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KMID : 1131320150170010053
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Journal of Korean Society of Computed Tomographic Technology
2015 Volume.17 No. 1 p.53 ~ p.62
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The studies on the quantitative analysisusing MATLAB of slice thickness, spatial resolution, and low contrast resolution for CT AAPM phantom
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Oh Hyun-Sik
Lee Kun-Ho
Chung Il-Chun
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Abstract
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Purpose : During the performance evaluation for CT device, it presents the objective data structured with the evaluated results quantified by computer using the MATLAB program for over coming the differences among testers that can occur on spatial resolution, low contrast resolution, and slice thickness (5 mm and 10 mm).
Methods and Materials : We performed the quantitative analysis using MATLAB for slice thickness, spatial resolution, and low contrast resolution with the 50 received images which have suitable judgement by scanning AAPM phantom using GE, PHILIPS, SIEMENS, and TOSHIBA
Slice thickness and spatial resolution were measured by using full width at half maximum(below FWHM). Spatial resolution was confirmed that FWHM interval more than 1.0 mm size. Low contrast resolution was measured that how close by using Roundness Index(below RI) until 6.4 mm size. The spatial resolution 9 images and low contrast resolution 10 images which have disapproved judgement were also had the quantitative analysis.
The statistic analysis was judged to have statistically significant differences when p-value is less than 0.05 through SPSS statistics 19.0 and T-test (paired t-test).
Results : For slice thickness 5 mm, the average qualitative evaluation group shows 4.98 mm and quantitative evaluation group shows 5.02. For slice thickness 10 mm, the average qualitative evaluation group shows 9.98 mm and quantitative evaluation group shows 9.86. No significant differences(p=0.07, p=0.06) with 5 mm and 10 mm. It confirmed the interval for all FWHM until 1.75, 1.50, 1.25, 1.00 mm as approved images on spatial resolution, and the average distance was 0.102 mm and the minimum distance 0.054 mm.
For disapproved images, all interval was not showed under 1.00 mm. For low contrast resolution, spproved image’s RI value shows average 0.81 and minimum 0.77. The disapproved image’s RI average shows 0.70. Statiscally significant differences were presented (all p<0.05) following hole size.
Conlusion : When slice thickness did not show statiscally significant differences for qualitative and quantitative tests, quantitative test usning MATLAB could be useful. When measured spartial resolution, it should be approved if interval distance shows over 0.05mm. For low contrast resolution, it is considered to meet circle 80% condition as qualitative test if RI value shows over 0.77. because of that, the method of this study should be standard to judge phantom image apprevemnet and considered to use secondary method for inspection oragization.
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KEYWORD
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slice thickness, low contrastresolution, spatialresolution, qualitativeevaluation, quantitative evaluation
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