Reduced radiation for adult thoracic CT - A practical approach

Purpose: To determine whether radiation dose to patients can be reduced for clinical thoracic CT scans without loss of diagnostic information. Materials and Methods: One hundred consecutive patients having clinical CT examinations of the thorax were included. The patients were divided into 4 groups, and the mAs setting determined from the patient's weight as follows (max. 300 and min. 100 mAs): group 1: mAs = weight in lbs. rounded to the next multiple of 10, plus 30 (mAs = wt(R) + 30); group 2: mAs = weight rounded to the next multiple of 10 (mAs = wt(R)); group 3: mAs weight rounded to the next multiple of 10, minus 20 (mAs = wt(R) - 20); group 4: mAs weight rounded to the next multiple of 10, minus 30 (mAs = wt(R) - 30). The neck, mediastinum, lungs, and upper abdomen were assessed for quality on a 4 point scale. Results: Only at the lowest mAs levels did we see some degradation of image quality in the lower neck with an increase in streak artifacts. The other body regions all showed good or excellent image quality. Conclusions: Radiation dosage can be reduced by more than half without loss of diagnostic quality, using this simple formula: mAs = weight in lbs. rounded to the next multiple of 10 minus 30 (mAs = wt(R) - 30).