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Resolution Crystal Bechmann Resolution is the ability of the imaging system to resolve or distinguish between two adjacent structures. The two subcategories of resolution are spatial and contrast resolution. Spatial resolution is the smallest detail that can be seen on an image. Contrast resolution is the ability of the imaging system to distinguish between small objects having about the same contrast. Basically resolution is the sharpness of the image on film and on digital. Sharpness is the structural lines that can be seen on the image. You are always going to have some degree in unsharpness, no matter what you do. Unsharpness is the result of the relationship among the size of the FSS, SID, OID. By changing any of these items can result in some unsharpness to your image. FSS(focal spot size) is a selection that you can make on the control panel and all that FSS is where the electrons are being made-for x-ray production. You can either pick a large or a small FSS. As the focal spot size increases then the unsharpness of the image will increase, therefore the recorded detail (resolution) will decrease. However if the FSS decreases then the unsharpness of the image will decrease, which will increase the recoded detail. Ideally the small focal spot size should be used, but you cannot always do that due to the particular body part being radiographed. All body parts have a different FSS that you must use to get the image to turn out the way you want it to. Also another reason that you cannot always use the small focal spot size is because it could burn out, because of the high ma that you are applying to the filament for x-ray production. That is usually why there are two focal spot so you can choose the right one, that you need for the particular exam that you are doing, and also for the technical factors that you are going to be using. Distance is another factor that affects resolution. For example increasing SID-the distance between the x-ray tube and the source (IR)-will decrease the amount of unsharpness which will give you an increase in the recorded detail in the image. And when the SID is decreased the unsharpness will increase and the recorded detail will decrease. The reason why increasing the SID increases detail is because when the x-ray beam exits the patient it continues to diverge with an increase in SID, the exit beam does not diverge as much because of the distance between the tube, patient, and image receptor. Another example is OID-the object to distance. Increasing the OID will increase the amount of unsharpness and decreases the recorded detail. And decreasing the OID decreases the amount of unsharpness and increases the recorded detail. You should always make sure that the object being radiographed is as close to the IR as possible. You are always going to have some distance between the IR and the object, because of the cassette (the thickness) or the Bucky board, there is not much that you can do about that, but you can help the object stay as close as it possibly can. All the items listed above affect both digital and film. But there are some differences between digital and film regarding resolution. For example, in film, the film screen combination can have an effect of resolution such as the material that it is made of and the film screen contact. For digital (spatial) resolution, a controlling factor is the pixel size, which a pixel is the smallest component of the matrix. The matrix is an image displayed as a combination of rows and columns of pixels. Depending on the monitor that the imaging system has will affect the spatial resolution. The greater the number the pixels the better the spatial resolution. Flat panel detectors in digital are said to have improved spatial resolution cause of the quicker access to the image because with digital you don’t have to process the film and when you process the film there is always some information that is lost during the process. But with the digital it eliminates processing of the plain film processing step. Which would improve your spatial resolution.