Figure 4

Visual demonstration of the process of image subtraction to reveal error pixels created by JPEG compression. A. A range of 8 example JPEG images from an abdominal CT scan, with compression Q values ranging from 5 to 100. B. A range of 8 images created by subtracting each of the images in (A) from the Q = 100 image. If the same window level as the original images in (A) is used, the error pixels are difficult to appreciate, so the images have been pseudocolored with a black to blue lookup table (LUT) and the contrast has been increased to better show the error pixels.