Evaluation of Skin Dose and Image Quality on Cone Beam Computed Tomography

콘빔CT 촬영 시 mAs의 변화에 따른 피부선량과 영상 품질에 관한 평가

  • Ahn, Jong-Ho (Department of Radiation Oncology, Sansung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Hong, Chae-Seon (Department of Radiation Oncology, Sansung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Kim, Jin-Man (Department of Radiation Oncology, Sansung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Jang, Jun-Young (Department of Radiation Oncology, Sansung Medical Center, Sungkyunkwan University School of Medicine)
  • 안종호 (성균관대학교 의과대학 삼성서울병원 방사선종양학과) ;
  • 홍채선 (성균관대학교 의과대학 삼성서울병원 방사선종양학과) ;
  • 김진만 (성균관대학교 의과대학 삼성서울병원 방사선종양학과) ;
  • 장준영 (성균관대학교 의과대학 삼성서울병원 방사선종양학과)
  • Published : 2008.03.31

Abstract

Purpose: Cone-beam CT using linear accelerator attached to on-board imager is a image guided therapy equipment. Because it is to check the patient's set-up error, correction, organ and target movement. but imaging dose should be cause of the secondary cancer when taking a image. The aim of this study is investigation of appropriate cone beam CT scan mode to compare and estimate the image quality and skin dose. Materials and Methods: Measurement by Thermoluminescence dosimeter (TLD-100, Harshaw) with using the Rando phantom are placed on each eight sites in seperately H&N, thoracic, abdominal section. each 4 methods of scan modes of are measured the for skin dose in three time. Subsequently, obtained average value. Following image quality QA protocol of equipment manufacturers using the catphan 504 phantom, image quality of each scan mode is compared and analyzed. Results: The results of the measured skin dose are described in here. The skin dose of Head & Neck are measured mode A: 8.96 cGy, mode B: 4.59 cGy, mode C: 3.46 cGy mode D: 1.76 cGy and thoracic mode A: 9.42 cGy, mode B: 4.58 cGy, mode C: 3.65 cGy, mode D: 1.85 cGy, and abdominal mode A: 9.97 cGy, mode B: 5.12 cGy, mode C: 4.03 cGy, mode D: 2.21 cGy. Approximately, dose of mode B are reduced 50%, mode C are reduced 60%, mode D are reduced 80% a point of reference dose of mode A. the results of analyzed HU reproducibility, low contrast resolution, spatial resolution (high contrast resolution), HU uniformity in evaluation item of image quality are within the tolerance value by recommended equipment manufacturer in all scan mode. Conclusion: Maintaining the image quality as well as reducing the image dose are very important in cone beam CT. In the result of this study, we are considered when to take mode A when interested in soft tissue. And we are considered to take mode D when interested in bone scan and we are considered to take mode B, C when standard scan. Increasing secondary cancer risk due to cone beam CT scan should be reduced by low mAs technique.