VIII.B.37.     Which of the following statements best describes the primary purpose of a collimator on a gamma camera:

    a.     It prevents scattered photons from reaching the detector.

    b.     It prevents cosmic radiation from reaching the detector.

    c.     It stops pre-detector scattered photons.

    d.     To allow photons from a given region of interest to strike the detector and try to minimize the contribution of photons originating from outside this region.