Fessibility Of Virtual Non-contrast CT Scan Derived From Gemstone Spectral CT Material Suppressed Iodine In Parotid Gland Lesion

ObjectiveTo explore the feasibility of virtual non-contrast CT scan(VNC)derived from gemstone spectral CT(GSI)material suppressed iodine(MSI)to replace traditional non-contrast CT(TNC)in parotid gland.MethodsThirty-three patients(forty-three lesions)with pathological diagnosis of parotid gland tumors underwent enhanced CT which included TNC,arterial phase(AP)and venous phase(VP)with GSI mode.With GSI Volume Viewer software from GE AW4.6 workstation,VNCap and VNCvp were acquired from AP and VP data respectively after processed.The mean CT values of different tissues(the parotid gland lesions,normal parotid gland,sternocleidomastoid,cervical vertebrae,sinus caroticus and submandibular gland),diagnostic performance(with/without lesions,calcification and intratumoral cystic degeneration),the image noise,signal-to-noise ratio(SNR),image quality using a 5-point scale andradiation dose [CT dose index volume(CTDIvol),dose length product(DLP),and effective dose(ED)] were compared between TNC and VNC.Differences were tested for statistical significance using Wilcoxon signed rank test or paired t-test in terms of measurement data,Chi-square for enumeration data.Results(1)The mean CT value: except for sinus caroticus and submandibular gland on VNCvp images,there were significant differences of the mean CT values of TNC between VNCap and VNCvp images(P < 0.05),respectivly.However,the absolute differences for mean CT value of differente tissues were less than 10 HU except cervical vertebrae.(2)Image quality: the image noise was higher on VNCap [8.1(7.2,11.5)] and VNCvp images [8.2(7.2,11.3)] than TNC images [7.3(6.1,9.3)],the SNR was lower on VNCap [6.9(4.9,7.4)] and VNCvp images [6.8(5.2,7.8)] than that on TNC images [8.4(6.3,10.2)],but the difference was insignificant(P>0.05).The image quality scores of VNCap [4(4,5)] and VNCvp images [4(4,5)]were lower than that of TNC [5(4,5)] and there was no significant difference between TNC and VNC images.What’s more,the image quality scores of VNC were all above 3,which could meet the diagnostic requirements.(3)Diagnostic performance: diagnostic performance evaluation showed that MSI images had the same ability in detecting lesions(100%)and intratumoral cystic degeneration(6.1%)with TNC andwere poorer in detecting calcification(33.3%)than TNC images(36.4%),and the differences were insignificant(P > 0.05).(4)Radiation dose:CTDIvol,DLP and ED of pure GSI contrast enhanced scanning mode were(22.17±5.5)mGy,(522.1±207.7)mGy·cm and(3.1±1.2)mSv respectively.CTDIvol,DLP and ED of conventional three-phase contrast enhanced mode were(32.9± 9.5)mGy,(753.8±395.6)mGy·cm and(4.5±2.3)mSv,respectively,with the difference being statistically significant.Pure GSI contrast enhanced scanning mode reduced CTDIvol,DLP,and ED by32.5%,30.7%,and 31.1%,respectively.ConclusionIn terms of parotid gland,MSI images are not only sufficient for diagnosis requirements,but also of highly concordance with TNC in diagnostic performance,which could reduce the radiation dose and have the potential capacity to replace TNC images.