Digital radiography of scoliosis with a scanning method: radiation dose optimization

The aim of this study was optimization of the radiation dose-image quality relationship for a digital scanning method of scoliosis radiography. The examination is performed as a digital multi-image translation scan that is reconstructed to a single image in a workstation. Entrance dose was recorded with thermoluminescent dosimeters placed dorsally on an Alderson phantom. At the same time, kerma area product (KAP) values were recorded. A Monte Carlo calculation of effective dose was also made. Image quality was evaluated with a contrast-detail phantom and Visual Grading. The radiation dose was reduced by lowering the image intensifier entrance dose request, adjusting pulse frequency and scan speed, and by raising tube voltage. The calculated effective dose was reduced from 0.15 to 0.05 mSv with reduction of KAP from 1.07 to 0.25 Gy cm(2) and entrance dose from 0.90 to 0.21 mGy. The image quality was reduced with the Image Quality Figure going from 52 to 62 and a corresponding reduction in image quality as assessed with Visual Grading. The optimization resulted in a dose reduction to 31% of the original effective dose with an acceptable reduction in image quality considering the intended use of the images for angle measurements.