Journal of radiological science and technology (대한방사선기술학회지:방사선기술과학)

Korean Society of Radiological Science (대한방사선과학회)
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Performance Characteristic of a CsI(Tl) Flat Panel Detector Radiography System

CsI(TI) Indirect Flat Panel Detector의 선질에 따른 물리적 영상 평가

  • Jeong, Hoi-Woun (Beakseok Culture University, Department of Radiological Science) ;
  • Min, Jung-Hwan (Shingu University, Department of Radiological Technology) ;
  • Kim, Jung-Min (Korea University, College of Health Science, Department of Radiological Science) ;
  • Park, Min-Seok (Korea Institute of Radiological & Medical Sciences, Research Institute of Radiological & Medical Sciences) ;
  • Lee, Gaung-Young (National Institute of Food and Drug Safty Evaluation)
  • 정회원 (백석문화대학교 방사선과) ;
  • 민정환 (신구대학교 방사선과) ;
  • 김정민 (고려대학교 보건과학대학 방사선학과) ;
  • 박민석 (한국원자력의학원 방사선의학연구소) ;
  • 이광용 (식품의약품안전평가원)
  • Received : 2012.05.09
  • Accepted : 2012.06.10
  • Published : 2012.06.30
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Abstract

The purpose of this work was to evaluate an amorphous silicon cesium iodide based indirect flat-panel detector (FPD) in terms of their modulation transfer function (MTF), Wiener spectrum (WS, or noise power spectrum, NPS), and detective quantum efficiency (DQE). Measurements were made on flat-panel detector using the International Electrotechnical Commission (IEC) defined RQA3, RQA5, RQA7, and RQA9 radiographic technique. The MTFs of the systems were measured using an edge method. The WS(NPS) of the systems were determined for a range of exposure levels by two-dimensional (2D). Fourier analysis of uniformly exposed radiographs. The DQEs were assessed from the measured MTF, WS(NPS), exposure, and estimated ideal signal-to-noise ratios. Characteristic curve in the RQA3 showed difference in the characteristic curve from RQA5, RQA7, RQA9. MTFs were not differences according to x-ray beam quality. WS(NPS) was reduced with increasing dose, and RQA 3, RQA5, RQA7, RQA9 as the order is reduced. DQE represented the best in the 1mR, RQA 3, RQA5, RQA7, RQA9 decrease in the order. The physical imaging characteristics of FPD may also differ from input beam quality. This study gives an initial motivation that the physical imaging characteristics of FPD is an important issue for the right use of digital radiography system.

간접형 CsI flat-panel detector (FPD)의 해상특성(modulation transfer function, MTF), 잡음특성(Wiener spectrum or noise power spectrum, NPS), 양자검출효율(detective quantum efficiency, DQE)을 측정하고 평가하기 위하여 본 실험을 실시하였다. IEC에서 권고한 실험방법을 따라 RQA3, RQA5, RQA7, RQA9의 방사선 선질을 사용하였다. MTF는 egde법을 사용하였다. Wiener spectrum은 조사 영역내에서 획득한 영상의 푸리에 변화를 통하여 구하였다. DQE는 MTF, WS(NPS), X선 입력 및 입력 광자량을 사용하여 평가하였다. 특성곡선은 RQA3와 RQA5, RQA7, RQA9과는 차이가 발생하였다. MTF는 X선 선질과는 상관없이 일정하였다. WS(NPS)은 X선 양이 증가 할수록 감소하였으며, RQA3, RQA5, RQA7, RQA9순으로 감소하였다. DQE는 1mR에서 가장 우수했으며, RQA3, RQA5, RQA7, RQA9순으로 감소하였다. FPD의 물리적 영상 특성을 입력 선질에 따라 다를 수 있다. 본 연구를 통하여 디지털 방사선 시스템의 바르게 사용하려면 FPD의 물리적 영상 특성을 아는 것이 중요함을 인식하게 되었다.

Keywords

References

  1. Doi K : Diagnostic imaging over the last 50 years: research and development in medical imaging science and technology. Phys Med Biol. 51(13), R5-R27, 2006 https://doi.org/10.1088/0031-9155/51/13/R02
  2. Sonoda M, Takano M, Miyahara J, and Kato H : Computed radiography utilizing scanning laser stimulated luminescence Radiology, 148(3), 833-838, 1983 https://doi.org/10.1148/radiology.148.3.6878707
  3. Dobbins JT, Ergun DL, Rutz L, Hinshaw DA, Blume H and Clark DC : DQE (f) of four generations of computed radiography acquisition devices Med. Phys. 22(10), 1581-1593, 1995 https://doi.org/10.1118/1.597627
  4. Zhao W and Rowlands JA : X-ray imaging using amorphous selenium: feasibility of a flat panel self-scanned detector digital radiology Med. Phys. 22(10), 1595-1604, 1995 https://doi.org/10.1118/1.597628
  5. Antonuk LE, Boudry J, and Huang W et al. : Demonstration of megavoltage and diagnostic X-ray imaging with hydrogenated amorphous silicon arrays Med. Phys. 19(6), 1455-1466, 1992 https://doi.org/10.1118/1.596802
  6. Granfors PR and Aufrichtig R : Performance of a $41{\times}41$-cm2 amorphous silicon flat panel X-ray detector for radiographic imaging applications. Med. Phys. 27(6), 1324-33, 2000 https://doi.org/10.1118/1.599010
  7. Finc C, Hallscheidt PJ, and Noeldge G et al. : Clinical comparative study with a large-area amorphous silicon flat-panel detector: image quality and visibility of anatomic structures on chest radiography. Am. J. Roentgenol. 178(2), 481-486, 2001
  8. Bacher K, Smeets P, Bonnarens K, De Hauwere A, Verstraete K and Thierens H : Dose reduction in patients undergoing chest imaging: digital amorphous silicon flat-panel detector radiography versus conventional filmscreen radiography and phosphor-based computed radiography. Am. J. Roentgenol. 181(4), 923-929, 2003 https://doi.org/10.2214/ajr.181.4.1810923
  9. ICRU (International Commission on Radiation Units and Measurements) Report No 41. Modulation Transfer Function of Screen-Film Systems, Bethesda, 1986
  10. ICRU (International Commission on Radiation Units and Measurements) Report No 54. Medical Imaging: The Assessment of Image Quality, Bethesda, 1996
  11. ICRU (International Commission on Radiation Units and Measurements) Report No 70. Image Quality in Chest Radiography, Bethesda, 2003
  12. 김정민, 이기성, 김유현 : 디지털 의료영상에서 위너 스펙트럼(Wiener spectrum)의 보정방법. 방사선기술 과학, 32(1), 17-24, 2009
  13. IEC (International Electrotechnical Commission) 62220-1. Medical electrical equipment Characteristics of digital X-ray imaging devices Part 1: determination of the detective quantum efficiency. Geneva, 2003.
  14. IEC (International Electrotechnical Commission) 61267 Medical diagnostic X-ray equipment Radiation conditions for use in the determination of characteristics, Geneva, 1994
  15. Illers H, Buhr E, and Hoeschen C : Measurement of the detective quantum efficiency (DQE) of digital X-ray detectors according to the novel standard IEC 62220-1. Radiat. Prot. Dosimetry, 114(1-3), 39-44, 2005 https://doi.org/10.1093/rpd/nch507
  16. Samei E, Flynn MJ : An experimental comparison of detector performance for direct and indirect digital radiography systems. Med Phy, 30(4), 608-622, 2003 https://doi.org/10.1118/1.1561285
  17. 김정민 : 디지털 특성곡선의 작도법. 방사선기술과학, 30(1), 67-73, 2007
  18. Fujita H, Tasai D-Y, and Itoh T, et al. : A simple method for determining the modulation transfer function in digital radiography. IEEE Trans Med Imaging 11(1). 34-39, 1992 https://doi.org/10.1109/42.126908
  19. 김정민, 디지털 의료영상에서 Edge method에 의한 Modulation Transfer Function 보정방법과 특이성, 방사선기술과학, 30(3), 251-257, 2007
  20. R. K. Swank. Absorption and noise in X-ray phosphors. J. Appl. Phys, 44(9), 4199-4203, 1973 https://doi.org/10.1063/1.1662918
  21. Team RDC. R: A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing, 2012.
  22. 박민석, X-선 스펙트럼 변화에 의한 CsI(Tl) 디지털 X-선 검출기 MTF의 에너지 의존성 평가, 고려대학교, 2012
  23. 김정민, 민정환, 정회원, 임은경, 양한준 :Regius 150 Computed Radiography 시스템의 Noise 평가에 관한 연구, 방사선기술과학, 29(4), 237-240, 2006