Effect of increase in thickness of additional Al filtration on Xª²ray image quality and patient doses

    HE Yingª²Hui1, DENG Zhenª²Sheng1, GAO Kai1, YU Houª²Jun1, ZHANG Xueª²Xin1, HE Hongª²De1, MU Xuanª²Qin2, SUN Liª²Jun1

    1Department of Radiology, Xijing Hospital, Fourth Military Medical University, Xi¬ðan 710033, China, 2Institute of Image Processing and Pattern Recognition , Xi¬ðan Jiaotong University, Xi¬ðan 710049, China

    ¡¾Abstract¡¿ AIM: To investigate the effect of different thickness of additional Al filtration on image quality and patient doses in diagnostic radiology. METHODS: A series of additional Al filtrations of 0, 1, 2, 3, and 4 mm in thicknesses were attached to the Xª²ray collimator respectively, and the radiographs of the phantoms with thicknesses of 8, 10, 13, 15, 20, and 25 cm, each thickness of which combines with different thickness of additional Al filtration mentioned above were acquired employing different Xª²ray tube voltage (kVp) with Xª²ray dose of about 1 ¦ÌGy/frame at the input of image intensifier. The effects of additional Al filtrations on the skin entrance dose, image quality, and Xª²ray tube loading were assessed. RESULTS: The entrance doses of the phantoms decreased squareª²inversely and tube current (mAs) used to get the images with the same ratio of signal to noise increased linearly with the increase in thickness of additional Al filtration. Receiver Operating Characteristic (ROC) assessment, showed that both effects of focus "blooming" on the image definition due to mAs increasing and the beam hardening on image contrast were not significant visually. CONCLUSION: The increase in thickness of additional Al filtration within a certain range may decrease the skin entrance dose of the patients relaª²tively and not affect significantly the Xª²ray image definition. ......