Application value of spectral detector CT monochromatic reconstruction in non-contrast cerebral CT

WANG Man; WANG Yining; WU Runze; ZHAO Xuemei; WANG Yun; JIN Zhengyu

doi:10.19300/j.2018.L5447

Abstract：Objective To explore the ability of spectral detector CT to improve the quality of non-contrast cerebral CT,and investigate the image quality and radiation dose of monochromatic reconstruction for non-contrast cerebral CT com-pared with conventional CT.Methods Sixty patients (male/female 13/47,average age 45.12±13.58 years)with the symp-toms of dizziness and headache from October 2016 to December 2016 were retrospectively enrolled.The patients were as-signed to Group A and B with 30 subjects in each group according to non-contrast cerebral CT performed by spectral detector CT or conventional detector CT.The data acquired on spectral detector CT were reconstructed to monochromatic 66 keV im-ages(Group A1)and polychromatic images(Group A2).The conventional detector CT acquired the images(Group B)using a standard-of-care protocol with the same radiation dose as the spectral CT.The attenuation and noise were measured on the white and gray matter.The signal-to-noise ratio (SNR)and contrast-to-noise ratio (CNR)were calculated and compared a-mong the 3 groups.The subjective image quality of image noise,artifact in posterior fossa,and gray and white matter depic-tion were assessed.The numerical data was compared by ANOVA and Tukey's post-Hoc multiple comparisons.The categor-ical data was compared by Kruskal-Wallis'test and Nemenyi's multiple comparison test.Bland-Altman analysis was used for the agreement of CT value between monochromatic and polychromatic images.The Kappa test was used for inter-rater agreement evaluation.Results The noise values were 1.87±0.38,2.14±0.46 and 2.25±0.49 HU in the Group A1,A2 and B,respectively.SNR and CNR were respectively 18.42 ±4.56 and 4.46±0.67 in Group A1,15.45±3.12 and 3.41±0.44 in the Group A2,14.33±3.52 and 3.52±0.55 in the Group B.The noise,SNR and CNR were significantly superior in the Group A1 than in Group A2 and B (all P<0.001),while not significantly different between the Group A2 and B (both P>0.05).The CT value in posterior fossa was significantly lower in the Group A2 than in the Group A1 (25.78±1.39 vs.29.47±1.82 HU,P<0.001),which means more severe artifact in the Group A2 than in the Group A1.The subjective image quality (quantile)was 1 (1.0,1.5),2 (2.0,2.8) and 3 (2.1,3.0) in the Group A1, A2 and B, respectively. The inter-rater agreement was good (Kappa=0.8).The effective dose(ED)of spectral detector CT and conventional CT were 1.83 mSv and 1.88 mSv,respectively. Conclusion The monochromatic 66 keV imaging improved image quality and reduced artifact in posterior fossa for non-contrast cerebral CT without radiation dose penalty compared with conventional CT.