Effects of region of interest to noise measurement in computed tomographic image
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Abstract
Background: In digital medical image, there are several factors affecting image quality such as image noise, spatial resolution, sharpness and contrast. Image noise of computed tomographic (CT) image can be quantified from the standard deviation (SD) of CT number in region of interest (ROI) of the image of a uniformity object. Therefore, the determination of ROI might be affected to noise measurement.
Objectives: The purpose of this study is to evaluate the effects of ROI determination by varying size, location and number of ROIs to noise measurement in CT images.
Materials and methods: CTDI phantom (32 cm diameter) was scanned using 120 kVp 180 mAs. The slice thickness were 1, 2, 3, and 5 millimeters. ROIs were placed at 40, 80, and 120 mm from the center of field of view (FOV) using 125, 250, 500, 1,000, and 2,000 mm2 with 1, 2, 4, 6, and 8 points each.
Results: It was shown that size and numbers of ROIs did not significantly (p<0.05) effect to image noise while the distance from the center of FOV and slice thickness significantly impact to the image noise (p>0.05).
Bull Chiang Mai Assoc Med Sci 2016; 49(2): 312-322. Doi: 10.14456/jams.2016.37
Article Details
Personal views expressed by the contributors in their articles are not necessarily those of the Journal of Associated Medical Sciences, Faculty of Associated Medical Sciences, Chiang Mai University.
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