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KMID : 1131320150170020069
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Journal of Korean Society of Computed Tomographic Technology
2015 Volume.17 No. 2 p.69 ~ p.78
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Evaluation of HD Algorithms in Temporal CT using High-Resolution scan mode
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Lee Jun-Pyo
Kim Kwang-Soo
Oh Hyun-Sik
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Abstract
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Purpose : In this study, We analyzed the Modulation Transfer Function (MTF) and Noise by HIRes Mode algorithm of GE Discovery 750HD model when it comes to the temporal bone CT scan that requires a high-resolution algorithm, The high noise image, compared to those with ASIR was not, and to evaluate the usefulness in clinical practice.
Materials and method : We scan the ACR phantom (Model #464, Gamex RMI, USA) using the Discovery 750HD CT device (GE healthcare, Waukesha, USA) which is 64 channels. The image was acquired after changing the algorithm to Standard, Bone, Bone Plus with HD Standard, HD Bone, HD Bone Plus additional HD Bone Plus ASIR 30%. Noise was measured by ACR CT Accreditation program(464-Automated CT software (Acts) v1.1 ),and using the MTF measuring program of the workstation, w as measured MTF. For the evaluation of Image Quality, by setting the ROI in the adult 23 people temporal bone image, so as to measure the noise. For the qualitative assessment, one person over 20 years of radiologist career and two people over 10 years of radiologist career participated in the test and A good image with three points, the second best image with 2 points and the most unfavorable image with 1 points were evaluated by evaluators. Statistically, The result was analyzed through the evaluation Fleiss’ Kappa for agreement between observers.
Result : HI Res Mode used before in MTF 50% and 10% in the ACR Phantom, when compared to the after, 8% and 16% in the Standard algorithm, respectively, 18% and 22% from Bone, 28% and 69% MTF value in Bone Plus increase was. After apply to HIRes mode with ASIR 30%, noise increase 15% and 17% at Standard, 22% and 23% at Bone, 32% and 70% each. Noise, using HIRes mode, averagely increase 23.99%, 37.06% and 66.17% at Standard, Bone, Bone Plus each and decrease 31.49%, 15.39%, 11.94% each after apply to ASIR. In the image of the patients noise was increased on average 61% at HD Bone Plus more than Bone Plus and decreased by 15% on average after applied to ASIR 30%. As a result of the qualitative evaluation, Non HD image is a point, HD is 2.29, emerged HD & ASIR 30% image point is 2.71. The algorithm is applied to the HD images using ASIR 30% suggests that relatively more good results. Result of the statist ical analysis in order to evaluate the observer reliability, Fleiss’ Kappa Coefficient appears at 0.922, the degree of coincidence between the observer and is regarded as very good and substantially coincide.
Conclusion : Currently, Our hospital did not apply to ASIR in Temporal bone CT. By applying the HD algorithm at HI Res Mode, to improve the spatial resolution, the increase in noise associated with this, decreasing by applying ASIR, and that it can be compared with the conventional method, to obtain a better image possible.
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KEYWORD
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High-Resolution scan mode, Spatial Resfolution, Temporal Bone CT, Noise
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