食管内置网状金属支架对放射治疗剂量的影响

目的：研究食管内置金属支架对放射治疗剂量的影响,以便在临床应用中进行适当修正。方法：采用热释光元件测量,测量探测器为国产Fj-427A热释光剂量仪,热释光元件为LiF(Mg,P,Cu)片状型剂量元件。分别测量两种（进口及国产）,食管内置网状金属支架及未放支架的石蜡体模,测量支架周围（即食管粘膜处）的剂量并与无支架时食管中心点的剂量进行比较。结果：国产支架单野垂直照射时沿射束方向,支架前点和后点对^60Co γ射线和416MV X射线剂量增加分别为16．2％和7．8％、15．4％和6．8％、12．8％和5．8％,进口支架单野垂直照射量增加分别为13．0％和7．0％及11．7％和6．0％,8．5％和3．2％;前后两野对穿照射剂量增加11．7％－24．0％,3个野交角照射支架周围（食管粘膜）均增加3．2％－16．2％。结论：置放食管网状金属支架后进行常规放射治疗时,单次剂量最好≤1．7Gy,前后对穿野照射时≤1．5Gy,建议使用直径＜1．5cm支架,选用3个野交叉照射。     

金属植入物对放射治疗剂量影响的研究

目的:测量金属内固定支架对放射治疗剂量的影响,对采用金属内固定的肿瘤患者放射治疗提供剂量修正的临床数据。方法:按照测量条件,将带有金属内固定支架的体模在螺旋CT下进行扫描,层厚为5mm,图像通过LANTIS网络传输系统传入放射治疗计划系统(treatment planning system,TPS)中进行模拟计算。按照相同条件,分别用6MV和15 MVX线照射,用热释光剂量仪和FAMER型电离室对钛镍合金支架界面以及界面上下一定深度分别测量,并与放射治疗计划系统计算结果比较。结果:实际测量与TPS计算存在一定误差,实测值明显大于TPS计算值,支架前表面的误差最大可达3.9%(6MV)和6.6%(15MV),支架后表面的误差最大为2.8%(6MV)和6.3%(15MV),距表面距离越远,误差越小。结论:镍钛合金支架患者放射治疗时,实际测量剂量比TPS计算剂量要大,有可能增加放射性损伤。TPS计算过程中,虽然对金属物进行了密度修正,但仍存在一定误差,有必要在制订放疗计划时对照射剂量进行修正。     

金属植入物对放射治疗剂量影响的研究

目的：测量金属内固定支架对放射治疗剂量的影响,对采用金属内固定的肿瘤患者放射治疗提供剂量修正的临床数据。方法：按照测量条件,将带有金属内固定支架的体模在螺旋CT下进行扫描,层厚为5mm,图像通过LANTIS网络传输系统传人放射治疗计划系统（treatment planning system,TPS）中进行模拟计算。按照相同条件,分别用6MV和15MVX线照射,用热释光剂量仪和FAMER型电离室对钛镍合金支架界面以及界面上下一定深度分别测量,并与放射治疗计划系统计算结果比较。结果：实际测量与TPS计算存在一定误差,实测值明显大于TPS计算值,支架前表面的误差最大可达3．9％（6MV）和6．6％（15MV）,支架后表面的误差最大为2．8％（6MV）和6．3％（15MV）,距表面距离越远,误差越小。结论：镍钛合金支架患者放射治疗时,实际测量剂量比TPS计算剂量要大,有可能增加放射性损伤。TPS计算过程中,虽然对金属物进行了密度修正,但仍存在一定误差,有必要在制订放疗计划时对照射剂量进行修正。     

食管内支架置入术联合放射治疗晚期食管癌临床探讨

目的:评价食管内支架置入术联合放射治疗晚期食管癌的临床可行性和疗效.方法:67例晚期食管癌伴狭窄患者分别行食管内支架置入术和支架联合放射治疗,比较食管内支架置入术组(A组)和食管内支架置入术联合放射治疗组(B组)患者的生存率和并发症发生率.结果:A组3、6、9、12个月的生存率分别为86.05%、67.53%、39.77%、14.71%:B组分别为87.49%、72.58%、53.14%、30.04%,两组差异无显著性(P=0.156 2).并发症总体发生率B组高于A组.A组再狭窄,返流性食管炎发生率明显高于B组(P＜0.05).结论:晚期食管癌伴狭窄患者支架置入术联合放射治疗未能明显提高生存率,但降低了狭窄和返流性食管炎的发生率.     

金属下颌骨修复板对界面组织放射剂量分布影响的研究

目的 :测量下颌骨修复板前、后相邻组织的放射剂量分布。材料与方法 :将钛和不锈钢下颌骨修复板插入体模 ,用60 Coγ射线照射实验模型 ,氟化锂热释光法对比测量两种金属板与不同距离的体模界面之百分放射剂量。结果 :发现射线从单方向进入时 ,“前”界面剂量增高 ,“后”界面剂量减低 ,剂量增高和减低主要发生在 3mm厚的组织范围内 ,钢板引起剂量变化的量高于钛板。采用两个平行野相对照射 ,金属板对界面剂量分布的影响得到互补。结论 :用 60 Co- γ射线时 ,钛板修复下颌骨缺损后是可以安全进行放射治疗的。     

腔内外联合放射治疗食管癌临床疗效分析

目的　探索 6MV医用直线加速器配合192 Ir后装治疗机治疗食管癌的临床疗效。方法　分析我科自 1994年 2月至 1998年 5月对已确诊的食管癌病人中 ,抽出病变位于胸段、病变长度≤ 8cm的病人 96例 ,随机分为两组 ,一组采用 6MV医用直线加速器配合192 Ir后装治疗机治疗 (以下简称联合放射治疗 )食管癌 48例与另一组同期采用 6MV医用直线加速器单纯外照射治疗食管癌 48例作对照研究 ,比较二者 1、3年生存率。结果　联合放射治疗组 1、3年生存率分别为 72 9%、3 1 3 % ,而单纯外放射治疗组 1、3年生存率分别为 5 6 3 %、2 2 9%。二者比较有显著性差异 (P <0 0 5 ) ;联合放射治疗组局部复发率低于单纯外放射治疗组。结论　腔内外联合放射治疗食管癌疗效明显优于单纯外放射治疗 ,可见 6MV医用直线加速器配合192 Ir后装治疗机治疗食管癌是临床上较好的治疗方法     

空腔和非均匀组织对不同照射技术的剂量学影响

目的 使用仿真人体模型,研究空腔及非均匀组织结构对不同照射技术的剂量学影响。方法 利用成都剂量体模,制作具有4 cm×4 cm×3 cm空腔结构的头颈部模体和胸部切片肺组织模体,按照实际治疗流程进行定位CT扫描和模拟定位机复位,在空腔和非均匀组织结构边界处及其内部粘贴3.2 mm×3.2 mm×0.8 mm超薄型热释光剂量片,采用不同照射技术设计治疗计划并在直线加速器上进行实际照射,对热释光剂量片数值进行分析。结果 头颈部仿真模体,单野、两野对穿和7个野IMRT计划照射测量结果均存在显著的空腔效应,并且随射野增加和放疗技术的复杂性,空腔效应有减小趋势;对胸部肺组织仿真模体,也存在类似空腔效应。结论 对人体组织内部空腔结构或非均匀组织结构,设计计划时应考虑空腔效应影响,给予更多射野或使用更加复杂的照射技术来减小空腔效应影响。     

镍钛合金支架置入术联合放射治疗晚期食管癌临床研究

目的 :评价食管镍钛合金支架置入术联合放射治疗晚期食管癌的临床可行性和疗效。方法 :对 88例晚期食管癌并穿孔、瘘、狭窄病人分别行镍钛合金带膜支架置入术和支架联合放射治疗 ,比较单纯支架治疗和联合放射治疗病人的生存率和疗效 ;观察JMZ型镍钛合金支架对放射治疗射线分布的影响。结果 :① 6、9、12个月的生存率联合放射治疗组病人分别为 77.3 %、52 .3 %、3 1.8% ,单纯支架组分别为 79.5%、50 .0 %、13 .6% ,两组比较无统计学意义 (P >0 .0 5) ,但合并症联合放疗组高于单纯支架组 ;②食管癌伴狭窄病人 12、2 4个月生存率联合放疗组分别为 73 .6%、3 6.8% ,单纯支架组分别为 3 0 %、0 ,两组比较有显著差异性 (χ2 =18.9841,P =0 .0 0 0 1) ;③JMZ型镍钛合金支架对食管癌放射治疗剂量分布影响在± 2 %左右。结论 :晚期食管癌合并穿孔、瘘病人支架置入术联合放射治疗不能提高生存率 ,而且增加合并症 ;支架置入术联合放射治疗可应用于合并食管狭窄的病人 ,提高一、二年生存率 ,值得临床进一步研究 ;JMZ型镍钛合金支架对食管放疗剂量无明显影响     

91例骨转移癌的放射治疗

目的　探讨放射治疗骨转移癌的止痛效果。方法　采用在模拟机下定位 ,直线加速器 6MV -X线及60 Coγ线体外照射。结果　放射治疗止痛和总有效率为 89% ,不同放射剂量、分割方式对骨转移癌痛均有效。结论　放射治疗止痛效果、疗效确切可靠 ,可作为癌性疼痛主要的止痛方法或首选方法。     

18例晚期食管癌支架置入术合并放疗的临床疗效

目的:探讨食管支架置入术合并放射治疗对晚期食管癌的价值.方法:回顾性地分析了18例未手术的晚期有明显梗阻的食管癌患者,全部均先行支架置入术,后行局部放射治疗,剂量DT50～66Gy.结果:所有患者吞咽梗阻症状都明显缓解,16例病人生存在半年以上,有6例病人生存已超过1年.结论:食管支架置入术能明显改善患者的进食状况,为进一步放射治疗提供机会.     

Radiotherapy dose perturbation of metallic esophageal stents

PURPOSE: Metallic esophageal stents frequently present during the treatment of esophageal cancer while using either external beam radiotherapy or brachytherapy. The dosimetric effects due to these metallic stents have not been reported. This work investigates these dose effects for various stent models presented during a radiotherapy procedure. METHODS AND MATERIALS: Two types of representative stent models, shell and ring stents, with various designs (e.g., composition and shell thickness or ring spacing), were studied. Three Monte Carlo code systems (EGS4/BEAM, EGSnrc/DOSRZnrc, and MCNP) were used to calculate the dose distributions for 6- and 15-MV external photon beams and for a (192)Ir brachytherapy source with and without a metallic esophageal stent in place. RESULTS: For a single external beam, a dose enhancement is generally observed in front of the stent (upstream) in the region within 4-mm distance of the stent surface. The enhancement at 0.5-mm distance from the stent surface can be as high as 20%. The dose behind the stent (downstream) is generally reduced. For a parallel-opposed pair (POP), a dose enhancement is always observed in the region within 3-mm distance of the stent surface. The enhancement at 0.5-mm distance from the stent surface can be as high as 10% for the 15-MV POP and 8% for the 6-MV POP. The dose effects depend on stent design (e.g., composition, thickness of shell stent, or ring spacing in ring stents). This dependence is reduced for a POP. In the case of the (192)Ir brachytherapy source, a dose enhancement is observed in the region within 1-mm distance from the stent surface. The dose enhancement is approximately 5% at 0.5-mm distance from the stent surface. CONCLUSION: The dose perturbations due to the presence of a metallic esophageal stent during the treatment of esophageal cancer while using either external beam radiotherapy or brachytherapy should be recognized. These perturbations result in an overdose in esophageal mucosa. The overdose is within 5%-10% at a depth of 0.5 mm in the esophageal wall.     

两种国产可伸展型食管金属内支架的比较和选择

通过对46例食管良、恶性挟窄置放50例/次国产可伸展型食管金属内支架的临床应用,报告了两种目前国内常见的金属内支架的结构和临床使用特点。其中.镍钛记忆合全支架是采用高度记忆特性的镍钛合金材料,进行特殊工艺处理后制成,该支架柔韧性好,扩张效果确切;带膜不锈钢支架用医用不锈钢丝,按一定的力学原理编织而成,有一定的膨胀性。特别是支架内外被复一层硅橡胶膜,具有屏障作用。因此。作者认为,镍钛记忆合金支架适用于各种疤痕挛缩和短段肿瘤病灶造成的食管狭窄;而带膜不锈铜支架适用于晚期肿瘤或术后瘤复发造成的狭窄,对于晚期食管癌并发食管气管瘘者具有良好的堵瘘效果。     

两种国产金属支架在治疗食管良恶性狭窄应用中的比较

目的:作者分析了63例食管内支架术的结果,旨在选择理想的金属支架.方法:本组63例食管良、恶性狭窄,使用2种支架材料,共安放69根,其中不锈钢支架19根、镍钛合金支架50根.结果:国产金属支架治疗食管良、恶性狭窄安全有效,又以镍钛合金被覆细腰喇叭形支架为最好,成功率高、副作用少.结论:镍钛合金支架优于不锈钢支架,在采用腔内支架治疗食管良、恶性狭窄中,应首选镍钛合金被覆细腰喇叭形支架.     

Feasibility study of entrance in vivo dose measurements with mailed thermoluminescence detectors.

BACKGROUND AND PURPOSE: The aim of this work is to set-up mailed entrance in vivo dosimetry by means of thermoluminescence dosimeters (TLDs) in the form of LiF powder in order to assess the overall accuracy of patient treatment delivery by comparing the doses delivered to patients with the doses calculated by the treatment planning system (TPS) in different institutions. PATIENTS AND METHODS: Two millimeter thick copper (for 6 MV photon beams) and 1.3 mm thick aluminium (for (60)Co gamma beams) build-up caps are developed. The characteristics of these build-up caps are tested by phantom measurements: the response of the TLD inside the build-up cap is compared to the ionisation chamber (IC) signal in the same irradiation conditions. A pilot study using the copper build-up cap is performed on 8 patients, treated with a 6 MV photon beam at the radiotherapy department of the University Hospital of Leuven. Additionally, a first run of mailed entrance in vivo dosimetry is performed by 18 radiotherapy centres in Europe. RESULTS: For 80 different phantom set-ups using copper and aluminium build-up caps, the mean TLD dose compared to the IC dose is 0.993+/-0.015 (1SD). Regarding the patient measurements in the radiotherapy department of the University Hospital of Leuven, the mean ratio of the measured entrance dose (TLD) to the entrance dose calculated by the TPS, is equal to 0.986+/-0.017 (1SD) (N=8), after correction of an error detected in one of the patient treatments. For the 18 radiotherapy centres participating in the mailed in vivo TLD study, the mean measured versus stated entrance dose for patients treated in a (60)Co and 6 MV photon beam is 1.004+/-0.021 (1SD) (N=143). CONCLUSIONS: From the results, it can be deduced that the build-up caps and the proposed calibration methodology allow the use of TLD in the form of powder to be applied in large scale in vivo dose audits.     

Build-up modification of commercial diodes for entrance dose measurements in 'higher energy' photon beams.

BACKGROUND AND PURPOSE: Several commercially available p-type diodes do not provide sufficient build-up for in-vivo dosimetry in 'higher' energy photon beams, and only limited information could be found in the literature describing the correction factor variation and/or the achievable accuracy for in-vivo dosimetry methods in this energy range. The first aim of this study is to assess and analyze the variation of diode correction factors for entrance dose measurements at higher photon energies. In a second step the total build up thickness of the diode has been modified in order to minimize the correction factor variation. MATERIALS AND METHODS: Diode correction factors accounting for non-reference conditions (field size, source surface distance, tray, wedge, and block) are determined in 18-25 MV photon beams provided by different treatment units for Scanditronix p-type diodes recommended for higher energy photon beams: old type and new type EDP-20, and EDP-30 diodes. Hemispherical build-up caps of different materials (copper, iron, lead) are used to increase the total build-up thickness. Perturbation effects with and without additional build-up caps are assessed for the three diode types. RESULTS: For unmodified diodes field size correction factors (C(FS)) vary between 1.7% and 6%, dependent on diode type and treatment unit. For example, for an old type EDP-20 the C(FS) variation at 18 MV is much higher on a GE linac (5%) as compared to the Philips machine (1.7%). Depending on diode type, this variation can be reduced to 1-2% when adding additional build-up. The variation of source to surface distance correction factors is almost independent of build-up thickness. By adding additional build-up the influence of trays and blocks can be almost eliminated. CONCLUSIONS: The correction factor variation of unmodified diodes reflects the variation of the electron contamination with treatment geometry. A total build-up thickness of 30 mm is found to be the 'best compromise' for the three types of diodes investigated when measuring entrance doses in the energy range between 18 and 25 MV.     

内支架置入对中晚期食管癌治疗价值的评估

目的采用内支架置入的方法对中晚期食管癌进行姑息性治疗,观察其疗效及不良反应.方法18例中晚期食管癌患者中,手术后吻合口肿瘤复发4例,合并食管-气管瘘及食管-纵隔瘘各1例.18例中晚期食管癌患者经食管造影显示狭窄段管腔直径均小于5mm,均先行球囊扩张,后置入支架.结果随访18个月,1例2个月后死于食管-气管瘘合并肺内感染,另1例6个月后死于消化道大出血.2例再狭窄后行放射治疗,其余患者均未出现进食障碍.结论内支架置入对中晚期食管癌治疗效果明显,操作简单、安全,无严重并发症,值得临床推广.     

面罩对不同射线治疗剂量影响的探讨

目的：测量在光子线及电子线照射下面罩对治疗剂量的影响。方法：采用PIW Marcus 23343型平行板电离室在专用的有机玻璃模体（PMMA）中测量光子线建成区别剂量的变化情况，采用Bruce等介绍的经验公式对测量结果进行修正，采用三维水箱测量电子线射野中心轴百分深度剂量，并利用平行板电离室对特定深度进行验证，结果：加上面罩后，8MV光子线建成区剂量有明显增加，近表面处相对增加约25％左右，8、12和15MeV的电子线的中心轴百分深度剂量曲线则普遍前移。结论：对于光子线主要考虑的是近表面建成区剂量的改变；对电子线则要考虑由于百分深度量前移而可能影响治疗靶区的最小剂量。三维适放射治疗中要注意治疗治疗计划系统（TPS）的计算结果是否考虑面罩对治疗剂量的影响。     

Three-dimensional photon dose distributions with and without lung corrections for tangential breast intact treatments

The influence of lung volume and photon energy on the 3-dimensional dose distribution for patients treated by intact breast irradiation is not well established. To investigate this issue, we studied the 3-dimensional dose distributions calculated for an 'average' breast phantom for 60Co, 4 MV, 6 MV, and 8 MV photon beams. For the homogeneous breast, areas of high dose ('hot spots') lie along the periphery of the breast near the posterior plane and near the apex of the breast. The highest dose occurs at the inferior margin of the breast tissue, and this may exceed 125% of the target dose for lower photon energies. The magnitude of these 'hot spots' decreases for higher energy photons. When lung correction is included in the dose calculation, the doses to areas at the left and right margin of the lung volume increase. The magnitude of the increase depends on energy and the patient anatomy. For the 'average' breast phantom (lung density 0.31 g/cm3), the correction factors are between 1.03 to 1.06 depending on the energy used. Higher energy is associated with lower correction factors. Both the ratio-of-TMR and the Batho lung correction methods can predict these corrections within a few percent. The range of depths of the 100% isodose from the skin surface, measured along the perpendicular to the tangent of the skin surface, were also energy dependent. The range was 0.1-0.4 cm for 60Co and 0.5-1.4 cm for 8 MV. We conclude that the use of higher energy photons in the range used here provides lower value of the 'hot spots' compared to lower energy photons, but this needs to be balanced against a possible disadvantage in decreased dose delivered to the skin and superficial portion of the breast.