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KMID : 1131320160180020087
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Journal of Korean Society of Computed Tomographic Technology
2016 Volume.18 No. 2 p.87 ~ p.94
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The Study on Metal Artifact Reduction Method of the Mixture of Contrast Medium and Normal Saline for Computed Tomographic Scan
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Jung Jae-Yeon
Kim Kyeong-Min
Kang Jung-Hun
Lee Kwang-Won
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Abstract
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Purpose : Recently, as the society progresses towards population ageing, a number of metallic implant surgeries are being performed. This study is investigating metal artifact reduction methods with various concentrations of contrast medium by combining contrast medium and normal saline for computed tomographic (CT) scan.
Subjects and Methods : SOMA TOM SENSATION16(Siemens, Germany) is used for the CT equipment, and the sample, which is the material like titanium used for TKR in orthopedics, is fixed between two normal salines. For the mixture of contrast medium and normal saline, 100cc contrast medium (concentration of 300) + 400cc normal saline, 50cc contrast medium (concentration of 300) + 450cc normal saline, 10cc contrast medium (concentration of 300) + 490cc normal saline, 100cc contrast medium (concentration of 370) + 400cc normal saline, 50cc contrast medium (concentration of 370) + 450cc normal saline, and 10cc contrast medium (concentration of 370) + 490cc normal saline are used. The mixture is placed on top and bottom, and left and right of titanium fixed with normal salines in order, and HU values of CT and standard deviations with respect to 120kVp/250mAs/slice 0.75mm, 1.5mm, 140kVp/250mAs/slice 0.75mm,1.5mm, and 140kVp/350mAs/slice 0.75mm, 1.5mm (tube voltage/tube current/slice thickness) are measured and compared with HU value obtained by measuring ROI at 1.5cm distance in 12 O clock and 6 O’clock from the center of titanium.
Results: When the mixture of 10cc contrast medium (concentration of 300) + 490cc normal saline was used top and bottom, and left and right, and when tube voltage/tube current/ slice thickness was 140kVp/250mAs/slice 0.75mm, HU value of CT and standard deviation (SD) of metal artifact were 18/27 and 14/25, respectively, showing the highest reduction. For tube voltage, 140kVp showed higher reduction than 120kVp, and for tube current, 250mAs showed higher reduction than 350mAs. Reduction was shown when the slice thickness was 0.75mm. When the mixture of 100cc contrast medium (concentration of 370) + 400cc normal saline was used in 120kVp/250mAs/slice 1.5mm, reduction measure was the lowest.
Conclusion : HU value of metal artifact from CT scan showed the highest reduction when the mixture of 10cc contrast medium (concentration of 300) + 490cc normal saline was used in 140kVp/250mAs/slice 0.75mm. Although correction value of HU value shows some large or small differences depending on the amount of artifact for each CT scan, the results are all improved in a positive way. Visual identification of CT scan made the difference in quality of scan seemed much bigger, compared to identification of the numerical values. If this study method is applied to the examination of existing metal patients, the quality of image can be improved.
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KEYWORD
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Metal Artifact, Contrast Medium, CT HU value
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