GZP型60Co近距离治疗源基于金属施源器剂量参数的蒙特卡罗研究

目的 研究金属施源器对GZP3型⁶⁰Co近距离治疗源剂量分布的影响,获得该源基于金属施源器的剂量学参数。方法 通过蒙特卡罗软件Geant4获得近距离治疗源周围(0~10 cm)的平均吸收剂量,并根据AAPM的TG43和TG43U1等报告推荐的计算公式获得该源基于金属施源器的剂量学参数。模拟中⁶⁰Co近距离治疗源位于半径为30 cm的球体水模中心。结果 获得基于金属施源器的GZP3型⁶⁰Co近距离治疗源1和2号通道的Λ为1.014 cGyh^-1U^-1(与无施源器相比分别偏差0.5%),3号通道的Λ为0.998 cGyh^-1U^-1(与无施源器相比分别偏差0.1%);中垂轴0.5~10.0 cm距离范围内的径向剂量函数,并获得该函数的拟合公式;角度0°~175°、距离0.5~10.0 cm范围内的各向异性函数。结论 本研究得到的基于金属施源器的剂量学参数为该源的临床使用提供更加精确的数据参考,在临床使用中应考虑金属施源器对于⁶⁰Co剂量分布的影响。     

热释光剂量仪测量体模植入125I粒子源的剂量学参数可行性

目的 探讨应用热释光剂量仪在体模中测量植入¹²⁵I粒子源(型号Sinko BT-125-1)的剂量学参数可行性。方法 将测量体模进行改进使其可适用于剂量学测量。根据AAPM TG43建议测量的参数包括剂量率常数Λ、径向剂量函数g_L(r)和各向异性函数F (r, θ)等,所测数据与文献中其他构造相似的¹²⁵I粒子源数据进行比较。结果 ¹²⁵I粒子源的Λ为0.928cGyh^－1U^－1。所测得的g_L(r)范围为径向距离在1.0~10.0 cm内所对应的值。F (r,θ)范围为角度在0°~90°内所对应的值。与型号Amersham 6711¹²⁵I粒子源相比,二者g_L(r)值的最大差异为9.6%。二者F (r=2 cm, θ=0)值的差异为10.2%。应用此体模进行测量总的不确定度<6.0%。     

儿童阴道横纹肌肉瘤60Co高剂量率三维后装治疗应用价值研究

目的 探讨⁶⁰Co高剂量率三维后装在儿童阴道横纹肌肉瘤放疗中的应用流程,并从剂量学角度分析可行性。方法 选取5例已行儿童阴道横纹肌肉瘤放疗患儿CT定位图像,分别设计3种治疗计划:计划A为3DCRT外照射,计划B为后装治疗,计划C为后装治疗联合外照射。根据EQD2评估CTV和OAR剂量学参数并单因素方差分析。结果 与计划A相比,计划C的CTV的D₉₀、D₅₀、D_mean更高(P=0.00),直肠、膀胱和股骨头剂量低,卵巢剂量略高(P=0.00)。与计划B相比,计划C的CTV 的D₉₀更高,D₅₀、D_mean较低,卵巢剂量较低,直肠、膀胱和股骨头剂量略高。计划B的直肠、膀胱D_{2 cm³}最低。结论 儿童阴道横纹肌肉瘤的放疗需根据原发肿瘤位置及手术后是否残留选择合适的治疗方式。CT引导的⁶⁰Co高剂量率三维后装治疗方式流程简单快捷,患儿耐受性好,靶区剂量高,正常组织保护好。     

磁场对Bebig型60Co HDR近距离治疗源剂量分布影响研究

目的 计算MRI引导近距离治疗中磁场对Bebig型⁶⁰Co HDR放射源周围剂量以及碰撞比释动能分布的扰动,判断在不同强度磁场下应用此型号放射源进行近距离治疗可行性。方法 基于蒙特卡洛Geant4软件,建立Bebig型⁶⁰Co近距离治疗源模型,然后置其于尺寸为10cm×10cm×10cm的均匀水模体中,并沿着x、y、z轴向划分大小为0.2mm×0.5mm×0.5mm的体元。在x轴向上分别施加磁场强度为0T、1.5T、3.0T均匀磁场,分别计算x轴向上距离治疗源中心10.0mm范围内碰撞比释动能与剂量分布以及两者比值随距离放射源中心远近变化情况。结果 1.5T的磁场对⁶⁰Co HDR治疗源附近空间范围内剂量分布无影响,而3.0T的磁场导致距离放射源中心r<6mm范围内剂量明显偏高,r=5.4mm处剂量增加了接近40%。碰撞比释动能与剂量比值在1.2mm60Co HDR近距离治疗源,在治疗过程中应用1.5T外部磁场是安全可靠的,而3.0T高场强磁场带来了剂量风险,在投入临床使用前必须进行安全验证评估。     

60Co陀螺刀的剂量特性验收测试

目的 介绍和评估 ⁶⁰Co陀螺刀的剂量学特性。方法 分别用0.015、0.600 cm³电离室,EDR2胶片和半导体探测器测量4个直径分别为5、12、30、50 mm准直器等中心剂量率。用0.015 cm³电离室检验机器的剂量—时间线性关系和机器出束稳定性。用0.015 cm³电离室探头与半导体探头测量治疗计划系统(TPS)计算和测量的相对误差,用胶片测量TPS计算等剂量线在x、y轴方向宽度误差。结果 0.015、0.600 cm³电离室,EDR2胶片和半导体探测器对50 mm准直器测量无差别,对5 mm准直器差别最大。半导体探测器测量的TPS与实测剂量误差最大为4.8%,大部分测量结果都<3.0%。50%等剂量线x轴方向差异最大为4.9 mm,其他都<2.0 mm。结论 ⁶⁰Co陀螺刀具有良好的剂量学特性,适合立体定向放疗。     

磁场对Bebig型60Co HDR近距离治疗源剂量分布影响研究

目的 计算MRI引导近距离治疗中磁场对Bebig型⁶⁰Co HDR放射源周围剂量以及碰撞比释动能分布的扰动,判断在不同强度磁场下应用此型号放射源进行近距离治疗可行性。方法 基于蒙特卡洛Geant4软件,建立Bebig型⁶⁰Co近距离治疗源模型,然后置其于尺寸为10cm×10cm×10cm的均匀水模体中,并沿着x、y、z轴向划分大小为0.2mm×0.5mm×0.5mm的体元。在x轴向上分别施加磁场强度为0T、1.5T、3.0T均匀磁场,分别计算x轴向上距离治疗源中心10.0mm范围内碰撞比释动能与剂量分布以及两者比值随距离放射源中心远近变化情况。结果 1.5T的磁场对⁶⁰Co HDR治疗源附近空间范围内剂量分布无影响,而3.0T的磁场导致距离放射源中心r<6mm范围内剂量明显偏高,r=5.4mm处剂量增加了接近40%。碰撞比释动能与剂量比值在1.2mm60Co HDR近距离治疗源,在治疗过程中应用1.5T外部磁场是安全可靠的,而3.0T高场强磁场带来了剂量风险,在投入临床使用前必须进行安全验证评估。     

CD44+CD24-/low在基底样乳腺癌中过表达与其恶性预后的相关性研究

目的探讨乳腺癌干细胞样标志物CD44⁺CD24^-/low在基底样乳腺癌(basal-like breast carcinoma, BLBC)中过表达与BLBC恶性预后的相关性。方法 在乳腺癌基因表达分型的基础上, 根据雌激素受体(ER)、孕激素受体(PR)、人类表皮生长因子受体2(Her-2)免疫表型的表达选取乳腺癌组织四组:管腔A组、管腔B/C组、Her-2高表达组及三阴性组;对三阴性组检测CK5/6、EGFR, 分为正常乳腺样型和BLBC型两组;对上述5组进行免疫组化Envision法染色, 选用抗体为CD44、CD24, 观察CD44⁺CD24^-/low表型表达并比较BLBC组与其它各组的差异。结果 (1)三阴性组共60例, CK5/6和或EGFR阳性者41例(68.3%), 确定为BLBC;CK5/6、EGFR阴性者19例(31.7%), 确定为正常乳腺样组;(2)CD44⁺CD24^-/low表型在BLBC组中占78.0%(32/41), 相对于管腔A组37.9%(11/29)、管腔B组25.9%(7/27)、Her-2高表达组17.2%(5/29)、正常乳腺样组26.3%(5/21), 表达增高并具有显著性(P＜0.05);(3)所有150例乳腺癌中(可评价145例)具有CD44⁺CD24^-/low免疫表型者其Ki-67指数增高相对于非CD44⁺CD24^-/low表型具有统计学差异(P＜0.001)。结论 BLBC型乳腺癌表达乳腺癌干细胞样标志物CD44⁺CD24^-/low显著高于其它各型乳腺癌, CD44⁺CD24^-/low与BLBC独特的恶性生物学行为相关。     

植物对放射性核素钴-60吸附与富集的研究进展

放射性核素钴-60(⁶⁰Co)由于意外事故或其他原因排放而进入生态环境后，可以被植物富集，并通过食物链进入人体形成内照射，对人体健康产生危害。某些植物对放射性核素具有较强的吸附与富集能力，可利用这一特点寻找超富集植物，用其修复钴污染土壤。此外，⁶⁰Co释放的γ射线照射植物能够改变其生长生理特性，由此分析不同植物对⁶⁰Co γ射线的敏感性，以期获得敏感指标，为核事故发生进行预测、预警提供技术支撑。本文通过对国内外文献调研，归纳和总结有关植物对⁶⁰Co吸附与富集能力方面的研究，以及植物受到⁶⁰Co γ射线照射后生理特性变化方面的研究，目的是探索植物对⁶⁰Co的富集能力以及用植物修复⁶⁰Co污染土壤的可行方法，为进一步植物修复研究提供理论依据。     

不可切除Ⅲ期NSCLC持续静脉泵注恩度联合同期放化疗前瞻性多中心Ⅱ期临床试验初步结果

目的 评估隔周持续静脉泵注恩度联合同期放化疗对不可切除Ⅲ期NSCLC的有效性及安全性。方法 2012—2015年共73例患者入组,年龄31~69岁,男52例、女11例,鳞癌41例、腺癌19例、大细胞癌1例、未分化癌2例。Ⅲ_A期27例、Ⅲ_B期36例。第1、3、5、7周每天接受恩度7.5 mg/m²持续泵注5 d,第2周开始接受6~7周的3DRT 60~66 Gy分30~33次,同期依托泊苷50 mg/m²第1—5天加顺铂50 mg/m²第1、8、28天重复化疗两程。CTCAE3.0评估不良反应。完成治疗后4周按RECIST 1.1标准评价近期疗效。结果 63例进行评价。1例患者因2级肾功能不全、1例因4级骨髓抑制未行第2程化疗,61例均完成治疗。完成治疗后4周评价疗效,CR 8例,PR 40例,SD 11例,PD 4例,客观缓解率76%。3+4级中性粒细胞减少23例,3+4级贫血9例,3+4级血小板减少10例。3级恶心或呕吐3例,3级放射性食管炎8例,1+2、3级RP分别为12、2例。未观察到2级以上心血管毒性发生。中随访时间13.6个月,随访期间21例死亡,15例死于肺癌进展。中位PFS 14.8个月。1年PFS、OS分别为51%、78%。结论 恩级泵注给药提高了患者依从性,联合同期放化疗不可切除Ⅲ期NSCLC近期疗效和耐受性良好,疗效评价尚需进一步累积病例和长期随访。     

调强放疗条件下鼻咽癌原发肿瘤体积对预后的影响

目的 探讨调强放疗条件下鼻咽癌原发肿瘤体积(PTV)对患者预后的影响。方法 330例接受调强放疗的鼻咽癌初治患者入组本研究。所有患者治疗前均行CT增强扫描,扫描图像资料输人三维治疗计划系统进行肿瘤轮廓勾画和PTV计算。在国际抗癌联盟2002年T分期框架内借助受试者工作特征曲线,将所有患者按PTV大小分为V₁(<10 cm³)、V₂(10~ 25 cm³)、V₃(>25~50 cm³)、V₄(>50 cm³)组。用 Kaplan Meier 法计算生存率并 Logrank 检验, Cox 回归模型分析原发肿瘤体积与患者预后的关系。结果 随访率100%。330例 鼻咽癌患者所测平均PTV为(34.2±27.1) cm³(0.4~153.7 cm³)。V₁、V₂、V₃、V₄组 3年总生存率分别为88.6%、90.0%、91.2%、74.2%(χ²=12.83, P=0.005)。PTV>50 cm³ (V₄组)和≤50 cm³(V₁+V₂+V₃) 者 3年无远处转移生存率和无瘤生存率及总生存率均明显下降 [77.4%∶89.9%(χ²=7.24, P=0.007)和64.5%∶85.1%(χ²=13.95, P=0.000) 及74.2%∶90.3% (χ²=11.76, P=0.001)]。多因素分析证实PTV同N分期一样,是影响患者生存的预后因素(χ²=0.00, P=2.580)。结论 鼻咽癌PTV可能是影响患者生存的一个重要的预后因素。     

Dosimetric characterizations of GZP6 60Co high dose rate brachytherapy sources: application of superimposition method

Background

Dosimetric characteristics of a high dose rate (HDR) GZP6 Co-60 brachytherapy source have been evaluated following American Association of Physicists in MedicineTask Group 43U1 (AAPM TG-43U1) recommendations for their clinical applications.

Materials and methods

MCNP-4C and MCNPX Monte Carlo codes were utilized to calculate dose rate constant, two dimensional (2D) dose distribution, radial dose function and 2D anisotropy function of the source. These parameters of this source are compared with the available data for Ralstron ⁶⁰Co and microSelectron¹⁹²Ir sources. Besides, a superimposition method was developed to extend the obtained results for the GZP6 source No. 3 to other GZP6 sources.

Results

The simulated value for dose rate constant for GZP6 source was 1.104±0.03 cGyh-1U-1. The graphical and tabulated radial dose function and 2D anisotropy function of this source are presented here. The results of these investigations show that the dosimetric parameters of GZP6 source are comparable to those for the Ralstron source. While dose rate constant for the two ⁶⁰Co sources are similar to that for the microSelectron¹⁹²Ir source, there are differences between radial dose function and anisotropy functions. Radial dose function of the ¹⁹²Ir source is less steep than both ⁶⁰Co source models. In addition, the ⁶⁰Co sources are showing more isotropic dose distribution than the ¹⁹²Ir source.

Conclusions

The superimposition method is applicable to produce dose distributions for other source arrangements from the dose distribution of a single source. The calculated dosimetric quantities of this new source can be introduced as input data to the GZP6 treatment planning system (TPS) and to validate the performance of the TPS.     

Monte Carlo calculation of the TG-43 dosimetric parameters of a new BEBIG Ir-192 HDR source.

BACKGROUND AND PURPOSE: High dose rate (HDR) brachytherapy is a highly extended practice in clinical brachytherapy today. Quality dose rate distribution datasets of the HDR sources used in a clinical treatment are required. Because of the different source designs, a specific dosimetry dataset is required for each source model. In the recently published BRAPHYQS-ESTRO Report, an overview of available dosimetric data for all HDR Ir-192 sources is given, pointing out the lack of data for one of the sources that is used by the BEBIG MultiSource afterloading system (BEBIG GmbH, Germany). The purpose of this study is to obtain detailed dose rate distributions in liquid water media around this source. MATERIAL AND METHODS: The Monte Carlo code GEANT4 was used to estimate dose rate in water and air-kerma strength around the Ir-192 source. All the details of the stainless steel encapsulated BEBIG HDR 1.1mm in external diameter has been included in the simulation. RESULTS: A complete dosimetric dataset for the BEBIG Ir-192 HDR source is presented. TG43 dosimetric functions and parameters have been obtained as well as a 2D rectangular dose rate table, consistent with the TG43 dose calculation formalism. The dosimetric parameters and functions obtained for the BEBIG HDR source have been compared with that obtained in the literature for others HDR sources, showing that the use of specific datasets for this new source is justified. CONCLUSIONS: This dataset can be used as input in the TPS and to validate its calculations. As policy of BRAPHYQS-ESTRO task group, this dataset will be incorporated to the website: available to users in excel format.     

铱-192新源剂量学参数测量方法研究

目的 通过192Ir新源径向剂量函数gL(r)和各向异性函数F(r,θ)的测量值与计算值的比较建立剂量学参数评价方法 .方法 用聚苯树脂材料制成实验体模,其上包括放射源出入孔和各测量位置上用于盛放热释光剂量计(TLD)管的孔.用体模在192Ir辐射场中测量参考方向上1～14 cm半径的剂量,用以计算gL(r);测量1、3、5 cm半径圆周上各向(0°～165°,间隔15°)剂量,用以计算F(r,θ).上述测量值与蒙特卡罗(MC)模拟计算值进行配对t检验比较差异.结果 gL(r)在1～14cm半径计算值为1.007～0.681,测量值为1.007～0.598(t=0.00～2.89,P值均>0.05).F(r,θ)在1、3、5 cm半径圆周上0°～165°的计算值分别为0.631～1、0.660～1、0.696～1,测量值分别为0.701～1、0.668～1、0.629～1(t=0.40～1.63、0.02～2.10、0.08～2.03,P值均>0.05).结论 TLD测量的192Ir源gL(r)和F(r,θ)值与MC计算结果 一致,其数据均可用于治疗计划系统.     

The use of cylindrical coordinates for treatment planning parameters of an elongated 192Ir source.

PURPOSE: The doses given to the intima, media, and adventitia are very crucial quantities in intravascular brachytherapy. To facilitate accurate computerized treatment planning calculations, we have determined dose distributions in away-and-along table format around an 192Ir wire source and developed pertinent dosimetric parameters in cylindrical coordinates. METHODS AND MATERIALS: The Monte Carlo method (MCNP4C code) was used to calculate the dose distributions for the AngioRad 192Ir wire source (model SL-77HS, Interventional Therapies). The calculations were carried out for photon, beta, and electron (conversion and Auger) contributions for radial distances from 0.03 to 2.0 cm with 0.01-cm increments, and up to 2.24 cm from the source center in the longitudinal direction with 0.04-cm resolution. Dose rate values are determined in away-and-along format (cylindrical coordinates) and then converted to spherical coordinate format. Dosimetric parameters, such as the geometry factor, G(r, theta), and anisotropy function, F(r, theta), are generated in both cylindrical (R, Z, phi) and spherical (r, theta, phi) coordinates. The use of a cylindrical coordinate system for treatment planning parameters is proposed as a more suitable approach for accurate calculations. RESULTS: The photon contribution to dose varies nearly inversely with radial distance (from the source center) along the perpendicular bisector with 0.199 x 10(-3) cGy U(-1) s(-1) (0.802 cGy Ci(-1) s(-1)) at 1 cm. The beta and electron contributions start at very high values of about 35.5 x 10(-3) cGy U(-1) s(-1) and 11.0 x 10(-3) cGy U(-1) s(-1), respectively, at 0.03 cm and fall off exponentially to negligible amount near 0.2 cm. The total dose rate at 0.2 cm is 1.428 x 10(-3) cGy U(-1) s(-1) (5.754 cGy Ci(-1) s(-1)). The radial dose function, g(R), is nearly unity between 0.2 cm and 2 cm. Due to the beta and electron dose contributions, g(R) increases steeply to 5.5 as radial distance decreases from 0.2 cm down to 0.03 cm. The F(R, Z) values are close to unity for the majority of the region of interest. In contrast, F(r, theta) experiences a steep rise as shallow angles are approached (closer to the source), related to the beta dose contributions. Accurate treatment planning calculations would be possible with linear interpolation of F(R, Z), but difficult with F(r, theta) in the spherical coordinate system and the original normalization point as recommended in the American Association of Physicists in Medicine Task Group 60 (AAPM TG-60) formalism. CONCLUSION: The AngioRad 192Ir wire source, model SL-77HS, was completely characterized dosimetrically using Monte Carlo methods. The use of cylindrical coordinates and a modified anisotropy function normalization point for dosimetric parameters of an elongated 192Ir source is more suitable for accurate computerized treatment planning calculations in intravascular brachytherapy.     

On the dosimetric accuracy of a Sievert integration model in the proximity of 192Ir HDR sources

PURPOSE: To investigate the efficacy of a Sievert integration model in dosimetry close to 192Ir high-dose-rate brachytherapy sources and validate its accuracy and potential to resolve dosimetric differences between these sources in the cm and mm distance ranges relevant to interstitial and intravascular brachytherapy applications, respectively. METHODS AND MATERIALS: The dosimetric quantities of the generalized Task Group 43 formalism, as well as dose rate profiles in polar and Cartesian coordinates, are calculated, and results are compared to corresponding Monte Carlo data in the literature. RESULTS: Sievert calculations were found in excellent agreement with corresponding Monte Carlo published results. Dose rate polar angle profiles in the cm distance range depended significantly on corresponding anisotropy function data, whereas in the mm distance range, dose rate polar angle profiles are governed by the corresponding geometry function profiles, because anisotropy proved insignificant. Radial dose functions of the sources were found comparable. A simple equation for the calculation of the dose rate constant of the sources within clinically acceptable accuracy is provided. CONCLUSIONS: The particular Sievert model proved capable of resolving dosimetric differences of the sources and provides results within clinical accuracy. Therefore, it constitutes a useful tool for dosimetry in clinical practice and especially in intravascular applications, where there is currently a lack of available dosimetric data.     

Dosimetric calculations and VIPAR polymer gel dosimetry close to the microSelectron HDR

In the present study, different dosimetric methods were investigated for their ability to predict the energy dose in the vicinity of the microSelectron HDR 192Ir brachytherapy source. The results of a time-efficient Sievert integral model of proven accuracy in the cm distance range from all 192Ir sources were benchmarked against accurate Monte Carlo derived dosimetric data in the close vicinity of the source. This comparison revealed that the Sievert model is capable of accurate dosimetry even in the mm distance range from the source. The dose rate distributions were compared with results obtained from different versions (v. 13.7 and 14.2.2) of the Plato BPS commercial treatment planning system, for an application following the Paris trial intravascular irradiation protocol. The results of brachytherapy planning system calculations were found reliable at radial distances of clinical relevance. Noticeable errors existed only in the extreme case of dose calculations at 2 mm from the source axis using Plato v. 13.7. Experimental dosimetric data for the intravascular application, as obtained through the VIPAR polymer gel-MRI method, were also evaluated for dose verification purposes. This method allowed with reasonable accuracy the verification of absolute dose distributions for peripheral vessel applications using 192Ir sources.     

Analysis of serial CT scans to assess template and catheter movement in prostate HDR brachytherapy

PURPOSE: As prostate high-dose-rate (HDR) brachytherapy becomes more prevalent, varying amounts of catheter displacement have been noted. To investigate the constancy of catheter position and its impact on dose distribution, we analyzed serial dosimetric CT scans. METHODS AND MATERIALS: The data from 50 patients were analyzed. During initial CT treatment planning, transverse images of the implant volume were collected, and all structures were digitized into the Nucletron Brachytherapy Planning System. Digitally reconstructed radiographs were generated with rendering of the catheter tips, ischial tuberosity, and perineal template. The distance from each catheter tip to the template and to the ischial tuberosity was measured. The distance between the ischial tuberosity and the template was similarly measured. A second CT set was obtained at different intervals and compared with the first measurement to assess catheter and/or template movement. In 10 patients, the second CT set was obtained before the third fraction in both 2-mm and 5-mm slice sequences, and the latter was used to re-create the HDR plan. RESULTS: Although no interfraction catheter movement relative to the template was found, the template-catheter unit moved in a caudal direction between HDR fractions. The amount of displacement was time dependent: 2 mm before the second fraction, 8 mm before the third, and 10 mm before the fourth. When comparing the first HDR treatment with the third, median decreases in the following dosimetric parameters were noted: dose to 90% of the prostate volume, 35% (r = 0-60); minimal dose to the base, 35% (r = 17-65); and maximal dose to 1 cm(3), 13% (r = 3-19%). CONCLUSION: The interstitial catheters did not slip within the template and were not caudally displaced independently but rather in conjunction with the template. The displacement occurred in a time-dependent fashion, and, without redress, significant dosimetric changes are encountered by the third fraction.