Abstract: The invention relates to methods and apparatus for cameras for gamma radiation, including cameras for positron emission tomography (PET). Included in the invention are cameras having radiation detector arrays splittable into sections, which then may be used to extend the axial field-of-view in a two-dimensional mode. Individual array sections may be equipped with collimators. Additionally, splittable PET cameras having detector arrays approximately one-fourth the diameter of conventional whole-body PET cameras are disclosed as having insertable conformal collimators comprising stacks of planar rings. The inner contours of the planar rings are adapted to accept objects to be imaged in the camera and to closely conform to the objects'surface contours.