| NIU Yan-tao,LIU Zhen-sheng,WANG Ge-xin.Analysis of the influence of aliasing effect on the digital X ray images[J].Chinese Journal of Radiological Medicine and Protection,2007,27(6):593-595 |
| Analysis of the influence of aliasing effect on the digital X ray images |
| Received:November 19, 2006 |
| DOI： |
| KeyWords:Digital radiography Image quality Aliasing effect |
| FundProject:北京市自然科学基金资助项目(7073090) |
| Author Name | Affiliation | | NIU Yan-tao | Department of Radiology, Beijing Tongren Hospital, Capital University of Medical Sciences, Beijing 100730, China | | LIU Zhen-sheng | Department of Radiology, Beijing Tongren Hospital, Capital University of Medical Sciences, Beijing 100730, China | | WANG Ge-xin | Department of Radiology, Beijing Tongren Hospital, Capital University of Medical Sciences, Beijing 100730, China | | 赵波 | Department of Radiology, Beijing Tongren Hospital, Capital University of Medical Sciences, Beijing 100730, China | | 郝晖 | Department of Radiology, Beijing Tongren Hospital, Capital University of Medical Sciences, Beijing 100730, China | | 燕树林 | Department of Radiology, Beijing Tongren Hospital, Capital University of Medical Sciences, Beijing 100730, China |
|
| Hits: 3061 |
| Download times: 1979 |
| Abstract:: |
| Objective To investigate the causes and eliminating methods of aliasing effect in digital radiography. Methods Stationary grid and rectangular wave test phantom were imaged on Kodak CR900 system. Lead strips of phantom were parallel to laser scanning direction or with an angle of 45 degrees when they were exposed on imaging plate. The representation ability for resolution test phantom in two types of imges were observed. Grid was imaged when its lead strips are parallel to or perpendicular to laser scanning direction. Two images were observed and contrasted on monitor using various magnifying rate. Results In phantom images, the lead bars below the frequency of 3.93 linepairs per mm could be discriminated, and it is Nyquist frequency of this system. But the lead bars with the frequency of 4.86 linepairs per mm could even been distinguished in the image of test phantom with an angle of 45 degrees. When grid lead bars were parallel to imaging plate scanning direction, resulting images displayed visable streak artifacts. The display degree has marked difference when grid strips were parallel or perpendicular to laser scanning direction. Streaks were not clear when the image was displayed as true size on monitor, but there widths changed in a large range as zoom in or zoom out. At the same time, the directions of streaks changed.Conclusions Optimum stationary grids should be selected in clinical practice according to limited resolution of CR system because aliasing effect would cause disadvantageous influence, and grid frequency should be greater than Nyquist frequency. Grid strip direction should be perpendicular to laser scanner direction in clinics to avoid streak artifacts. There are notable affection to image seeming on monitor when using different magnifying rate, and using integral times of real image size were suggested. |
| HTML View Full Text View/Add Comment Download reader |
| Close |
|
|
|
