[en] The quality of CT image can be reliably measured by the signal-to-noise (SNR) ratio. A simple numerical method is proposed to calculate the SNR ratio of CT image. The objective of this study is to determine the image quality of the local CT imaging procedure, in terms of resolution, contrast, and noise as a function of the number of projections. The test study used for this study was a solid homogeneous cylindrical Perspex block of 12 mm diameter. The sample always placed at the center of the sample holder. This is 16 bit digital output from the data acquisition system. For each scanned data, tomographic reconstruction was carried out using cone beam reconstruction software. Signal noise ratio (SNR) was calculated from raw reconstructed images data. Simple algorithm was used to carry out the basic statistical calculations and to generate the horizontal and vertical density plot. (author)