Feasibility study on dual-layer spectral detector CT-derived virtual non-contrast images substitute for true non-contrast images / 中华放射学杂志

ABSTRACT

Objective To explore the feasibility of the virtual non-contrast images derived from dual-layer spectral detector CT (SDCT) substitute for true non-contrast images.Methods From July 2017 to September 2017,40 patients under-went pre-and arterial-venous dual-phase post-contrast abdominal imagining on a SDCT in Shanghai Jiaotong University School of Medicine Affiliated Ruijin Hospital.The images were retrospectively analyzed.The arterial VNC images (VNC-a) and venous VNC images (VNC-v)were derived from spectral based image (SBI) datasets of arterial and portal venous phase using a dedicated software respectively.Then mean CT attenuation,mean image noise,signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were compared with one-way ANOVA analysis among TNC,VNC-a,VNC-v images in liver,spleen,pancreas,abdominal aorta,inferior vena cava,psoas muscle,L4 vertebra and perirenal fat.And Bland-Altman plots was used to analyze the CT attenuation equivalence between TNC and VNC.Subjective image quality was assessed with a 5-point scale and compared with Friedman H test.The dose length product (DLP) of pre-and post-contrast scans were recorded.Results The CT attenuation of abdominal aorta,perirenal fat,L4.vertebra among three kinds of images had significant differences (P＜0.05)which overestimated the CT attenuation of perirenal fat and underestimated CT attenuation of abdominal aorta and vertebra compared to TNC,VNC.Except for pancreas,the image noise of all other tissues among three kinds of images had significant differences,images noise of VNC images were lower than TNC images (P＜0.05).The SNR of liver,spleen,psoas muscle and inferior vena cava and CNR of pancreas,abdominal aorta,inferior vena cava,L4 vertebra and perirenal fat were statistically significant among the three images (P＜0.05).Except for vertebra and perirenal fat,good equivalence between VNC and TNC images were observed in all relevant tissues with Bland-Altman analysis.Image quality subjective scoring of TNC,VNC-a,and VNC-v were 5.00(1.00),5.00(0.75),5.00(1.00) respectively which had no significant differences (P=0.20).The DLP of TNC,arterial and venous phase scan were (255.2±62.0),(258.9±62.9),(252.0±61.2)mGy·cm,and the total DLP of dual-phase contrast enhanced scan was (766.2± 185.3) mGy· cm.The DLP of TNC accounted for 33.3％(255.2/766.2) of the total DLP,and effective dose of TNC was (3.83±0.90)mSv.Conclusions CT attenuation in VNC image which exhibited lower image noise was identical to TNC images in the majority of abdomen tissues except for vertebra and perirenal fat.and the VNC image.The VNC image which reduces radiation dosage derives from SDCT enhanced image might be used as a substitute for the TNC image.