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KMID : 1131320140160020069
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Journal of Korean Society of Computed Tomographic Technology
2014 Volume.16 No. 2 p.69 ~ p.78
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Performance Evaluation of Automated organ based current modulation for radio-sensitive organs at patient's anterior surface in phantom: for Lens, Thyroid, Breast
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Um Hyo-Sic
Lee Sang-Woo
Kim Seon-Ki
Ha Dong-Yoon
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Abstract
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Purpose : To evaluate image quality and dose reduction rate at radio-sensitive organs located on patient’s anterior surface when using Automated organ-based current modulation(AOBCM).
Materials and Methods : By using AOBCM which can reduce surface dose at patient’s anterior surface, dose reduction rate and image quality in chest, head, neck were evaluated. To estimate dose reduction rate and image quality, anthropomorphic phantom(ART-200X, Fluke biomedical, Nevada, USA) made of tissue equivalent materials was used.
Somatom Definition AS(Siemens Healthcare, Munich, Germany) and Optima CT 660(GE Healthcare, Milwaukee, Wisconsin, USA) were used. Reference scan and experimental scan which use AOBCM, were performed with each CT scanner. Fluorescence glass dosimeter, GD- 352M(Asahi TechnoGlass, Kansahi, Japan), was used to measure dose and image noise which is equal to CT number’s standard deviation in ROI was used to evaluate image quality.
Results : The rate of dose reduction on anterior surface when performing chest, head, and neck scan was 21.1%, 29.6% and 32.9% on average(p≤0.034), respectively, and for Siemens, 23.2%, 29.0% and 54.2% on average(p≤0.004), respectively, for GE. When using AOBCM, numerical values that increase in noise are 0.2, 0.2, 2.5, 0.4, 0.8, 0.4, 0.8 for Siemens and 3.6, 2.4, 9.5, 0.9, 2.5, 3.0, 3.4 for GE at breast, chest wall, lung parenchyma, eyeball, cerebral parenchyma, thyroid soft tissue of neck respectively.
Conclusion : Dose at patient’s anterior surface was decreased when using AOBCM. When performing same examination by different CTs, maintainin same conditions, and select appropriate noise index when using ODM, then exposure dose at radio-sensitive organs can be reduced. For neck scan however, dose at anterior and posterior surface were both decreased so it needs to be studied further.
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KEYWORD
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Organ based tube current modulation, Organ Dose Modulation, Dose reduction
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