Patent Number: 
Section: claims

1. A radiation tomographic imaging apparatus comprising:a scanning device for scanning a predefined region in a subject;a prescribing device for prescribing beforehand a position at which an image of said subject is to be produced at a higher priority in the scan region in said subject; anda reconstructing device for sequentially reconstructing an image of said subject from projection data sequentially obtained by said scanning device,wherein once projection data at said prescribed higher priority position has been obtained from said scanning device, said reconstructing device interrupts an ongoing reconstruction and reconstructs an image at said higher priority position before reconstructing any other images, such that a reconstruction order of the image is not dependant on a given scan direction. 2. The radiation tomographic imaging apparatus of claim 1, wherein said scanning device outputs position information on the scan position to said reconstructing device, and said reconstructing device interrupts reconstruction of other projection data before said scanning device conducts a scan at said higher-priority position based on the position information from said scanning device. 3. The radiation tomographic imaging apparatus of claim 1, wherein:said reconstructing device reconstructs an image at a position subsequent to said higher-priority position after reconstructing said projection data at said higher-priority position. 4. The radiation tomographic imaging apparatus of claim 1, further comprising:a display device for displaying an image of said subject reconstructed by said reconstructing device,wherein said display device displays an image at said higher-priority position reconstructed by said reconstructing device until all projection data are obtained by said scanning device. 5. The radiation tomographic imaging apparatus of claim 1, further comprising:a display device for displaying an image of said subject reconstructed by said reconstructing device,wherein said display device displays a reconstructed image at said higher-priority position until images from all projection data are reconstructed by said reconstructing device. 6. The radiation tomographic imaging apparatus of claim 1, wherein:said scanning device comprises a radiation source and a radiation detector disposed to face said radiation source with a subject placed therebetween. 7. The radiation tomographic imaging apparatus of claim 1, wherein:said scanning device employs X-rays as radiation. 8. A radiation tomographic imaging apparatus comprising:a scanning device for consecutively scanning a predefined position in a subject;a prescribing device for prescribing beforehand a time at which obtained projection data is to be reconstructed at a higher priority at the scan position in said subject; anda reconstructing device for sequentially reconstructing an image of said subject from projection data sequentially obtained by said scanning device,wherein once said projection data at said prescribed higher-priority time has been obtained from said scanning device, said reconstructing device interrupts an ongoing reconstruction and reconstructs an image of said subject at said higher priority time before reconstructing any other images, such that a reconstruction order of the image is not dependant on a given scan direction. 9. The radiation tomographic imaging apparatus of claim 8, wherein:said scanning device outputs the scan time to said reconstructing device, andsaid reconstructing device interrupts reconstruction of other projection data before said scanning device conducts a scan at said higher-priority time based on said scan time. 10. The radiation tomographic imaging apparatus of claim 8, wherein said reconstructing device reconstructs said projection data obtained following said higher-priority time after reconstructing said projection data at said higher-priority time. 11. The radiation tomographic imaging apparatus of claim 8, further comprising:a display device for displaying an image of said subject reconstructed by said reconstructing device,wherein said display device displays an image at said higher-priority time reconstructed by said reconstructing device until all projection data are obtained by said scanning device. 12. The radiation tomographic imaging apparatus of claim 8, further comprising:a display device for displaying an image of said subject reconstructed by said reconstructing device,wherein said display device displays a reconstructed image at said higher-priority time until images from all projection data are reconstructed by said reconstructing device. 13. The radiation tomographic imaging apparatus of claim 8, wherein:said scanning device comprises a radiation source and a radiation detector disposed to face said radiation source with a subject placed therebetween. 14. The radiation tomographic imaging apparatus of claim 8, wherein:said scanning device employs X-rays as radiation. 15. An imaging method using a radiation tomographic imaging apparatus having a radiation source and a radiation detector disposed to face said radiation source with a subject placed therebetween, said method comprising the steps of:defining a reference position in said subject placed at a certain position;prescribing an image production position in said subject at which reconstruction is to be made at a higher priority, based on said reference position;scanning a predefined region in said subject placed at the certain position while rotating at least one of said radiation source and radiation detector around said subject; andsequentially reconstructing an image at every image production position based on the projection data sequentially obtained at said step of scanning, wherein said step of scanning and said step of reconstructing run simultaneously, and once said projection data at said higher-priority position has been obtained at said step of scanning, said step of reconstructing interrupts an ongoing reconstruction and reconstructs an image at said higher priority position before reconstructing any other images, such that a reconstruction order of the image is not dependant on a given scan direction. 16. The imaging method of claim 15, further comprising:a displaying step of displaying an image of said subject reconstructed at said step of reconstructing after said step of reconstructing,wherein said displaying step displays an image at said higher-priority position reconstructed at said reconstructing step until the scan on said scan region is completed at said step of scanning. 17. The imaging method of claim 15, further comprising:a displaying step of displaying an image of said subject reconstructed at said step of reconstructing after said step of reconstructing,wherein said displaying step displays a reconstructed image at said higher-priority position until images from all projection data are reconstructed at said step of reconstructing. 18. The imaging method of claim 15, wherein:said step of reconstructing performs reconstruction on said projection data at a position subsequent to said higher-priority position after reconstructing said projection data at said higher-priority position.