Value of novel dual-layer spectral detector CT in preoperative T staging of rectal cancer / 中华放射学杂志

ABSTRACT

Objective:To explore the optimal keV for the visualization of rectal cancer and to investigate its diagnostic performance in the preoperative T staging of rectal cancer using virtual monoenergetic image (VMI) on a novel dual-layer spectral detector CT.Methods:Totally 43 patients with pathologically confirmed rectal cancer were involved in this retrospective study in Ruijin Hospital, Shanghai Jiao Tong University School of Medicine from May to October 2019. All the patients underwent novel dual-layer spectral detector CT scanning within 1 week before surgery. The 40, 50, 60, 70 keV VMI and 120 kVp conventional polyenergetic image (PI) were reconstructed based on the venous phase imagings. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the rectal cancer were measured and the image quality was scored using a 5-point scale to obtain the best keV VMI. Taking pathological results as golden standard, the accuracy rate of T staging was calculated and compared between the best keV VMI and 120 kVp PI. The CT attenuation, SNR and CNR were compared with one-way ANOVA analysis among the 5 groups of images.Image quality scores were assessed with Friedman test,and the accuracy rate was compared by McNemar test or Fisher exact test.Results:The SNR and CNR of rectal cancer at 40-70 keV VMI was better than 120 kVp PI ( P<0.05), the SNR at 40 keV VMI was the highest among all the VMI ( P<0.05), the CNR at 40 keV VMI was better, but there was no significant difference between 40 and 50 keV VMI ( P>0.05). The image scores at 40-60 keV VMI were all significantly superior to those of the 120 kVp PI ( P<0.001). 40 keV VMI was the best image. The accuracy rate of 40 keV VMI (67.4%, 29/43) was higher than that of 120 kVp PI (48.8%, 21/43) in the T stage ( P=0.008). The 40 keV VMI had a higher diagnostic accuracy rate (83.7%, 36/43) and specificity （58.8%, 10/17） in diagnosis of locally advanced rectal cancer (T3-4, P=0.016, 0.031). Conclusion:The image quality of novel dual-layer spectral detector CT at 40 keV VMI is good, which can improve the accuracy rate of preoperative T staging of rectal cancer.