Evaluating noise in digitized radiographic images by means of histogram

To evaluate the performance of three digital devices regarding the noise added to digital radiographic images containing different optical densities. A radiographic image was digitized repeatedly ten times using two scanners (HP 4c/T and HP 5370C) and a digital camera (Nikon 990). A histogram tool measured a mean pixel value and the standard deviation of the region of interest in each image. Both values were used to calculate the image noise at the different optical densities. The noise values found were different for all devices and optical densities. There was a statistically significant difference (p