NEMA NU2-2001을 이용한 Siemens CTI ECAT EXACT 47 스캐너의 표준 성능 평가 (Performance Evaluation of Siemens CTI ECAT EXACT 47 Scanner Using NEMA NU2-2001) |
Author |
김진수,이재성,이동수,정준기,이명철, |
Jin Su Kim, M.S., Jae Sung Lee, Ph.D., Dong Soo Lee, M.D., June-Key Chung, M.D., and Myung Chul Lee, M.D. |
Affiliation |
서울대학교 의과대학 핵의학교실, 방사선응용생명과학 협동과정 Department of Nuclear Medicine, Interdisciplinary Program in Radiation Applied Life Science Major, Seoul National University College of Medicine, Seoul, Korea |
Abstract |
Purpose: NEMA NU2-2001 was proposed as a new standard for performance evaluation of whole body PET
scanners. In this study, system performance of Siemens CTI ECAT EXACT 47 PET scanner including spatial
resolution, sensitivity, scatter fraction, and count rate performance in 2D and 3D mode was evaluated using this
new standard method.
Methods: ECAT EXACT 47 is a BGO crystal based PET scanner and covers an axial field of
view (FOV) of 16.2 cm. Retractable septa allow 2D and 3D data acquisition. All the PET data were acquired
according to the NEMA NU2-2001 protocols (coincidence window: 12 ns, energy window: 250 - 650 keV). For the
spatial resolution measurement, F-18 point source was placed at the center of the axial FOV((a) x=0, and y=1,
(b)x=0, and y=10, (c)x=10, and y=0cm) and a position one fourth of the axial FOV from the center ((a) x=0,
and y=1, (b)x=0, and y=10, (c)x=10, and y=0cm). In this case, x and y are transaxial horizontal and vertical,
and z is the scanner s axial direction. Images were reconstructed using FBP with ramp filter without any
post-processing. To measure the system sensitivity, NEMA sensitivity phantom filled with F-18 solution and
surrounded by 1-5 aluminum sleeves were scanned at the center of transaxial FOV and 10 cm offset from the
center. Attenuation free values of sensitivity were estimated by extrapolating data to the zero wall thickness.
NEMA scatter phantom with length of 70 cm was filled with F-18 or C-11solution (2D: 2,900 MBq, 3D: 407 MBq),
and coincidence count rates were measured for 7 half-lives to obtain noise equivalent count rate (NECR) and
scatter fraction. We confirmed that dead time loss of the last frame were below 1%. Scatter fraction was
estimated by averaging the true to background (scatter + random) ratios of last 3 frames in which the fractions
of random rate are negligibly small.
Results: Axial and transverse resolutions at 1cm offset from the center were
0.62 and 0.66 cm (FBP in 2D and 3D), and 0.67 and 0.69 cm (FBP in 2D and 3D). Axial, transverse radial, and
transverse tangential resolutions at 10cm offset from the center were 0.72 and 0.68 cm (FBP in 2D and 3D), 0.63
and 0.66 cm (FBP in 2D and 3D), and 0.72 and 0.66 cm (FBP in 2D and 3D). Sensitivity values were 708.6 (2D),
2931.3 (3D) counts/sec/MBq at the center and 728.7 (2D), 3398.2 (3D) counts/sec/MBq at 10 cm offset from the
center. Scatter fractions were 0.19 (2D) and 0.49 (3D). Peak true count rate and NECR were 64.0 kcps at 40.1
kBq/mL and 49.6 kcps at 40.1 kBq/mL in 2D and 53.7 kcps at 4.76 kBq/mL and 26.4 kcps at 4.47 kBq/mL in 3D.
Conclusion: Information about the performance of CTI ECAT EXACT 47 PET scanner reported in this study will be
useful for the quantitative analysis of data and determination of optimal image acquisition protocols using this
widely used scanner for clinical and research purposes. (Korean J Nucl Med 38(3):259-267, 2004) |
Keyword |
Performance, NEMA NU2-2001, PET |
Full text Article |
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