| Project/Area Number |
02670890
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
外科・放射線系歯学
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| Research Institution | Tokyo Medical and Dnetal University |
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Principal Investigator |
KATOH Tsuguhisa Tokyo Medical and Dnetal University, Faculty of Dentistry, Assistant., 歯学部, 助手 (70095107)
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| Co-Investigator(Kenkyū-buntansha) |
IDA Nizue Tokyo Medical and Dental University, Faculty of Dentistry, Lecturer., 歯学部, 講師 (10014226)
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| Project Period (FY) |
1990 – 1991
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| Project Status |
Completed (Fiscal Year 1991)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1991: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1990: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | Sialography / Digital image processing / Dual energy subtraction / デジタル画像処理 / ディアルエネルギ-差分法 / デイジタル画像処理 / 電算機シミュレ-ション |
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| Research Abstract |
(1) Grade up of the image processing system
Random access memories and a magnetic optical disk unit were added to the image processing computer. The processing speed and capacity of image file storage were advanced. The soft ware system for the dual energy subtraction to suppress the bone image. It took within 10 minutes to process all the procedure for subtraction including input scan of x-ray film.
(2) Simulation for optimization
The optimum selection of x-ray filter materials, tube potential and intensifying screen was searched for by means of computer simulation, and found that the combination of gadrinium or tungsten for dichromizing x-ray filter, Gd_2O_2S and CaWO_4 for the screen and copper or tin for in-cassette-filter and 1OOkVcp for tube potential were expected to have high performance.
(3) Phantom experiment
Phantoms were made of polyethyrene tube of various diameter filled with contrast agents and bone phantom wedge and a water bath. In the images of these phantoms produced by this method, codes of contrast media thicker than 0.5mm were recognized. The remarkable reduction of contrast of the contrast media and increment of the noise were, however, observed.
(4) Discussion
It was theoretically proved that reduction of the iodine contrast was due to the similarity of the energy dependency of attenuation coefficient among the bone and the iodine. The increment of the noise was caused by the statistically additive nature of the granuality of the film-screen systems. Especially, the noise in the high edergy image, which was produced by high speed screen place behind the copper/tin filter, magnified by factor 4 or 5. It was concluded, therefore, that the present dual energy subtraction technique was not suitable for improvement of image quality of the sialography.
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