Image quality assessment using modulation transfer functions for some selected computed tomography facilities in Ghana

In diagnostic radiology, the purpose of image quality is to obtain optimum information about the medical condition of a patient with minimum radiation dose. In this work, a method of image quality assessment based on Modulation Transfer functions (MTF) was applied in three computed tomography facilities. The method involves the use of a sharp edge that was imaged to produce an edge spread function (ESF). The ESF was then differentiated to obtain the line spread function (LSF), from which the MTF was calculated by a Fourier transform. Images of Catphan700 phantom and an Aluminium test piece were analyzed and used to measure the spatial resolution of the three CT systems. Results of the three CT systems with Catphan700 phantom show that, the CT system at KATH provides improved image quality over the CT systems at 37MH and SGMC with 10% MTF spatial resolution of 7.181p/cm ± 0.68, 5.611p/cm ± 0.68, and 5.671p/cm ± 0.68 respectively. However, results of spatial resolution analysis at the three facilities using the aluminium test piece was found to be lower compared to Catphan700 phantom, with a significant deviation of 0.62. The 10% MTF values calculated at KATH, 37MH and SGMC using the aluminium test piece were found to be 2.661p/cm ± 0.94, 2.321p/cm ± 0.94 and 2.001p/cm ±0.94 respectively from the routine head scan protocol. Also, the total 10% MTF of the three CT systems using Catphan700 phantom was measured to be 3.271p/cm, 2.101p/cm and 2.301p/cm at KATH, 37MH and SGMC respectively. In conclusion, the results of MTF values calculated with the aluminium test piece can be suitable for determining the spatial resolution of CT systems using the method described in this research work with a reference 10% MTF of 2.8 11p/cm and 50% MTF of 1.211p/cm within tolerance of ±0.94 and ±0.29% respectively. (au)