基于头颈部千伏级锥形束CT的剂量计算研究

目的 探讨用机载千伏级锥形束CT (CBCT)对鼻咽癌患者治疗前扫描图像直接进行剂量计算的可行性.方法 选取治疗前行扇形束CT (FBCT)和CBCT扫描的11例鼻咽癌患者,将体位校正后重新扫描的CBCT图像传输至治疗计划系统中.在治疗计划系统中将FBCT和CBCT图像融合,将FBCT的计划移植至CBCT上.选择CBCT图像自己的HU-ED校正曲线重新进行剂量计算,与FBCT计划的靶区和正常器官的剂量体积直方图以及等中心层面剂量分布的γ通过率分析(阈值3%/3 mm)结果进行比较.结果 11例鼻咽癌患者中CBCT和FBCT计划的剂量体积直方图相似,等中心层面剂量分布中平均γ通过率为98.0%±1.33%.FBCT计划和CBCT计划的靶区受量差异都<1%,正常组织器官受量差异<2%.结论 治疗过程中得到的CBCT图像能用来进行剂量计算.

Abstract：

Objective To study the feasibility of dose calculation using kilovoltage X-ray cone-beam CT (KVCBCT) imaging for head-and-neck radiation therapy.Methods 11 patients with nasopharyngeal carcinoma were scanned with KVCBCT to adjust position before treatment, and rescanning images with KVCBCT after correction were input a treatment-planning system.The dose was recalculated by applying the patients′ treatment plans based on planning CT to the KVCBCT images.The dose distributions and dose volume histograms (DVH) of the tumor and critical structures were compared with the original treatment plan.Results The DVH and dose distribution of the plan based on the KVCBCT are compared with that of the planning CT, and they shows a good consistency for the 11 cases.The doses calculated from the planning CT and KVCBCT were compared on the isocenter planes.Using γ analysis with a criterion of 3%/3 mm, 98.0%±1.33% of the points on the isocenter planes in the planning CT and KVCBCT.The difference of the dose to target volume was<1% and to normal structure was<2%.Conclusions This study indicated that CBCT images can be used to make a treatment plan with its individual hounsfield unit-electron density calibration curve.     

兆伏级锥形束CT影像质量定量分析

目的 定量分析不同成像条件下兆伏级锥形束CT(MVCBCT)的影像质量,为临床应用提供参考.方法 采用西门子ONCOR直线加速器上的MVCBCT设备,在不同的成像条件下扫描影像质昔模体.通过分析影像均匀性、噪声、空间分辨率、对比度分辨率及成像剂量来评估其影像质量,并与常规大孔径CT影像进行定量比较.结果 MVCBCT影像噪声随加速器出束跳数(MU)增加而减少.均匀性指数与成像MU数及重建矩阵无线件关系.空间分辨率上采用256×256重建矩阵除5MU条件下为0.25 lp/mm,其他皆为0.4 lp/mm.随MU数增加对比度分辨率增加.成像剂量上头颈患者接受最大剂量为1.2 cGy/MU,中心位置剂量为0.8～0.9 cGy/MU,腹部最大和中心处分别为1.3cGy/MU和0.7 cGy/MU.结论 MVCBCT的噪声、均匀性、空间分辨率及对比度分辨率都差于常规扇形束CT.通过选择恰当成像参数和重建参数,可在患者接受尽量低成像剂量的同时获得足够分辨率来分辨骨组织、空腔及部分软组织用于影像引导放疗.     

兆伏级锥形束CT影像质量定量分析

Objective To quantitatively analyze the image quality of megavoltage cone-beam CT (MVCBCT) under different scanning conditions to provide reference in clinical applications. Methods Si-emens ONCOR linear accelerator with MVCBCT was used to scan the phantom under different conditions. The image quality was evaluated in terms of image noise, uniformity, spatial resolution, contrast resolution, the number of Monitor Units(MUs) used in imaging,and the size of the reconstruction matrix. The comparison of the image quality between MVCBCT and conventional simulator CT was also analyzed. Results The image noise was decreased with the increase of the number of MUs. The uniformity index showed that the system u-niformity was weakly dependent on MU numbers or the size of the reconstruction matrix. Except for the ima-ges with 5 MUs,all other images had the spatial resolution of 0.4 lp/mm with a reconstruction matrix of 256 ×256. Better low contrast resolution was achieved by using more MUs. For typical pelvis and head-and-neck patients,the imaging dose at the center was 0.8 cGy/MU and 0.7 cGy/MU, respectively,and the maxi-mum dose was about 1.2 cGy/MU. For typical abdomen patients,the image maximum dose and center dose was 1.3 cGy/MU and 0.7 cGy/MU,respectively. Conclusions The image quality of MVCBCT is inferior to the conventional kilo-voltage CT. However,with the optimization of the parameters in imaging,we can a-chieve sufficient image contrast in the bone,air and some soft-tissue structures with low imaging dose to pa-tients. Such images can be used for IGRT.     

兆伏级锥形束CT影像质量定量分析

Objective To quantitatively analyze the image quality of megavoltage cone-beam CT (MVCBCT) under different scanning conditions to provide reference in clinical applications. Methods Si-emens ONCOR linear accelerator with MVCBCT was used to scan the phantom under different conditions. The image quality was evaluated in terms of image noise, uniformity, spatial resolution, contrast resolution, the number of Monitor Units(MUs) used in imaging,and the size of the reconstruction matrix. The comparison of the image quality between MVCBCT and conventional simulator CT was also analyzed. Results The image noise was decreased with the increase of the number of MUs. The uniformity index showed that the system u-niformity was weakly dependent on MU numbers or the size of the reconstruction matrix. Except for the ima-ges with 5 MUs,all other images had the spatial resolution of 0.4 lp/mm with a reconstruction matrix of 256 ×256. Better low contrast resolution was achieved by using more MUs. For typical pelvis and head-and-neck patients,the imaging dose at the center was 0.8 cGy/MU and 0.7 cGy/MU, respectively,and the maxi-mum dose was about 1.2 cGy/MU. For typical abdomen patients,the image maximum dose and center dose was 1.3 cGy/MU and 0.7 cGy/MU,respectively. Conclusions The image quality of MVCBCT is inferior to the conventional kilo-voltage CT. However,with the optimization of the parameters in imaging,we can a-chieve sufficient image contrast in the bone,air and some soft-tissue structures with low imaging dose to pa-tients. Such images can be used for IGRT.     

兆伏级锥形束CT影像质量定量分析

Objective To quantitatively analyze the image quality of megavoltage cone-beam CT (MVCBCT) under different scanning conditions to provide reference in clinical applications. Methods Si-emens ONCOR linear accelerator with MVCBCT was used to scan the phantom under different conditions. The image quality was evaluated in terms of image noise, uniformity, spatial resolution, contrast resolution, the number of Monitor Units(MUs) used in imaging,and the size of the reconstruction matrix. The comparison of the image quality between MVCBCT and conventional simulator CT was also analyzed. Results The image noise was decreased with the increase of the number of MUs. The uniformity index showed that the system u-niformity was weakly dependent on MU numbers or the size of the reconstruction matrix. Except for the ima-ges with 5 MUs,all other images had the spatial resolution of 0.4 lp/mm with a reconstruction matrix of 256 ×256. Better low contrast resolution was achieved by using more MUs. For typical pelvis and head-and-neck patients,the imaging dose at the center was 0.8 cGy/MU and 0.7 cGy/MU, respectively,and the maxi-mum dose was about 1.2 cGy/MU. For typical abdomen patients,the image maximum dose and center dose was 1.3 cGy/MU and 0.7 cGy/MU,respectively. Conclusions The image quality of MVCBCT is inferior to the conventional kilo-voltage CT. However,with the optimization of the parameters in imaging,we can a-chieve sufficient image contrast in the bone,air and some soft-tissue structures with low imaging dose to pa-tients. Such images can be used for IGRT.     

兆伏级锥形束CT影像质量定量分析

Objective To quantitatively analyze the image quality of megavoltage cone-beam CT (MVCBCT) under different scanning conditions to provide reference in clinical applications. Methods Si-emens ONCOR linear accelerator with MVCBCT was used to scan the phantom under different conditions. The image quality was evaluated in terms of image noise, uniformity, spatial resolution, contrast resolution, the number of Monitor Units(MUs) used in imaging,and the size of the reconstruction matrix. The comparison of the image quality between MVCBCT and conventional simulator CT was also analyzed. Results The image noise was decreased with the increase of the number of MUs. The uniformity index showed that the system u-niformity was weakly dependent on MU numbers or the size of the reconstruction matrix. Except for the ima-ges with 5 MUs,all other images had the spatial resolution of 0.4 lp/mm with a reconstruction matrix of 256 ×256. Better low contrast resolution was achieved by using more MUs. For typical pelvis and head-and-neck patients,the imaging dose at the center was 0.8 cGy/MU and 0.7 cGy/MU, respectively,and the maxi-mum dose was about 1.2 cGy/MU. For typical abdomen patients,the image maximum dose and center dose was 1.3 cGy/MU and 0.7 cGy/MU,respectively. Conclusions The image quality of MVCBCT is inferior to the conventional kilo-voltage CT. However,with the optimization of the parameters in imaging,we can a-chieve sufficient image contrast in the bone,air and some soft-tissue structures with low imaging dose to pa-tients. Such images can be used for IGRT.     

兆伏级锥形束CT影像质量定量分析

Objective To quantitatively analyze the image quality of megavoltage cone-beam CT (MVCBCT) under different scanning conditions to provide reference in clinical applications. Methods Si-emens ONCOR linear accelerator with MVCBCT was used to scan the phantom under different conditions. The image quality was evaluated in terms of image noise, uniformity, spatial resolution, contrast resolution, the number of Monitor Units(MUs) used in imaging,and the size of the reconstruction matrix. The comparison of the image quality between MVCBCT and conventional simulator CT was also analyzed. Results The image noise was decreased with the increase of the number of MUs. The uniformity index showed that the system u-niformity was weakly dependent on MU numbers or the size of the reconstruction matrix. Except for the ima-ges with 5 MUs,all other images had the spatial resolution of 0.4 lp/mm with a reconstruction matrix of 256 ×256. Better low contrast resolution was achieved by using more MUs. For typical pelvis and head-and-neck patients,the imaging dose at the center was 0.8 cGy/MU and 0.7 cGy/MU, respectively,and the maxi-mum dose was about 1.2 cGy/MU. For typical abdomen patients,the image maximum dose and center dose was 1.3 cGy/MU and 0.7 cGy/MU,respectively. Conclusions The image quality of MVCBCT is inferior to the conventional kilo-voltage CT. However,with the optimization of the parameters in imaging,we can a-chieve sufficient image contrast in the bone,air and some soft-tissue structures with low imaging dose to pa-tients. Such images can be used for IGRT.     

兆伏级锥形束CT影像质量定量分析

Objective To quantitatively analyze the image quality of megavoltage cone-beam CT (MVCBCT) under different scanning conditions to provide reference in clinical applications. Methods Si-emens ONCOR linear accelerator with MVCBCT was used to scan the phantom under different conditions. The image quality was evaluated in terms of image noise, uniformity, spatial resolution, contrast resolution, the number of Monitor Units(MUs) used in imaging,and the size of the reconstruction matrix. The comparison of the image quality between MVCBCT and conventional simulator CT was also analyzed. Results The image noise was decreased with the increase of the number of MUs. The uniformity index showed that the system u-niformity was weakly dependent on MU numbers or the size of the reconstruction matrix. Except for the ima-ges with 5 MUs,all other images had the spatial resolution of 0.4 lp/mm with a reconstruction matrix of 256 ×256. Better low contrast resolution was achieved by using more MUs. For typical pelvis and head-and-neck patients,the imaging dose at the center was 0.8 cGy/MU and 0.7 cGy/MU, respectively,and the maxi-mum dose was about 1.2 cGy/MU. For typical abdomen patients,the image maximum dose and center dose was 1.3 cGy/MU and 0.7 cGy/MU,respectively. Conclusions The image quality of MVCBCT is inferior to the conventional kilo-voltage CT. However,with the optimization of the parameters in imaging,we can a-chieve sufficient image contrast in the bone,air and some soft-tissue structures with low imaging dose to pa-tients. Such images can be used for IGRT.     

兆伏级锥形束CT影像质量定量分析

Objective To quantitatively analyze the image quality of megavoltage cone-beam CT (MVCBCT) under different scanning conditions to provide reference in clinical applications. Methods Si-emens ONCOR linear accelerator with MVCBCT was used to scan the phantom under different conditions. The image quality was evaluated in terms of image noise, uniformity, spatial resolution, contrast resolution, the number of Monitor Units(MUs) used in imaging,and the size of the reconstruction matrix. The comparison of the image quality between MVCBCT and conventional simulator CT was also analyzed. Results The image noise was decreased with the increase of the number of MUs. The uniformity index showed that the system u-niformity was weakly dependent on MU numbers or the size of the reconstruction matrix. Except for the ima-ges with 5 MUs,all other images had the spatial resolution of 0.4 lp/mm with a reconstruction matrix of 256 ×256. Better low contrast resolution was achieved by using more MUs. For typical pelvis and head-and-neck patients,the imaging dose at the center was 0.8 cGy/MU and 0.7 cGy/MU, respectively,and the maxi-mum dose was about 1.2 cGy/MU. For typical abdomen patients,the image maximum dose and center dose was 1.3 cGy/MU and 0.7 cGy/MU,respectively. Conclusions The image quality of MVCBCT is inferior to the conventional kilo-voltage CT. However,with the optimization of the parameters in imaging,we can a-chieve sufficient image contrast in the bone,air and some soft-tissue structures with low imaging dose to pa-tients. Such images can be used for IGRT.     

兆伏级锥形束CT影像质量定量分析

Objective To quantitatively analyze the image quality of megavoltage cone-beam CT (MVCBCT) under different scanning conditions to provide reference in clinical applications. Methods Si-emens ONCOR linear accelerator with MVCBCT was used to scan the phantom under different conditions. The image quality was evaluated in terms of image noise, uniformity, spatial resolution, contrast resolution, the number of Monitor Units(MUs) used in imaging,and the size of the reconstruction matrix. The comparison of the image quality between MVCBCT and conventional simulator CT was also analyzed. Results The image noise was decreased with the increase of the number of MUs. The uniformity index showed that the system u-niformity was weakly dependent on MU numbers or the size of the reconstruction matrix. Except for the ima-ges with 5 MUs,all other images had the spatial resolution of 0.4 lp/mm with a reconstruction matrix of 256 ×256. Better low contrast resolution was achieved by using more MUs. For typical pelvis and head-and-neck patients,the imaging dose at the center was 0.8 cGy/MU and 0.7 cGy/MU, respectively,and the maxi-mum dose was about 1.2 cGy/MU. For typical abdomen patients,the image maximum dose and center dose was 1.3 cGy/MU and 0.7 cGy/MU,respectively. Conclusions The image quality of MVCBCT is inferior to the conventional kilo-voltage CT. However,with the optimization of the parameters in imaging,we can a-chieve sufficient image contrast in the bone,air and some soft-tissue structures with low imaging dose to pa-tients. Such images can be used for IGRT.     

千伏级锥形束CT图像对食管癌放疗剂量计算可行性研究

目的 探讨千伏级锥形束CT图像(KVCBCT)对食管癌放疗剂量计算的可行性。方法 比较Trilogy加速器采集的Catphan600模体KVCBCT图像CT值稳定性及离轴曲线重合度并建立CT值-密度转换曲线用于剂量计算。在模体和 10例食管癌患者常规CT上设计逆向调强计划,并将计划移植到相对应的KVCBCT图像上。基于KVCBCT的转换曲线计算靶区及周围组织受量,并与常规CT计算结果行配对t检验。结果 KVCBCT的CT值变化范围均在1.6%内,且未发现有随时间变化趋势。常规CT和KVCBCT的CT值离轴曲线重合度较高,大部分成像区域差别在1%内。模体调强计划常规CT与KVCBCT所得剂量统计参数最大差别为1.33%,对食管癌患者调强计划两者剂量差别在3.65%内。等中心层面剂量分布有较好一致性。结论 使用食管癌KVCBCT图像进行剂量计算是准确可行的,在临床上具有实际应用意义。     

瓦里安CBCT在ICRP标准人女性模体胸部IGRT剂量及风险

目的 利用蒙特卡洛模拟和ICRP110标准女性模体定量研究瓦里安CBCT默认参数胸部扫描的剂量分布和辐射风险。方法 利用EGSnrc/BEAMnrc模拟CBCT千伏射线源材料、厚度、结构等建立模型。标定MCSIM程序以计算ICRP模体在标准胸部参数扫描(110 kV、20 mA、262 mAs)后的剂量分布,其中绝对剂量转换系数依照TG-61规范在球形模体中获得。通过水模体中的PDD、Profile、CTDI以及Alderson仿真模体中的点剂量测量验证蒙特卡洛模拟结果。利用BEIR Ⅶ等模型评估辐射风险。结果 按照3%/1 mm标准,PDD和Profile的不确定度均<2%。CTDI模体测量与计算值差异<2.9%,Alderson模体内差异≤0.05 cGy。ICRP110模体的左肺、右肺、左乳、右乳、心脏、甲状腺、气管、松质骨、密质骨的 D_mean分别为1.28、1.39、1.74、1.80、1.46、0.48、0.88、0.85、1.84 cGy。单次扫描对应的缺血性心脏病、乳腺癌、肺癌、甲状腺癌、气管癌的相对风险值分别为1.001、1.009、1.019、1.000、1.008。结论 CBCT成像在影像引导胸部放疗过程中的累积剂量及其远期风险不可忽略且应被合理管控。     

兆伏锥形束CT在头颈部肿瘤精确放疗摆位误差的研究

目的 分析兆伏锥形束CT(MVCBCT)引导的头颈部肿瘤精确放疗中摆位误差.方法 头颈部肿瘤共22例(鼻咽癌15例,腮腺癌4例,脑胶质瘤术后3例),其中接受三维适形放疗7例、调强放疗15例,照射剂量为56.0～70.4 Gy分28～32次6～7周完成.19例用头颈肩面罩固定,3例头部面罩固定.所有患者均行CT模拟,勾画靶区和危及器官.每周治疗前拍1次MVCBCT图像,每位患者接受4～7次MVCBCT.分析相对于计划CT上中心在头脚、垂直、左右方向上的摆位误差.结果 左右、前后和头脚方向中任一方向>0.3 cm 28次,>0.4 cm 15次,>0.5 cm 9次,头脚方向要比左右、前后方向超过近0.1 cm.头脚和左右中心偏移方向的频次差别不大,而在垂直方向则更多的向后偏移达4:1.相对来说头脚方向摆位误差较左右、前后方向大,随着放疗时间延长各方向偏移的平均值均有增大趋势.结论 头颈部肿瘤精确放疗时CTV至PTV边界外扩并不需均匀外放,垂直方向上治疗中心向前偏移概率明显超过向后,头脚方向比左右、前后方向摆位误差大;随着放疗的进行3个方向上的摆位误差都有增大趋势.     

医科达Synergy加速器ⅩⅥ系统CBCT扫描头颈部模体的误差研究

目的 探讨医科达Synergy加速器ⅩⅥ系统图像自动匹配结果的准确性。方法 应用仿真模体ART头部进行仿真模拟计划设计后进行模体CBCT扫描,测量在不同匹配区域、不同匹配方法以及在不同方向上定量移床后扫描的匹配误差,获取数据进行分析。结果 在定量移床后模体扫描匹配误差与相应移床量数据基本吻合,x、y、z轴向总误差分别为(0.11±0.41)、(－0.04±2.6)、(0.28±0.74) mm。在不同匹配区域、不同匹配方法下进行自动匹配,各组数据差异较小。但对不同匹配区域、不同匹配方法上存在一些配对差异。结论 ⅩⅥ系统的自动匹配功能在头颈部应用上匹配精确,对偏移误差辨识准确可信度高。但对不同匹配区域、不同匹配方法上存在一定优劣对比,在实际运用中可根据实际情况择优应用。     

宫颈癌调强放疗中直肠体积与位置变化及对吸收剂量影响

目的 探讨宫颈癌患者调强放疗(IMRT)中直肠体积与位置变化及对吸收剂量的影响。方法 对随机选取 10例宫颈癌根治性IMRT患者采集分次治疗前锥形束CT (CBCT)图像,与原始计划CT图像基于骨性解剖结构进行刚体配准,勾画出CBCT图像直肠轮廓并映射回原始计划CT图像,分析直肠体积与位置变化并评价直肠接受≥45 Gy体积占总体积百分比(V₄₅)改变。直肠体积与 V₄₅相关性分析采用Spearman法。结果 10例患者共采集227次CBCT图像进行分析,其中直肠体积变化为(35.0±7.3)~(97.7±14.7) cm³,直肠中心位移左右方向为(0.14±0.06) cm、前后方向为(0.24±0.10) cm、头脚方向为(0.55±0.28) cm,直肠 V₄₅为(9.19±2.46)%~(60.54±11.67)%。直肠体积与 V₄₅相关性分析显示 7例患者呈正相关(r=0.582~0.743,P值均<0.01);治疗中 V₄₅≤50%次数共68次,占30.0%。结论 宫颈癌IMRT中直肠体积与位置及其实际吸收剂量在分次放疗间变化较大,大部分患者体积与 V₄₅之间呈正相关。     

间歇式屏气CBCT图像采集优选模式研究

目的 旨在建立一种实用型间歇式屏气CBCT图像采集优选模式。方法 利用自制呼吸运动模型模拟肿瘤患者膈肌附近肿块在屏气和自由呼吸状态下的运动情况并行CBCT扫描。扫描模式有常规屏气CBCT扫描(主要分为屏气间隙暂停扫描、进行自由呼吸、自由呼吸不计入扫描过程)及间歇式屏气CBCT扫描Ⅰ型和Ⅱ型(主要分为若干个屏气和自由呼吸时段,以近3∶1比例作间歇式调配并一次完成扫描),将常规屏气CBCT扫描作为标准技术,与2种间歇式屏气CBCT扫描就图像质量及使用该图像实现三维配准的精度进行量化比较分析。间歇式屏气CBCT图像质量参数与常规屏气CBCT图像行配对t检验。结果 2种间歇式屏气CBCT图像均产生运动伪影,其重建像素值与常规扫描相比较为一致(P>0.05),均匀性无明显改变(P=0.02、0.53),但图像信噪比分别减少30%和60%(P<0.05)。图像配准误差除上下方向最大为0.4 cm以外,其余均在0.1 cm以内。结论 在体模研究阶段,间歇式屏气CBCT扫描图像采集模式并未明显降低图像质量和配准精度,其实际临床的可行性还需在大量患者身上进一步得到验证。     

千伏级锥形束CT图像质量和稳定性及三维影像体积重建精度研究

目的 定量评价瓦里安加速器机载千伏级锥形束CT (CBCT)的图像质量、稳定性及三维影像体积重建精度。方法 应用CBCT系统分别采用全扇形扫描和半扇形扫描方式重复扫描Catphan600模体,用治疗计划系统评价图像质量参数(低对比度分辨率、空间分辨率、均匀性及噪声)及体积重建精度;并以常规大孔径模拟CT (FBCT)图像为基准做定量比较,观察其长期稳定性。结果 CBCT空间分辨率与FBCT无差别(6 lp/cm∶6 lp/cm,T=18.00,P>0.05)。CBCT_Full-Fan与CBCT_Half-Fan低对比度分辨率均高于FBCT (1.65%与1.74%∶1.03%,T=6.00,P<0.05),其均匀性也高于FBCT (0.005与0.033∶0.003,T=6.00,P<0.05),各项对比度-噪声比也都低于FBCT (T=30.00,P<0.05)。在有效扫描范围内CBCT体积重建精度较高且长期稳定性较好。结论 千伏级CBCT图像质量差于常规FBCT,但仍可实现肿瘤和软组织成像且稳定性好和三维影像体积重建精度高。     

头颈部肿瘤放疗中两种图像引导系统比较研究

目的 比较ExacTrac X线和CBCT两种图像引导系统在头颈部肿瘤放疗中的误差差异。方法 随机选取20例行头颈部放疗患者均分为两组:A组采用红外线小球摆位后行ExacTrac X线拍摄双斜位片,与计划DRR配准后得到左右、上下、前后方向的平移误差和旋转误差,六维放疗床调整误差并记录摆位配准时间;B组采用人工摆位后行CBCT获取图像,与定位CT图像配准得到上述方向平移误差和绕上下方向误差,四维方向上调整误差并记录摆位配准时间。采用配对t检验比较两组差异。结果 A组与B组左右、上下、前后方向平移误差分别为(0.59±0.25)、(0.62±0.25)(1.56±0.28) mm与(0.52±0.31)、(0.74±0.17)、(1.58±0.34) mm (P=0.43、0.21、0.90);旋转误差中A组左右、上下、前后方向分别为(0.54±0.17)°、(0.72±0.27)°、(0.44±0.22)°,B组绕上下方向为(1.26±0.33)°(P=0.01)。摆位配准时间A组小于B组(108.0 s∶165.8 s,P=0.00)。     

基于3DCT、4DCT和CBCT增强扫描测量正常食管壁厚度的研究

目的 比较3DCT、4DCT和CBCT增强扫描图像测量的正常食管壁厚度,为食管癌靶区的勾画提供参考。方法 对2009—2016年间50例肺癌或转移性肺癌患者行胸部增强3DCT、4DCT模拟定位扫描,并于首次3DCRT时进行增强CBCT扫描。分别在3DCT、4DCT呼气末时相(4DCT₅₀)、4DCT最大密度投影图像(4DCT_MIP)及CBCT图像上勾画正常食管,逐层测量各段食管壁厚度取平均值。对同段食管在不同CT图像上管壁厚度的比较行成组t检验,对不同段食管在同种CT图像上管壁厚度的比较行单因素方差分析。结果 3DCT与4DCT₅₀图像间胸段及腹段食管壁厚度差异无统计学意义(P=0.056~0.550);3DCT与4DCT_MIP、CBCT图像间胸段和腹段食管壁的厚度差异有统计学意义(P=0.000~0.004);4DCT_MIP与CBCT图像间胸上、中段食管壁厚度差异有统计学意义(P=0.008、0.001)。在3DCT、4DCT_MIP、4DCT₅₀图像上,胸下段食管壁均较胸上、中段厚(P=0.008~0.041),腹段食管壁较胸段厚(P均=0.000);在CBCT图像上,胸上、中、下段之间的差异均无统计学意义(P=0.088~0.945)。结论 在3DCT、4DCT₅₀图像上勾画胸段食管原发肿瘤GTV时正常食管壁厚度的判断可以使用同一标准,但在4DCT_MIP、CBCT图像上采用5 mm作为勾画GTV时正常食管壁厚度的判定标准尚需谨慎。