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KMID : 1131320160180020073
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Journal of Korean Society of Computed Tomographic Technology
2016 Volume.18 No. 2 p.73 ~ p.86
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The Usefulness of Applying The Iterative MAR Algorithm for Improving of The Deterioration of CT Image Quality came from The High-Density Material
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Kang Ji-Won
Jo In-Wan
Kim Hyeun-Joo
Jeong Woo-Joon
Go Byeung-Geun
Lee Jeong-Tak
Yoo Hoi-Seong
Yoo Byeong-Heon
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Abstract
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Purpose: In this research we tried to know the limitation and how much IMAR algorithm useful is in the clinical field by the evaluation of image and ana lysis using image data from phatom research and clinical research which used the Iterative MAR(Metal Artifact Reduction) algorithm from Inc. C that chose the way to get the data through its own HU of the kinds of metal in the human body(Titanium:4.5g/cm³ Around 6500HU, Stainless steel:7.8g/cm³ Around 50000HU, Gold:19.3g/cm³ Over 100000HU).
Materials and Methods : We made the phantom with the dense material used in the replacement arthroplasty(L-spine : Titanium, Hip joint : Stainless steel), made of platinum for aneurysm in cerebral vessels and gold for dental filling. Also we used these machines, Somatom Derinition Flash from Inc. 5 and 64-MDCT Discovery 750 HD from Inc. G. we had studied from 1st May to 31st Oct. in 2015 using the image data from the patients to visit the hospital for f/u test.
We used Advantage workstation program for alnalysis. We chose the ROI sized 2mm at the same part of Black Streak artifact and White streak artifact to record the average of the CT value after measuring it 20 times. Calculating the attenuation number, using the CT value measured, we calculate the attenuation number for each machines as the percentage to know how much the attenuation decrease, then compared and analyzed that.
We got the image data after scan and set the same WW/WL of image data through Advantage Workstation program for research about clinical image. After then two groups, one consists of 2 radiologists and another one consists of 3 radiology technicians, evaluate how much the artifact reduce and the factors deciding the image quality such as resoultion and contrast.
Result : As a result of converting attenuation coefficient into a percentage in the phantom research, Black streak artifact and White streak artifact of GDC coil image with MAR algorithm were 94% and 51% but both of them of GDC coil image with IMAR algorithm were 1% and 37%. Both of them decreased by 93% and 14% each. In Titanium, Black streak artifact decreased by 6%, from 17% to 11% and White streak artifact decreased by 19%, from 21% to 2% after using IMAR algorithm instead of MAR. In stainless steel Black streak artifact decreased by 5%, from 7% to 2% and White streak artifact decreased by 27%, from 34% to 7%. According to this phantom research, GDC coil, titanitum, and stainless steel are evaluated ‘adequate’ which had 3points in most of categories. Gold is the only one evaluated ‘good’ which had 4points in most of categories. This is the result of using IMAR algorithm instead of WFBP in the clinical image research, after converting attenuation coefficient into a percentage. Black streak artifact decreased by 17%, from 24% to 7%, and White streak artifact decreased by 7%, from 9% to 2% in plantium(GDC coil). In gold for dental filling, Black streak artifact decreased by 23%, from 33% to 10%, and White streak artifact decreased by 25%, from 30% to 5%. Also in stainless steel, Black streak artifact decreased by 48%, from 52% to4%, and White streak artifact decreased by 45%, from 46% to 1%.
According to the evlauation for clinical images, GDC coil, titanium, and Stainless got 4points which meant ‘good’ in most of categories. Gold evaluated ‘adequate’, 3points in most of categories.
Condusion : IMAR algorithm is more useful to reduce metal artifact caused by dense material rather than MAR algorithm. Using IMAR algorithm can provide information of various kinds to tissue with less artifact around metal foreign body, so it will be much more helpful for accurate diagnois.
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KEYWORD
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IMAR, MAR, Platinum, Gold, Titanium, Stainless, Metal Artifact Reduction
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