Images acquired using 320-MDCT with adaptive iterative dose reduction with wide-volume acquisition: visual evaluation of image quality by 10 radiologists using an abdominal phantom.

OBJECTIVE: The purpose of this study is to assess visual evaluations of CT images and to determine by how much radiation exposure dose could be reduced without compromising the image quality. MATERIALS AND METHODS: An abdominal CT phantom was scanned at 14 different tube currents. Raw data were reconstructed with adaptive iterative dose reduction (AIDR) 3D and filtered backprojection (FBP). We divided 64 different image pairs into five groups. Group A consisted of 14 image pairs acquired with AIDR 3D and FBP, groups B and D consisted of 13 pairs with a one-level exposure dose decrease in AIDR 3D and FBP, respectively, and groups C and E consisted of 12 pairs with a two-level exposure dose decrease in AIDR 3D and FBP, respectively. Ten radiologists participated in the reading session. Statistical analyses were calculated with analysis of variance and the paired Student t test. RESULTS: Analysis of variance of six criteria revealed that the results were better in groups A, D, and E when AIDR 3D was applied. Better results were obtained with FBP in groups B and C. When we subjected evaluations of the renal parenchyma to the Student t test, we found that the assigned scores were better with AIDR 3D in groups A, D, and E and better with FBP in groups B and C. Similar results were obtained for the other evaluation criteria. CONCLUSION: Visual subjective evaluation showed that images of acceptable quality could be obtained at dose reductions of approximately 10% in the high-dose range and about 20% in the moderate-dose range.