CT pulmonary angiography using low tube voltage combination with different noise index, low concentration contrast agent: image quality and radiation dose / 中华放射学杂志

ABSTRACT

Objective To investigate the image quality,radiation dose and iodine intake of CT pulmonary angiography (CTPA) in patients using low tube voltage (100 kVp) combination of different noise indexes (NI) and low concentration contrast agent.Methods A total of 80 patients with suspected pulmonary embolism (PE) and other pulmonary diseases who had undergone CTPA were divided into four groups (A,B,C and D),with 20 patients in each group.Group A underwent 120 kVp CT scan protocol in combination with NI=25 and 370 mg iodine/ml contrast agent,while groups B,C and D underwent 100 kVp CT scan protocol in combination with NI=30,35,40,and 320 mg iodine/ml contrast agent,respectively.All images were restructured using 60％ adaptive statistical iterative algorithm 2.0.Objective image quality evaluation included CT values of pulmonary artery,noise values of pulmonary artery,signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).Subjective image evaluation used a 5-point scoring method and was conducted by two independent radiologists.The CT dose index of volume (CTDIvol),dose-length product (DLP) and iodine intake was recorded,and the mean value was calculated.The DLP was converted to the effective dose (ED).Analysis of Variance or Kruskal-Wallis test was used to evaluate the differences among the four groups in terms of image quality,radiation dose and iodine intake.Results There was a significant difference in CT values of pulmonary artery among the groups A,B,C and D (P＜0.05),and the CT values of pulmonary artery of group A was the lowest.There was no significant differences in noises of pulmonary artery,SNR,CNR and subjective indexes scores among the groups A,B,C and D (P＞0.05).There was a significant difference in iodine intake among the groups A,B,C and D,iodine intake of the group A was the highest,iodine intake of the group D was the lowest.The iodine intake of groups B,C and D decreased by 12.4％ (42/340),13.2％ (45/340) and 15.0％ (51/340) relative to group A,respectively.There was a significant difference in radiation dose among the groups A,B,C and D,The CTDIvol,DLP and ED of group D decreased by 45.3％ (3.9/8.6),48.6％ (120/247) and 48.3％ (2.02/4.18) relative to group A,respectively (P＜0.01).Conclusion Low tube voltage combination with high NI value and low concentration contrast agent can more effectively reduce the radiation dose and iodine intake for CTPA while maintaining diagnostic image quality.