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KMID : 1131320150170010109
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Journal of Korean Society of Computed Tomographic Technology
2015 Volume.17 No. 1 p.109 ~ p.116
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Study for the patient's exposure dose reduction due to the tracker scan delay time setting changes after contrast media injection into the veins of lower extremeity IV line at Liver dynamic CT scan
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Jeon Chan-Il
Kim Ki-Won
Park Kye-Yeon
Kwon Min-Woo
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Abstract
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Purpose : If the patients didn’t have an IV line to the upper extremity(Antecubital vein) or the patinet’s vascular access was difficult, patients must have IV line on foot(Dosalis pedis vein). In this case, it was recongnized that there was a difference in time between the threshold value of tracker after the contrast injection and the HU of set ROI value, and were differences in patient exposure dose according to the locate scan delay time setting. So, compared to how much the dose reduced according to the set, the purpose of this study was to reduce unnecessary exposure dose of the patient by appropriate tracker scan delay time setting.
Materials and Methods : Until August from January, 2014, we analyzed the entire adult male and female. Of total number of 2100 tests, 35 tests was collected at SIEMENS Sensation 16, and 13 tests was collected at TOSIBHA AQUILION ONE. We collected and analyzed the summed CTDI, DLP data value when tracking after the contrast injection. We used quantitative analysis programs (SPSS statistics 18 programs) and the maximum values, the minimum values and the average values were derived.
Results : Of total number of 48 patients, 34 patients were males and 14 patinets were females. For male patients, the average age is 62 years old. For female patients, the average age is 67 years old. Analysing of the results, in Sensation16, after the contrast injection, The time it takes go beyond 100 HU values is minimum 6.25 seconds and maximum 17.5 seconds. In AQILLION ONE, The time it takes go beyond 140 HU values is minimum 8 seconds and maximum 20 seconds. Compared to the tests in upper extremity IV line and on foot IV line, we found that DLP values remain a difference up to 6 times more than doubled and the scan starting time remain a dfference up to 7-14sec. Also, we analyzed that the average scan starting time is 22sec, when the actual test based on this result, we know that the exposure dose of the patient can be reduced by from minimum 50% to maximum 80%.
Conclusion : After we have IV line on foot(Dosalis pedis vein), if we reset delay time in range of 8 in minimum to 10 seconds, we can reduce unnecessary exposure from minimum 50% to maximum 80%.
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KEYWORD
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liver dynamic CT, bolus traker, DLP, scan delay time
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