Research ArticlePhysics and Instrumentation

Evaluation of Penalized-Likelihood Estimation Reconstruction on a Digital Time-of-Flight PET/CT Scanner for 18F-FDG Whole-Body Examinations

Elin Lindström, Anders Sundin, Carlos Trampal, Lars Lindsjö, Ezgi Ilan, Torsten Danfors, Gunnar Antoni, Jens Sörensen and Mark Lubberink
Journal of Nuclear Medicine July 2018, 59 (7) 1152-1158; DOI: https://doi.org/10.2967/jnumed.117.200790

Article Figures & Data

Figures

  • FIGURE 1.
    FIGURE 1.

    NEMA image quality phantom reconstruction data showing background variability (A) and CNR as function of sphere diameter (B). Reconstruction methods were TOF OSEM (3 iterations, 16 subsets, 5-mm gaussian postprocessing filter, and PSF) and BSREM (including TOF and PSF) with β-factors of 133, 267, 400, and 533 and 50-cm FOV.

  • FIGURE 2.
    FIGURE 2.

    Coronal whole-body 18F-FDG PET images of patient with inflammatory disease, demonstrating ovarian uptake (arrows) by SUVmax obtained with respective reconstruction method. Images were reconstructed with 70-cm FOV and 3 min/bp acquisition, using TOF OSEM (3 iterations, 16 subsets, 5-mm gaussian postprocessing filter, and PSF) and BSREM (including TOF and PSF) with β-factors of 133, 267, 400, and 533.

  • FIGURE 3.
    FIGURE 3.

    Quantitative data from 18F-FDG PET/CT examinations of 11 patients with total of 25 lesions. Box plots show noise level (A), SBR (B), and SNR (C) for different reconstruction methods, and correlation plot shows SUVmax (D) for BSREM compared with TOF OSEM. Reconstruction methods were TOF OSEM (3 iterations, 16 subsets, 5-mm gaussian postprocessing filter, and PSF) and BSREM (including TOF and PSF) with β-factors of 133, 267, 400, and 533; 70-cm FOV; and 3 min/bp acquisition. All data were normalized to data obtained by TOF OSEM. Dashed line represents line of identity.

  • FIGURE 4.
    FIGURE 4.

    Coronal whole-body 18F-FDG PET images of patient with adenocarcinoma, demonstrating SUVmax of lesion (arrows) obtained with respective reconstruction method (gray scale 0–6). Images were reconstructed with 70-cm FOV using TOF OSEM (3 iterations, 16 subsets, 5-mm gaussian postprocessing filter, and PSF) and BSREM (including TOF and PSF) with β-factors of 133, 267, 400, and 533 for 3, 2, and 1 min/bp acquisitions.

  • FIGURE 5.
    FIGURE 5.

    Mean noise level (A), SNR (B), and SUVmax (C) for different reconstruction methods and PET acquisition durations (3, 2, and 1 min/bp). Reconstruction methods were TOF OSEM (3 iterations, 16 subsets, 5-mm gaussian postprocessing filter, and PSF) and BSREM (including TOF and PSF) with β-factors of 133, 267, 400, and 533 and 70-cm FOV. All data were normalized to data obtained by TOF OSEM.

  • FIGURE 6.
    FIGURE 6.

    Trade-off curves showing SNR vs. noise (A) and SBR vs. noise (B) for reconstructions using TOF OSEM (3 iterations, 16 subsets, 5-mm gaussian postprocessing filter, and PSF) and BSREM (including TOF and PSF) with β-factors of 133, 267, 400, and 533 and transaxial FOV of 50 cm (blue) and 70 cm (red). Decreasing β-factor is seen with increasing noise for BSREM data points in both plots. All data were normalized to TOF OSEM with 70-cm FOV, and data points represent mean values. For reference, additional reconstructions with 70-cm FOV using TOF OSEM with PSF and 3 iterations, 16 subsets, and 3-mm gaussian postprocessing filter, and TOF OSEM with PSF and 6 iterations, 16 subsets, and 5-mm gaussian postprocessing filter, are also shown in both graphs.

  • FIGURE 7.
    FIGURE 7.

    Visual scoring of image quality by 2 observers per arbitrary scale (1, poor; 2, moderate; 3, good; 4, very good). Seven different aspects of image quality were considered, and last category in plot represents summarized total mean score. There were 5 sets of images for each of 10 patients. Reconstruction used TOF OSEM (3 iterations, 16 subsets, 5-mm gaussian postprocessing filter, and PSF) and BSREM (including TOF and PSF) with β-factors of 133, 267, 400, and 533; 50-cm FOV, and 3 min/bp acquisition.

Tables

  • TABLE 1

    Quantitative Measures of Reference Sphere in Healthy Liver Tissue Using TOF OSEM and BSREM

    BSREM
    MeasureTOF OSEM*β-factor, 133β-factor, 267β-factor, 400β-factor, 533
    Volume (cm3)19.2 (18.0–19.6)
    SUVmax2.9 (2.1–4.0)4.2 (2.7–5.4)3.1 (2.2–4.0)2.8 (2.0–3.7)2.6 (2.0–3.5)
    SUVmean2.1 (1.6–2.6)2.0 (1.6–2.5)2.0 (1.6–2.5)2.1 (1.6–2.6)2.1 (1.6–2.6)
    SUVSD0.2 (0.2–0.4)0.4 (0.3–0.6)0.3 (0.2–0.4)0.2 (0.2–0.3)0.2 (0.1–0.3)
    Noise level*0.11 (0.09–0.16)0.22 (0.18–0.28)0.13 (0.11–0.17)0.10 (0.08–0.13)0.09 (0.07–0.11)

    • ↵* Measured in liver and defined as SUVSD divided by SUVmean.

    • Data are mean followed by range. TOF OSEM used 3 iterations, 16 subsets, 5-mm gaussian postprocessing filter, and PSF. BSREM included TOF and PSF with β-factors of 133, 267, 400, and 533; 70-cm FOV; and 3 min/bp.

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