Scientific Session 13 — Chest ImagingWednesday, May 3, 2017
2995. Submillisievert Chest CT With Advanced Modeled Iterative Reconstruction
Agrawal R, Sodagari F, Savas H*, Grant T, Yaghmai V. Northwestern University-Feinberg School of Medicine, Chicago, IL
Address correspondence to V. Yaghmai (email@example.com)
Objective: The purpose of our study was to determine the lowest CT radiation dose parameters for detection of various lung conditions in an anthropomorphic adult-sized chest phantom.
Materials and Methods: An anthropomorphic adult-sized chest phantom containing six models of disease (ground-glass opacity, bronchial polyp, solid nodule, ground-glass nodule, bronchiectasis, and tree-in-bud) was scanned with a third-generation dual source scanner. Scans were performed with 70, 80, 100, and 120 kV and fixed mAs ranging from 7 to 75 mAs and were reconstructed using an advanced modeled iterative reconstruction algorithm. Two blinded chest radiologists reviewed the images independently and scored overall image quality and lesion conspicuity using a five-point scale. A score of 3 was considered acceptable for both image quality and lesion conspicuity. Radiation dose and image noise were recorded for each acquisition and contrast-to-noise ratio (CNR) was calculated. Wilcoxon signed rank test and Spearman correlation coefficient were used for analysis.
Results: The lowest radiation dose parameters with acceptable conspicuity score for bronchial polyp, solid nodule, ground-glass nodule, ground-glass opacity, and bronchiectasis were 70 kVp/7 mAs (0.05 mSv). The conspicuity for tree-in-bud pattern was acceptable at 70 kVp/40 mAs (0.28 mSv). The lesion conspicuity scores between the two radiologists were comparable (p > 0.05) for all lung conditions studied. The lowest radiation dose parameters for acceptable image quality were 70 kVp/10mAs (0.07 mSv). Subjective image quality was directly proportional to the CNR (r = 0.736; p = 0.015) and inversely proportional to the image noise (r = –0.925; p = 0.0001) for each acquisition.
Conclusion: Extremely low radiation dose values that allow diagnostic quality chest CT in adults may be possible with kV settings coupled with advanced modeled iterative reconstruction. Robust reduction in radiation dose for chest CT examinations, at levels similar to a chest radiograph, is possible at low kilovoltage settings with advanced modeled iterative reconstruction.