Performance evaluation of SimPET-L and SimPET-XL: MRI-compatible small-animal PET systems with rat-body imaging capability

Minjee Seo; Guen Bae Ko; Kyeong Yun Kim; Jeong-Whan Son; Jung Woo Byun; Yun-Sang Lee; Kyeong Min Kim; Jang Woo Park; Kipom Kim; Taekwan Lee; Jae Sung Lee

doi:10.1186/s40658-023-00534-x

Performance evaluation of SimPET-L and SimPET-XL: MRI-compatible small-animal PET systems with rat-body imaging capability

EJNMMI Phys. 2023 Mar 7;10(1):16. doi: 10.1186/s40658-023-00534-x.

Authors

Minjee Seo^{1

2}, Guen Bae Ko³, Kyeong Yun Kim³, Jeong-Whan Son³, Jung Woo Byun², Yun-Sang Lee², Kyeong Min Kim⁴, Jang Woo Park⁴, Kipom Kim⁵, Taekwan Lee⁶, Jae Sung Lee^{7

8

9}

Affiliations

¹ Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, South Korea.
² Department of Nuclear Medicine, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, South Korea.
³ Brightonix Imaging Inc., Seoul, 04782, South Korea.
⁴ Korea Institute of Radiological and Medical Sciences, Seoul, 01812, South Korea.
⁵ Brain Research Core Facility, Korea Brain Research Institute, 61 Cheomdan-ro, Dong-gu, Daegu, 41062, South Korea.
⁶ Brain Research Core Facility, Korea Brain Research Institute, 61 Cheomdan-ro, Dong-gu, Daegu, 41062, South Korea. tklee@kbri.re.kr.
⁷ Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 03080, South Korea. jaes@snu.ac.kr.
⁸ Department of Nuclear Medicine, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, South Korea. jaes@snu.ac.kr.
⁹ Brain Research Core Facility, Korea Brain Research Institute, 61 Cheomdan-ro, Dong-gu, Daegu, 41062, South Korea. jaes@snu.ac.kr.

Abstract

Background: SimPET-L and SimPET-XL have recently been introduced with increased transaxial fields of view (FOV) compared with their predecessors (SimPET™ and SimPET-X), enabling whole-body positron emission tomography (PET) imaging of rats. We conducted performance evaluations of SimPET-L and SimPET-XL and rat-body imaging with SimPET-XL to demonstrate the benefits of increased axial and transaxial FOVs.

Procedures: The detector blocks in SimPET-L and SimPET-XL consist of two 4 × 4 silicon photomultiplier arrays coupled with 20 × 9 array lutetium oxyorthosilicate crystals. SimPET-L and SimPET-XL have an inner diameter (bore size) of 7.6 cm, and they are composed of 40 and 80 detector blocks yielding axial lengths of 5.5 and 11 cm, respectively. Each system was evaluated according to the National Electrical Manufacturers Association NU4-2008 protocol. Rat imaging studies, such as ¹⁸F-NaF and ¹⁸F-FDG PET, were performed using SimPET-XL.

Results: The radial resolutions at the axial center measured using the filtered back projection, 3D ordered-subset expectation maximization (OSEM), and 3D OSEM with point spread functions correction were 1.7, 0.82, and 0.82 mm FWHM in SimPET-L and 1.7, 0.91, and 0.91 mm FWHM in SimPET-XL, respectively. The peak sensitivities of SimPET-L and SimPET-XL were 6.30% and 10.4% for an energy window of 100-900 keV and 4.44% and 7.25% for a window of 250-750 keV, respectively. The peak noise equivalent count rate with an energy window of 250-750 keV was 249 kcps at 44.9 MBq for SimPET-L and 349 kcps at 31.3 MBq for SimPET-XL. In SimPET-L, the uniformity was 4.43%, and the spill-over ratios in air- and water-filled chambers were 5.54% and 4.10%, respectively. In SimPET-XL, the uniformity was 3.89%, and the spill-over ratio in the air- and water-filled chambers were 3.56% and 3.60%. Moreover, SimPET-XL provided high-quality images of rats.

Conclusion: SimPET-L and SimPET-XL show adequate performance compared with other SimPET systems. In addition, their large transaxial and long axial FOVs provide imaging capability for rats with high image quality.

Keywords: Instrumentation; Molecular imaging; NEMA performance; PET/MRI.

Abstract

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