A robotic arm, movable in three rotational degrees of freedom has a base end and a distal end supporting SPECT imaging detectors. A patient support assembly is movable in a linear degree of freedom. A controller causes the robotic arm to move the SPECT imaging detectors, in three dimensions, around the patient's body to obtain SPECT images. The control causes the patient support assembly to move along the linear degree of freedom, maintaining alignment of the patient's body with the SPECT imaging detectors.