In recent years, tomographic imaging using a tomosynthesis technique has been used actively. The theory of this tomosynthesis technique has been known long before (for example, refer to patent document 1), and recently, tomographic imaging that enjoys ease of image reconstruction performed using the tomosynthesis technique has been proposed (for example, refer to patent documents 2 and 3). Especially, many such cases can be found in dental and mammographic fields (for example, refer to patent documents 4, 5 and 6).
Conventionally, as one of radiation imaging apparatuses that employ the tomosynthesis technique by choice, there is a dental panoramic imaging apparatus. In this panoramic imaging apparatus, since an X-ray detector (hereinafter, referred to as a detector) has a limitation in its movement, the apparatus is designed to focus on a tomographic plane (which is referred to as a referential tomographic plane) according to a trajectory which is set mechanically in an imaging space. The imaging space refers to a space in which there is an X-ray path connecting the X-ray tube and the detector which are rotated around the jaw of a patient.
Therefore, the focuses of produced images are optimized best only when the tooth row exists at and along the referential tomographic plane in the imaging space. However, when the tooth row is out of alignment from the referential tomographic plane, images are produced with poor focusing, so that the images blur. From this point of view, when it is desired to observe blurred portions of produced images at higher resolution, positioning of the patient is performed again to focus the blurred portions more clearly and data are acquired again, or, the blurred portions are subjected to intraoral imaging to obtain clearer images.
Meanwhile, in recent years, an X-ray panoramic imaging apparatus described in patent document 7 has been developed, in which a detector capable of acquiring X-ray detection data at a faster speed (for example, 300 FPS) is used and all the detection data are inputted into a computer to apply the tomosynthesis technique to the detection data. In this apparatus, the detection data are processed based on the tomosynthesis technique to produce panoramic images of tomographic planes. In this apparatus, the position of a tomographic plane can be changed in the front-back direction of the plane and a panoramic image of the changed tomographic plane can be produced. For this image production, information indicative of distances of plural tomographic planes which are spatially parallel to the detection surface of the detection (such information is called as shift & add quantities or gains) is obtained by using a phantom or by theoretical calculation. For imaging, a pair of the X-ray tube and the detector is rotated around the patient's jaw, during which data are acquired. The central position of this rotation approaches to the tooth row and departs from it during the imaging. The acquired data are then subjected to software processing based on the tomosynthesis technique that uses the foregoing distance information, which provides images with less blur.