RESUMO
Objective:To explore the feasibility of long board detector of digital radiography(DR)in clinical application.Methods:The long board detector(detector)was erected and placed upright.The scale long ruler with marked metal lead wire was placed at 20 cm in front of the center of long axis of the board of detector,which paralleled medial axis.Three test cards of spatial resolution were respectively placed at three positions(upper,middle and lower)of detector,and they were stuck on the board of detector as 30cm intervals between each other and 45° position.The exposures were conducted at 100,150,and 200 cm of source image distance(SID).The incident doses were tested,which obtained from different SID spots of upper,middle and lower positions of detector.The spatial resolutions of 3 positions were determined through observed the images of cards.The ratio of the marked scale length with metal lead wire to actual length of lead wire was measured through the projection of the scale length,so as to obtain the amplification rate of different spot positions.The spatial distribution of effective focal plane on the direction of long axis of detector,and the morphological change of that were observed.Results:When SID spots were respectively 100,150 and 200cm,the amplification rates of images decreased with increasing SID.The difference of amplification rates among three SID spots was significant(F=223.80,P<0.001).There was significant difference in the corresponding radiation doses among different SID spots(F=7.57,P<0.05).The spatial resolution was constantly 1.8 LP/mm.There was heel effect along with the direction of short axis of detector.The effective focal spot on the direction of long axis of detector appeared up-down symmetrical display.Conclusion:The long board detector of DR equipment has realized the capture for the images of the overall length of spine or the overall length of lower limbs in one exposure,which can meet the clinical requirement,and improve the detection efficiency of X-ray.