Research ArticleCLINICAL INVESTIGATIONS

Reproducibility of Tumor Blood Flow Quantification with 15O-Water PET

Martin A. Lodge, Heather A. Jacene, Roberto Pili and Richard L. Wahl
Journal of Nuclear Medicine October 2008, 49 (10) 1620-1627; DOI: https://doi.org/10.2967/jnumed.108.052076

Article Figures & Data

Figures

  • FIGURE 1. 
    FIGURE 1. 

    Circular ROIs (diameter, 15 mm) were manually placed over the most metabolically active part of tumor, as seen in last frame of dynamic 18F-FDG images (A). ROIs were defined in 3 adjacent image slices (not shown). This volume of interest was subsequently applied to 2 15O-water image series (B and C) under assumption that patient did not move between 15O-water and 18F-FDG studies.

  • FIGURE 2. 
    FIGURE 2. 

    Example time–activity curves for replicate 15O-water studies performed on same patient. Data for first (A) and second (B) administrations are shown. Circles represent (image-derived) input function and squares denote tumor data. Solid line near tumor data is model fit that produced parameter estimates shown in each figure.

  • FIGURE 3. 
    FIGURE 3. 

    Bland–Altman analysis of reproducibility of k1 for tumors (TBF). (A) Replicate measures of k1 are plotted against each other. Solid symbols represent data acquired on Advance scanner; open symbols represent data acquired on Discovery RX scanner. (B) Absolute difference between replicate k1 measurements are plotted as function of their mean and show clear proportionality. (C) After log transformation, dsd for k1 was calculated as 0.178. Dashed lines denote 95% CIs on either side of mean (1.96 × dsd).

  • FIGURE 4. 
    FIGURE 4. 

    Bland–Altman analysis of reproducibility of k2 for tumors (efflux rate constant). (A) Replicate measures of k2 are plotted against each other. Solid symbols represent data acquired on Advance scanner; open symbols represent data acquired on Discovery RX scanner. (B) Absolute differences between replicate k2 measurements are plotted as function of their mean and show clear proportionality. (C) After log transformation, dsd for k2 was calculated as 0.259. Dashed lines denote 95% CIs on either side of mean (1.96 × dsd).

  • FIGURE 5. 
    FIGURE 5. 

    Bland–Altman analysis of reproducibility of Vd for tumors. (A) Replicate measures of Vd are plotted against each other. Solid symbols represent data acquired on Advance scanner; open symbols represent data acquired on Discovery RX scanner. (B) Absolute differences between replicate Vd measurements are plotted as function of their mean and show no clear proportionality. (C) dsd for Vd was calculated as 0.082 mL/g. Dashed lines denote 95% CIs on either side of mean (1.96 × dsd).

Tables

  • TABLE 1

    Differences Between Advance and Discovery RX PET Scanners

    ParameterAdvanceDiscovery RX
    Detector materialBismuth germanateLutetium yttrium orthosilicate
    Detector size (mm)
     Tangential4.04.2
     Axial8.16.3
    Detector thickness (mm)3030
    Detectors per block6 (tangential) × 6 (axial)9 (tangential) × 6 (axial)
    Blocks (axial direction)34
    Detector rings (axial direction)1824
    Image slices3547
    Slice thickness (mm)4.253.27
    Crystals per ring672630
    Detectors in whole gantry12,09615,120
    Septa (mm)
     Length12054
     Thickness10.8
    Discriminator (keV)
     Lower level300425
     Upper level650650
    Coincidence timing window (ns)12.56.5
    Attenuation correction68Ge pin source64-slice CT
    Randoms correctionDelayed channelSingles
  • TABLE 2

    Statistical Parameters Used to Quantify Reproducibility

    AbbreviationParameterCalculation
    dsdSD of the differenceEmbedded Image where d is the difference data and n is the number of pairs
    wSDWithin-subject SDEmbedded Image
    wCVWithin-subject coefficient of variation (%)For data in original units:
    Embedded Image, where Embedded Image is the mean.
    For log-transformed data:
    Embedded Image
    Repeatability (expressed as a percentage of the mean)Embedded Image
  • TABLE 3

    Descriptive Statistics for Kinetic Parameters Derived from All Patient Studies

    Injection 1Injection 2
    ParameterMeanMedianSDMeanMedianSD
    k1 (mL/min/g)1.030.521.280.990.651.09
    k2 (1/min)1.581.001.791.521.011.60
    Va (dimensionless)0.130.080.130.120.080.14
    Vd (mL/g)0.660.670.220.670.680.22
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