| Part I Virtual Non-contrast Spectral Imaging for Evaluation of Gastric Cancer: aPreliminary StudyPurpose: To evaluate whether the virtual non-contrast(VNC) spectral imaging may be able to replace the traditional true non-contrast(TNC) imaging for the diagnosis of gastric cancer.Materials and Methods: From October 2013 to December 2014, fifty-four patients with pathologically diagnosed gastric cancer underwent gemstone spectral imaging(GSI)including non-contrast TNC, arterial and portal venous phase acquisitions. The quality of VNCs and TNC images were evaluated on a five-point scale by two radiologists who were specialized in abdominal CT diagnosis. Interobserver agreement with regarding to image quality was assessed by Cohen’s kappa analysis. The contrast-to-noise ratio(CNR) of carcinoma-normal gastric wall in the TNC and VNCs images were calculated, and between group differences were comparied by one-way ANOVA analysis. As the gold standard by pathological results, diagnosis accuracy of gastric serosal invasion in TNC and VNCs were calculated and compared by chi-square test. Effective radiation dose was calculated and compared.Results: Among the 54 patients, 13 had tumor in the fundus of stomach, 6 in the body of stomach, 25 in the antrum of stomach, 3 in both fundus and body of stomach, and 2almost around the whole stomach. Interobserver agreement with regarding to image quality was excellently coincident(k > 0.700). There was no significant difference among the image quality of TNC, VNCa and VNCp. The mean CNR of carcinoma-normal gastric wall in the TNC and VNCs images was 0.51±0.16, 0.77±0.21, 0.65±0.18, respectively. Themean CNR of VNCa and VNCp were significantly higher than that of TNC(P<0.05).There was no significant difference of diagnosis accuracy of gastric serosal invasion among TNC and VNCs. Radiation absorbed dosage of x-ray in the combined GSI dual-phase protocol was 11.51±3.26 m Sv when compared to 13.53±4.54 m Sv in the traditional triple-phase protocol, with significant reducation of 14.92%(p<0.05).Conclusions: The VNC images obtained from arterial phase and portal venous may be seemed as a surrogate for conventional non-contrast scan in gastric carcinoma diagnosis in some degree.Part II Application the Monochromatic Images of Spectral CT in TN Staging of Gastric CancerPurpose: To evaluate the clinical utility of monochromatic images of spectral CT in staging of gastric cancers.Materials and Methods: 54 patients diagnosed of gastric cancers underwent dual-phasic scans(arterial phasem [AP] and portal venous phasem [PP]) with spectral CT.Two types of images were reconstructed to analysis: conventional 120 k Vp polychromatic images, and monochromatic image sets with energie range from 40 to 140 ke V. The polychromatic and monochromatic images were compared in T and N stagings based on pathological results.Results: The overall accuracy rates of T staging were 74.1% and 81.5% in the conventional k Vp images, and N staging 72.2% and 77.8% in the monochromatic images respectively, with no statistically difference(p>0.05).Conclusions: The monochromatic images obtained with spectral CT may improve the T and N staging accuracy rate of gastric cancer with no statistically significance. A large sample size research should be further studied. |
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