진단참고 준위를 적용한 선량 변화에 따른 영상 품질의 변화 평가

Abstract

The changes in image characteristics according to dose change were measured within the 1st and 3rd quartiles of the diagnostic reference level(DRL). The changes in pixel values and exposure index(EI) according to dose changes in the digital radiology system were measured, and the signal-to-noise ratio(SNR) and contrast-to-noise ratio(CNR) were calculated for the regions of interest(ROI) selected in the carina of trachea, right lung, left lung, heart, sub-diaphragm, and background. Noise power spectrum(NPS) were obtained only from the background portion and analyzed by dividing it into raw data and DICOM data. As the radiation exposure increased exponentially, the average pixel value increased sequentially, and as the radiation exposure sequentially increased, the EI increased sequentially, and each showed a very high correlation. The SNR of the raw data increased as the radiation exposure increased, however the SNR of the DICOM data increased very little. The CNR of the raw data changed greatly in the lung field region and little in the rest, however the range of change decreased in the case of the DICOM data. The NPS of background gradually decreased as the radiation exposure increased in the case of raw data, however in the case of DICOM data, the NPS increased as the radiation exposure increased. However, the NPS of DICOM data was less than 1/100 of the NPS of raw data, thus it was practically impossible to observe. Most of the image quality changes were not significant when the radiation exposure increased by applying the 1st and 3rd quartile ranges of the DRL, however the contrast of the lung area was observed to increase.