Optimization of image quality and patient dose in paediatric radiology using Monte Carlo modeling

Abstract

A Monte Carlo model of an x-ray imaging system was used to investigate the effect of various parameters contributing to the image quality in the paediatric radiography.The optimization task was defined as finding the best possible configuration of technical parameters as kVp-setting, additional filtration, anti-scatter grid and contrast-detail material, which results in the optimal image quality with respect to the absorbed dose in the patient. As a figure of merit, the ideal observer’s signal-to-noise ratio was used. The quotient of SNR and the average absorbed dose in the phantom as a function of the x-ray tube potential was calculated to characterize the performance of the imaging system with a strictly defined detection task. This ratio represents the dose-to-information coefficient. Moreover, the contrast for a nodule was calculated as a function of the energy of the x-ray tube. The simulations were done with the BEAMnrc user code. A phantom was modeled as a homogeneous block of tissue with dimensions representing 0-year-old, 3-year-old, 10-year-old and 15-year-old patients. The image formation was computed at the stage of x-ray detection by a CsI x-ray image intensifier.For the task of detecting an Iodine contrast detail, the optimal settings were found to be at tube potential of about 50 kVp and filtering the beam additionally with 0.125 mm of Copper. For newborn, the anti-scatter grid was found to have a reverse effect on the dose-to-information factor, where the maximum efficiency was reached at the energy of 65 kVp when no antiscatter grid was used.Monte-Carlo modeling proved to be a very helpful tool in the optimization process of image quality and patient dose.KeywordsMonte Carlo simulationspaediatric radiologydose optimizationimage quality