低辐射剂量肾动脉CTA的扫描参数及重建方法优化研究

摘要

目的:探讨基于原始数据的迭代重建技术在80 kVp条件下肾动脉CTA检查的可行性,并优化其重建参数.方法:回顾性搜集临床怀疑泌尿系病变并已行泌尿系CT增强检查的连续病例40例,根据扫描管电压分为两组:80 kVp组(20例)和120 kVp组(20例).分别以5种不同迭代重建强度(S1 -S5)对80 kVp组图像进行重建,并与滤波反投影法(FBP)重建的120 kVp组图像进行比较,图像质量评价包括客观评价与主观评价,客观评价指标包括:目标血管和空气CT值、对比噪声比(CNR)、信噪比(SNR).主观评价由2名有经验的影像诊断医师对80 kVp最佳图像组和120 kVp组图像进行盲法评估并检验两者读片一致性,包括整体图像质量和图像细节.记录辐射剂量报告表,并计算出每一个患者的 SSDE.结果:80 kVp 组 CTDIvol 为(10. 26 ± 1. 45) mGy, SSDE为(16. 33 ± 2. 36) mGy. 120 kVp组的 CTDIvol 为(14. 95±2. 79) mGy,SSDE为(22. 83±1. 96) mGy.两者差异均具有统计学意义(P＜0. 05).图像质量客观评价:80 kVp组和120 kVp组双侧肾动脉CT值差异有统计学意义(P＜0. 05);80kVp组最佳组(S4)和120kVp组的CNR和SNR差异均有统计学意义(P＜0. 05).主观评价:2名诊断医师对S4图像和120 kVp组图像的整体图像质量、图像细节及病变诊断信心的差异均无统计学意义(P＞0. 05),并表现出了较好的一致性.结论:基于原始数据的迭代重建技术80 kVp条件下所得肾动脉CTA图像满足临床诊断要求并且降低了患者所接受的辐射剂量,建议使用 SAFIRE-4为肾动脉CTA的迭代重建强度.%Objective:To study the feasibility of renal artery CTA at 80kVp with the technique of iterative reconstruction based on raw data, and to find out the optimal reconstruction parameters. Methods:Forty consecutive patients with suspected renal lesion were enrolled in this study, all patients had enhanced CT of urinary system. According to the tube voltage of scanning, patients were divided into two groups:80kVp group (n = 20) and 120kVp group (n=20). Five sets of different iterative reconstructive strength (S1 -S5) were used for the reconstruction of 80kVp group, which were compared with the images of 120kVp group reconstructed with filtered back projection (FBP). Image quality was evaluated quantitatively and qualitatively, with the parameters including CT value of target vessel and air, contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were used as the objective and quantiitative parameters. For qualitative assessment, the optimal images of 80kVp and 120kVp groups including the whole image quality and detail image quality were evaluated blindly by two experienced radiologists subjectively, the inter-observer agreement was also evaluated. CTDIvol was recorded, and SSDE was also calculated for each patient. Results: The CTDlvol for 80kVp group was(10. 26±1. 45) mGy and SSDE was (16. 33 ± 2. 36) mGy, respectively: However, the CTDIvol for 120kVp group was (14. 95 ± 2. 79)mGy and SSDE was (22. 83 ± 1. 96)mGy, respectively, with statistic difference (P＜10. 05). For objective quantitative evaluation, there was significant statistical difference in CT value of bilateral renal artery between these two groups (P＜0. 05), as well as CNR and SNR for optimal renal artery in CTA (S4) of 80kVp group and in 120kVp group (P＜0. 05). For subjective qualitative assessment of the 2 radiologists, significant statistical difference was not existed in the whole image quality, detail image quality and diagnostic confidence between S4 of 80kVp group and 120kVp group (P＞0. 05). Conclusion:The image quality of renal artery CTA at 80kVp with the technique of iterative reconstruction based on raw data was satisfactory for clinical application, which has a potential to reduce the radiation dose, and SAFIRE-S4 is suggested to use for the strength of iterative reconstruction in renal CTA.