The Optimal Monoenergetic Spectral Image Level Of Coronary CTA On A Dual-layer Spectral Detector CT With Half-dose Contrast Media

Objective: To investigate the optimal monoenergetic level of spectral reconstructio ns in coronary computed tomography angiography(coronary CTA)on a dual-layer spectral detector CT(SDCT)with half-dose contrast media.Methods: Two hundred patients with suspected coronary artery disease were enrol led in this prospective coronary CTA study and randomly divided into a routine-d ose contrast media group and a half-dose contrast media group(each n = 100).C oronary CTA was performed using SDCT with prospective ECG-gated mode.A tu be voltage of 120 kVp was used,along with an automated tube current modulatio n.A dose of iodixanol 270 mgI/mL of 0.8 mL/kg and 0.4 mL/kg was administere d to the routine and half-dose groups,respectively.For the routine-dose group,120 kVp polychromatic images with a model-based iterative reconstruction(IMR)(G roup A)were reconstructed.For the half-dose group,three monoenergetic levels o f images were reconstructed(Group B,45 keV;Group C,50 keV;and Group D,55 keV).Objective indicators(mean CT values;noise;signal-to-noise ratio,SNR;and contrast-to-noise ratio,CNR)and subjective indicators(contrast,sharpness,su bjective noise,and acceptability)in each group were compared.Results: There were no significant differences in demographics or radiation dose(1.83 ± 0.51 mSv vs.1.80 ± 0.53 mSv,P = 0.78)between the routine-and halfdose groups.The average iodine loads were 15.33 ± 2.26 g and 7.48 ± 1.14 g,r espectively.Mean CT values,SNR,CNR,and subjective contrast in Group C wer e higher than those in Group A(P < 0.05),and there were no significant differen ces in other indicators between Group C and Group A(P > 0.05).The objective and subjective noise in Group B were worse than those in Group A(P < 0.05).The contrast,sharpness,and acceptability of Group D were all worse than those of Group A(P < 0.05).Conclusion: Compared to routine polychromatic images,50 keV monoenergetic im ages can provide equivalent or improved coronary image quality in coronary CTA performed on SDCT with half the amount of contrast media.