1. A method for a dentomaxillofacial X-ray imaging comprising: providing an X-ray beam having a first radiation spectrum and a flat cross-sectional form towards a predetermined dentomaxillofacial area of a patient; arranging an image receptor in a carrier positioned outside the head of a patient, said image receptor being transversal to said X-ray beam; while radiating said image receptor with said X-ray beam through said dentomaxillofacial area: moving said X-ray beam and said carrier with the inserted image receptor in a first rotational or linear direction, whereupon a first image of the dentomaxillofacial area is created on said image receptor, said image being constituted about first intensity values that are proportional to the radiation with said first spectrum transmitted through said dentomaxillofacial area; providing an X-ray beam having a second radiation spectrum and the flat cross-sectional form towards said predetermined dentomaxillofacial area of the patient; utilizing said image receptor arranged in said carrier outside the head of the patient; while radiating said image receptor with said X-ray beam: moving said X-ray beam and said carrier with the inserted image receptor in a second rotational or linear direction that is opposite to said first direction, whereupon a second image of the same dentomaxillofacial area is created on said image receptor, said image being constituted about second intensity values that are proportional to the radiation with said second spectrum transmitted through said dentomaxillofacial area; subtracting said first intensity values and said second intensity values from each other, whereupon a resultant image is formed; and providing the resultant image as such or after processing for further use.