The Korean Journal of Nuclear Medicine (대한핵의학회지)

The Korean Society of Nuclear Medicine (대한핵의학회)
권호 표지

A Computer Simulation for Small Animal Iodine-125 SPECT Development

소동물 Iodine-125 SPECT 개발을 위한 컴퓨터 시뮬레이션

  • Jung, Jin-Ho (Department of Biomedical Engineering, Sungkyunkwan University School of Medicine and Department of Nuclear Medicine, Samsung Medical Center) ;
  • Choi, Yong (Department of Biomedical Engineering, Sungkyunkwan University School of Medicine and Department of Nuclear Medicine, Samsung Medical Center) ;
  • Chung, Yong-Hyun (Department of Biomedical Engineering, Sungkyunkwan University School of Medicine and Department of Nuclear Medicine, Samsung Medical Center) ;
  • Song, Tae-Yong (Department of Biomedical Engineering, Sungkyunkwan University School of Medicine and Department of Nuclear Medicine, Samsung Medical Center) ;
  • Jeong, Myung-Hwan (Department of Biomedical Engineering, Sungkyunkwan University School of Medicine and Department of Nuclear Medicine, Samsung Medical Center) ;
  • Hong, Key-Jo (Department of Biomedical Engineering, Sungkyunkwan University School of Medicine and Department of Nuclear Medicine, Samsung Medical Center) ;
  • Min, Byung-Jun (Department of Biomedical Engineering, Sungkyunkwan University School of Medicine and Department of Nuclear Medicine, Samsung Medical Center) ;
  • Choe, Yearn-Seong (Department of Biomedical Engineering, Sungkyunkwan University School of Medicine and Department of Nuclear Medicine, Samsung Medical Center) ;
  • Lee, Kyung-Han (Department of Biomedical Engineering, Sungkyunkwan University School of Medicine and Department of Nuclear Medicine, Samsung Medical Center) ;
  • Kim, Byung-Tae (Department of Biomedical Engineering, Sungkyunkwan University School of Medicine and Department of Nuclear Medicine, Samsung Medical Center)
  • 정진호 (성균관대학교 의과대학 생명의공학과, 삼성서울병원 핵의학과) ;
  • 최용 (성균관대학교 의과대학 생명의공학과, 삼성서울병원 핵의학과) ;
  • 송태용 (성균관대학교 의과대학 생명의공학과, 삼성서울병원 핵의학과) ;
  • 정용현 (성균관대학교 의과대학 생명의공학과, 삼성서울병원 핵의학과) ;
  • 정명환 (성균관대학교 의과대학 생명의공학과, 삼성서울병원 핵의학과) ;
  • 홍기조 (성균관대학교 의과대학 생명의공학과, 삼성서울병원 핵의학과) ;
  • 민병준 (성균관대학교 의과대학 생명의공학과, 삼성서울병원 핵의학과) ;
  • 최연성 (성균관대학교 의과대학 생명의공학과, 삼성서울병원 핵의학과) ;
  • 이경한 (성균관대학교 의과대학 생명의공학과, 삼성서울병원 핵의학과) ;
  • 김병태 (성균관대학교 의과대학 생명의공학과, 삼성서울병원 핵의학과)
  • Published : 2004.02.28
Download PDF
⟨ Previous Next ⟩

Abstract

Purpose: Since I-125 emits low energy (27-35 keV) radiation, thinner crystal and collimator could be employed and, hence, it is favorable to obtain high quality images. The purpose of this study was to derive the optimized parameters of I-125 SPECT using a new simulation tool, GATE (Geant4 Application for Tomographic Emission). Materials and Methods: To validate the simulation method, gamma camera developed by Weisenberger et al. was modeled. Nal(T1) plate crystal was used and its thickness was determined by calculating detection efficiency. Spatial resolution and sensitivity curves were estimated by changing variable parameters for parallel-hole and pinhole collimator. Peformances of I-125 SPECT equipped with the optimal collimator were also estimated. Results: in the validation study, simulations were found to agree well with experimental measurements in spatial resolution (4%) and sensitivity (3%). In order to acquire 98% gamma ray detection efficiency, Nal(T1) thickness was determined to be 1 mm. Hole diameter (mm), length (mm) and shape were chosen to be 0.2:5:square and 0.5:10:hexagonal for high resolution (HR) and general purpose (GP) parallel-hole collimator, respectively. Hole diameter, channel height and acceptance angle of pinhole (PH) collimator were determined to be 0.25 mm, 0.1 mm and 90 degree. The spatial resolutions of reconstructed image of the I-125 SPECT employing HR:GP:PH were 1.2:1.7:0.8 mm. The sensitivities of HR:GP:PH were 39.7:71.9:5.5 cps/MBq. Conclusion: The optimal crystal and collimator parameters for I-125 Imaging were derived by simulation using GATE. The results indicate that excellent resolution and sensitivity imaging is feasible using I-125 SPECT.

목적:. I-125는 저에너지(27-35 keV) 방사선을 방출하기 때문에 두께가 얇은 섬광결정과 조준기를 사용할 수 있어 고분해능, 고민감도 영상획득에 유리한 물리적 특성을 가지고 있다. 이 연구의 목적은 새로운 시뮬레이션 도구인 GATE (Geant4 Application for Tomographic Emission)를 사용하여 최적의 I-125 SPECT 시스템 파라미터를 도출하는 것이다. 대상 및 방법: 시뮬레이션 방법의 신뢰성을 검증하기 위해, Weisenberger 등이 개발한 감마 카메라 시스템을 모사하였다. 섬광체로 평판형 Nal(T1)을 사용하였으며, 두께는 검출효율을 계산해서 결정하였다. 평행구멍조준기와 바늘구멍조준기의 여러 파라미터가 공간분해능과 민감도에 미치는 영향을 평가하였다. 그리고 최적화된 조준기를 결합한 I-125 SPECT의 성능을 평가하였다. 결과: 시뮬레이션에 대한 신뢰성 검증연구 결과, 측정과 시뮬레이션에서 공간분해능(4%)과 민감도(3%)가 유사함을 확인하였다. Nal(T1) 두께는 I-125 감마선을 98% 검출할 수 있도록 1 mm로 결정하였다. 시뮬레이션 결과 고분해능 평행구멍조준기로 구멍크기가 0.2 mm이고 길이가 5 mm인 사각구멍조준기를 선택하였고, 범용 평행구멍조준기로 구멍크기가 0.5 m이고, 길이가 10 mm인 육각구멍조준기를 선택하였다. 바늘구멍조준기는 구멍지름이 0.25 mm이고 채널높이가 0.1 mm이며, 허용각도가 90도인 조준기를 선택하였다. 최적화된 고분해능 평행구멍조준기, 범용 평행구멍조준기, 바늘구멍조준기를 결합한 I-125 SPECT의 재구성 영상 공간분해능은 각각 1.2 mm, 1.7 mm, 0.8 mm였으며, 민감도는 39.7 cps/MBq, 71.9 cps/MBq, 5.5 cps/MBq이었다. 결론: GATE 시뮬레이션으로 I-125 영상에 적합한 섬광결정 파라미터 및 조준기 파라미터를 도출하였다. 이 연구결과는 I-125 SPECT로 탁월한 고분해능, 고민감도 영상을 얻을 수 있음을 보여준다.

Keywords

References

  1. Koh CS, Nuclear Medicine. 3nd ed. Seoul: Korea Medical Book Publisher ; 1997. p. 47-50
  2. Weisenberger AG, Bradley EL, Majewski S, Saha MS. Development of a Novel Radiation Imaging Detector System for In Vivo Gene Imaging in Small Animall Study. IEEE Trans Nucl Sci 1998;45:1743-9 https://doi.org/10.1109/23.685298
  3. Weisenberger AG, Wojcik R, Bradley EL, Brewer P, Majewski S, Qian J, et al. SPECT-CT System for Small Animal Imaging. IEEE Trans Nucl Sci 2003;50:74-9 https://doi.org/10.1109/TNS.2002.807949
  4. McElroy DP, MacDonald LR, Beekman FJ, Wang Y, Patt BE, Iwanczyk JS, et al. Performance Evaluation of A-SPECT: A High Resolution Desktop Pinhole SPECT System for Imaging Small Animals. IEEE Trans Nucl Sci 2002;49:2139-47 https://doi.org/10.1109/TNS.2002.803801
  5. Beekman FJ, McElroy DP, Berger F, Gambhir SS, Hoffman EJ, Dherry SR. Towards In VIVO Nuclear Microscopy: Iodine-125 Imaging in Mice Using Micro-Pinholes. Eur J Nucl Med 2002;29:933-8 https://doi.org/10.1007/s00259-002-0805-6
  6. Weisenberger AG, Kross B, Majewski S, Wojcik R, Bradley EL, Saha MS. Design Features and Performance of a CsI(Na) Array Based Gamma Camera for Small Animal Gene Research. IEEE Trans Nucl Sci 1998;45:3053-8 https://doi.org/10.1109/23.737663
  7. http://lphe.epfl.ch/-PET/research/gate/OpenGATE/
  8. Knoll GF. Radiation Detection and Measurement. 3rd ed. New York: John Wiley & Sons, Inc.; 1999. p. 53-5
  9. Sorenson JA, Phelps ME. Physics in Nuclear Medicine. 2nd ed. Philadelphia: W.B. Saunders; 1987. p. 331-45
  10. Bong JK, Kim HJ, Lee JD, Kwon SI. Computer Simulation for Effects of Scintillator and Parallel Hole Collimator on Gamma Probe Imaging. Journal of Korea Society of Medical Biological Engineering. 1998;19:563-70
  11. Staelens S, Strul D, Santin G, Vandenberghe S, Koole M, D'Asseler Y, et al. Monte Carlo Simulations of a Scintillation Camera Using GATE: Validation and Application Modelling. Phys Med Biol 2003;48:3021-42 https://doi.org/10.1088/0031-9155/48/18/305
  12. Jeong MH, Choi Y, Chung YH, Song TY, Jung MH, Hong KJ, et al. Position Mapping, Energy Calibration, and Flood Correction Improve the Performances of Small Gamma Camera Using Position Sensitive PMT. Conference Record of the 2003 IEEE Nuclear Science Symposium and Medical Imaging Conference
  13. Wojcik R, Majewski S, Kross B, Steinbach D, Weisenberger AG. High Spatial Resolution Gamma Imaging Detector Based on a 5' Diameter R3292 Hamamatsu PSPMT. IEEE Trans Nucl Sci 1998;45:487-91 https://doi.org/10.1109/23.682432