双能锥形束CT的分解算法和成像物体尺寸依赖性研究  

Two decomposition algorithms of dual-energy cone beam CT and their dependence on the phantom sizes

作　　者：李晨光 牛田野 周莉[3] 邓军[4] 邹程媛 李莎[6] 刘宏嘉 董正坤 华凌 蒲亦晨 曲靓子 李乔[5] 张艺宝 Li Chenguang;Niu Tianye;Zhou Li;Deng Jun;Zou Chengyuan;Li Sha;Liu Hongjia;Dong Zhengkun;Hua Ling;Pu Yichen;Qu Liangzi;Li Qiao;Zhang Yibao(Institute of Medical Technology,Peking University Health Science Center,Beijing 100191,China;Shenzhen Bay Laboratory y Shenzhen 518118,China;Department of Radiation Oncology,State Key Laboratory of Biolherapy and Cancer Center,West China Hospital,Sichuan University,Chengdu 610041,China;Department of Therapeutic Radiology,Yale University School of Medicine,New Haven 06511,USA;People's Hospital of Deyang City,Deyang 618000,China;Key Laboratory of Carcinogenesis and Translational Research(Ministry of Education/Beijing),Department of Radiation Oncology,Peking University Cancer Hospital&Institute,Beijing 100142,China)

机构地区：[1]北京大学医学部医学技术研究院,北京100191 [2]深圳湾实验室,深圳518118 [3]四川大学华西医院肿瘤中心放疗科生物治疗国家重点实验室,成都610041 [4]耶鲁大学医学院放射肿瘤学系,纽黑文市06511,美国 [5]德阳市人民医院,德阳618000 [6]北京大学肿瘤医院暨北京市肿瘤防治研究所放疗科,恶性肿瘤发病机制及转化研究教育部重点实验室,北京100142

出　　处：《中华放射医学与防护杂志》2022年第4期269-276,共8页Chinese Journal of Radiological Medicine and Protection

基　　金：北京市自然科学基金(Z210008);国家重点研发计划(2019YFF01014405);国家自然科学基金(11505012,11905150,82073333);北京大学肿瘤医院科学研究基金学科骨干项目(2021-1);北大百度基金资助项目(2020BD029);北京大学医学部教育教学研究立项项目(2020YB34);恶性肿瘤发病机制及转化研究教育部/北京市重点实验室开放基金(2022开放-2)。

摘　　要：目的分析"直接分解"和"迭代分解"两种双能锥束CT(DECBCT)分解算法对于不同尺寸模体图像质量和物质分解精度的影响。方法利用CatPhan604模体和定制套环组合,模拟不同尺寸的患者成像部位,在Edge加速器锥形束CT(CBCT)系统上分别获取高能140 kVp和低能100 kVp的CBCT,并分别利用两种算法进行DECBCT的物质分解。分别计算了CTP682模块中各插件的电子密度(ED)和对比度噪声比(CNR),用于评估两种算法的分解精度和输出图像质量。结果基于模体手册中提供的真值,两种算法的ED准确度均较高,其中仅最小尺寸模体的4种插件材料存在统计学差异(z=-4.21、4.30、2.87、5.45,P<0.05),但平均相对误差均<1%。迭代分解算法的CNR显著优于直接分解,相对提高比例为51.8%~703.47%。模体尺寸的增大会显著降低ED的精度,相对误差最大增幅为2.52%。大尺寸模体也会降低迭代分解的图像质量,CNR最大降幅达39.71。结论在不损失电子密度计算精度的前提下,相比于直接分解,迭代分解算法在不同尺寸模体的DECBCT构建中显著降低了图像噪声,提高了对比度。Objective To analyze the effects of two decomposition algorithms of dual-energy cone beam CT(DECBCT)(direct decomposition and iterative decomposition)on the image quality and material decomposition accuracy of different sizes of phantoms.Methods Different sizes of imaging parts of patients were simulated using the combination of CatPhan604 phantoms and customized annuluses.CBCT with high energy of 140 kVp and low energy of 100 kVp were acquired using the Varian Edge CBCT system.Then the material decomposition of DECBCT images was performed using the two algorithms.The electron density(ED)and contrast-to-noise ratio(CNR)of each material in the CTP682 module were calculated.They were used to assess the decomposition accuracy and image quality of the two algorithms.Results Based on the values in the Catphan604 manual,both algorithms have high ED accuracy.Only the ED accuracy of four materials of the smallest sized phantom showed statistical difference(z=-4.21,4.30,2.87,5.45,P<0.05),but the average relative error was less than 1%.The CNR of the iterative decomposition algorithm was significantly higher than that of the direct decomposition,increasing by 51.8%-703.47%.The increase in the phantom size significantly reduced the accuracy of ED,and the increased amplitude of the relative error was up to a maximum of 2.52%.The large phantom size also reduced the image quality of iterative decomposition,and the decreased amplitude of CNR was up to a maximum of 39.71.Conclusions Compared with the direct decomposition,the iterative decomposition algorithm can significantly reduce the image noise and improve the contrast without losing the accuracy of electron density in the DECBCT construction of different sizes of phantoms.

关 键 词：双能锥形束CT 图像域分解 图像质量 图像引导放疗 

分 类 号：R730.55[医药卫生—肿瘤]