Linearity Test of CT Number and Spatial Resolution Using ACR 464 Phantom for Image Quality Assessment on a 16-Slice CT Scanner

Abstract

This study was conducted to test the linearity of CT Numbers and spatial resolution in CT scan images using the American College of Radiology (ACR) 464 Phantom. The objectives of this study are to determine the correlation coefficient of the linear relationship between CT Numbers and electron density, as well as to determine the spatial resolution and the effect of slice thickness on CT scan image quality. The slice thickness variations used were 1.0 mm, 2.0 mm, and 4.0 mm. CT Numbers were obtained by placing a circular ROI with a diameter of 20 mm, using a tube voltage of 120 kV and a tube current of 300 mA. The measurement results showed that the linearity correlation coefficients between CT Numbers and electron density were 0.9997 for a slice thickness of 1.0 mm, 0.9996 for 2.0 mm, and 0.9995 for 4.0 mm, with all values passing the test requirement of R² ≥ 0.99. The spatial resolution measurements resulted in values of 0.5 lp/mm, 0.6 lp/mm, and 0.7 lp/mm for each slice thickness, all of which met the minimum requirement of 0.5 lp/mm according to the BAPETEN Regulation No. 2 of 2018 regarding the acceptance criteria for X-ray CT scanner conformity tests.