Journal of the Korean Society of Radiology (한국방사선학회논문지)

The Korean Society of Radiology (한국방사선학회)
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Influence of CT Reconstruction on Spatial Resolution

CT 영상 재구성의 공간분해능에 대한 영향

  • Chon, Kwon Su (Department of Radiological Science, Daegu Catholic University)
  • 천권수 (대구가톨릭대학교 방사선학과)
  • Received : 2018.01.26
  • Accepted : 2018.02.28
  • Published : 2018.02.28
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Abstract

Computed tomography, which obtains section images from reconstruction process using projection images, has been applied to various fields. The spatial resolution of the reconstructed image depends on the device used in CT system, the object, and the reconstruction process. In this paper, we investigates the effect of the number of projection images and the pixel size of the detector on the spatial resolution of the reconstructed image under the parallel beam geometry. The reconstruction program was written in Visual C++, and the matrix size of the reconstructed image was $512{\times}512$. The numerical bar phantom was constructed and the Min-Max method was introduced to evaluate the spatial resolution on the reconstructed image. When the number of projections used in reconstruction process was small, artifact like streak appeared and Min-Max was also low. The Min-Max showed upper saturation when the number of projections is increased. If the pixel size of the detector is reduced to 50% of the pixel size of the reconstructed image, the reconstructed image was perfectly recovered as the original phantom and the Min-Max decreased as increasing the detector pixel size. This study will be useful in determining the detector and the accuracy of rotation stage needed to achieve the spatial resolution required in the CT system.

전산화단층촬영기법은 투영 영상을 재구성하여 단면 영상을 획득하는 기법으로 다양한 분야에 적용되고 있다. 재구성된 영상의 공간분해능은 장치, 대상, 재구성 과정에 의존한다. 본 논문은 평행빔 구조에서 투영 영상의 개수 및 검출기의 픽셀 크기가 재구성된 영상의 공간분해능에 미치는 영향을 조사하였다. 재구성 프로그램은 Visual C++로 작성하였으며 단면 영상은 $512{\times}512$ 크기로 하였다. 공간분해능의 특성을 평가하기 위해 수학적 막대 팬텀을 구성하였고, Min-Max 방법을 도입하였다. 재구성에 사용되는 투영의 개수가 작은 경우 허상이 나타났으며 Min-Max도 낮았다. 투영의 개수를 지속적으로 증가시키면 재구성된 영상의 공간분해능을 나타내는 Min-Max는 상향 포화되었다. 검출기의 픽셀 크기를 재구성되는 단면 영상의 픽셀 크기의 50%로 줄이면 영상은 거의 완벽하게 복원되고, 검출기픽셀 크기가 증가할수록 Min-Max는 감소하였다. 본 연구는 CT장치 설계 시 요구되는 공간분해능을 달성하기 위해 필요한 검출기 및 회전 스테이지의 정밀도를 결정하는데 도움이 될 것이다.

Keywords

References

  1. G. N. Hounsfield, "Computerized transverse axial scanning (tomography): I. Description of system," The British. Journal Radiology, Vol. 46, pp. 1016-1022, 1973. https://doi.org/10.1259/0007-1285-46-552-1016
  2. W. A. Kalender, "X-ray computed tomography," Physics in Medicine and Biology, Vol. 51, pp. R29-R43, 2006. https://doi.org/10.1088/0031-9155/51/13/R03
  3. W. Sun, S. B. Beown, R. K. Leach, "An Overview of Industrial X-ray Computed Tomography," NPL Report ENG 32, 2012.
  4. J. Hsieh, Computed Tomography: Principles, Design, Artifacts, and Recent Advances, SPIE Press, Washington, 2009.
  5. J. Bushberg, J. A. Seibert, E. M. Leidholdt, Jr., J. M. Boone, "The Essential Physics of Medical Imaging," 3rd Eds, Lippincott Williams & Wilkins, Philadelphia, 2012.
  6. M. K. Kalra, M. M. Maher, T. L. Toth, L. M. Hamberg, M. A. Blake, J. Shepard, S. Saini, "Strategies for CT Radiation Dose Optimization," Radiology, Vol. 230, No. 3, pp. 619-628, 2004. https://doi.org/10.1148/radiol.2303021726
  7. P. Prakash, M. K. Kalra, A. K. Kambadakone, H. Pien, J. Hsieh, M. A. Blake, D. V. Sahani, "Reducing Abdominal CT Radiation Dose With Adaptive Statistical Iterative Reconstruction Technique," Investigative Radiology, Vol. 45, No. 4, pp. 202-210, 2010. https://doi.org/10.1097/RLI.ob013e3181dzfeec
  8. A. K. Hara, R. G. Paden, A. C. Silva, J. L. Kujak, H. J. Lawder, W. Pavlicek, "Iterative Reconstruction Technique for Reducing Body Radiation Dose at CT: Feasibility Study," Gastrointestinal Imaging, American Journal of Roentgenology, Vol. 193, No. 3, pp. 764-771, 2009. https://doi.org/10.2214/AJR.09.2397
  9. E. Tamm, X. J. Rong, D. D. Cody, R. D. Ernst, N. E. Fitzgerald, V. Kundra, "Quality Initiatives: CT Radiation Dose Reduction: How to Implement Change without Sacrificing Diagnostic Quality," RadioGraphics, Vol. 31, No. 3, pp. 1823-1832, 2011. https://doi.org/10.1148/rg.317115027
  10. W. M. William, K. H. Amy, M. Mahadevappa, V. S. Dushyant, P. William, "How I Do It: Managing Radiation Dose in CT," Radiololgy, Vol. 273, No. 3, pp. 657-672, 2014.
  11. J. E. Costello, N. D. Cecava, J. E. Tucker, J. L. Bau, "CT Radiation Dose: Current Controversies and Dose Reduction Strategies," American Journal of Roentgenology, Vol. 201, No. 6, pp. 1283-1290, 2013. https://doi.org/10.2214/AJR.12.9720
  12. Y. Lifeng, L. Xin, L. Shuai, M. K. James, C. R. Juan, Q. Mingliang, C. Jodie, G. F. Joel, H. M.Cynthia, "Radiation dose reduction in computed tomography: techniques and future perspective," Image in Medicine, Vol. 1, No. 1, pp. 65-84, 2009. https://doi.org/10.2217/iim.09.5
  13. A. Ziegler, T. Kohler, R. Proksa,, "Noise and resolution in images reconstructed with FBP and OSC algorithms for CT," Medical Physics, Vol. 34, No. 2, pp. 585-598, 2007. https://doi.org/10.1118/1.2409481
  14. J. D. Evans, D. G. Politte, B. R. Whiting, J. A. O' Sullivan, J. F. Williamson, "Noise-resolution tradeoffs in x-ray CT imaging: A comparison of penalized alternating minimization and filtered backprojection a lgorithms," Medical Physics, Vol. 38, No. 3, pp. 1444-1458, 2011. https://doi.org/10.1118/1.3549757
  15. A. C. Kak, M. Slaney, Principles of Computerized Tomographic Imaging, IEEE Press, New York, 1988.
  16. P. M. Joseph, "An Improved Algorithm for Reprojecting Rays through Pixel Images," IEEE Transactions on Medical Imaging, Vol. 1, No. 3, pp. 192-196, 1982. https://doi.org/10.1109/TMI.1982.4307572
  17. G. N. Ramachandran, A. V. Lakshminarayanan, "Three-dimensional reconstruction from radiographs and electron micrographs: application of convolutions instead of Fourier transforms," Proceedings of National Academy of Sciences of the United States of America, Vol. 68, No. 9, pp. 2236-2240, 1971.
  18. A. L. C. Kwan, J. M. Boone, Kai Yang, S. Y. Huang, "Evaluation of the spatial resolution characteristics of a cone-beam breast CT scanner," Medical Physics, Vol.34, No. 1, pp. 275-281, 2007.
  19. A. Daatselaar, P. Stelt, J. Weenen, "Effect of number of projections on image quality of local CT," Dentomaxillofacial Radiology, Vol. 33, No. 6, pp. 361-369, 2004. https://doi.org/10.1259/dmfr/23496562