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KMID : 1131320150170020147
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Journal of Korean Society of Computed Tomographic Technology
2015 Volume.17 No. 2 p.147 ~ p.156
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The evaluation of space dose and exteranl leakage dose by scattered radiation in Dual Source CT Examination: in comparison with Single Source
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Park Jin-Seok
Lee Ho-Seok
Lee Min-Yung
Nam Yoon-Chul
Kang Byung-Sam
Park Hoon-Hee
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Abstract
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Purpose : To know dose distribution as measuring space dose and outside leakage dose with comparing Dual energy, dual source and single energy, and to figure out suitable defense facility at present for dual source equipment using many hospitals because the standard defense facility inside CT exam room at present designed to single source standard facility.
Materials & Methods : CT equipment were used that Somatom Definition Flash(Siemens Healthcare, Forchheim, Germany) and Discovery CT 750(General Electric Medical System, Milwaukee, Wisconsin USA) 64 MDCT.
For measuring space dose by scatter ray, Ion Chamber (RDACAL MOD 10×5-180, USA) of Radical Company was used, and for leakage dose measuring, Ion Chamber (RADCAL MOD 10×5-1800, USA) of the same company was used.
Also, Alderson Rando phantom (CNMC Company, USA), which is a model of a human body, was used.
As the method of experiment, it was compared that single source dual energy, dual source dual energy and single energy, single source single energy, and space dose.
As tube voltage, it was measured that 1m, 1.5m, 2m different gap from Isocenter standard by distance with same tube current and exposure time doing dual energy 80 kv-140kv and single energy 120 kv.
Also, it was measured with same fixed CTDIvol as making the same expected dose index of two exam methods.
As adapting exam protocol using present clinic, for comparing dual energy and single energy and Chest embolism protocol, dual source and single source, it measured space dose with Thoracoabdominal angio protocol.
Lastly, using the maximum possible exposure condition for measuring dual energy leakage dose, it measured total 3 spots that the front console glass, examiner door and patient door 1m height from ground, and it measured 20 times repeat for reducing error.
As statistic technique, student t-test was used to compare the space dose of single energy, dual energy and single source, dual source.
Results : 1. As comparing the space dose of dual energy and single energy of GE company, it showed dual energy was higher average 2% applied the same CTDIvol for equal of two exam methods expected dose index, and no significant difference (P=0.858).
2. As comparing the space dose of dual energy and single energy of Siemens company, it showed dual energy was higher average 7% applied the same CTDIvol for equal of two exam methods expected dose index, and no significant difference (P=0.159).
3. As comparing the space dose of dual energy and single energy applied present clinical exam protocol of GE company, it showed dual energy was higher average 6%, but no significant difference (P=0.319).
4. As comparing the space dose of dual energy and single energy applied present clinical exam protocol of Siemens company, it showed single energy was higher average 64%, therefore shows significant difference (p<0.001).
5. The leakage doses were measured under 0.01 mR on all three spots for all two companies.
Conclusion : Examiners who use dual source CT should apply to clinical environment with equipments merits and demerits, and also need to consider the effort to reduce radiation dose.
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KEYWORD
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Dual source, Dual energy, Single source, Single energy
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