ABSTRACT
Objective To evaluate the feasibility of applying spectral CT material suppressed iodine (MSI) imaging as virtual plain CT scan to replace traditional non-contrast (TNC) CT in head and neck neoplasms. Methods A total of 52 patients with initial diagnosis of head and neck neoplasms underwent TNC CT scanning and spectrum mode enhanced scanning in the head and neck with spectral CT. With GSI Volume Viewer software from GE AW4.6 workstation, the enhanced scanning data were processed and MSI images were acquired. The CT values of different tissues (fat, erector spinae, cervical vertebrae, thyroid, and brain parenchyma) and the enhancement rate in erector spinae, carotid sinus were compared between MSI and TNC images. Image quality was objectively evaluated in noise and SNR for MSI and TNC images, while the subjective evaluation included the visibility of lesions, subjective acceptance rate, diagnostic efficacy (with/without lesions or lesion calcification, necrosis). Radiation dose including volume CT dose index (CTDIvol) and effective dose (ED) was compared between MSI and TNC. Results (1) CT values of erector spinae on MSI and TNC imaging were(52 ± 6)and(52 ± 7)HU respectively, and the difference between the two image modes was not significant(t=0.39,P>0.05). CT values on MSI and TNC Imaging were[-74 (-86,-59)HU]and[-79(-73,-61)HU]for fat (Z=-2.71, P0.05). The difference of carotid sinus enhancement rate was significant 5.75(4.70,6.73) and 4.37(3.91,5.61) respectively, Z=-5.50, P0.05).Unacceptable and acceptable cases in imaging quality of MSI were 3 and 49 respectively, while those were 2 and 50 in TNC group. Subjective acceptance rate between MST and TNC images was not significantly different(?2=0.01,P>0.05). (5) Diagnostic performance evaluation showed that the consistency of two observers was good in detecting lesions, necrosis and calcification between MSI and TNC image, with K value 0.93, 0.83 and 0.90 respectively (P<0.05). (6) Radiation doses between pure energy spectrum enhanced mode and conventional pre plus post contrast enhanced mode were compared. And differences of CTDIvol[11.78(10.98,17.30) mGy]and[23.89 (22.42, 29.98) mGy] respectively],ED [1.89(1.63,2.29) mSv]and[3.77(3.21,4.16 ) mSv] respectively] were significant(Z=-6.28, P<0.05). Pure energy spectrum enhanced mode reduced 39.07% of CTDIvol and 45.75%of ED respectively. Conclusions MSI imaging can be a potential substitute for TNC imaging. And it has clinical values in the diagnosis of head and neck neoplasms.