Assessment of conventional x-ray machine resolution using modulation transfer function

Abstract

X-ray image resolution is important for resolving different structure since the diagnosis depends on visual perception ; therefore the main object of this study was to assess the diagnostic X-ray machine resolution using MTF in order to find the optimum exposure factor that preserve X-ray machine resolution. In order to determine the spatial resolution and to find the optimum KV, the phantom is placed on the detector surface then an image is acquired, with constant equal to 2 and KV of 40, 42, 44 and 46 kVp respectively. The images of the phantom were scanned to a computer, and Interactive Data Language IDL was used to apply modulation transfer function for the lines image to find the resolution for different KV and thickness. The result of this study showed that the resolution at 40 KV is better for the object image with low frequency 0.5 cycle/mm at 40 KV which is equal to 96% and reach 100% at 44 KV. The object with higher frequency 0.63 it is resolution increases from 48% at 40 KV progressively till it reach 92% at 46 KV. In summary the resolution get better for object image with higher frequency as the x-ray quanta increases but objects with lower frequency approaches the optimum level before that considerably.