| NIU Yan-tao,QI Wei-wei,ZHANG Fu-li.A comparative study of energy responses of computed radiography system and screen-film system[J].Chinese Journal of Radiological Medicine and Protection,2005,25(1):83-84 |
| A comparative study of energy responses of computed radiography system and screen-film system |
| Received:October 18, 2004 |
| DOI： |
| KeyWords:Computed radiography X-ray imaging Automatic exposure control |
| FundProject: |
| Author Name | Affiliation | | NIU Yan-tao | Department of Radiology, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China | | QI Wei-wei | Department of Radiology, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China | | ZHANG Fu-li | Department of Radiology, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China | | 李眉 | Department of Radiology, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China | | 梁熙虹 | Department of Radiology, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China |
|
| Hits: 2903 |
| Download times: 1844 |
| Abstract:: |
| Objective To investigate the relationships between CR image pixel values and exposure factors (kVp,mAs), thickness of exposed subject, and those between conventional screen-film optical density and exposure factors (kVp,mAs), thickness of exposed subject. The relationships of these two kinds of energy response were compared. The feasibility of using CR image pixel values and measure values of IP mean incident exposure as parameters for setting up phototimer was studied. Methods Homogeneous acrylic phantoms 10, 15 and 20 cm thick were imaged with a traditional X-ray system and a CR system at 50-90, 70-120, 90-140 kVp and AEC density grade -2. Automatic exposure responses of the two systems at various tube voltages, same exposed subject thickness and grade selection were compared. Grid were used simultaneously for all radiography. Incident IP exposures were measured with an ionization chamber. Results Under the conditions of meeting clinical diagnostic requirements, the exposure of CR system was two times of that of rare earth screen-film system approximately. Tube voltages vs pixel value curves were similar to those of tube voltages vs exposure curves in CR system. When the thickness of the projected subject remained 10 cm, the screen- film density difference in 50-90 kVp was 1.21, and the pixel value difference was 270. When 20 cm thick, the density difference in 90-130 kVp was 0.30, and the pixel value difference was 100. When 15 cm thick, they were 0.62 and 160 seperately. Conclusion The speed value of Kodak CR 900 system is closely similar to that of medium screen-film systems. The exposure index value in flat field image and IP mean incident exposure could be used as factors to setup phototimer of AEC. The regularities between film density and kVp, pixel value and kVp, as well as differences in them, are important to the callibration of AEC system. |
| HTML View Full Text View/Add Comment Download reader |
| Close |
|
|
|
