The invention relates to tomographic imaging device (1). The device (1) comprises a radiation detector (3) for measuring radiation traveling through an object to be imaged, the radiation detector (3) being configured to measure radiation only at a plurality of selected sampling positions on a curved track around an axis (z). A planning unit (12) is configured to determine the selected sampling positions on the basis of an estimated contour (44; 53) of the object (21) in a plane (x-y) substantially perpendicular to the axis (z). Further, the invention relates to a method for operating the device (1). The invention is particularly applicable in computed tomography imaging.