Research ArticleImaging

Determining the Minimal Required Radioactivity of 18F-FDG for Reliable Semiquantification in PET/CT Imaging: A Phantom Study

Ming-Kai Chen, David H. Menard and David W. Cheng
Journal of Nuclear Medicine Technology March 2016, 44 (1) 26-30; DOI: https://doi.org/10.2967/jnmt.115.165258

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Figures

  • FIGURE 1.
    FIGURE 1.

    (A) Standard Jaszczak ECT phantom with solid spheres replaced by hollow spheres. (B) Hollow spheres with diameters of 3.4, 2.1, 1.5, 1.2, 1.0, and 0.5 cm. (C) Image of spheres filled with 18F-FDG (165 kBq/mL). (D) Transaxial reconstructed images at 0, 4, 6, 8, 10, 12, 13.5, 14.5, 15.5, 16.5, 17.5, and 18.5 h of decay (displayed in 3-min reconstruction).

  • FIGURE 2.
    FIGURE 2.

    Impact of radioactivity concentration on SUVmax (A) and SUVavg (B) in spheres of various sizes using 10-min acquisition. Radioactivity concentrations on x-axis correspond to acquisition time points of approximately 0, 4, 6, 8, 10, 12, 13.5, 14.5, 15.5, 16.5, 17.5, and 18.5 h.

  • FIGURE 3.
    FIGURE 3.

    Impact of total radioactivity on SUVmax (A) and SUVavg (B) in 3.4-cm sphere at various acquisition times. SUVmax is significantly overestimated at earlier acquisitions (47 at 1-min acquisition compared with 9–10 at later acquisitions). Likewise, SUVavg is overestimated at earlier acquisitions (33.6 at 1-min acquisition compared with 7–8 at later acquisitions). Counting rates are not corrected for random counts or dead time.

  • FIGURE 4.
    FIGURE 4.

    Use of radioactivity concentration–acquisition time product to determine reproducibility of SUVmax in spheres of various sizes. SUVmax is overestimated within a low range of concentration–time product. Data for typical (A) and expanded (B and C) x-axes are shown.

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