基于剂量分布指数选择胸部肿瘤最优放疗计划的可行性分析

用剂量分布指数(Dose distribution index,DDI)回顾分析50例胸部肿瘤患者的放疗计划,根据肿瘤的位置将病例分成3组:常规组、病灶靠近需保护敏感组织组、胸壁组。每位患者设计3份备选计划,每个备选计划均计算DDI得分,最终有一个备选计划用于实际治疗。靶区的覆盖与治疗区所有组织同等重要时,70.0%(35/50)DDI得分高的计划与实际治疗选择的计划一致,当给予靶区或者脊髓和肺更高的权值后,不一致的结果中又有86.7%(13/15)得分高的与实际治疗选择保持一致。DDI指数提供了一种基于剂量体积直方图(Dose volume histogram,DVH)的客观评价备选放疗计划优劣的工具,尤其在DVH显示非常接近的备选计划中,DDI指数仍可很好的区分其不同,对最终胸部放疗计划的选取提供可靠的依据。     

基于iCBCT图像的盆腔肿瘤放疗计划剂量计算相关研究

为了探讨iCBCT图像用于盆腔肿瘤剂量计算的准确性,本研究选取某院使用Halcyon加速器行放疗的病例30例,利用Eclipse 15.6计划系统重新设计容积旋转调强(VMAT)放疗计划,随后将首次治疗采集的摆位CBCT图像(iCBCT)与计划CT图像(p CT)进行配准,并将每例病例的VMAT计划(pCT计划)移植到iCBCT图像上,基于iCBCT图像标定的CT值-相对电子密度曲线重新进行剂量计算,生成新的治疗计划(iCBCT计划)。采用SPSS 26.0软件对两种计划的剂量学参数进行t检验分析。结果显示,i CBCT计划和pCT的计划相比,计划靶区(Planning target volume,PTV)剂量学参数中D₂、D₉₈、D_mean、适形指数(Conformity index,CI)和均匀性指数(Homogeneity index,HI)结果均较接近,差异平均值依次为0.71%、0.53%、0.97%、0.25%和0.95%,差异无统计学意义(p>0.05)。所统计的危及器官中,左右股骨头、直肠和膀胱的D...     

放疗过程中剂量学变化研究——基于KV-CBCT左侧乳腺癌根治术后图像

通过对定位CT和KV-CBCT制定的左侧乳腺癌根治术后调强计划的比较,探讨调强放疗过程中的靶区和危及器官的剂量学变化特点。选取18例左侧乳腺癌根治术患者,按照定位CT制定治疗计划(PCT)并执行治疗,同时获取第1、6、11、16和21次治疗时的KV-CBCT图像。复制一套定位CT图像和所有结构,再进行容积密度分配(BDA)和计划的复制,形成BDA计划(PBDA),处方剂量50 Gy/25次/5周,90%的靶区达到处方剂量。将获取的5组KV-CBCT图像导入计划系统,并与定位CT进行图像配准、结构复制和BDA,分别制定5组KV-CBCT的移植计划(PREP)和5组全新KV-CBCT计划(PCBCT)。PREP的各项计划参数与PCT相同,但PCBCT是在KV-CBCT图像上完全重新制定的调强计划。每组PREP和PCBCT均给予5 Gy,90%的靶区达到处方剂量。5组PREP和PCBCT计划各自叠加合成为P∑REP和P∑CBCT,两种计划的总处方剂量均为50 Gy/25次/5周。根据剂量体积直方图(DVH)比较PCT、PBDA、P∑REP和P∑CBCT的剂量分布差异,计划间的剂量比较行配对t检验。结果显示,PBDA与PCT具有相似的靶区适形性和剂量均匀性(p0.05)。P∑.05靶区的均匀性与适形性均显著差于PCT的相应值(t=-2.96、-3.57,p0.05)。而P∑CBCT的适形性与均匀性则显著优于P∑形性与均(t=-4.01、-6.24,p0.05),但与PCT相比,并无显著差异(p0.05)。与PCT相比,PBDA有相似的危及器官受量,计划间无显著差异(p0.05)。P∑.05中的右侧乳腺Dmax、左侧肺V5、左侧肺V30、左侧肺Dmean和心脏V30均显著高于PCT的相应结构(t=-5.32、-3.57、-2.81、-2.99、-4.06,p0.05)。与P∑.05相比,P∑CBCT中的所有危及器官受量均得到显著下降(t=4.65、3.88、5.32、3.16、4.95、2.79、4.55,p0.05)。因此,在左侧乳腺癌改良根治术调强放疗过程中,由于受心肺运动等多因素影响,靶区和危及器官受量变化显著,需要通过KV-CBCT图像引导和BDA方法实时或自适应来调整治疗计划,以达到更高的治疗增益比。     

乳腺癌调强放射治疗影像引导锥形束CT匹配区域选择对靶区精度的影响及临床应用

探究乳腺癌调强放射治疗影像引导锥形束CT(Cone-beam CT, CBCT)匹配区域的选择对靶区精度的影响，为临床应用提供参考。回顾性分析2020年1月至10月乳腺癌保乳术后行放疗患者22名，比较入组病例不同匹配框对靶区匹配精度的影响，设置胸骨组（对照组1）、胸椎组（对照组2）与胸骨胸椎+靶区组（研究组）3种不同匹配区域进行配准，每组测量记录匹配误差、CBCT与定位CT靶区术腔边界金属夹位移数据。共获得匹配误差与靶区金属夹位移数据各528组，对所得数据采用独立样本非参数检验分析并计算3组金属夹的3D矢量距离。胸骨组与研究组匹配误差除旋转误差X轴方向差异有统计学意义，其余方向差异均无统计学意义（p>0.05），胸椎组与研究组的匹配误差均无统计学意义（p>0.05）。胸骨组与研究组靶区金属夹在X、Y、Z三个方向位移分别为：（1.59±1.61） mm与（1.23±1.19） mm (p=0.045)、（1.65±1.44） mm与（1.89±1.52） mm(p=0.006)、（1.13±1.18） mm与（1.37±1.31） mm (p=0.999)；胸椎组与研究组靶区...     

食管癌放射治疗计划的剂量学比较

比较食管癌患者应用螺旋断层(Tomo Helical,TH)、径照断层(Tomo Direct,TD)、容积旋转调强(Volumetric modulated arc therapy,VMAT)和固定野动态调强(Intensity modulated radiation therapy,IMRT)4种放疗计划的剂量学差异。选取18例食管癌患者,利用Pinnacle9.2计划系统设计单弧360°VMAT放疗计划和5野IMRT放疗计划。利用Tomo HDTM2.0.7计划系统设计TH放疗计划和5野TD放疗计划。利用剂量体积直方图(Dose volume histogram,DVH)统计靶区剂量参数、适形性指数(Conformity index,CI)和均匀性指数(Heterogeneity index,HI),肺、心脏、脊髓剂量体积参数,出束时间和治疗跳数。TH计划靶区适形性和靶区均匀性略优于TD计划,VMAT计划靶区适形性和靶区均匀性略优于IMRT计划,且前两种计划明显优于后两种;TH计划和VMAT计划肺V20Gy、V30Gy,心脏V30Gy、V40Gy分别优于TD计划和IMRT计划;但是TD计划肺V5Gy具有其他计划都不具有的优势。TH计划优于TD计划优于VMAT计划优于IMRT计划。但如果考虑性价比,本研究认为对于食管癌VMAT计划是首选;如果考虑放射治疗计划的质量,TH计划是首选;但如果靶区体积比较大,肺的低剂量无法达到临床要求时,可以考虑用TD计划解决这一难题。     

非对称散射核法去除锥形束CT计算机图像散射伪影

为去除锥形束CT计算机图像散射伪影,提出一种基于非对称笔形束核的散射反卷积去除算法,该算法采用MC模拟获取适应CT几何结构下的笔形束散射非对称数据,利用线性拟合算法对非对称核进行建模和拟合,通过计算机GPU实现基于拟合非对称散射核的快速运算从而实现快速的CT图像散射伪影校正。实验结果表明:该方法可以在5s内实现图像非一致性从15%下降至5%以下,该方法可以适用于临床应用。     

基于图像质量优化的锥束CT几何校正法

为了解决CBCT图像中因机械误差所导致的几何伪影的问题,提出一种基于图像质量优化的锥束CT几何校正方法。本方法通过引入CBCT图像几何伪影的评价指数,将评价指数作为衡量几何伪影严重程度的目标函数,通过迭代修正标定模体上标记点的坐标,进而达到校正几何参数和消除CBCT图像几何伪影的目的。仿真实验结果显示:CBCT系统的几何参数误差由19.07%降到2.21%,图像中的几何伪影明显减少;在真实实验数据中,该方法有效消除CBCT图像的几何伪影。本方法降低了标定模体加工误差对校正精度的影响,同时大幅度降标定模体的制作成本。     

450keV锥束CT系统的散射校正研究

在450keV锥束工业CT成像系统中,对投影数据进行适当的散射校正是一步重要的数据校正.结合国内外散射校正方法研究的现状,对一种用散射校正板来进行散射校正方法的原理和实现进行了深入的研究.实验结果表明,这种校正方法能够对450KeV锥束CT成像系统进行有效地散射校正.     

基于半扇束扫描的CT图像迭代重建算法

为解决探测器尺寸受限导致的CT图像重建区域面积受限以及X射线辐射剂量较大问题,提出一种半扇束扫描模式下的CT图像迭代重建算法。该算法将探测器水平偏置,稀疏角度下采集物体投影数据,利用ART-TV迭代算法对投影数据进行重建,达到预设迭代次数后,输出重建图像。实验结果表明:半扫描可扩大重建面积,降低探测器成本;利用迭代重建算法,降低剂量的同时重建优质CT图像。     

老年非小细胞肺癌肺复张后的二次IMRT研究

本研究以探讨老年非小细胞肺癌(NSCLC)在调强放疗(IMRT)期间,其患侧肺的复张对受照体积及其计划剂量参数的影响。选择了15例Ⅱ-Ⅳ期老年NSCLC合并肺不张患者,以放疗前(CT1)和放疗32 Gy时(CT2)扫描的CT图像为依据,分别设计调强计划P60和P32+P28。结果发现:CT2-GTV(Gross tumor volume,CT2上的大体肿瘤体积,其他同)和CT2-PTV(Planned target volume,CT2上的计划靶区,其他同)的平均受照体积,显著低于CT1-GTV和CT1-PTV,而CT2-Lung患侧的平均体积则较CT1-Lung患侧有了显著增加,结果有统计学意义(p<0.05)。除了食管V50(接受50 Gy剂量的食管体积,%)外,实验中其余正常组织的各项受照剂量指标间差异均有统计学意义(p<0.05)。因此老年NSCLC合并肺不张患者,在放疗32 Gy后,即有必要复查肺是否已复张,并重新设计IMRT计划,使得老年NSCLC患者在肺复张后的心肺受照剂量更低。     

Radiotherapy reliability analysis based on PSA method

The reliability of radiotherapy was evaluated and effective approaches were obtained in order to improve radiotherapy quality by using the Probabilistic Safety Assessment(PSA) method. This study investigated the feasibility of the PSA method being applied to radiotherapy through Image-guided Radiotherapy(IGRT) and chest tumor irradiation. A fault tree has been constructed after analyzing causal relationship of the events.After calculating Risk A, a total inaccuracy radiotherapy probability and the importance of all base events were obtained. The probability of inaccurate radiotherapy was 2.87%. Under the condition that the target delineation was perfectly right, the accuracy of radiotherapy significantly improved. With the calculation without Conebeam Computed Tomography(CBCT) being corrected before irradiation, the accuracy significantly decreased.The most important events were connected with the human factor. Improving human technical level could enhance radiotherapy quality control efficiently.     

Slice-wise reconstruction for low-dose cone-beam CT using a deep residual convolutional neural network

Because of the growing concern over the radiation dose delivered to patients, X-ray cone-beam CT(CBCT) imaging of low dose is of great interest. It is difficult for traditional reconstruction methods such as Feldkamp to reduce noise and keep resolution at low doses. A typical method to solve this problem is using optimizationbased methods with careful modeling of physics and additional constraints. However, it is computationally expensive and very time-consuming to reach an optimal solution. Recently, some pioneering work applying deep neural networks had some success in characterizing and removing artifacts from a low-dose data set. In this study,we incorporate imaging physics for a cone-beam CT into a residual convolutional neural network and propose a new end-to-end deep learning-based method for slice-wise reconstruction. By transferring 3D projection to a 2D problem with a noise reduction property, we can not only obtain reconstructions of high image quality, but also lower the computational complexity. The proposed network is composed of three serially connected sub-networks: a cone-to-fan transformation sub-network, a 2D analytical inversion sub-network, and an image refinement sub-network. This provides a comprehensive solution for end-to-end reconstruction for CBCT. The advantages of our method are that the network can simplify a 3D reconstruction problem to a 2D slice-wise reconstruction problem and can complete reconstruction in an end-to-end manner with the system matrix integrated into the network design. Furthermore, reconstruction can be less computationally expensive and easily parallelizable compared with iterative reconstruction methods.     

Biological effects of human lung cells MRC-5 in CBCT positioning for image-guided radiotherapy

Image-guided radiotherapy (IGRT) provides precise positioning for the tumor target,but it may bring extra irradiation dose in the target positioning with a cone beam CT (CBCT) which has been increasingly used in IGRT.In this work,we focused on biological effects of thelow-dose irradiation in IGRT,which have not been considered so far.Primary human fibroblasts cells from the lung and MRC-5 were irradiated by a CBCT.DNA doublestrand breaks (γ-H2AX foci) and micronucleus frequency of the irradiated samples were analyzed.Compared to the control,the γ-H2AX foci yields of the samples irradiated to 16 mGy increased significantly,and the micronuclei rate of the samples irradiated for 3 days increased notably.The dose by imaging guidance device can be genotoxic to normal tissue cells,suggesting a potential risk of a secondary cancer.The effects,if confirmed by clinical studies,should be considered prudentially in designing IGRT treatment plans for the radiosensitive population,especially for children.     

基于蒙特卡罗数学模型评价不同螺距冠状动脉CCTA受检者辐射剂量的特点与验证

收集61例采用双源CT Flash大螺距冠状动脉CCTA (Coronary Computed Tomography Angiography,CCTA)受检者资料,按WHO亚洲人体质量指数(BMI )标准将研究对象分为三组:正常组(12例)、超重组(41例)和肥胖组(8例),应用蒙特卡罗(Monte Carlo)数学模型软件计算三组受检者大螺距与常规螺距行CCTA的器官剂量,比较两种螺距CCTA时受检者的器官剂量分布特点及两种螺距CCTA的有效剂量变化幅度,并与大螺距模式下CT设备直接读取法所得有效剂量值进行比较。结果表明,用蒙特卡罗软件计算的双源CT大螺距CCTA受检者的器官剂量比常规螺距技术的剂量降低约70%,其中心脏、胸腺的器官剂量下降最为明显,降幅最大约80%;三组CCTA受检者大螺距较常规螺距的有效剂量(E)均降低明显(p<0.05),正常组使用大螺距技术后有效剂量E降幅最为明显;大螺距模式下数学模型软件模拟有效剂量E与CT设备所测有效剂量E间的偏差度小于50%。说明Monte Carlo数学模型软件可用于检查前预估或回顾性分析CCTA扫描时受检者的器官剂量与有效剂量的分布情况,并预判CCTA大螺距模式对受检者的胸部器官剂量和有效剂量,从而达到了降低辐射剂量的目的,尤其对BMI较小的受检者(如儿童)控制辐射风险更具意义。对开展低剂量CT技术具有一定实际意义。     

乳腺癌保乳术后瘤床同步加量两种放疗技术的比较

比较早期乳腺癌保乳术后瘤床同步加量三维适形野中野放疗(FIF-CRT)与容积旋转调强放疗(VMAT)技术靶区及危及器官的剂量学差异。选取15例左侧乳腺癌保乳术后女性患者,对每位患者分别设计三维适形野中野放疗计划和容积旋转调强计划。在剂量体积直方图上比较靶区的适形度指数、均匀性指数、靶区覆盖率和危及器官的受照剂量体积和所需机器跳数(MU),并进行统计学差异分析。VMAT计划较FIF-CRT计划,PTV1处方剂量覆盖率增加了5.62%(p0.001);瘤床PGTV处方剂量覆盖率增加了10.64%(p0.001);VMAT计划PTV的适形度指数(CI)和均匀性指数(HI)均优于FIF-CRT计划。两种计划左肺V20,心脏的V10和Dmax均无统计学差异,但VMAT的左肺V5、V10和Dmean,心脏的V5,右乳和右肺的V5、Dmean,脊髓的Dmax明显增高且有统计学差异(p0.05);VMAT的左肺V30、V40和心脏的V20低于FIF-CRT计划;VMAT和FIF-CRT的平均机器跳数分别是745 MU和250 MU(p0.001)。早期乳腺癌保乳术瘤床同步加量VMAT放疗与FIF-CRT相比能明显改善靶区的剂量覆盖率和均匀性,但正常组织高剂量区域受照体积减少,低剂量区域受照体积增加,机器跳数增加。     

食管癌患者调强放射治疗前后血清CEA、SCC、VEGF检测的临床意义

为研究食管癌患者调强放射治疗前后血清癌胚抗原(CEA)、鳞状细胞癌相关抗原(SCC)和血管内皮生长因子(VEGF)水平的变化及临床意义,以2016年1月至2017年12月在本院接受放疗的食管癌50例为研究组,健康体检者30例为对照组,采用酶联免疫吸附法(ELISA)检测放射治疗前、后患者血清CEA、 SCC、VEGF的含量,分析调强放射治疗前后上述指标的变化,以及它们与临床TNM分期、肿瘤浸润度的关系。结果表明,调强放射治疗前患者血清CEA、SCC、VEGF水平显著高于放疗后(p＜0.05),治疗后患者血清中上述各项指标均有明显下降(p＜0.05),但仍高于对照组;不同临床分期TNM患者上述指标有显著性差异,其中Ⅲ期最高;不同肿瘤浸润深度患者上述指标也有明显差异,其中T₄ 期最高(p＜0.05)。以上结果说明,血清CEA、 SCC、VEGF在肿瘤浸润深度、不同临床TNM分期及调强放疗前后的食管癌患者血清含量不同,上述结果对制定食管癌患者的个性化治疗方案以及观察治疗疗效有重要意义。     

锥束CT平行双丝法获取几何参数研究

几何参数的精确获取是锥束CT高质量成像的关键条件,因此锥束CT几何参数的精确获取是CT技术研究的重点之一。本文设计了一种易于制作、操作简便、集成化的模体,提出了锥束CT几何参数获取方法：平行双丝法。首先介绍了平行双丝法获取重要参数的原理及公式推导,通过仿真计算,论证了方法的鲁棒性。然后对该方法进行了实验验证,结果表明,平行双丝法具有参数获取精度高、鲁棒性好等优点,是一种较好的锥束CT几何参数获取方法。     

Evaluation of radiation dose and positioning accuracy on X-ray volume imaging system for image-guided radiotherapy

Linear accelerators equipped with X-ray volumetric cone-beam Imaging (XVI) system enable verification of location of patients and displacement of tumors for image-guided radiotherapy (IGRT). The objective of this study is to evaluate the positioning accuracy using the XVI system for image-guided patient setup and to establish a lower-dose imaging protocol without sacrificing positioning accuracy for routine treatment courses. Several low-dose imaging protocols are proposed by modifying tube voltage from 120 to 100 kV and lowering tube current from 40 to 10 mA. The positioning accuracy of both bone and gray value registration methods provided by XVI system were also evaluated. Phantom study revealed that the gray value algorithm was more accurate than the bone algorithm in position and registration. However, both translational and rotational accuracies were less than 0.15 mm and 0.8^° at all dimensions, which were considered negligible in clinical applications. In addition, the lower-dose protocol (100 kV, 10 mA) produced relative much less radiation dose compared to the default CBCT protocol in the XVI system. In conclusion, our proposed lower-dose protocol results in significant radiation dose reduction without compromising positioning accuracy and may have the potential to be adopted for clinical usage in the future.     

A method to determine the planar dose distributions in patient undergone radiotherapy

A 2D-array equipped with 729 vented plane parallel ion-chambers has been calibrated as a portal dose detector for radiotherapy in vivo measurements. The array has been positioned by a radiographic film stand at 120 cm from the source orthogonal to the radiotherapy beam delivered with the gantry angle at 180°. The collision between the 2D-array and the patient’s couch have been avoided. In this work, using the measurements of the portal detector, we present a method to reconstruct the dose variations in the patient treated with step and shoot intensity-modulated beams (IMRT) for head-neck tumours. For this treatment morphological changes often occur during the fractionated therapy.In a first step an in-house software supplied the comparison between the measured portal dose and the one computed by a commercial treatment planning system within the field of view of the computed tomography (CT) scanner. For each patient, the percentage P_γ of chambers, where the comparison is in agreement within a selected acceptance criteria, was determined 8 times. At the first radiotherapy fraction the γ-index analysis supplied P_γ values of about 95%, within acceptance criteria in terms of dose-difference, ΔD, and distance-agreement, Δd, that was equal to 5% and 4 mm, respectively. These acceptance criteria were taken into account for small errors in the patient’s set-up reproducibility and for the accuracy of the portal dose calculated by the treatment planning system (TPS) in particular when the beam was attenuated by inhomogeneous tissues and the shape of the head-neck body contours were irregular. During the treatment, some patients showed a reduction of the P_γ below 90% because due to radiotherapy treatment there was a change of the patient’s morphology.In a second step a method, based on dosimetric measurements that used standard phantoms, supplied the percentage dose variations in a coronal plane of the patient using the percentage dose variations measured by the 2D-array portal detector. The results showed that the dose variations due to the change of the patient’s morphology reached 15% and such discrepancies were displayed on the digitally reconstructed radiography of the patient. The dose discrepancies were confirmed by the hybrid plan obtained by the treatment planning system. The good results here reported show that once it is possible to have the portal dose distributions even for other gantry angles, these tests could be introduced in the clinical protocol to have major support to decide when to repeat the patient’s CT scan and to re-plan the new IMRT dose calculation.