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KMID : 1131320150170010007
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Journal of Korean Society of Computed Tomographic Technology
2015 Volume.17 No. 1 p.7 ~ p.16
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The study of scan delay time setting with Test bolus method using cardio-thoracic ratio in Cardiac CT scan
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Kim Kwon-Soo
Kim Song-Yi
Lim Ki-Bin
Kang Sung-Ho
Lim Jae-Sik
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Abstract
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Purpose : Test bolus method presents no regular guide line even though it is generally used method. It is implemented the method of estimating maximum HU value in ascending aorta after setting nearly 10 seconds delay time. But this scan method is hard to operate accurate scan because of relatively long holding breath time of patient despite average time of getting maximum HU value is nearly 20 seconds. Therefore, in Cardiac CT scan, we want to find out proper delay time in test bolus method by comparison evaluation about correlation of maximum HU value of ascending aorta and time after previewing cardio-thoracic ratio in SPR(scan projection radiography) phase.
Materials and methods : This study used Somatom Definition Flash 128 Channel DS Source(Siemens Health-care, Germany). The data was acquired from 130 patients(men:72 person, women:58 person, average age:58.83) who got Cardiac CT scan in university hospital(2014.1~2014.7). To estimate maximum HU value of ascending aorta, 10cc contrast media and 30cc saline was sequentially injected 5cc/sec. After 8 seconds from injection, time of getting maximum HU value of ascending aorta in time change was estimated. Heart size, heart rate, cardiac disorder is independent variable. Result was quantitatively and qualitatively analyzed.
Results : After quantitative analysis, time of maximum HU value in ascending aorta was estimated 19.02±2.91 in cardio-thoracic ratio under 0.49, 19.81±4.77 in cardio-thoracic ratio under 0.5~0.59, 25.3±6.94 in cardio-thoracic ratio under 0.6~0.69, 28.98±7.1 in cardio-thoracic ratio under 0.7~0.79, 34.75±1.5 in cardio-thoracic ratio over 0.8. It shows significance difference in correlation analysis (r=.580 p<0.001). But in cardio-thoracic ratio, it shows negative correlation with maximum HU value in ascending aorta (r=-.458 p<0.001). Additionally, cardio-thoracic ratio has significance difference in patient cardiac disorder (p=.000). And time of getting maximum HU value in ascending aorta has significance difference (p=.000). However, Heart rate has no correlation with other variable. Time of getting maximum HU value in ascending aorta is most influenced from cardio-thoracic ratio, maximum HU value in ascending aorta, cardiac disorder (p<0.05),. In summary, the Most influenced cause of time of getting maximum HU value in ascending aorta is cardio-thoracic ratio (β=33.652, p=.000). It was increased 3.3652 seconds when cardio-thoracic ratio increased 0.1. In case of patient who has cardiac disorder (β=3.486, p=.021), it has 3.486 seconds longer than patient who has no cardiac disorder in time of getting maximum Hu value in ascending aorta.
Conclusion : From previewing Cardio-thoracic ratio of patient from SPR image before getting Cardiac CT scan, considering Cardio-thoracic ratio under 0.6 has 19.89 seconds Test bolus delay time in average, Cardio-thoracic ratio over 0.6 has 0.1 increase makes 3 seconds increase in Test bolus delay time would reduce inconvenience in respiratory deficient of patient. And it also reduce movement of thoracic, it would be contributed to successful Cardiac CT scan using Test bolus method getting accurate maximum HU value in ascending aorta.
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KEYWORD
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Test bolus, Time to peak, size of heart
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