대한핵의학회지 (The Korean Journal of Nuclear Medicine)

대한핵의학회 (The Korean Society of Nuclear Medicine)
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3차원 GSO PET/CT 스캐너(Philips GEMINI PET/CT의 특성 평가

Performance Characteristics of 3D GSO PET/CT Scanner (Philips GEMINI PET/DT)

  • 김진수 (서울대학교 의과대학 핵의학교실, 방사선응용생명과학 협동과정) ;
  • 이재성 (서울대학교 의과대학 핵의학교실, 방사선응용생명과학 협동과정) ;
  • 이병일 (서울대학교 의과대학 핵의학교실, 방사선응용생명과학 협동과정) ;
  • 이동수 (서울대학교 의과대학 핵의학교실, 방사선응용생명과학 협동과정) ;
  • 정준기 (서울대학교 의과대학 핵의학교실, 방사선응용생명과학 협동과정) ;
  • 이명철 (서울대학교 의과대학 핵의학교실, 방사선응용생명과학 협동과정)
  • Kim, Jin-Su (Department of Nuclear Medicine, Interdisciplinary Program in Radiation Applied Life Science Major, Seoul National University College of Medicine) ;
  • Lee, Jae-Sung (Department of Nuclear Medicine, Interdisciplinary Program in Radiation Applied Life Science Major, Seoul National University College of Medicine) ;
  • Lee, Byeong-Il (Department of Nuclear Medicine, Interdisciplinary Program in Radiation Applied Life Science Major, Seoul National University College of Medicine) ;
  • Lee, Dong-Soo (Department of Nuclear Medicine, Interdisciplinary Program in Radiation Applied Life Science Major, Seoul National University College of Medicine) ;
  • Chung, June-Key (Department of Nuclear Medicine, Interdisciplinary Program in Radiation Applied Life Science Major, Seoul National University College of Medicine) ;
  • Lee, Myung-Chul (Department of Nuclear Medicine, Interdisciplinary Program in Radiation Applied Life Science Major, Seoul National University College of Medicine)
  • 발행 : 2004.08.31
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초록

목적: Philips GEMINI PET/CT 스캐너는 GSO 섬광결정을 사용해 제작된 전신용 PET/CT 스캐너이다. 이 연구에서는 NEMA에서 새롭게 제안한 NEMA NU2-2001에 따라 GEMINI PET/CT 스캐너의 공간분해능, 민감도, 산란분획, NECR 등을 평가하고 그 결과를 BGO, LSO등의 섬광결정의 특성과 비교하였다. 대상 및 방법: GEMINI는 Philips ALLEGRO PET과 MX8000 D multi-slice CT 스캐너를 결합한 PET/CT 스캐너로서 검출기는 GSO 섬광결정 ($4{\times}6{\times}20mm^3$)을 사용하였고 축방향 시야는 18 cm이다. 공간분해능. 민감도, 산란분획, NECR 등을 평가하기 위하여 PET 데이터를 획득하였다(동시계수창: 8 ns, 에너지창: $409{\sim}664$ keV). 공간분해능 측정을 위하여 축횡단면의 중심에서 1 cm, 10 cm 떨어진 지점의 각 3지점((a) x=0, y=1, (b)x=10, y=0, (c)x=0, y=10)에서 영상을 획득한 다음 여과후역투사방법(램프필터 사용)과 3D RAMLA를 이용하여 영상재구성을 하고 FWHM을 구하였다. 민감도 측정을 위하여 선선원(F-18)을 축횡단면의 중심과 중심에서 10 cm 벗어난 지점에서 5개의 알루미늄관을 차례로 씌워 매질감쇠에 따라 달라지는 참계수를 구하고 이 값을 회귀분석하여 감쇠매질이 없는 이상적인 상황에서의 민감도를 측정하였다(랜덤계수가 참계수의 1%이내). 산란분획과 NECR을 측정하기 위하여 F-18 선선원(1110 MBq)을 산란팬텀에 주입하여 7반감기동안 계수를 획득하였다. SSRB을 사용하여 3D 데이터를 재구성한 다음 랜덤계수율이 참계수율이 1% 미만인 영역에서 산란분획을 구하고 각 횡단면의 값을 평균하여 전체 산란분획을 얻었다. 이 값을 기초로 각 프레임, 각 횡단면에 대한 랜덤계수율, 산란계수율, NECR을 구하였다. 결과: 스캐너의 중심에서 1 cm 벗어난 지점에서 횡축방향, 축방향 공간분해능은 (1) 5.3, 6.5 mm (FBP), (2) 5.1, 5.9 mm (3D RAMLA)이었다. 횡단면의 중심에서 10 cm 벗어난 지점에서 횡축반경방향, 횡축접선방향, 축방향 공간분해능은 (1) 5.7, 5.7, 7.0 mm (FBP), (2) 5.4, 5.4, 6.4 mm (3D RAMLA)이었다. 감쇠매질이 없는 이상적인 상황에서의 민감도는 횡단면의 중심에서 3,620 counts/sec/MBq, 횡단면의 중심에서 10 cm 벗어난 지점에서 4,324 counts/sec/MBq이었다. 산란분획은 40.6%, 최대 참계수율과 최대 NECR은 각각 88.9 kcps @ 12.9 kBq/mL, 34.3 kcps @ 8.84 kBq/mL이었다. 결론: 이 실험에서 NEMA NU2-2001을 이용해 GSO 섬광결정을 사용해 제작된 PET/CT에 대한 성능 평가를 실시하였다. 이는 BGO, LSO 섬광결정을 사용해 제작된 PET 스캐너의 특성과 비교할 수 있는 자료를 제공하며 PET 영상 획득 시 객관적 평가와 분석에 유용하였다.

Purpose: Philips GEMINI is a newly introduced whole-body GSO PET/CT scanner. In this study, performance of the scanner including spatial resolution, sensitivity, scatter fraction, noise equivalent count ratio (NECR) was measured utilizing NEMA NU2-2001 standard protocol and compared with performance of LSO, BGO crystal scanner. Methods: GEMINI is composed of the Philips ALLEGRO PET and MX8000 D multi-slice CT scanners. The PET scanner has 28 detector segments which have an array of 29 by 22 GSO crystals ($4{\times}6{\times}20$ mm), covering axial FOV of 18 cm. PET data to measure spatial resolution, sensitivity, scatter fraction, and NECR were acquired in 3D mode according to the NEMA NU2 protocols (coincidence window: 8 ns, energy window: $409[\sim}664$ keV). For the measurement of spatial resolution, images were reconstructed with FBP using ramp filter and an iterative reconstruction algorithm, 3D RAMLA. Data for sensitivity measurement were acquired using NEMA sensitivity phantom filled with F-18 solution and surrounded by $1{\sim}5$ aluminum sleeves after we confirmed that dead time loss did not exceed 1%. To measure NECR and scatter fraction, 1110 MBq of F-18 solution was injected into a NEMA scatter phantom with a length of 70 cm and dynamic scan with 20-min frame duration was acquired for 7 half-lives. Oblique sinograms were collapsed into transaxial slices using single slice rebinning method, and true to background (scatter+random) ratio for each slice and frame was estimated. Scatter fraction was determined by averaging the true to background ratio of last 3 frames in which the dead time loss was below 1%. Results: Transverse and axial resolutions at 1cm radius were (1) 5.3 and 6.5 mm (FBP), (2) 5.1 and 5.9 mm (3D RAMLA). Transverse radial, transverse tangential, and axial resolution at 10 cm were (1) 5.7, 5.7, and 7.0 mm (FBP), (2) 5.4, 5.4, and 6.4 mm (3D RAMLA). Attenuation free values of sensitivity were 3,620 counts/sec/MBq at the center of transaxial FOV and 4,324 counts/sec/MBq at 10 cm offset from the center. Scatter fraction was 40.6%, and peak true count rate and NECR were 88.9 kcps @ 12.9 kBq/mL and 34.3 kcps @ 8.84 kBq/mL. These characteristics are better than that of ECAT EXACT PET scanner with BGO crystal. Conclusion: The results of this field test demonstrate high resolution, sensitivity and count rate performance of the 3D PET/CT scanner with GSO crystal. The data provided here will be useful for the comparative study with other 3D PET/CT scanners using BGO or LSO crystals.

키워드

참고문헌

  1. American College of Radiology. ACR technical standard for medical nuclear physics performance monitoring of PET imaging equipment. 2001
  2. Daube-Witherspoon ME, Karp JS, Casey ME, DiFilippo FP, Hines H, Muehllehner G, et al. PET performance measurements using the NEMA NU 2-2001 standard. J Nucl Med 2002;43:1398-409
  3. Kim JS, Lee JS, Lee DS, Chung J-K, Lee MC. Performance evaluation of Siemens CTI ECAT EXACT 47 scanner using NEMA NU2-2001. Korean J Nucl Med 2004;38:259-67
  4. Casey ME, Young J, Wheelock T, Schmand M, Bendriem B, Nutt R, et al. Physical performance of a high resolution PET/CT scanner. J Nucl Med 2004;45(suppl):100 [abstract]
  5. Kim JS, Lee JS, Lee DS, Chung J-K, Lee MC. Performance evaluation of Philips GEMINI PET/CT using NEMA NU2-2001 standard. J Nucl Med 2004;45(suppl):101 [abstract]
  6. Lodge MA, Dilsizian V, Line BR. Performance assessment of the Philips GEMINI PET/CT Scanner. J Nucl Med 2004;45(suppl):425[abstract]
  7. National Electrical Manufacturers Association: NEMA standards publication NU2-2001: performance measurements of positron emission tomographs. Rosslyn, VA, National Electrical Manufacturers Association, 2001
  8. Surti S, Karp JS. Imaging characteristics of a 3-dimensional GSO whole-body PET camera. J Nucl Med 2004;45:1040-9
  9. Daube-Witherspoon ME, Matej S, Karp JS, Lewitt RM. Application of the row action maximum likelihood algorithm with spherical basis functions to clinical PET imaging. IEEE Trans Nucl Sci 2001;48:24-30 https://doi.org/10.1109/23.910827
  10. Browne J, de Pierro AB. A row-action alternative to the EM algorithm for maximizing likelihood in emission tomography. IEEE Trans Med Imaging 1996;15:687-99 https://doi.org/10.1109/42.538946
  11. Barnes D, Egan G, O'Keefe G, Abbott D. Characterization of dynamic 3-D PET imaging for functional brain mapping. IEEE Trans Med Imaging 1997;16:261-9 https://doi.org/10.1109/42.585760
  12. Bailey DL. Quantitative procedures in 3D PET. In: Bendriem B, Townsend DW, editors. The theory and practice of 3D PET. Dordrecht: Kluwer Academic Publishers; 1998. p. 118-9
  13. Yang Y, Tai YC, Siegel S, Newport DF, Bai B, Li Q, et al. Optimization and performance evaluation of the microPET II scanner for in vivo small-animal imaging. Phys Med Biol 2004;49:2527-45 https://doi.org/10.1088/0031-9155/49/12/005
  14. Tai C, Chatziioannou A, Siegel S, Young J, Newport D, Goble RN, et al. Performance evaluation of the microPET P4: a PET system dedicated to animal imaging. Phys Med Biol 2001;46:1845-62 https://doi.org/10.1088/0031-9155/46/7/308
  15. Cherry SR, Shao Y, Silverman RW, Meadors K, Siegel S, Chatziioannou A et al. MicroPET: a high resolution PET scanner for imaging small animals. IEEE Trans Nucl Sci 1997;44:1161-6 https://doi.org/10.1109/23.596981
  16. Cherry SR, Sorenson JA, Phelps ME. Physics in nuclear medicine. 3rd ed. Philadelphia: Elsevier Science; 2003. p. 104
  17. Cherry SR, Sorenson JA, Phelps ME. Physics in nuclear medicine. 3rd ed. Philadelphia: Elsevier Science; 2003. p. 137
  18. Karp JS, Surti S, Daube-Witherspoon ME, Freifelder R, Cardi CA, Adam LE, et al. Performance of a brain PET camera based on anger-logic gadolinium oxyorthosilicate detectors. J Nucl Med 2003;44:1340-9
  19. Laymon CM, Bowsher JE. Performance of the log likelihood function for discriminating artifactual from artifact free PET atteunatioin correction images. J Nucl Med 2004;45(suppl):160 [abstract]