| 摘要 |
An X-ray image transmitted through a patient is radiated on a phosphor member having a wide field of view and dimensions of about 40 cmx40 cm, and is converted into an optical image. The optical image is radiated on a light detector through a light guide member at substantially the same magnification. The light detector has pixels arranged in a 2,000x2,000 two-dimensional matrix form. Each pixel has a photocell and a MOSFET connected to each photocell. The photocell is electrically equivalent to a parallel circuit consisting of a photosensitive portion and an electrode capacitor. An extra capacitor is parallel-connected to the parallel circuit and a switch can turn on/off a connection between the extra capacitor and the photocell. When the optical image is radiated on the photocells, each photocell generates charges corresponding to the light amount, and the light amount is recorded in the electrode capacitor or the electrode capacitor and the extra capacitor, as a charged electrical amount. When this electrical amount is read out by shift registers, the optical image can be read out as a time-serial electrical signal. In a fluoroscopy mode with a small dose, the extra capacitor is not used. However, in a radiography mode with a large dose, the extra capacitor is used so as to increase a capacitance of the capacitors connected to the photocell. Thus, X-ray detection in X-ray fluoroscopy and radiography modes can be performed with a wide field of view.
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