A Study on the Evaluation of Exposure Dose and Image Quality as a Function of Exposure Conditions in Head Radiography for Children

Abstract

In this study, we analyzed exposure dose and image quality as a function of exposureconditions in head radiography in radiation-sensitive children less than five years old. To compareexposure doses, we used measures of the absorbed dose, such as DAP and ESD. For image quality,the PSNR was used to quantitatively assess noise characteristics. The SRS-78 program was usedto simulate changes in X-ray beam quality in order to determine optimal exposure conditions. The DICOM header information of Infinitt Piview was used to examine skull AP and lateralradiography conditions for head radiographies performed in children less than five years oldbetween January 2018 and December 2019. Average exposure conditions and EI and DAP valueswere calculated. An acryl phantom was used as a simulated patient, and a VICTOREEN NEROmAx 8000 and ionization chamber were used to calculate the ESD value and entrance surfacedose as a function of kVp and mAs. Sample images for various exposure conditions were obtainedto measure and analyze SNR, PSNR, RMSE, and MAE. Then, simulations were conducted tostudy the characteristics of photon energy and spectrum changes relating to changes in kV. Forthe first head radiograph, the ESD value was 0.611 mGy using average exposure conditions of66 kVp and 12.5 mAs. As kVp and mAs were increased, the DAP and ESD values also increased,while the EI value decreased. When kVp and mAs were decreased, the DAP and ESD valuesalso deceased, while the EI value increased. For the second radiograph, in which there was nodegradation of image quality, the ESD value was 1.596 mGy at 32 mAs and 0.308 mGy at 6.3 mAs(for a fixed kVp), a 5.2-fold difference from the first radiograph. When the value of mAs wasfixed, the ESD value was 1.029 mGy at 81 kVp and 0.314 mGy at 52 kVp, a 3.3-fold difference fromthe first radiograph. The average photon energy was 43.6 keV at 81 kV, 38.1 keV at 66 kV, and 33keV at 52 kV. The air kerma value was 169.8 at 81 kV, 119.8 at 66 kV, and 75.27 at 52 kV, a 2.25-fold difference. The first HVL was 2.868 mmAl at 81 kV, 2.311 mmAl at 66 kV, and 1.832 mmAlat 52 kV, a difference in beam quality of about 1.56-fold. This study confirmed that the exposuredose reached a maximum difference of 5.2-fold without the degradation of image quality andwith changes in kVp and mAs. The first step toward reductions in exposure doses is to educatehospitals that radiation exposure among children is a problem. We also hypothesize that interestin and study of radiation exposure among children will lead to the acquisition of good-qualityimages with reductions in radiation dose.