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| Factors affecting CT and CTC in detecting colon focus |
| OUYANG Lin, LI Min, ZHOU Shui-tian, LIN Mou-gu, CHEN Xiao-wu |
| Image Department of PLA, 175th Hospital, Zhangzhou Fujian 363000, China |
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Abstract Objective: By simulating the characters of colon nodule focus, study the influence of the colon focus characters, CT scan scheme, view window and CT virtual colonscopy(CTC) on CT finding. Materials and Methods: Make 30 nodules by using emulational material, these nodules are made into 5 different types, including 0.5cm size with hunch shape, 0.3cm size with hunch shape, 0.2cm size with hunch shape, 0.2cm size with flat shape, 0.2cm size with higher density and flat shape, each type includes 6 nodules, then place them at the colon wall. Scan these nodules with different schemes, including 8.0mm/2.5mm/17.5(slice/collimation/pitch) and 5.0mm/1.0mm/7.0, and reconstruct CTC image. Read these primary scan images with 3 different kinds of view window, then evaluate the display of these nodules. Result: At window wide 1000HU, center level -500HU, primary image and CTC image of scheme 8.0mm/2.5mm/17.5 display all 0.5cm and 0.3cm nodules, with clear brim, and the nodules size accord with their practical size, however, for 0.2cm nodules, the primary image only looms out faintly 1 higher density with flat shape nodule, CTC only looms out 3 hunch shape nodule, and 1 higher density with flat shape nodule. Primary image and CTC image of scheme 5.0mm/1.0mm/7.0 display all nodules but nodule of 0.2cm size with lower density with flat shape. At window center level -1000HU, the brim of these nodules were blurred, with “faint margin” sign. At window center level 0HU, 0.3cm and 0.2cm nodules were not displayed, 0.5cm nodule displayed dim and smaller. Conclusion: The characters of emulational colon nodule, scan scheme, view window and CTC together influence CT to detect focus, CTC is more sensitive than primary transection image in finding out small focus.
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Received: 31 December 2006
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2007, Vol. 18 
