Robert Franz Buchmann DO, Presenter: Nothing to Disclose

S. Bruce Greenberg MD, Abstract Co-Author: Nothing to Disclose

We have shown a 45% reduction in radiation exposure with no loss in image quality for torso CT imaging of children by shifting from filtered back projection to Adaptive Iterative Dose Reduction (AIDR 3D). Our purpose was to evaluate if additional dose reduction or improved image quality could be obtained by changing from helical to wide-detector technique.  

The study groups include 100 children who had undergone helical torso CT and 50 who had undergone wide-detector torso CT. Wide-detector technique is a step and shoot technique that allows for up to 16cm of coverage per rotation with stitching of multiple rotation acquisitions. The helical group average age was 9.4 years (SD 5.7) and the wide-detector group 10.0 years (SD 5.9) which was not significantly different (p = 0.54). Size-Specific Dose Estimates (SSDE) were calculated for each study. Image noise was used as a proxy for image quality. Three 1.0 cm2 round regions of interest (ROI) were created, two in the right paraspinal muscles at the levels of the right pulmonary artery and the right kidney and one in the right gluteus maximus muscle. The standard deviation in each ROI constituted the measure of image noise. Unpaired t tests compared the SSDE and image noise for each group.

The results are summarized in the table. No significant difference in the SSDE was present between the two study groups (p = 0.58). Children less than 7 years old undergoing wide-detector acquisition had a mean SSDE of 2.8 mGy (SD 0.5) while those undergoing helical acquisition had a mean SSDE of 3.2 mGy (SD 0.9). This difference was not significant (p = 0.09) but showed a trend towards reduced dose in younger children. Image noise in the abdomen was improved by wide-detector technique, but the difference was not significant (p = 0.18). A 7% reduction in pelvis image noise by wide-detector technique was significant (p = 0.04).    

Radiation exposure was not significantly improved by the use of wide-detector scanning, but a trend towards modest improvement in younger, smaller children was observed. Pelvis image quality was significantly improved and a trend towards improvement in the abdomen was observed. Helical images are likely to have increased noise compared to wide-detector technique due to inherent smearing associated with helical technique.

The information acquired allows for optimization of computed tomography in children.

Buchmann, R, Greenberg, S, Is Wide-detector Better than Helical Acquisition in Children Undergoing Torso CT Imaging?.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13017978.html