Evaluation of a radiation dose reduction strategy for pediatric chest CT

The purpose of our study was to quantify the effect of changes made to the CT chest protocol on patient dose, image quality, and image noise when using a kilovoltage (kVp)-lowering strategy. We retrospectively selected 120 children who underwent chest CT: 60 in 2006 and 60 in 2008. In each group there were 30 children weighing less than 15 kg and 30 between 15 and 60 kg. In 2006 the CT protocol was 120 kVp and the reference current (mAs) was 65. In 2008, the kVp was 80 for < 15 kg and 100 for 15-60 kg, with reference mAs of 55. For each examination, the volume CT dose index (CTDI(vol)) and dose-length product (DLP) were recorded. Effective dose (ED) was estimated using the DLP method. Image noise was measured. Overall image quality was subjectively evaluated. For a weight < 15.0 kg, the CTDI(vol), DLP, and ED were reduced by 73%, 75%, and 73%, respectively (p < 0.05). For the weight range 15-60 kg, the CTDI(vol), DLP, and ED were reduced by 45%, 44%, and 48%, respectively (p < 0.05). Measured noise increased by 55% in the younger children and 41% in the older group (p < 0.05). All studies were considered diagnostically adequate. Significant radiation dose reduction can be achieved for routine pediatric chest CT by weight-based decreases in kVp in addition to low mAs. Increased noise was considered an acceptable trade-off for decreased dose, and image quality was acceptable.