Analysis on the Positional Accuracy of the Non-orthogonal Two-pair kV Imaging Systems for Real-time Tumor Tracking Using XCAT

XCAT를 이용한 실시간 종양 위치 추적을 위한 비직교 스테레오 엑스선 영상시스템에서의 위치 추정 정확도 분석에 관한 연구

  • Jeong, Hanseong (School of Mechanical Engineering, Pusan National University) ;
  • Kim, Youngju (School of Mechanical Engineering, Pusan National University) ;
  • Oh, Ohsung (School of Mechanical Engineering, Pusan National University) ;
  • Lee, Seho (School of Mechanical Engineering, Pusan National University) ;
  • Jeon, Hosang (Department of Radiation Oncology, Pusan National University Yangsan Hospital) ;
  • Lee, Seung Wook (School of Mechanical Engineering, Pusan National University)
  • 정한성 (부산대학교 기계공학부) ;
  • 김영주 (부산대학교 기계공학부) ;
  • 오오성 (부산대학교 기계공학부) ;
  • 이세호 (부산대학교 기계공학부) ;
  • 전호상 (양산부산대학교병원 방사선종양학과) ;
  • 이승욱 (부산대학교 기계공학부)
  • Received : 2015.08.06
  • Accepted : 2015.08.28
  • Published : 2015.09.30


In this study, we aim to design the architecture of the kV imaging system for tumor tracking in the dual-head gantry system and analyze its accuracy by simulations. We established mathematical formulas and algorithms to track the tumor position with the two-pair kV imaging systems when they are in the non-orthogonal positions. The algorithms have been designed in the homogeneous coordinate framework and the position of the source and the detector coordinates are used to estimate the tumor position. 4D XCAT (4D extended cardiac-torso) software was used in the simulation to identify the influence of the angle between the two-pair kV imaging systems and the resolution of the detectors to the accuracy in the position estimation. A metal marker fiducial has been inserted in a numerical human phantom of XCAT and the kV projections were acquired at various angles and resolutions using CT projection software of the XCAT. As a result, a positional accuracy of less than about 1mm was achieved when the resolution of the detector is higher than 1.5 mm/pixel and the angle between the kV imaging systems is approximately between $90^{\circ}$ and $50^{\circ}$. When the resolution is lower than 1.5 mm/pixel, the positional errors were higher than 1mm and the error fluctuation by the angles was greater. The resolution of the detector was critical in the positional accuracy for the tumor tracking and determines the range for the acceptable angle range between the kV imaging systems. Also, we found that the positional accuracy analysis method using XCAT developed in this study is highly useful and will be a invaluable tool for further refined design of the kV imaging systems for tumor tracking systems.


Grant : Development of 500 cGy level radiation therapy system based on automatic detection and tracing technology with dual-head gantry for 30% reducing treatment time for cancel tumors

Supported by : IITP


  1. Lin T, Cervino LI, Tang X, Vasconcelos N, Jiang SB: Fluoroscopic tumor tracking for image-guided lung cancer radiotherapy. Physics in Medicine and Biology 54(4):981-992 (2009).
  2. Shirato H, Shimizu S, Kitamura K, et al. Four-dimensional treatment planning and fluoroscopic real-time tumor tracking radiotherapy for moving tumor. International Journal of Radiation Oncology Biology Physics 48(2):435-442 (2000).
  3. Berbeco, RI, Jiang SB, Sharp GC, et al. Integrated radiotherapy imaging system (IRIS): design considerations of tumour tracking with linac gantry-mounted diagnostic x-ray systems with flat-panel detectors. Physics in Medicine and Biology 49(2): 243-255 (2004).
  4. Kamino Y, Takayama K, Kokubo M, et al. Development of a four-dimensional image-guided radiotherapy system with a gimbaled X-ray head. International Journal of Radiation Oncology Biology Physics 66(1):271-278 (2006).
  5. Wiersma, RD, Mao WH, Xing L: Combined kV and MV imaging for real-time tracking of implanted fiducial markers. Medical Physics 35(4):1191-1198 (2008).
  6. Poels K, Depuydt T, Verellen D, et al. A complementary dual-modality verification for tumor tracking on a gimbaled linac system. Radiotherapy and Oncology 109(3):469-474 (2013).
  7. Jong Seo Chai: Radiation therapy device of dual head type. No. 10-1465650 (2013).
  8. Segars WP, Mahesh M, Beck TJ, Frey EC, Tsui BM.: Realistic CT simulation using the 4D XCAT phantom. Medical Physics 35(8):3800-8 (2008).
  9. Segars WP, Jason B, Jack F, Sylvia H, et al. Population of anatomically variable 4D XCAT adult phantoms for imaging research and optimization. Medical Physics 40(4):043701 (2013).
  10. Jules B, Jon R: Homogeneous Coordinates. The Visual Computer: International Journal of Computer Graphics 11(1):15-26 (1994).
  11. Shirato H, Harada T, Harabayashi T, et al. Feasibility of insertion/implantation of 2.0-mm-diameter gold internal fiducial markers for precise setup and real-time tumor tracking in radiotherapy. International Journal of Radiation Oncology Biology Physics 56(1):240-247 (2003).
  12. Shimizu S, Shirato H, Kitamura K, et al. Use of an implanted marker and real-time tracking of the marker for the positioning of prostate and bladder cancers. International Journal of Radiation Oncology Biology Physics 48(5):1591-1597 (2000).