摘要
目的:探究深度学习图像重建(deep learning image reconstruction,DLIR)在基于能谱CT虚拟平扫(vir-tual non-contrast scan,VNC)的CT尿路成像(CT urography,CTU)中的图像质量和肾结石测量精度.方法:回顾性分析2022年9月至2023年4月期间于我院行腹盆平扫和CTU的90例患者的临床和影像学资料.所有患者均在常规行腹盆CT平扫后,进行能谱模式的多期CTU扫描.真实平扫采用ASIR-V 70%权重进行重建(TNC-AR70组).基于基于实质期及排泌期数据分别获得2组VNC图像,再分别结合DLIR中档和高档权重重建得到4组VNC图像,即实质期-VNC-DLIR中档(venous phase-VNC-DLIR medium,VP-VNC-DM)组、实质期-VNC-DLIR高档(venous phase-VNC-DLIR high,VP-VNC-DH)组、排泌期-VNC-DLIR中档(delay phase-VNC-DLIR medium,DP-VNC-DM)组、排泌期-VNC-DLIR高档(delay phase-VNC-DLIR high,DP-VNC-DH)组.记录平扫、实质期及排泌期的辐射剂量.在5组图像上分别测量CT值、噪声(SD)、信噪比(signal-to-noise ratio,SNR)和对比噪声比(contrast-to-noise ratio,CNR),并进行组间比较.由2位资深放射诊断医师,用李克特五级量表法(Likert Scale)计分方法对图像质量和病灶显示度进行主观评价.此外,以TNC作为标准,采用Bland-Altman分析VNC上肾结石的CT值和体积的测量差异.结果:在客观图像质量评价上,VNC-DH组图像质量优于TNC-AR70,且5组图像间的CT值差异无统计学意义(P＞0.05);DP-VNC-DH组的图像噪声最低,SNR、CNR最高.在主观评价方面,DP-VNC-DH组的图像质量评分最高,而VP-VNC-DH组在病灶显示度方面表现最佳.在结石的CT值和体积测量上,4组VNC重建图像与真实平扫之间均无统计学差异(P＞0.05).结论:在CTU检查中,基于DLIR重建技术的VNC图像质量优于基于ASIR-V 70%重建的真实平扫,推荐结合使用实质期和排泌期的DLIR-H重建VNC图像代替真实平扫,以减少CTU扫描的辐射剂量.
Abstract
Objective To investigate the effect of dual-energy CT(DECT)virtual non-contrast(VNC)images recon-structed by deep learning image reconstruction(DLIR)on the image quality and measurements of renal calculus in CT urog-raphy(CTU).Methods The clinical and imaging data of 90 patients who underwent abdominal and pelvic non-contrast CT examination followed by a nephrographic-phase DE CTU during September 2022 to April 2023 were retrospectively ana-lyzed.The non-contrast CT images were reconstructed with ASIR-V with 70%weight(TNC-AR70).Four groups of VNC im-ages were reconstructed based on medium level and high level DLIR for venous phase and delay phase,namely venous phase-VNC-DLIR medium(VP-VNC-DM),venous phase-VNC-DLIR high(VP-VNC-DH),delay phase-VNC-DLIR medium(DP-VNC-DM),and delay phase-VNC-DLIR high(DP-VNC-DH).The radiation doses of TNC and VNC in venous phase and delay phase were recorded.The mean CT value,image noise(SD),signal-to-noise ratio(SNR)and contrast-to-noise(CNR)were recorded and compared among the five groups.Two radiologists independently assessed the overall image qua-lity and lesion visibility with 5-point Likert scale.Additionally,according to results of TNC,Bland-Altman was used to ana-lyze the measurement differences between VNC and TNC in mean CT value and mean size of renal calculus.Results In the objective assessments,the image quality of the VNC-DH group was better than that of TNC-AR70,and there was no statisti-cally significant difference in CT value among the five groups of images(P＞0.05).DP-VNC-DH showed the lowest SD and the highest SNR and CNR values.In the subjective assessments,DP-VNC-DH achieved the best subject scores on image qua-lity,and VP-VNC-DH achieved the best subject scores on lesion visibility.Furthermore,Bland-Altman analysis showed that there was a strong overall agreement between VNC and TNC for renal calculus characterization(all P＞0.005).Conclu-sions VNC generated by DLIR may provide high-quality image compared with the non-contrast images reconstructed with ASIR-V 70%in CTU.The combination of the VNC images generated by DLIR-H from venous phase and delay phase could replace TNC scanning,reducing the radiation dose of CTU scans.
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