Relationship between Image Quality and Changes in Spatial Resolution for the Gamma Camera

The purpose of this study is to examine quantitatively the relationship between visual image quality and degradation in spatial resolution for a gamma camera by the increase in distance from collimator. The relationship between the proportion (p) of images identifced the difference of image quality and the difference (ΔFWHM) in FWHM between paired images was showed in a sigmoid curve. Using Dendy's method, minimum level to be correctly identified the difference of image quality on three out of four occasion (p= 0.75) was corresponded to 0.4 mm in ΔFWHM. Using fuzzy theory, the level to be identified the difference of image quality was examind under various conditions. The truth-value of fuzzy sets-degraded or slightly degraded and not-degraded in image quality between paired images-was gained the peak at 0.5 mm of JFWHM. It was founded that changes o f 0.4-0.5 mm in FWHM-corresponding about 2 cm distance from collimator-could be sufficiently identified in the difference of image quality.