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Original Article   

The Quarterly Journal of Nuclear Medicine and Molecular Imaging 2022 Sep 19

DOI: 10.23736/S1824-4785.22.03409-4


language: English

Total variation regularized expectation maximization reconstruction improves 68Ga-FAPI-04 PET/CT image quality as compared to ordered subset expectation maximization reconstruction

Hanxiang LIU 1, 2, 3, Lin LIU 1, 2, 3, Shijie XU 4, Zhonglin LU 5, Greta S. MOK 5, Yingwei WANG 1, 2, 3, Yi TAO 1, 2, 3, Yue CHEN 1, 2, 3

1 Department of Nuclear Medicine, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, PR China; 2 Nuclear Medicine and Molecular Imaging Key Laboratory of Sichuan Province, Luzhou, Sichuan, PR China; 3 Academician (Expert) Workstation of Sichuan Province, PR China; 4 United Imaging Healthcare, Shanghai, PR China; 5 Biomedical Imaging Laboratory (BIG), Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau SAR, PR China


BACKGROUND: This study aimed to investigate improvements in 68Ga-FAPI PET/CT image quality due to using total variation regularized expectation maximization (TVR-EM) and ordered subset expectation maximization (OS-EM) reconstruction.
METHODS: Data from a total of 24 patients were retrospectively analyzed in this study. Positron emission tomography (PET) images were reconstructed using OS-EM and TVR-EM for 2 and 3 minutes-per-bed (min/bed) acquisition. The SUVmean of a region-of-interest on the liver, image noise, signal-to-noise ratios (SNR), the SUVmax of the lesions and the tumour-to-background ratios (TBR) were measured and compared between the 2 methods. Subjective image qualities were evaluated by two experienced radiologists using a 5-point score scale (5-excellent, 1-poor).
RESULTS: In total, 132 lesions were analyzed. The image noise in TVR-EM reconstruction groups was lower than in the OS-EM groups (all p < 0.05). The SNR, SUVmax of lesions and the TBR were higher for the TVR-EM reconstruction groups compared to OS-EM groups (all p < 0.05). Also, the SUVmax of the lesions in the TVR-EM groups increased by at least 12% compared to OS-EM 3 min/bed group. The SUVmax for small (<10 mm) and large lesions (> 10 mm) in the TVR-EM 2 min/bed group were significantly larger compared to the OS-EM 3 min/bed groups (all p <0.05). The highest image quality score resulted from the TVR-EM 3 min/bed group with a penalization factor of 0.25 (3.92 ± 0.19).
CONCLUSIONS: TVR-EM reduces image noise and improved the SNR, SUVmax and TBR of the lesions. It also enables fast acquisition without compromising image quality compared to standard OS-EM.

KEY WORDS: Total variation regularized expectation maximization; Ordered subset expectation maximization; Image reconstruction; PET/CT; FAPI

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