Clinical application of gemstone spectral imaging associated with patient-based low dose of contrast medium protocol for carotid CT angiography

Objective To investigate the clinical value of gemstone spectral imaging (GSI) associated with patient-based low dose of contrast medium protocol in carotid CTA. Methods One hundred and twenty patients who were suspected with stenotic carotid artery or carotid plaque were prospectively enrolled in the study. All of them were divide into two groups by random number table. Group A (routine group): 60 were scanned with 120 kVp after the administration of moderate-concentration CM(320 mg /ml) with 5 ml/s injection velocity, Group B (low dose group): 60 were scanned with GSI which was reconstructed using 50 % ASiR after the administration of the same CM with 3 ml/s injection velocity. The contrast dose [(test bolus peak time + 2 s – 5 s) × injection velocity] was calculated. Images of the two groups were compared in terms of arterial attenuation, signal-noise-ratio (SNR), contrast-to-noise ratio (CNR), and subjective image quality (IQ) score. The value of CT dose index volume (CTDIvol), dose length product (DLP) and effective dose (ED) was recorded, respectively. Data were analyzed by using independent samples t test or Mann-Whitney U test. Results The mean attenuation, noise, SNR, CNR, subjective image quality score, contrast dose, CTDIvol, DLP and ED of routine group was (363 ± 56)HU, (13 ± 4)HU, 30 ± 10, 38±13, 3.0 score, (69 ± 13) ml, 13.61 mGy,527 mGy · cm and 3.11 mSv, respectively. The above variables of low-dose-group was (378 ± 69) HU, (9 ± 4)HU, 48 ± 19, 62 ± 24, 2.0 score, (49 ± 7) ml, 12.72 mGy, 478 mGy · cm and 2.82 mSv, respectively. The mean attenuation and subjective IQ score of carotid artery had no significant differences statistically between two groups (P>0.05), respectively. The noise, SNR, CNR, contrast dose, CTDIvol, DLP and ED had significant differences statistically between two groups (P< 0.05), respectively. Conclusion Compared with 120 kVp protocol, the use of GSI associated with patient-based low dose of contrast medium protocol in carotid CTA could provide equivalent image quality and higher SNR and CNR of carotid artery with a smaller amount of iodine and a lower radiation dose. Key words: Tomography, X-ray computed; Carotid artery; Contrast medium