ASSESSMENT EFFECTIVE FACTORS OF QUALITY PLANAR NUCLEAR MEDICINE IMAGES USING MODULATION TRANSFER FUNCTION

Spatial resolution is one of the important features of evaluating the function of nuclear medicine imaging systems. The aim of this study was evaluating the capability of the spatial resolution in images of nuclear medicine planar by calculating the modulation transfer function (MTF). Nuclear medicine imaging of capillary tube with activity 1 mCi was performed by planar method in different distances and different matrix sizes, in two different environments as follows: without scattered radiation (under ideal condition); with scattered radiation (in real condition by filling water phantom). Then the line spread function for each of them was obtained by drawing a linear profile on the images and MTF and the error of sum of squares were calculated by using Gaussian curve fitting and Fourier transform. The results of calculating MTF in the planar images showed that under ideal condition, as well as in real condition, MTF is a function of the distance that exists between the source and the detector and the matrix size. The error sum of squares in different imaging conditions, changed and it increased by increasing the distance and matrix size. (0.84 to 61.29 in real conditions and from 0.10 to 57.02 in ideal conditions). The presence of scattered radiation had a significant effect on the spatial resolution of imaging system. We can achieve more suitable spatial resolution by using larger matrix size and also reducing the distance of source and the detector. Having accurate awareness about spatial resolution in the imaging systems in different matrix sizes and different distances can be useful in nuclear medicine imaging.