OtherSPECIAL CONTRIBUTION

The 2006 Henry N. Wagner Lecture: Of Mice and Men (and Positrons)—Advances in PET Imaging Technology

Simon R. Cherry
Journal of Nuclear Medicine November 2006, 47 (11) 1735-1745;

Article Figures & Data

Figures

  • FIGURE 1. 
    FIGURE 1. 

    Images and photographs illustrating the major advances in PET instrumentation and methods since 1990 discussed in text: whole-body PET (image courtesy of Dr. Magnus Dahlbom, UCLA) (A), 3D PET (B), LSO and related scintillators (photograph courtesy of Dr. Charles Melcher, Siemens) (C), iterative reconstruction methods (images courtesy of Dr. Richard Leahy, USC) (D), PET/CT (image courtesy of Dr. David Townsend, University of Tennessee) (E), and preclinical PET (mouse image courtesy of Dr. Craig Abbey, UCSB) (F).

  • FIGURE 2. 
    FIGURE 2. 

    Basic physics of PET. 18F atom (yellow) on FDG or FDG-6-phosphate molecule decays, emitting positron that scatters in tissue until it loses enough energy to undergo annihilation with an electron, in which mass of positron and electron are converted into 2 back-to-back 511-keV photons.

  • FIGURE 3. 
    FIGURE 3. 

    Illustration of TOF PET: detection of 2 annihilation photons in PET scanner (A), uniform-probability weighting of annihilation site in standard PET (B), and use of TOF information to constrain location of annihilation site during image reconstruction (C).

  • FIGURE 4. 
    FIGURE 4. 

    Illustration of non-colinearity of annihilation photons in PET. Angle is greatly exaggerated; distribution of angles around 180° is gaussian, with SD of only 0.25°.

  • FIGURE 5. 
    FIGURE 5. 

    Contribution of physics factors (positron range, non-colinearity, and detector scatter) to resolution attainable in PET: clinical PET scanner, with detector ring diameter of 80 cm, consisting of 2-cm-thick LSO detectors, and imaging radiotracer labeled with 18F (A); small-animal PET scanner, with detector ring diameter of 8 cm, also consisting of 2-cm-thick LSO detectors and imaging 18F-labeled radiotracer (B). Contribution of positron range, non-colinearity, and detector scatter is shown in each case.

  • FIGURE 6. 
    FIGURE 6. 

    Photograph of MRI-compatible PET insert based on arrays of LSO scintillator coupled through short lengths of optical fibers to position-sensitive APDs and MRI-compatible electronics. This insert fits inside bore of 7-T animal MRI scanner, permitting simultaneous PET and MRI studies.

  • FIGURE 7. 
    FIGURE 7. 

    Schematic illustration of current configuration and sensitivity for 3D whole-body PET (A) compared with configuration in which whole body is within field of view (B). Axial extent of PET detectors is indicated by blue, and sensitivity is indicated by the intensity of red.

  • FIGURE 8. 
    FIGURE 8. 

    Concept of whole-body PET/MRI scanner, and images that such a system might produce (PET image courtesy of Siemens Medical Solutions; whole-body T1-weighted MR image courtesy of Dr. Heinz-Peter Schlemmer, University of Tübingen).

Tables

  • TABLE 1

    Properties of PET Scintillators

    ScintillatorRelative light output (NaI(Tl) = 100)Decay time (ns)Thickness for 90% efficiency at 511 keV (cm)
    NaI(Tl)1002306.6
    BGO153002.4
    LSO, LYSO70402.7
    GSO:Ce25603.3
    BaF2280.8 (15%), 640 (85%)5.1
    CsF52.55.4
    LaBr3150354.9

    • GSO = gadolinium oxyorthosilicate.

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