双能CT单能谱70keV图像与常规CT 120kVp图像的等效性

Images equivalence of dual-energy computed tomography virtual monochromatic spectral 70 keV images and conventional polychromatic single-energy 120 kVp images

目的探讨双能CT单能谱70keV图像与常规CT 120kVp图像的等效性。方法采用CTU-41型头颈躯干仿真体模,行DECT虚拟单能谱和常规CT成像,联合原始数据迭代重建法SAFIRE(3)和FBP重建算法得到70keV/FBP、70keV/SAFIRE(3)、120kVp/FBP、120kVp/SAFIRE(3)共4组图像,按部位采用配对t检验比较各组织和器官CT值和噪声。结果丘脑、颅骨外空气、胆囊、肝实质、脾脏、前列腺在70keV与120kVp图像上CT值的差异均无统计学意义(P均>0.0083);70keV图像上侧脑室、小脑、胸腺、心脏、肺、胃泡和直肠肠管内空气的CT值低于120kVp图像,下颌骨、胸椎、腰椎、股骨头中央部70keV图像CT值高于120kVp图像,差异均有统计学意义(P<0.006);SAFIRE(3)与FBP算法的70keV单能谱图像、120kVp图像CT值的差异无统计学意义(P均>0.0083)。70keV图像与120kVp图像噪声的差异无统计学意义(P均>0.0083);SAFIRE(3)算法单能谱70keV图像、常规CT 120kVp图像与其FBP重建算法相比较,噪声降低约(25.29±9.39)%和(27.93±8.39)%(P均<0.0083)。结论 70keV与120kVp图像的CT值在部分组织器官不等效;70keV与120kVp图像的噪声水平无明显差异;迭代算法对DECT单能谱成像和常规CT成像均能明显降低图像噪声,提高图像质量。

Objective To explore the equivalence of virtual monochromatic spectral 70 keV images synthesized from the dual-energy computed tomography（DECT）and conventional polychromatic single-energy 120 kVp CT images.MethodsDECT and conventional polychromatic single-energy CT were performed on the male anthropomorphic phantom which including head neck and torso.Sinogram affirmed iterative reconstruction（SAFIRE level3）algorithm and filtered back projection（FBP）algorithm were used,and 70keV/FBP,70keV/SAFIRE（3）,120kVp/FBP,120kVp/SAFIRE（3）images were reconstructed and obtained,respectively.The objective image noises and CT values were measured.The results were analyzed using the paired t-test and mixed-effects model with Bonferroni correction.Results Regardless of reconstruction algorithm,the CT values between 70 keV and 120 kVp images in thalamus,the air outside skull,gall bladder,liver,spleen,prostate were considered no statistical significant differences（all P0.0083）,while the CT values of 70 keV images in lateral ventricle,cerebellum,thymus,heart,lung,the stomach and the air inside rectum were lower than that of120 kVp images,while the CT values of 70 keV images in mandibular,thoracic vertebra,lumbar spine,central part of femoral head were higher than that of 120 kVp images（all P0.006）.The objective image noises between 70 keV and120kVp images with the same reconstruction algorithm were considered no statistical significant differences（all P0.0083）,but the 70 keV or 120 kVp images with SAFIRE level3 and FBP algorithm were considered statistical significant differences（all P0.0083）,the images noises of 70 keV and 120 kVp with SAFIRE level3 algorithm were reduced about（25.29±9.39）% and（27.93±8.39）%compared with FBP algorithm.Conclusion In parts of the tissues and organs,the CT values between 70 keV and 120 kVp images were not equivalent.The objective image noises between 70 keV and120kVp images were equivalent.DECT and conventional polychromatic single-energy CT with iterative algorithm can significantly reduce the image noise and enhance image quality.