A radiation system includes a first radiation source and a first detector positioned opposite to each other configured to image a body portion, and a second radiation source and a second detector positioned opposite to each other configured to image a region of interest in the body portion. The first radiation source has a first spot size and the first detector has a first pixel size. The second radiation source has a second spot size and the second detector has a second pixel size. The first spot size of the first radiation source may be different from the second spot size of the second radiation source, and/or the first pixel size of the first detector may be different from the second pixel size of the second detector.
