Comparison Radiation Dose of Z-Axis Automatic Tube Current Modulation Technique with Fixed Tube Current Multi-Detector Row CT Scanning of Lower Extremity Venography

하지 정맥조영술 MDCT에서 고정 관전류 기법과 Z-축 자동 관전류 변동 제어에 의한 선량 비교

  • Yoo, Beong-Gyu (Department of Radiologic Technology, Wonkwang Health Science College) ;
  • Lee, Jong-Seok (Department of Radiologic Technology, Wonkwang Health Science College) ;
  • Jang, Keun-Jo (Department of Radiology, Presbyterian Medical Center) ;
  • Jeon, Sang-Hwan (Department of Nuclear Engineering, Hanyang University) ;
  • Kim, Yong-Soo (Department of Nuclear Engineering, Hanyang University) ;
  • Kweon, Dae-Cheol (Department of Radiology, Seoul National University Hospital)
  • 유병규 (원광보건대학 방사선과) ;
  • 이종석 (원광보건대학 방사선과) ;
  • 장근조 (예수병원 영상의학과) ;
  • 전상환 (한양대학교 원자력공학과) ;
  • 김용수 (한양대학교 원자력공학과) ;
  • 권대철 (서울대학교병원 영상의학과)
  • Published : 2007.09.30

Abstract

Z-axis automatic tube current modulation technique automatically adjusts tube current based on size of body region scanned. The purpose of the current study was to compare noise, and radiation dose of multi-detector row CT (MDCT) of lower extremity performed with Z-axis modulation technique of automatic tube current modulation with manual selection fixed tube current. Fifty consecutive underwent MDCT venography of lower extremity with use of a MDCT scanner fixed tube current and Z-axis automatic tube current modulation technique (10, 11 and 12 HU noise index, $70{\sim}450\;mA$). Scanning parameters included 120 kVp, 0.5 second gantry rotation time, 1.35:1 beam pitch, and 1 mm reconstructed section thickness. For each subject, images obtained with Z-axis modulation were compared with previous images obtained with fixed tube current (200, 250, 300 mA) and with other parameters identical. Images were compared for noise at five levels: iliac, femoral, popliteal, tibial, and peroneal vein of lower extremity. Tube current and gantry rotation time used for acquisitions at these levels were recorded. All CT examinations of study and control groups were diagnostically acceptable, though objective noise was significantly more with Z-axis automatic tube current modulation. Compared with fixed tube current, 2-axis modulation resulted in reduction of CTDIvol (range, $-6.5%{\sim}-35.6%$) and DLP (range, $-0.2%{\sim}-20.2%$). Compared with manually selected fixed tube current, 2-axis automatic tube current modulation resulted in reduced radiation dose at MDCT of lower extremity venography.

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