OtherBasic Science Investigations

PET Performance Measurements for an LSO-Based Combined PET/CT Scanner Using the National Electrical Manufacturers Association NU 2-2001 Standard

Yusuf E. Erdi, Sadek A. Nehmeh, Tim Mulnix, John L. Humm and Charles C. Watson
Journal of Nuclear Medicine May 2004, 45 (5) 813-821;

Article Figures & Data

Figures

  • FIGURE 1.
    FIGURE 1.

    (A) Setup for axial and transaxial measurement. The point source was suspended from a needle in either an axial or a transaxial orientation, as shown in the insets. A template was used to position the point source for improved accuracy. (B) Scatter phantom with an embedded line source on the table. The acquisitions started at 740 MBq in the line source and continued for more than 8 half-lives (∼15 h). This experiment yielded data for counting rate performance and scatter fraction. (C) Location of the line source for the sensitivity measurement (arrow). Tubes were pulled out from the back of the scanner after each measurement. In addition to the center, the measurement was repeated at a 10-cm radial offset by raising the table. (D) Image quality measurement. Four smaller spheres in the IEC body phantom and the background showed activity. Activity was also present in the form of a line source in the scatter phantom.

  • FIGURE 2.
    FIGURE 2.

    Trues, randoms, and NECRs observed during the counting rate test.

  • FIGURE 3.
    FIGURE 3.

    Axial sensitivity profile at the center of the FOV and at 10 cm off center.

  • FIGURE 4.
    FIGURE 4.

    For each acquisition (j), the highest and lowest values of the relative counting rate error (Δri,j) over each slice (i), in percentage units. The vertical line indicates the level of aNEC,peak (14.7 kBq/mL) activity. At this activity level the maximum bias is less than 8.5%.

  • FIGURE 5.
    FIGURE 5.

    A transverse slice through the sphere phantom showing placement of the ROIs used for the analyses.

  • FIGURE 6.
    FIGURE 6.

    (A) The central-slice images of the image quality measurement. Top row: 4:1 contrast ratio. Bottom row: 8:1 contrast ratio. For each contrast, reconstructions using 3 common algorithms are shown. (B). Coronal slices through the 17- and 22-mm spheres, for each contrast ratio and reconstruction algorithm.

  • FIGURE 7.
    FIGURE 7.

    The relative lung residual (ΔClung) in percentage units, for each slice. (A) 4:1 contrast ratio. (B) 8:1 case contrast ratio.

Tables

  • TABLE 1

    Activity Concentrations for Image Quality Measurement

    Area measuredActivity concentration
    4:1 (kBq/mL)8:1 (kBq/mL)
    Background4.785.66
    Hot spheres19.0546.20
    Scatter phantom ratios3.825.53
    Assayed hot-to-background ratio3.998.17
  • TABLE 2

    Spatial Resolution Values

    Distance (cm)DirectionDescriptionFWHM* (mm)FWTM* (mm)
    AxialTransaxialAxialTransaxial
    1TransverseAverage x and y for both z6.36.612.413.0
    1AxialAverage for both z6.15.812.312.0
    10Transverse radialAverage 2 transverse for both z7.47.113.012.5
    10Transverse tangentialAverage 2 transverse for both z6.86.913.113.3
    10Axial resolutionAverage 2 transverse for both z7.06.813.913.6

    • ↵* Measures refer to the orientation of the point source. Preferred values are in bold type.

  • TABLE 3

    Percentage Contrast, Background Variability, and Average Lung Residual for n = 4

    Sphere size (mm)Contrast (%)Background variability (%)
    2i × 8s*4i × 16s†FBP2i × 8s*4i × 16s†FBP
    101222223.56.28.1
    131729293.25.36.4
    172938382.94.44.7
    224148482.83.83.6
    284560672.73.43.0
    375162662.63.12.7
    Lung (average relative error)31130

    • ↵* Two iterations and 8 subsets.

    • ↵† Four iterations and 16 subsets.

  • TABLE 4

    Percentage Contrast, Background Variability, and Average Lung Residual for n = 8

    Sphere size (mm)Contrast (%)Background variability (%)
    2i × 8s*4i × 16s†FBP (relative deviation)2i × 8s*4i × 16s†FBP
    10152525 (3.3)5.17.48.7
    13243432 (2.3)5.06.67.2
    17364342 (4.0)4.86.06.0
    22485351 (1.7)4.75.55.4
    28466271 (3.5)4.65.24.9
    37445556 (11)4.54.94.2
    Lung (average relative error)32130

    • ↵* Two iterations and 8 subsets.

    • ↵† Four iterations and 16 subsets.

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