Low-Dose Computed Tomography With Adaptive Statistical Iterative Reconstruction and Low Tube Voltage in Craniocervical Computed Tomographic Angiography: Impact of Body Mass Index

Objectives To assess radiation dose and image quality using Adaptive Statistical Iterative Reconstruction (ASIR) in craniocervical computed tomographic angiography and to further evaluate the impact of body mass index (BMI) on image quality. Methods A total of 178 consecutive patients (112 men, 66 women; age range, 25-79 years) were enrolled in this prospective study and randomly divided into 2 groups: group A (conventional group): 120 kV, filtered back-projection reconstruction, and group B (low-dose group): 100 kV, 40% ASIR reconstruction. Radiation dose and image quality between groups A and B were compared. Correlation coefficients were calculated between quantitative image quality measurement and BMI, and between radiation dose and BMI using Pearson correlation. Two experienced radiologists independently evaluated the image quality with 4-point scores, and interrater reliability was calculated using analysis. Results The volume CT dose index, dose-length product, and effective dose of group B were lower than those of group A (each P < 0.01), with decreases of 23.99%, 25.15% and 25.47% respectively. Positive correlations existed between radiation dose and BMI for both groups A and B (each P < 0.01). Group B had lower image noise, higher attenuation, higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), and higher subjective score than did group A (each P < 0.01). Computed tomographic values had negative correlations with BMI for the head, neck, and shoulders in both groups A and B (each P < 0.01). Image noise, SNR, and CNR had no correlations with BMI for the head and neck in both groups (each P > 0.01). On the contrary, image noise had a positive correlation, and SNR and CNR had a negative correlations with BMI for the shoulders in group A (each P < 0.01), but in contrast, no such correlations were found in group B (each P > 0.01). Conclusions In craniocervical CTA, ASIR can improve the image quality and reduce radiation dose in patients. Furthermore, ASIR reduced the variances of image quality of different body sizes in the shoulders.