A scanning-based radiation detector apparatus for recording an image of an object comprises a 1D detector unit exposed to a fan-shaped ionizing radiation beam, after having interacted with the object； a device for moving the 1D detector unit and the fan-shaped beam relative the object while repeatedly detecting to thereby create a 2D image of the object； and a control device for controlling the repeated detections. The one-dimensional detector unit has an ionizing radiation sensitive thickness, which is larger than the thickness of the fan-shaped beam when impinging on the one-dimensional detector unit. To obtain a short exposure time of each 1D image, but still a high spatial resolution in the 2D image, a 1D image of the fan-shaped beam is recorded every n'th length unit of the movement, where n is not lower than essentially half the thickness of the fan-shaped beam in that length unit, but lower than the ionizing radiation sensitive thickness of the 1D detector unit in that length unit.
