Objective noise in chest CT images with standard dose and reduced (25%, 50%, 75%) dose level were 11.2 ±
3.5 and 13.3 ± 3.7, 16.2 ± 4.3, 20.3 ± 6.5 respectively. Subjective image noise was rated as acceptable at
25-75% radiation dose reduction for CT images reconstructed with ASIR. No significant artifacts were
seen affecting diagnostic interpretation. Visibility of small thoracic structures and image contrast on ASIR
images were rated as acceptable for all dose levels. There was good interobserver agreement between the
two radiologists (k=0.8, p