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Relationship between the image quality and noise-equivalent count in time-of-flight positron emission tomography

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Abstract

Objective

The aim of this study was to investigate the relationship between the NEC and TOF-PET image quality.

Methods

The National Electrical Manufactures Association and International Electrical Commission (NEMA IEC) body phantom with a 10-mm diameter sphere was filled with an 18F-FDG solution with a 4:1 radioactivity ratio. The PET data were acquired in the three-dimensional list mode for 20 min. We created frame data ranging from 1 to 5 min acquisition time, which were then reconstructed using the baseline ordered-subsets expectation maximization (OSEM), the OSEM + point spread function (PSF) algorithm, OSEM + time-of-flight (TOF) algorithm and OSEM + PSF + TOF algorithm. The PET images were analyzed according to the noise-equivalent count (NEC), the coefficients of variance of the background (CVBG), the maximum count (CVmax) and the contrast (CVCONT). The results were compared with the recommended value according to the guidelines for the oncology FDG-PET/CT protocol.

Results

The NEC was higher than the recommended value at 3 min or longer acquisition time. The CVBG lower than 15 % were obtained at 3 min acquisition time without TOF and at 2 min acquisition time with TOF. The CVBG of 10 % or lower were obtained at 5 min or longer acquisition time without TOF and at 4 min or longer acquisition time with TOF. Both the CVmax and CVCONT lower than 10 % were obtained at 3 min or longer acquisition time without TOF and at 1 min acquisition or longer with TOF. No particular relationships were observed between the frame number and degree of the variation in the image quality. The CVCONT significantly correlated with the NEC for the data reconstructed without TOF information, while there were no significant correlations between these useful metrics for the data reconstructed with TOF.

Conclusion

This study demonstrated that the NEC is not a useful metric for the evaluation of the image quality on TOF-PET images.

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Authors and Affiliations

  1. Division of Medical Quantum Science, Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan

    Akira Maebatake, Go Akamatsu, Kenta Miwa & Masayuki Sasaki

  2. Division of Molecular Imaging, Institute of Biomedical Research and Innovation, Kobe, Japan

    Go Akamatsu

  3. Division of Radiology, Department of Medical Technology, Kyushu University Hospital, Fukuoka, Japan

    Yuji Tsutsui & Kazuhiko Himuro

  4. Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan

    Shingo Baba

Authors
  1. Akira Maebatake
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  2. Go Akamatsu
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  3. Kenta Miwa
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  4. Yuji Tsutsui
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  5. Kazuhiko Himuro
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  6. Shingo Baba
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  7. Masayuki Sasaki
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Correspondence to Masayuki Sasaki.

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Maebatake, A., Akamatsu, G., Miwa, K. et al. Relationship between the image quality and noise-equivalent count in time-of-flight positron emission tomography. Ann Nucl Med 30, 68–74 (2016). https://doi.org/10.1007/s12149-015-1032-0

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  • DOI: https://doi.org/10.1007/s12149-015-1032-0

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