Noisy images are generally the result of insufficient counts in the projection data, insufficient filtering, or both. scan for longer times use more radioactivity filter more add adjacent slices together acquire (or process) the images with smaller matrix size (thus increasing the number of counts per pixel) consider using “smart” reconstruction programs such as OS-EM or ML-EM instead of filtered backprojection I see rings in my reconstructed images.Generally, “ring” or “circular” artifacts (see accompanying image) are caused by less then adequate uniformity of camera response. This means that a uniform source of radioactivity, like a flood source, does not appear uniform in the images (projection data) acquired into the computer. A full discussion of this phenomenon can be found many other places. Usually, the cure for these artifacts is fairly simple. (Note: In the slice shown containing the rods, the cold areas between each sector and at the center of the phantom are the rods that support the spheres and the hold-down bolt, respectively, and are not artifacts.)Present day image reconstruction software usually takes care of this problem by “allowing” (translation: “forcing”) the user to acquire uniformity correction images, usually with a high number of counts – 100 million is a typical number. This image is processed to “map” the non-uniformities in the camera response and generate a correction matrix.Please see your camera’s or computer’s User Manual to determine the method of acquiring and applying flood correction images to your scans. Typically, this is necessary as often as every month to as long as every 6 – 12 months, depending on the camera and its stability.