随统计体积的增大而减小。小肠剂量受施源器重建偏差影响最大。对CTV D₉₀、膀胱D_2cc、直肠D_2cc、小肠D_2cc,当环形施源器,宫腔施源器,二者同时发生3 mm重建偏差时产生的影响偏差分别为0.90%、1.62%、1.74%,1.33%、1.53%、1.78%,0.89%、1.85%、1.97%,0.86%、3.04%、3.50%。结论 三维后装中施源器重建偏差会对剂量产生一定的影响,为提高后装放疗的精确性,需要对施源器重建过程进行全面质量控制。     

鼻咽癌后装腔内放疗个体化施源器剂量学分析

目的:评估热塑面罩固定鼻咽个体化施源器剂量的准确性及其应用价值.方法:选择10例后装放疗患者,分别制作鼻咽个体化施源器并使用面罩固定.每次治疗前均行CT扫描,并在计划系统中重建出施源器位置,获取铱源驻留位点坐标,通过与计划CT比较,计算出施源器位移偏差,进而评估后装治疗剂量的准确性.结果:非面罩固定最远端源驻留位点(P1)平均偏差在X、Y、Z三个方向为(1.62士0.24)、(2.32士0.22)和(2.50士0.28)mm,近端(P5)为(1.13±0.11)、(1.22±0.20)和(1.80±0.15)mm.经面罩固定后个体化施源器最远端源驻留位点(P1)平均位移则分别为(0.82±0.06)、(0.70±0.07)和(0.94±0.08) mm,近端(P5)为(0.70士0.02)、(0.46土0.01)和(0.60土0.03)mm.面罩固定施源器位移偏差导致的感兴趣点(源旁2 cm)剂量误差＜1.2％.结论:使用热塑面罩固定个体化施源器剂量准确,适合鼻咽癌腔内后装治疗.     

三维后装治疗计划快速质量保证方法建立

目的 研究后装治疗计划中肿瘤大小、放射源强度、处方剂量与源驻留时间的相关关系,建立一种可用于对后装计划快速质控的方法。方法 选取在本院治疗的181例妇科肿瘤患者计划,分别为Fletcher施源器全部三管84例,单独宫腔管58例和阴道施源器39例。每例患者治疗前扫描CT,并由医生勾画靶区和危及器官,治疗计划使用IPSA优化。记录每一例计划的源强,处方剂量,源驻留时间和接受处方剂量的肿瘤体积,计算适形度指数(CI)和剂量时间之积并与体积相关参数(Rv)的k值,分析CI分布特点及与Rv值的相互关系。另外46例妇科肿瘤患者后装计划使用该方法做质控验证。结果 三种施源器的后装计划的适形指数均呈正态分布,Fletcher施源器CI的平均值为0.720±0.067,k=1 394,R=0.894,Fletcher施源器单独宫腔管CI的平均值为0.697±0.076,k=1 428,R=0.940,阴道施源器CI的平均值为0.742±0.067,k=1 362,R=0.909。结论 使用该方法可以快速评估计划的靶区体积,放射源强度,处方剂量与治疗时间是否匹配,根据反馈的结果查找偏差原因,保证后装治疗计划按照临床要求,高效快速准确的实施。     

施源器对192Ir源近距离治疗剂量的影响

目的 研究不同施源器对¹⁹²Ir源近距离治疗剂量分布的影响。方法 核通公司#101.001、#084.350柱形施源器内管分别为塑料和不锈钢,串球为塑料,串球半径为1.00、1.25、1.50、1.75 cm。利用EGSnrc程序模拟体模中有施源器时的剂量分布,对比计划系统计算结果,分析材料、厚度和源驻留点个数不同情况下施源器对剂量分布影响。结果 由两种施源器产生的剂量偏差与施源器半径之间无明显关系,有施源器存在时患者实际受量比计划量小,施源器#101.001产生的剂量偏差≤1%,施源器#084.350产生的剂量偏差接近3%,改变驻留点个数剂量偏差保持不变。结论 对现阶段近距离治疗,在条件允许情况下尽量选用塑料材质施源器,长远来看为提高近距离治疗精确性,对现有剂量计算算法进行改进,考虑含有不锈钢等金属施源器对剂量分布的影响。     

经鼻咽旁插植组织间后装治疗在鼻咽癌放疗后程加量中的应用

背景与目的:后装近距离治疗常常用于早期鼻咽癌放射治疗后程加量,但常规施源器置入方法定位不准、重复性差,无法向咽旁追量.本研究采用存鼻窦内窥镜引导下进行咽旁插植后装放疗的新方法,旨在解决常规后装治疗的上述缺陷.方法:选择2005年9月至2006年8月初治和复发鼻咽癌外照射后仍有鼻咽粘膜下肿瘤残留超过1 cm或/和咽旁浸润但侵犯范围较局限的患者23例,在鼻窦内窥镜引导下经鼻腔进行鼻咽及咽旁施源器插植术,术后经CT扫描定位并确认插植位置合格后,利用三维近距离治疗系统进行鼻咽、咽旁肿瘤靶区勾画、剂量优化和组织问近距离治疗,测量治疗前后施源器植入的深度,并观察近距离治疗的疗效及并发症.结果:施源器均准确插入肿瘤区,插植位置100%合格.插人和拔出施源器时粘膜下植入深度分别为(9.59±2.72)mm和(9.43±2.30)mm,两者差异无统计学意义(t=0.23,P＞0.05);漂移长度为(0.75±0.75)mm.治疗后3个月内肿瘤完全消失,无肿瘤局部复发,无远处转移.随访3～15个月(中位随访时间6个月),随访率100%,无大出血、感染等手术并发症,无腭穿孔、鼻咽坏死等严重后装放疗并发症;3例鼻甲粘连,经分解后完全缓解.结论:经鼻窦内窥镜鼻咽、咽旁插植定位准确,固定良好,安全可行;对鼻咽癌放疗后鼻咽、咽旁残留病灶进行组织问近距离治疗近期疗效良好,无严重近期并发症.     

驻留点权重标准差与施源器位置不确定性对宫颈癌患者剂量影响分析

目的 研究三维后装中驻留点权重标准差与施源器位置不确定性对宫颈癌患者受量影响。方法 选取已完成治疗的根治性宫颈癌患者20例,均使用Fletcher施源器(Nucletron#189.730),基于原CT图像和结构信息,重新设定一组新计划,记录原计划和新计划中驻留点权重并计算驻留点权重标准差(DWSD),按照DWSD大小患者2个计划被分成高低两组,即LDWSD组(0.141~0.299)和HDWSD组(0.211~0.337),利用Oncentra^® Brachy V4.3计划系统模拟Fletcher施源器中宫腔施源器,阴道施源器发生±1 mm位移时的剂量分布。统计CTV的D₁₀₀、D₉₀和V₁₅₀,、膀胱、直肠、小肠的D_0.1cc、D_1cc和D_2cc,分析DWSD与施源器位置不确定性对三维后装剂量的影响。结果DWSD越大,由施源器位置不确定性产生的剂量偏差就越大。当宫腔施源器、阴道施源器发生1 mm位移时,CTV的HDWSD组D₁₀₀、D₉₀、V₁₅₀比LDWSD组分别高3.0%、23.8%、4.8%和0.5%、1.2%、5.2%,膀胱、直肠、小肠HDWSD组D_0.1cc、D_1cc、D_2cc都高于LDWSD组,其中小肠最明显,分别高44.0%、22.8%、16.8%和10.3%、14.4%、12.4%。结论 宫颈癌三维后装计划的评估应考虑驻留点权重因素,可以减小由施源器位置不确定导致的剂量偏差。     

乌德勒支施源器在宫颈癌3D-IGBT应用观察

目的 观察乌德勒支施源器在局部晚期宫颈癌3D-IGBT中的临床应用情况,揭示其在IC-IS的应用规律。方法 回顾分析45例接受根治性放疗的局部晚期宫颈癌患者,外照射后行3D-IGBT,其中45例130次IC-IS入组。将满足计划目标剂量分次定义为A组(37例86人次),余为B组(22例44人次),成组t检验差异。结果 施源器使用15、20、25 mm卵圆体的频率分别为50.0%、20.0%、30.0%,30 mm型号无使用。共置插植针499根,6、7、10、11孔位使用频率分别为23.1%、21.2%、21.2%、24.1%。A组平均插植针数为3.7根明显少于B组4.2根(P=0.008)。A组的HR-CTV平均体积为(40.71±18.43) cm³小于B组(51.81±14.74) cm³(P=0.001),A组HR-CTV的宽和高小于B组(P=0.011、0.006);而厚相似(P=0.595)。高与插植深度的差两组相似(P=0.366),宽与左右针孔间距的差A组小于B组(P=0.007)。结论 局部晚期宫颈癌行IC-IS时,乌德勒支施源器的卵圆体多选用25 mm及以下型号,插植孔位多选用6、7、10、11号。在插植针数≥4根、深度≥3 cm时,宽度是影响计划剂量的主要因素。     

3D打印多通道施源器在宫颈癌术后患者近距离治疗中研究北大核心CSCD

目的比较3D打印多通道施源器与常规阴道单通道施源器用于近距离治疗的剂量学差异,为宫颈癌术后患者的近距离治疗提供一定的指导依据。方法选取25例自2019年1月—2020年11月接受^(192)Ir高剂量率近距离治疗的宫颈癌术后合并阴道上皮内瘤变Ⅲ级的患者,每位患者均采用3D打印多通道施源器和常规阴道单通道施源器进行CT扫描定位,并制定相应计划及评估,运用逆向剂量优化算法计算后得出剂量体积直方图,比较两组施源器用于近距离治疗时的高危临床靶区、膀胱及直肠受照剂量的差异,选择最优计划实施治疗。结果采用3D打印个体化多通道施源设计计划的D_(90)%、D_(100)%、V_(100)%、V_(150)%与常规单通道施源器设计的计划相比,差异均无统计学意义(P>0.05);膀胱、直肠的D2cm3与常规相比均明显降低,差异有统计学意义(均为P<0.05)。结论采用3D打印技术制作的多通道个体化施源器靶区适形性好,可更好地保护膀胱和直肠,有一定的治疗优势。     

Applicator reconstruction in MRI 3D image-based dose planning of brachytherapy for cervical cancer

Background and purpose

To elaborate a method for applicator reconstruction for MRI-based brachytherapy for cervical cancer.

Materials and methods

Custom-made plastic catheters with a copper sulphate solution were made for insertion in the source channels of MR-CT compatible applicators: plastic and titanium tandem ring applicators, and titanium needles. The applicators were CT and MR scanned in a phantom for accurate 3D assessment of applicator visibility and geometry. A reconstruction method was developed and evaluated in 19 patient MR examinations with ring applicator (plastic: 14, titanium: 5). MR applicator reconstruction uncertainties related to inter-observer variation were evaluated.

Results

The catheters were visible in the plastic applicator on T1-weighted images in phantom and in 14/14 clinical applications. On T2-weighted images, the catheters appeared weaker but still visible in phantom and in 13/14 MR clinical applications. In the titanium applicator, the catheters could not be separated from the artifacts from the applicator itself. However, these artifacts could be used to localize both titanium ring applicator (5/5 clinical applications) and needles (6/6 clinical applications). Standard deviations of inter-observer differences were below 2 mm in all directions.

Conclusion

3D applicator reconstruction based on MR imaging could be performed for plastic and titanium applicators. Plastic applicators proved well to be suited for MRI-based reconstruction. For improved practicability of titanium applicator reconstruction, development of MR applicator markers is essential. Reconstruction of titanium applicator and needles at 1.5 T MR requires geometric evaluations in phantoms before using the applicator in patients.     

Computed Tomography–Guided Optimization of Needle Insertion for Combined Intracavitary/Interstitial Brachytherapy With Utrecht Applicator in Locally Advanced Cervical Cancer

PurposeThere are no international guidelines for optimal needle insertion during interstitial intracavitary brachytherapy (IS-ICBT) for cervical cancer. We aimed to investigate the clinical feasibility and added value of computed tomography (CT) guidance to optimize needle insertion in IS-ICBT using the Utrecht applicator and to evaluate needle shifts.Methods and MaterialsWe enrolled 24 patients who were treated with interstitial-brachytherapy. Two CT scans each were performed for every patient: (1) after applicator insertion without needles (CT_preneedle) and (2) after needle insertion (CT_postneedle). In addition to magnetic resonance imaging after external-beam radiation therapy, CT_preneedle was used to determine optimal needle locations and insertion lengths based on applicator and organs at risk positioning on the day of treatment; CT_postneedle was used for IS-ICBT planning. The needle-channel axis was used as a reference to determine needle-shift evolution.ResultsA total of 266 interstitial needles were inserted in 76 of 93 BT fractions with high intra- and interpatient variations in the number of inserted needles. Based on CT_preneedle findings, needle insertion was avoided in 9, 4, 2, and 2 patients at the first, second, third, and fourth fractions, respectively. The unloaded needle frequency was 4%. Average needle contribution to total dwell time was 37.2% ± 19.2%. Shifting was observed in 68% of the needles (mean shift 2.0 ± 2.3 mm), mostly in the posterior direction, and in needles with a larger insertion length. Needle reinsertion was not needed in any patient. No complication due to needle insertion was observed, except for minor vaginal bleeding in 1 patient after needle removal.ConclusionsThe adaptive CT-guided IS-ICBT application was feasible and resulted in fewer unloaded needle insertions or complications and more efficient use with higher needle contribution to the treatment. Needle shift was frequent but did not require needle reinsertion with the proposed method.     

插植针植入棒在妇科肿瘤术后残端近距离腔内放疗的应用

目的 探讨自制插植针植入棒施源器在妇科肿瘤术后阴道残端近距离腔内放疗的可行性和安全性,评估其临床应用价值。方法 收集中山大学肿瘤防治中心收治的妇科肿瘤术后患者62例,所有患者均有术后放疗指征,需接受三维近距离后装放疗补量。根据患者阴道残端情况选用不同型号插植针植入棒模板,依照预设通道在模板内放置阴道管和插植针。按照统一标准勾画靶区及危及器官,制定放疗计划,高危临床靶区（HR-CTV）处方剂量为5.5 Gy/次,通过剂量体积参数图评估靶区和危及器官体积、受照剂量等参数。结果 62例患者均在插植针植入棒模板引导下顺利完成后装放疗,共行140次插植治疗,剂量参数HR-CTV包绕90%靶区体积的平均剂量D_90%为（575.48±22.30）cGy,包绕膀胱、直肠、乙状结肠2 cm³体积的平均剂量D_2cm³分别为（328.69±102.71）cGy、（369.14±46.59）cGy、（27.28±71.27）cGy,小肠未进入靶区照射范围无统计,靶区体积大小、危及器官剂量之间的差异具有统计学意义（P<0.05）。结论 插植针植入棒施源器在妇瘤术后残端近距离腔内放疗有明显临床优势,满足预计划剂量要求,操作简易,具有良好应用前景。     

插植针植入棒在妇科肿瘤术后残端近距离腔内放疗的应用

目的 探讨自制插植针植入棒施源器在妇科肿瘤术后阴道残端近距离腔内放疗的可行性和安全性,评估其临床应用价值。方法 收集中山大学肿瘤防治中心收治的妇科肿瘤术后患者62例,所有患者均有术后放疗指征,需接受三维近距离后装放疗补量。根据患者阴道残端情况选用不同型号插植针植入棒模板,依照预设通道在模板内放置阴道管和插植针。按照统一标准勾画靶区及危及器官,制定放疗计划,高危临床靶区（HR-CTV）处方剂量为5.5 Gy/次,通过剂量体积参数图评估靶区和危及器官体积、受照剂量等参数。结果 62例患者均在插植针植入棒模板引导下顺利完成后装放疗,共行140次插植治疗,剂量参数HR-CTV包绕90%靶区体积的平均剂量D_90%为（575.48±22.30）cGy,包绕膀胱、直肠、乙状结肠2 cm³体积的平均剂量D_2cm³分别为（328.69±102.71）cGy、（369.14±46.59）cGy、（27.28±71.27）cGy,小肠未进入靶区照射范围无统计,靶区体积大小、危及器官剂量之间的差异具有统计学意义（P<0.05）。结论 插植针植入棒施源器在妇瘤术后残端近距离腔内放疗有明显临床优势,满足预计划剂量要求,操作简易,具有良好应用前景。     

A fast algorithm for homogeneous Ir-192--afterloading irradiation of cylindrical surfaces

A fast algorithm was required to homogenise the dose on a cylinder mantle around a single straight applicator for Ir-192 afterloading. For linear applicators, an approximation formula for homogenisation of dose on one arbitrary cylinder mantle around the catheter is derived that predicts the required rise of dwell time tEnd at the end of the applicator. The other positions are loaded with a constant dwell time tMitte. The dwell time at the end tEnd appears to be independent of applicator length and can be described as a function of tMitte. In contrast to homogeneous loaded applicator, the dwell time in the central positions becomes also almost independent of catheter length, and is strictly proportional to the optimisation radius. TLD measurements and comparisons with a commercial planning system show the applicability of the procedure. This guarantees a homogeneous dose distribution even when modifications of the application length or optimisation distance become necessary. The algorithm can also be used to control the results of a planning system independently.     

Applicator reconstruction for HDR cervix treatment planning using images from 0.35 T open MR scanner

Background and purposes

Magnetic resonance (MR) imaging is widely recognised as the modality of choice for imaging soft tissue such as the target volume and critical structures relevant to high dose rate (HDR) brachytherapy of the cervix. This work sets out to assess some of the issues faced when introducing this technique clinically compared to the more widely used computed tomography (CT). MR can be used either as the sole imaging modality, or in conjunction with CT.

Materials and methods

Distortion of the images produced by the MR scanner was assessed with a geometrical phantom. Distortion local to the titanium applicators, introduced by the susceptibility of the applicators themselves, was also measured. The technique used to reconstruct applicators is briefly described. An inter-operator study was performed to assess the variability of applicator reconstruction between operators when MR images are used alone to reconstruct the applicators.

Results

A 14-cm cube within which distortion was less than 2 mm at all points was identified. The inter-operator study showed some variability in applicator reconstruction with both MR and CT (median MR/CT 1.3 mm/0.9 mm, range 0-3.6 mm/0-3.3 mm). Inter-operator variation in planning target volume (PTV) V100% and PTV D90% for MR/CT was 6.1%/3.0% and 7.4%/6.3%, respectively, and D_2cc OAR doses varied by up to 1.0 Gy between operators for both MR and CT.

Conclusions

In this study distortion was minimal within a defined volume and inter-observer errors were comparable on MR and CT when used to define applicators and when applied to dose-volume histograms (DVHs). However this does not assure the technique is appropriate with other scanners and applicator sets without further commissioning.