A dual-energy scanning-based radiation detecting apparatus comprises a line detector; a device for scanning said line detector across an object while said line detector is exposed to an ionizing radiation beam, which has impinged on said object, to thereby record a plurality of line images of said object; a filter device arranged in the path of said ionizing radiation beam upstream of said object to filtrate said ionizing radiation beam, the filter device being capable of operating in two operation modes having different filter characteristics; and a control device for altering operation mode of the filter device subsequent to at least every second of said line images being recorded.