Radiology: Volume 259: Number 2-May 2011
Sarabjeet Singh, MBBS, MMST Mannudeep K. Kalra, MD Matthew D. Gilman, MD Jiang Hsieh, PhD Homer H. Pien, PhD Subba R. Digumarthy, MD Jo-Anne O. Shepard, MD
Purpose: To compare lesion detection and image quality of chest computed tomographic (CT) images acquired at various tube current-time products (40-150 mAs) and reconstructed with adaptive statistical iterative reconstruction (ASIR) or filtered back projection (FBP).
Materials and Methods: In this Institutional Review Board-approved HIPAA-compliant study, CT data from 23 patients (mean age, 63 years ± 7.3 [standard deviation]; 10 men, 13 women) were acquired at varying tube current-time products (40, 75, 110, and 150 mAs) on a 64-row multidetector CT scan¬ner with 10-cm scan length. All patients gave informed consent. Data sets were reconstructed at 30%, 50%, and 70% ASIR-FBP blending. Two thoracic radiologists as¬sessed image noise, visibility of small structures, lesion conspicuity, and diagnostic confidence. Objective noise and CT number were measured in the thoracic aorta. CT dose index volume, dose-length product, weight, and transverse diameter were recorded. Data were analyzed by using analysis of variance and the Wilcoxon signed rank test.
Results: FBP had unacceptable noise at 40 and 75 mAs in 17 and five patients, respectively, whereas ASIR had acceptable noise at 40-150 mAs. Objective noise with 30%, 50%, and 70% ASIR blending (11.8 ± 3.8, 9.6 ± 3.1, and 7.5 ± 2.6, respectively) was lower than that with FBP (15.8 ± 4.8) (P < .0001). No lesions were missed on FBP or ASIR im-ages. Lesion conspicuity was graded as well seen on both FBP and ASIR images (P < .05). Mild pixilated blotchy texture was noticed with 70% blended ASIR images.
Conclusion: Acceptable image quality can be obtained for chest CT images acquired at 40 mAs by using ASIR without any substantial artifacts affecting diagnostic confidence.
