Evaluation of BMI-based tube voltage selection in CT colonography: A prospective comparison of low kV versus routine 120kV protocol.

Abstract

To explore the value of individualized kVp selection based on the patient's body mass index (BMI, kg/m2 ) in CT colonography (CTC). Seventy-eight patients underwent two CTC scans: conventional 120kVp in supine position (Group A) with 30% Adaptive statistical iteration algorithm (ASIR-V) and BMI-based lower kV p in prone position (Group B): tube voltage was suggested by an experienced investigator according to the patient's body mass index (BMI; calculated as weight divided by height squared; kg/m (2)).70kV for BMI<23kg/m2 (Group B1, n=27), 80kV for 23≤BMI≤25kg/m2 (Group B2, n=21) and 100kV for BMI>25kg/m2 (Group B3, n=30). Group A, corresponding to the BMI value in Group B, was divided into A1, A2, and A3 subgroups for analysis. Groups B used ASIR-V of different weights (30%-90% ASIR-V). The Hounsfield Unit (HU) and SD values of the muscles and the intestinal cavity air were measured, and the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) of images were calculated. Imaging quality was evaluated by two reviewers and statistically compared. The 120kV scans were preferred more than 50% of the time. All images had excellent quality with good consistency between reviewers (Kappa>0.75, p<0.05). The radiation dose was reduced in groups B1, B2 and B3 by 63.62%, 44.63%, and 32.14%, respectively, compared with group A (p<0.05). The SNR and CNR values between group A1/A2/A3 and B1/B2/B3+60%ASIR-V were not statistically significant (p<0.05). There was no statistically significant difference between the subjective scores of group B combined with 60%ASIR-V and group A (p>0.05). BMI-based individualized kV CTC imaging significantly reduces overall radiation dose while providing an equal image quality with the conventional 120kV.