Radiological imaging apparatus and radiological imaging method and radiological imaging support method

#The present invention relates to a radiological imaging apparatus and radiological imaging method, and more particularly, to a radiological imaging apparatus and radiological imaging method ideally applicable to perform radiological imaging using X-ray computed tomography and positron emission computed tomography (hereinafter referred to as “PET”) and to perform radiological imaging using X-ray computed tomography and single photon emission computed tomography (hereinafter referred to as “SPECT”).

#As radiological imaging methods using a human body as a test object, X-ray computed tomography, PET and SPECT, etc. are available. In PET and SPECT, a physical quantity is measured on an integral value (in a flying direction) of radiation emitted from a human body, and back projection of the integral value makes it possible to compute a physical quantity of each voxel in the human body and perform imaging. For such imaging, it is necessary to process an enormous amount of data. Rapid development of computer technology in recent years makes it possible to provide tomography of the human body with high speed and accuracy.

#With PET and SPECT, it is possible to detect functions and metabolism at a level of molecular biology that cannot be detected by X-ray computed tomography and so on, and it is possible to provide a function image of the body of a medical examinee.

#FIG. 1 is a longitudinal sectional view showing a radiological imaging apparatus used for a radiological imaging method according to a preferred embodiment of the present invention;

#FIG. 2 is a sectional view taken along a line II—II of FIG. 1;

#FIG. 3A is a longitudinal sectional view showing an X-ray source of FIG. 1 when a shutter is closed;

#In the radiological imaging apparatuses described in the above publications, two different examinations are carried out with shifted positions, that is, an examination for detecting X-rays passing through an examinee is carried out, and then, an examination for detecting γ-rays emitted from the examinee is carried out after the examinee is shifted. In such radiological examinations described in the above publications, since the positions of the examinations are inevitably shifted, another problem arises that the correspondence may not be found accurately between pieces of image data obtained by the imaging apparatuses when the examinee moves between the imaging apparatuses or the angle of the examinee changes. This problem was found by the inventor et al. After due study on solutions of the problem, the inventor et al. found the fact that X-rays passing through the examinee administered with radiopharmaceutical are detected and γ-rays emitted by the radiopharmaceutical in the examinee are detected at the position of the examinee irradiated with X-rays, so that image data created by using first information obtained by a γ-ray detection signal can be accurately combined with image data created by using second information obtained by an X-ray detection signal. Further, the inventor et al. also found that the above-described problem can be solved by positioning at least of an X-ray detection part in a region formed between one end and the other end of a γ-ray detecting section in the longitudinal direction of the bed. Specific examples will be discussed below.

#With reference now to FIG. 1 and FIG. 2, a radiological imaging apparatus which is a preferred embodiment of the present invention will be explained below. A radiological imaging apparatus 1 of this embodiment comprises an image pickup apparatus 2, an examinee holding apparatus 14, a signal discriminator 19, a coincidence counter 26, a computer (e.g., a workstation) 27, a storage device 28, a display device 29, and a general controller 47. The examinee holding apparatus 14 includes a supporting member 15 and a bed 16 installed on the top of the supporting member 15 in a manner movable in a longitudinal direction. The image pickup apparatus 2 is installed in a direction perpendicular to the longitudinal direction of the bed 16 and has a radiation detector ring 3 and an X-ray source circumferential transfer device 7. The radiation detector ring 3 includes a ring-shaped holding section 5 and a number of radiation detectors 4 aligned like a ring inside the ring-shaped holding section 5. A through hole section 30 where the bed 16 is inserted is formed inside the radiation detectors 4 of the radiation detector ring 3. A number of radiation detectors 4 (10000 in total) are placed in a plurality of arrays in the axial direction as well as in the circumferential direction of the through hole section 30 in the ring-shaped holding section 5. A number of radiation detectors 4 included in the radiation detector ring 3 constitute a cylindrical radiation detecting section 65. In this embodiment, all the radiation detectors 4 aligned like a ring in the circumferential direction are not moved in the circumferential direction or in the axial direction of the through hole section 30. The radiation detector 4 is a semiconductor radiation detector and has a semiconductor device of a 5-mm cube serving as a detecting section, the device consisting of cadmium telluride (CdTe). The detecting section may consist of gallium arsenide (GaAs) or cadmium zinc telluride (CZT). The ring-shaped holding section 5 is placed on the supporting member 6. The supporting members 6 and 15 are connected to each other and are fixed on the floor of an examination room.

#The X-ray source circumferential transfer device 7 comprises an X-ray source apparatus 8 and a ring-shaped X-ray source apparatus holding section 13. The X-ray source apparatus holding section 13 is attached on one end of the ring-shaped holding section 5 on the outer surface of the ring-shaped holding section 5. A ring-shaped guide rail 12 is placed on one end of the X-ray source apparatus holding section 13. The guide rail 12 and the X-ray source apparatus holding section 13 surround the through hole section 30. The X-ray source apparatus 8 has an X-ray source 9, an X-ray source drive 10, and an axial transfer arm 11. The X-ray source drive 10 comprises a motor 17 and a power transmission mechanism (not shown) having a reduction gear mechanism in a casing. The power transmission mechanism is connected to the rotational axis of the motor 17. The axial transfer arm 11 is attached to the casing of the X-ray source drive 10 and stretches into the through hole section 30. The X-ray source 9 is attached to the axial transfer arm 11. The axial transfer arm 11 stretches in the axial direction of the through hole section 30 and moves the X-ray source 9 in the axial direction of the through hole section 30. The axial transfer arm 11 stretches in response to driving of the motor 18 placed on the X-ray source drive 10. The X-ray source drive 10 is attached to the guide rail 12 in such a way as not to fall and to be movable along the ring-shaped guide rail 12. The X-ray source drive 10 has a pinion (not shown) to receive a rotational force from the above-described power transmission mechanism. This pinion engages with a rack provided for the guide rail 12.