In computed tomography metal objects and motion can cause inconsistent projection values. During the image reconstruction this inconsistent data leads to artifacts, reducing the image quality. Through this, metal objects cause starshaped streaks, overlaying the whole image. Furthermore, motion results in blurred high frequency image objects. This work discusses the usability of two no-reference metrics for image quality assessment. The quality of an image is associated with the sharpness of the edges. Both methods are based on the detection of just noticeable blur depending on the image contrast. It is shown that one metric is usable for motion artifacts and the other one for metal artifacts.