四象限铅栅模体法对SPECT固有空间分辨力和线性影响研究OA

Objective:To explore effect of four-quadrant lead grid phantom method,including orientation,count rate,and source distance,on the intrinsic spatial resolution and linearity of single photon emission computed tomography(SPECT),so as to take a reference for testing methods of quality control and performance of SPECT.Methods:According to the national health industry standard"Specification for testing of quality control in gamma cameras and single photon emission computed tomography(SPECT)"(WS523-2019),a point source was positioned at 1.5,1.7,1.9,2.1 and 2.3 m(range from 1.5 to 2.3 m)away from the surface of the detector of lead grid phantom.The four-quadrant lead grid phantom method was adopted to detect the intrinsic spatial resolution and linearity of the images that were obtained by dual-detector of two used SPECT equipment at Cancer Hospital of Peking Union Medical College.The counts(60,100,200,300,500,600 and 1000 k)were collected respectively at each point source after the four-quadrant lead grid phantom was installed.Based on the minimum quadrant formula of resolvable quadrant of the four-quadrant lead grid phantom that was judged by visual estimation,the full width at half maximum(FWHM)of the line source image,and the degree of linear distortion of different quadrants of visual estimation were quantitatively calculated.The intrinsic spatial resolution and spatial linearity of the dual-detector of two SPECT equipment were detected and obtained,and the consistency of the minimum distinguishable quadrant and linearity in images of different orientations of the four-quadrant lead grid was analyzed.Results:After the source distance was fixed,the images of different orientations of four-quadrant lead grid of dual detector of two SPECT equipment were obtained when the collected counts of the four-quadrant lead grid phantom were respectively 60 k,100 k,200-300 k,and 500-1000 k.The distinguishable intrinsic spatial resolutions of simultaneously visual estimation on 8 orientations of four-quadrant lead grid were successively indistinguishable,the 4th quadrant(6.125 mm),the 3rd quadrant(5.25 mm),and 2nd quadrant(4.375 mm).The simultaneously intrinsic spatial linearity were successively,indistinguishable,without linear distortion,without linear distortion,and without linear distortion.The intrinsic spatial resolution and the results of linearity detection in dual-detector of two SPECT equipment were same when the collected count of the detected images of four-quadrant lead grid phantom was fixed,and the detected source distance was from 1.5 m to 2.3 m.Conclusion:The four-quadrant lead grid phantom method can complete the detection for intrinsic spatial resolution and linearity of SPECT equipment.The change of source distance of detection within 1.5 and 2.3 m would not produce effect on the detected results.In detection,the collected count of image of each frame should be≥200 k,and the placed orientation of lead grid should be optimized at 4 positions of top or bottom.