股骨头人工关节对盆腔放疗剂量分布的影响

目的 测量钴、镉、钼合金股骨头人工关节在放疗过程中次级射线引起的散射效应,以及其作为高原子序数材料对剂量分布的影响.方法 测量6、10 MV X射线入射方向距关节0.5、1.0、2.0 cm处剂量,出射方向距关节3.0、5.0、7.0 cm处剂量及距关节头部5.0、10.0 cm的剂量曲线.结果 6、10 MV X射线入射方向距关节0.5、1.0、2.0 cm处剂量偏差在0%～5%之间,随能量增加背散射效应更加显著.射线出射方向距关节3.0、5.0、7.0 cm处剂量偏差为21.6%～30.8%,射野和深度相同时随能量增加剂量偏差减少,同一能量和深度下剂量偏差随射野增加而减少.透射剂量曲线显示关节头部对剂量衰减作用极为显著.结论 在进行盆腔放疗时尽量避免射野穿过关节,或者至少降低穿越关节的射野权重.

Abstract：

Objective To study the scattering effect of Co-Cr-Mo hip prosthesis which was high Z material for patients undergoing pelvic irradiation.Methods The hip prosthesis was set in water phantom (30 cm×30 cm×30 cm), determing points were chosen on the entrance side of both 6 MV and 10 MV beams at the distance of 0.5 cm, 1.0 cm, 2.0 cm to the hip prosthesis, and also on the exit side of both 6 MV and 10 MV beams at the distance of 3.0 cm, 5.0 cm, 7.0 cm to the hip prostheses.Dose behind the hip prosthesis at depths of 5.0 cm and 10.0 cm for 6 MV and 10 MV beams are also measured.ResultsThe dose deviation on the beams′ entrance side is between 0 to 5.0%, the backscatter effect was more obviously with the higher energy beam.The dose deviation on the beams′ exit side was between 21.6%-30.8%.With the same field size and depth, dose deviation becomes smaller when the beam energy was higher;while with the same energy and depth, dose deviation becomes smaller when the field size was bigger.Dose profiles behind the head of the hip prosthesis indicate obvious attenuation of the beam.Conclusions Beam arrangements that avoid the prosthesis should be considered first or we should at least reduce the weight of the beam that pass through the prosthesis.     

两种放疗计划系统对仿真体模和患者及均匀体模进行剂量计算结果比较

目的 通过Eclipse与Pinnacle3 V 7.4f两种TPS对仿真体模、患者及均匀组织体模的CT图像进行剂量计算,比较两种TPS进行非均匀组织计算的结果差异,并与均匀体模的结果进行比较.方法 对患者、仿真体模以及均匀体模的CT图像利用两种TPS作相同计划,比较临床常用指标(肺V20和V30计划靶区的D95以及等中心点和等中心层面内8个兴趣点的剂量)的结果差异.结果 对患者及仿真体模而言,虽然两TPS对等中心点剂量计算的结果差异较小,但其他指标却存在较大差异(利用二级准直器照射时患者计划靶区D95的差异最大可达10.17%,仿真体模为4.64%;利用多叶光栅照射时患者计划靶区D95的差异最大达10.74%,仿真体模为5.66%;对于计划靶区边缘1-4点的剂量差异,患者有超过10.00%的情况,仿真体模最大为7.65%;肺V30的差异也较大).而对均匀体模而言,两TPS对各指标的计算差异却较小.结论 两TPS对仿真体模计算的结果差异比患者小,而对患者及仿真体模计算的结果差异要大于对均匀组织体模的.     

3D dose delivery verification using repeated cone-beam imaging and EPID dosimetry for stereotactic body radiotherapy of non-small cell lung cancer

Purpose

To implement a 3D dose verification procedure, based on in-room cone-beam CT imaging and portal dosimetry, for lung cancer patients treated with stereotactic body radiotherapy (SBRT).

Materials and methods

MV cone-beam CT scans were made for patient positioning and calibrated for dose calculation purposes. Prior to treatment, the treatment fields were captured using a calibrated electronic portal imaging device (EPID). A Monte Carlo dose reconstruction model was used to estimate the 3D dose delivered to the patient inside the cone-beam CT images. The planned and delivered dose distributions were compared for 4 patients and 10 treatment fractions using dose-volume histograms and gamma analysis.

Results

The gamma analysis showed a good agreement between the planned and delivered dose distributions for patients without changes in anatomy. The delivered mean dose per fraction inside the target volume deviated on average 1.1 ± 1.4% from the planned dose. For the critical organs, only minor differences were observed between the reconstructed and planned dose.

Conclusions

A method was presented that allows verification of the dose delivered in 3D for lung cancer patients treated with SBRT. The procedure is independent of the treatment planning system and uses in-room MV cone-beam CT imaging and portal dosimetry.     

扫描液体电离室型电子射野影像装置的剂量响应研究

目的　研究扫描液体电离室型电子射野影像装置 (EPID)的剂量响应特性及其各种影响因素 ,如机架角、照射野大小、图像获取模式 ,以便进一步利用EPID进行剂量验证方面的研究。方法　所有实验均在装备有PortalVisionTMMK2型电子射野影像装置的Varian 6 0 0C/D加速器上实现。为了得到剂量响应曲线 ,需要建立入射到探头的射线强度与EPID像素值之间的关系。首先 ,通过改变源到探头电离室的距离得到不同的射线强度。其次 ,针对任一剂量率条件 ,用EPID拍摄 3幅数字射野图像取平均 ,取射野中心轴附近 11× 11个像素点的平均值作为EPID响应。最后 ,根据相同条件下测得的剂量率和对应的像素值 ,绘制剂量响应曲线。改变机架角、照射野大小和图像获取模式 ,得到一系列剂量响应曲线。结果　EPID输出像素值与入射剂量率之间并非线性关系。EPID剂量响应曲线与图像获取模式关系密切 ,在离轴点略受机架角的影响 ,但不受射野大小的影响。结论　由于射野图像获取模式明显地影响EPID剂量响应曲线的形状 ,所以对不同获取模式应该分别刻度。机架角的影响可通过在不同机架角下刻度加以消除。EPID剂量响应与射野大小无关的事实为日常剂量响应刻度提供了便利 ,即用一种射野条件刻度就可以准确地应用于其它射野条件     

移动条野技术的放射生物学和剂量学基础及改进

目的：阐明常规移动条独特的优点及其局限性，并对其进行改进。方法：从放射生物学方面包括时间剂量因子、分次剂量因子和体积剂量因子等三个方面及从剂量学方面分析了移动条野照射技术，针对其局限笥，引进了由靶区长度每次剂量，总剂量和疗程时间决定的照射野宽度与每次铥距离的计算模型。结果：移动条野照射技术在一定条件下能提高肿瘤的生物效应，同时减少正常组织的反应。结论：移动条野照射技术有其本身的适应证和应用价值。     

基于4D剂量分布下适形放疗和滑窗调强放疗模体研究

目的:基于4D剂量分布,探究呼吸运动对三维适形放疗(3DCRT)和滑窗调强放疗(SW-IMRT)的计划剂量分布的影响,评估在4D剂量模式下呼吸运动引起剂量误差的大小。方法:使用动态胸部模体(CIRS-008A),设定振幅分别为5、10 mm的cos 4( x)和sin ( x)波形的...     

Dose-response relationship and dose optimization in radiotherapy of postoperative keloids

Background and purpose

The treatment dose and fractionation dose that are considered in postoperative keloids had been reported in the previous studies. We performed retrospective analysis to elucidate the factors influencing the treatment outcome.

Materials and methods

From 1979 to 1994, 194 lesions in 119 patients received postoperative radiotherapy after excision with the total dose ranging from 16 Gy/8 fr to 40 Gy/8 fr (mean: biologically effective dose (BED) 33.5 Gy). Kilo-voltage X-rays (55 or 100 kVp) or electron beams (4 or 6 MeV), including entire keloid scars, and any suture/puncture holes with a margin around the lesion were used. The median follow-up period was 36 months (range 12-164 months).

Results

Symptomatic pain and itching relief were achieved in 96% and 91%, respectively. The relapse rate was 11% at 20 Gy in five fractions or higher dose, while 43% at less than 20 Gy. On the other hand, the incidence of adverse effects was significantly higher for patients receiving more than 20 Gy in five fractions.

Conclusion

There was a significant correlation between the relapse rate and the total dose of irradiation, and between adverse effects and the total dose. To correlate local control and adverse effects, we proposed 20 Gy in five fractions as the optimal dose for the postoperative of keloids. A significant correlation between relapse rate and the interval time between excision and radiotherapy was not found in our current study.     

射野影像重建模体内剂量分布的研究

目的建立一种反向投影算法（模型）,由射野影像和患者的CT图像,计算体内的三维剂量分布,进行剂量验证.方法该模型计算体内剂量分布步骤如下：（a）使用电子射野影像系统获取射野影像,将射野影像转换为射出剂量;（b）从射出剂量分布重建入射原射线注量分布;（c）由患者的三维信息（CT图像）,计算得到体内的原射线剂量分布;（d）体内散射核叠加,求出体内散射线剂量分布,与原射线剂量相加,即得到体内的剂量分布.使用C语言编程实现算法.通过设置规则、不规则及调强射野,对均匀和不均匀、规则和不规则5种模体进行剂量验证实验,并将计算结果与测量结果进行比较.结果所有实验在射野内、剂量梯度小的区域计算的剂量和测量的剂量的偏差＜5%.在射野边界附近低密度肺组织内的计算剂量和测量的剂量的偏差＞5%.结论所建立的反向投影模型用于剂量验证,其准确性可满足临床要求.但模型还需进一步完善,以准确计算电子失平衡区的剂量.     

基于患者出射EPID剂量验证的在体调强放疗质控技术研究

背景与目的：调强放疗（intensity-modulated radiation therapy,IMRT）中剂量投照失误可导致严重后果,而目前常用的治疗前计划验证方法并不能反映患者真实投照剂量。实现一种评估患者在体剂量执行准确度的方法,能够在分次治疗中及时发现较大剂量错误,避免发生患者投照剂量过高或不足。方法：复旦大学附属肿瘤医院收治的患者首次实施治疗前行锥形束计算机断层成像（cone beam computed tomography,CBCT）扫描,与定位CT图像进行配准保证治疗体位与模拟定位时一致,实时治疗中使用电子射野影像装置（electronic portal imaging device,EPID）获取患者出射剂量影像,并把首次出射EPID影像作为剩余分次治疗的基准值,后续分次实时治疗野结束后快速将其出射EPID影像与对应基准影像进行γ分析比较,以验证治疗计划是否准确执行于患者身上。设计模体实验对治疗部位错误和摆位误差情况进行分析,来评估本方法识别放疗差错的准确性。结果：本方法可有效地识别出IMRT放疗中患者治疗部位错误和非平行于射野角度方向的摆位误差,但对平行于射野角度方向的摆位误差并不敏感,30例鼻咽癌患者临床应用结果中能够直观显示分次治疗间摆位重复性情况。结论：基于EPID实现的一种在体剂量验证方法能够对调强放疗中患者实时剂量的准确性进行评估,在单个治疗野结束后可快速检测出较大治疗错误。     

Tangential breast irradiation: a multi-centric intercomparison of dose using a mailed phantom and thermoluminescent dosimetry.

PURPOSE: To measure the accuracy of radiation therapy of the breast planned with 2D and 3D algorithms. MATERIALS AND METHODS: The accuracy of radiation therapy of the breast with 2D and 3D algorithms was investigated as a national intercomparison using a semi-anatomical breast phantom. The dose was measured with thermoluminescent (TL) dosemeters. RESULTS: The mean deviation of measured to planned dose at isocentre was -2.7%. The influence of some planning and irradiation factors is evaluated. CONCLUSION: The study demonstrates that beam energy and the use of CT have no marked influence on the accuracy of dose calculations, care has to be exercised when wedges are used and even with sophisticated 3D algorithms there is a systematic error in the dose received by the patient.     

非晶硅平板电子射野影像用于放射治疗剂量学质量控制检验的应用

背景与目的:非晶硅平板型电子射野影像系统(amorphous silicon electronic portal imaging device,a-Si EPID)具有良好的剂量学品质,作为一种快速的二维剂量测量系统,在常规质量控制、调强照射野验证及实时患者剂量监测等方面具有广阔的应用前景.为将非晶硅平板电子射野影像用于放射治疗的剂量学检验,本研究针对其射野影像建立了修正模型,并应用于加速器照射野的常规质量保证工作.方法:对a-Si EPID常用的图像刻度模式进行剂量刻度改进以用于照射剂量测量:通过一种由若干个小野组合形成"泛野"的方式来克服传统的泛野获取方式的缺陷,从而较准确地修正a-Si EPID各像素单元之间的灵敏度差异;并建立离轴剂量的响应曲线和修正数学模型.以修正后的a-Si EPID射野影像测量照射野的剂量分布并与三维水箱中电离室扫描的结果进行比较验证.结果:经所建立的模型进行剂量刻度和修正后,高剂量区,a-Si EPID与电离室测量结果偏差＜2%,在半影区,a-Si EPID测量的剂量分布曲线比电离室测量结果略为陡峭.结论:非晶硅平板型电子射野影像(a-Si EPID)系统具有良好的物理剂量学品质,可以用作照射野常规质控检验和调强放射治疗射野剂量能量分布的快速工具.     

羟基磷灰石股骨假体在全髋关节置换术中应用效果的 Meta 分析

目的：通过 Meta 分析评价羟基磷灰石股骨假体的有效性以及安全性。方法计算机检索 Cochrane Library、PubMed、EMBASE、CBM、CNKI 和万方数据库。纳入在全髋关节置换( total hip arthroplasty,THA )术中应用羟基磷灰石涂层髋关节假体柄与非羟基磷灰石涂层髋关节假体柄的临床随机对照试验,按照 Jadad 量表进行质量评估,并采用 RevMan 5.2软件进行 Meta 分析。结果共纳入11个随机对照试验,共899例(实验组456例,对照组443例),结果显示,与对照组相比,使用羟基磷灰石涂层假体柄的患者在 HHS 评分：[RD＝0.01,95%CI (-0.07,0.09),P＝0.81]差异并无统计学意义,假体周围透亮线[RD＝0.01,95%CI (-0.07,0.09),P＝0.81]差异并无统计学意义,假体周围骨形成[RD＝0.00,95%CI (-0.04,0.04),P＝0.97]差异并无统计学意义,异位骨化发生率[RD＝-0.01,95%CI (-0.09,0.07),P＝-0.78],10年以上翻修率[RD＝-0.01,95%CI (-0.04,0.02),P＝0.65]差异并无统计学意义。结论羟基磷灰石涂层假体柄在 THA 术中并没有更好的临床优势。因质量评价与纳入文献数量的限制,有待更高质量、更大样本的随机对照研究的进一步验证。     

Improvement of small-field penumbra and dose distributions on a 4 MV accelerator

The penumbra and dose distributions for small X ray fields from a 4 MV accelerator, designed for 80 cm source-to-surface distance (SSD) but used at 100 cm SSD, were observed to be similar to those obtained from cobalt-60 units. Penumbra was reduced and flatter isodose curves were obtained by the addition of tungsten trimmers at a distance of 48 cm from the X ray source. This stratagem improves the definition of irradiation volume of small fields which are common in the treatment of lesions in the head and neck.     

An observer study for direct comparison of clinical efficacy of electronic to film portal images

: To directly compare clinical efficacy of electronic to film portal images.

: An observer study was designed to compare clinical efficacy of electronic to film portal images acquired using a liquid matrix ion-chamber electronic portal imaging device and a conventional metal screen-film system. Both images were acquired simultaneously for each treatment port and the electronic portal images were printed on gray-level thermal paper. Four radiation oncologists served as observers and evaluated a total ot 44 sets of images for four different treatment sites: lung, pelvis, brain, and head/neck. Each set of images included a simulation image, a double-exposure portal film, and video paper prints of electronic portal images. Eight to nine anatomical landmarks were selected from each treatment site. Each observer was asked to rate each landmark in terms of its clinical visibility and to rate the ease of making the pertinent verification decision in the corresponding electronic and film portal images with the aid of the simulation image.

Resultings for the vesibility of landmarks and for the verification decision of treatment ports were similar for electronic and film images for most landmarks. However, vertebral bodies and several landmarks in the pelvis suchs as the acetabulum and pubic symphsis were more visible in the portal film images than in the electronic portal images.

The visibility of landmarks in electronic portal images is comparable to that in film portal images. Verification of treatment ports based only on electronic portal images acquired using an electronic portal imaging device is generally achievable.     

Intensity-modulated radiotherapy using implanted fiducial markers with daily portal imaging: assessment of prostate organ motion

PURPOSE: To assess our single institutional experience with daily localization, using fiducials for prostate radiotherapy. METHODS AND MATERIALS: From January 2004 to September 2005, 33 patients were treated with 1,097 intensity-modulated radiation treatments, using three implanted fiducials. Daily portal images were obtained before treatments. Shifts were made for deviations > or =3 mm in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) dimensions. RESULTS: Of 1,097 treatments, 987 (90%) required shifts. Shifts were made in the LR, SI, and AP dimensions in 51%, 67%, and 58% of treatments, respectively. In the LR dimension, the median distance shifted was 5 mm. Of 739 shifts in the SI dimension, 73% were in the superior direction for a median distance of 6 mm, and 27% were shifted inferiorly for a median distance of 5 mm. The majority of shifts in the AP dimension were in the anterior direction (87%). Median distances shifted in the anterior and posterior directions were 5 mm and 4 mm, respectively. The median percentage of treatments requiring shifts per patient was 93% (range, 57-100%). Median deviations in the LR, SI, and AP dimensions were 3 mm, 4 mm, and 3 mm, respectively. Deviations in the SI and AP dimensions were more often in the superior rather than inferior (60% vs. 29%) and in the anterior rather than posterior (70% vs. 16%) directions. CONCLUSIONS: Interfraction prostate motion is significant. Daily portal imaging with implanted fiducials improves localization of the prostate, and is necessary for the reduction of treatment margins.