1. A method for medical imaging comprising: a) performing a multi-detector computed tomography (MDCT) scan of a patient to produce MDCT scan data; b) reconstructing MDCT image slices from the MDCT scan data; c) performing a cone-beam computed tomography (CBCT) scan of the patient using a CBCT beam source to produce CBCT scan data, wherein performing the CBCT scan comprises positioning a patterned lead sheet between the CBCT beam source and the patient to partially block x-rays from the CBCT beam source, such that the CBCT scan data is produced from a partially blocked CBCT beam; d) reconstructing CBCT image slices from the CBCT scan data; e) performing 3D rigid registration of the MDCT image slices and the CBCT image slices to obtain fused reconstructed images of the patient; wherein the method further comprises: storing a scatter distribution for the patient; and correcting for scatter by using scatter estimates derived from the scatter distribution together with a kernel-based scatter model.