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KMID : 1131320160180020049
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Journal of Korean Society of Computed Tomographic Technology
2016 Volume.18 No. 2 p.49 ~ p.57
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A Study on the standardization of radiation does in CT: Stand Dose Abdominal CT
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Kang Seung-Won
Chung Yong-Hwan
Nam Tae-Hyun
Kim Tae-Eun
Gwon Sun-Ahn
Min Kwan-Hong
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Abstract
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Purpose : The purpose of this study is to minimize the dose difference by conducting a calibration of each device by the inspectors and standardize for the radiation dose that the patient receives in 1 phase Standard Dose abdominal CT(SDA CT)
Materials and Methods: It targeted at the 3,000 adult patients (over 16 years) who underwent SDA CT examination until November 2015 from January 2015. 64-slice MDCT (Brilliance CT, Philips Medical Systems. The Netherlands) 3 units, 256-slice MDCT (256iCT, Philips Medical Systems, The Netherlands) 2 units, a total five MDCT was used. Experimental data was collected by using Dose track and analyzed by using Medcalc(Version 10.0) and median Dose Length Product (median DLP) was compared and analyzed by using Box & whisker plot chart. In this paper, the target value of the median DLP of SDA CT was 530mGy * cm, the error tolerance range was± 10%. (Target standard DLP value)
Experimental procedure was preceded by three major. First. we researched median DLP value of the current protocolin the case of Calibration of the dose for each device and changed a targeted mAs value by applying the formula to get in an error tolerance range when there was a difference between DLP values which was targeted at. Secondly, we researched the median DLP of SDA CT for each 10 inspectors and when finding the differences, inspectors were trained modified protocol to get in tolerance error range. Third, the image evaluation was preceded at 4-point scale of the retrospective evaluation (Retrospective Study) by 2 radiologists.
Result : In equipment Dose Calibration, five devices A, B, C, D, E’s median DLP value were 490.2mGy * cm~626.6mGy *cm and median DLP value of D, E were 10.5%, 18.2% respectively. These were not met on the target range. Using the formula, after changing current mAs of D and E to 340mAs, 320mAs, the results showed 486.7mGy * cm~568.1 mGy * and it met on the reference range. In 10 RT inspector dose Calibration, the median DLP value appeared 491.5mGy * cm~601.75mGy * cm. Median DLP value of Inspector RTl and RT10 showed 12.5%, 13.5% respectively. These were not met on the target range. Except RT1, RT10, Median DLP values were met on the reference target range after changing the Protocol to 498.5mGy*cm ~ 550.3mGy*cm. In the image evaluation by 2 radiologists, all of the images was decipherable.
Conclusion : There was a dose difference between the equipment brands, outdated model and detector were able to make a dose difference. Even variety of conditions of using automatic exposure control device can make a dose difference, but if there is the effort to apply the method of this paper, it is considered to be able to minimize the dose differences between the same examinations.
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KEYWORD
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Target Reference mAs, Target DLP, Dose calibration
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