Measurement of Slice Thickness of a Medical Image using a Wedge Phantom

Slice thickness measurement is an essential parameter of performance evaluation for the medical imaging system. This study demonstrates the characteristics of slice thickness measurement for medical images using a wedge digital phantom. A wedge-shaped digital phantom was generated and the ideal edge response function (ERF) was extracted from line profile in single slice. The corresponding slice profile was calculated by the derivative of ERF. The wedge phantom obtained by applying gaussian convolving to a digital phantom was also generated to produce similarities to real medical images. Unlike an ideal slice profile, it was estimated by the full width half maximum (FWHM) of the Gaussian function fitting. In addition, we evaluate the effect of background noise and wedge angle for the wedge phantom. The estimated FWHM of the image with noise added was increased by 10.4% compared to the image without noise. However, the FWHM from the line profiles averaging on the noise-added image was estimated by 0.2% reduction than the noise-free image. The line profiles averaging improves the accurate measurement of slice thickness by decreasing the noise. Despite the wedge angle changing from 45 to 30 degrees, the resulting FWHM was estimated to have less than 1% difference. However, the length of the line profile to be acquired should be increased as the wedge angle increases.