| 摘要 |
<p>PROBLEM TO BE SOLVED: To suppress unnecessary radiation exposure to a non-objective area of photographing in an examinee. SOLUTION: This cone beam type X-ray CT device is constituted so that, by the positional control of leaf pieces 5A and 5B for forming X-ray beams, the deficient rear-side half-size portion of X-ray beams are expanded from a front-side half-size cone beam CBa deficient in the rear-side half-size portion to shift to a full-size cone beam CB at the time of starting photographing and the front-side half-size cone beam of the X-ray beam expanding from the beam CB is contracted to the sifted to a rear-side half-size cone beam CBb at the time of finishing photographing. Then, unnecessary radiation exposure to the non-objective area Mb of photographing is suppressed than in the conventional practice in accordance with the portion of the X-ray beams restricted during a shifting period between a half-size cone beam and a full-size cone beam.</p> |
