Organ-based tube current modulation in Chest CT – Effect on radiation dose and noise

Purpose: Organ-based tube current modulation (OBTCM) is designed for anterior dose reduction in CT. This study assessed the dose reduction capability of using organ dose modulation from two vendors at a range of kVp settings in chest CT. The secondary purpose was to assess noise between dose-modulation systems. Methods and Materials: A Lungman phantom with Thermo-Luminescent Dosimeters circumferentially attached around the phantom surface was scanned with and without OBTCM at 80-135/140 kVp using a Toshiba Aquillion Prime and a GE Revolution CT scanner. Equivalent dose was measured. Noise was measured in ROIs in the vertebral body, pulmonary trunk and in free air anterior to the phantom at the level of the carina. Comparisons were performed using Wilcoxon Signed-Rank test. Results: Using GE, dose reductions between 1.1 mSv (12%) and 1.56 mSv (24%) (p<0.01) were found in the anterior segment and no differences were found posteriorly and laterally. Total dose reductions between 0.64 (8%) and 0.98 mSv (13%) were found across kVp levels (p<0.01). With Toshiba anterior dose reductions of 6 to7% and total dose reduction of 0.34 to 0.76 mSv across kVp levels (p<0.02) were found. A dose difference of 60% between right and left lateral position was found with and without OBTCM (p<0.0001). Between OBTCM and non-OBTCM mean noise change across scanners and ROI positions was not clinically relevant, i.e. ranging from -0.6 to 1.5 HU. Conclusion: Both OBTCM systems are capable of anterior and total dose reduction with slightly altered noise at all kVp levels.