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KMID : 1131320150170010025
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Journal of Korean Society of Computed Tomographic Technology
2015 Volume.17 No. 1 p.25 ~ p.32
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Dose Reduction for Pediatric Low Tube Voltage CT Scans by Adjusting Scan parameter
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Kim Hye-Jin
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Abstract
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Purpose : CT tube is easy to get overloaded due to high tube current when low kilovoltage is chosen for pediatric CT scans. The purpose of this study was to find out the best way to prevent overloading and reduce radiation dose by adjusting rotation time or pitch.
Materials and Methods : We made CT tube overloaded using ATOM Dosimetery phantom by setting CT parameters as follows: 80 kVp, 200 mAs, 0.28sec rotation time, and 1.1 pitch. Auto exposure control (CareDose 4D) was not used. While maintaining scan time and CTDIvol, we compared DLP and noise by changing rotation time or pitch, respectively.
Results : When pitch changed from 1.1 to 0.5 or rotation time changed from 0.28s to 0.5s, change of DLP value were 63.9 mGyㆍcm and 70.8 mGyㆍcm, respectively. DLP value was 9.7% lower when adjusting pitch only than adjusting rotation time only. Image noise increased from 4.61 to 4.95 in left lung (p=0.060), while DLP values decreased in the rest of measured lesions; from 5.57 to 5.41 in heart (p=0.633), from 7.30 to 6.86 in muscle (p=0.230), and from 6.40 to 6.25 in right lung (p=0.325).
Conclusion : In case of low kilovoltage CT scans, adjustment of pitch, rather than rotation time, can reduce radiation dose when adequate mAs cannot be applied due to too high CT tube current.
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KEYWORD
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Pediatric CT, radiation dose, optimization
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