Research ArticleCONTINUING EDUCATION

Small-Animal PET: What Is It, and Why Do We Need It?

Rutao Yao, Roger Lecomte and Elpida S. Crawford
Journal of Nuclear Medicine Technology September 2012, 40 (3) 157-165; DOI: https://doi.org/10.2967/jnmt.111.098632

Article Figures & Data

Figures

  • FIGURE 1.
    FIGURE 1.

    Photograph of microPET Focus 120 scanner (Siemens Preclinical Solutions). (Courtesy of Maurice M. Weaver.)

  • FIGURE 2.
    FIGURE 2.

    Mouse is placed in tube designed to facilitate anesthesia and positioning consistency. (Courtesy of David B. Stout.)

  • FIGURE 3.
    FIGURE 3.

    Diagram illustrating difference between head-on and oblique projections in terms of detector response spread (shaded area between crystals detecting coincidence event).

  • FIGURE 4.
    FIGURE 4.

    18F-FDG image on left (coronal view) was acquired first as reference 90 min after injection of 9.4 MBq (254 μCi) of activity via tail vein of tumor-bearing C3H mouse. Mouse was then injected with 2.7 MBq (72 μCi) of 124I-labeled derivative of pyropheophorbide-a, a bifunctional diagnostic and therapeutic agent (75). Mouse was imaged for 30 min at 4.5, 24, 48, and 72 h after injection. Concentration ratios of bifunctional agent in tumor (solid-line circle in each image) to that in animal body (dashed outline in middle image) were 2, 5, and 8 at 24, 48, and 72 h after injection, respectively, indicating that agent has desired properties to be used in therapeutic and monitoring applications. Color palette (shown to right of 18F image) was scaled to minimum/maximum of transverse slice passing through center of tumor site (indicated by green bars) in each dataset. Display scheme was same for all images. 18F = 18F-FDG; 124I = 124I-pyropheophorbide derivative.

  • FIGURE 5.
    FIGURE 5.

    Electrocardiogram-gated 18F-FDG studies in normal and infarcted rats obtained using clinical cardiac analysis software QGS (56). Polar maps display end-systolic 18F-FDG uptake. Ejection fractions for normal and infarcted rats are 81% and 45%, respectively. ED = end-diastolic; EF = ejection fraction; ES = end-systolic. (Adapted with permission of (55).)

  • FIGURE 6.
    FIGURE 6.

    Uptake of 11C-(R)-(−)-RWAY in rat brain. Regions of interest were placed on left and right hippocampi (A), using coronal PET images with reference to rat brain atlas (B). Total uptake of radioactivity is shown in control rats (C) and cyclosporin A–treated rats (E). Similarly, binding potential images are shown in control rats (D) and cyclosporin A–treated rats (F). Cyclosporin A treatment significantly boosted uptake of 11C-(R)-(−)-RWAY, indicating blockade of efflux pump at blood–brain barrier. BP = binding potential; CsA = cyclosporin A; ROI = region of interest. (Reprinted with permission of (59).)

Tables

  • TABLE 1

    Commercially Available Small-Animal PET Scanners and Their Key System Specifications

    FOV (mm)At CFOV…
    ManufacturerModelTransaxialAxialFWHM spatial resolution (mm)Sensitivity (%)Energy window (keV)Reference
    Bioscan/MedisoNanoPET45–123941.28.3250–750(69)
    CarestreamAlbira8040–148<1.33–9Not available(70)
    Gamma Medica/GE HealthcareLabPET11038–1131.31.1–5.4250–650(15)
    PhilipsMosaic HP1281202.71.1410–665(71)
    Raytest Isotopenmessgeräte GmbHClearPET941101.51.9250–750(72)
    Sedecal, S.A.rPET-168471.50.5250–650(72)
    Siemens Preclinical SolutionsmicroPET Focus 120100761.37.1250–750(73)
    microPET Focus 220190761.33.4250–750(74)
    microPET Inveon DPET1001271.49.3250–625(32)

    • CFOV = center field of view.

  • TABLE 2

    Sample PET Tracers Used in Oncology

    Target pathophysiologyTracerWorking principle
    Metabolism (glycolysis)18F-FDGUptake and metabolism: tumor cells have higher rate of glucose, to which 18F-FDG is analog.
    Cell proliferation3′-deoxy-3′-18F-fluorothmidine (18F-FLT)Malignant transformation increases cell proliferation, which upregulates thymidine.
    Gene expression9-(4-fluoro-18F-3-hydroxymethylbutyl) guanine (18F-FHBG)Radiolabeled probe is phosphorylated by selected gene product and is trapped within cell. Thus, magnitude of probe accumulation in cell reflects level of gene expression.
    Tumor angiogenesis89Zr-bevacizumabVascular endothelial growth factor (VEGF) plays pivotal roles in regulating tumor angiogenesis. 89Zr-bevacizumab is anti-VEGF antibody and binds to VEGF.
    Hypoxia18F-fluoromisonidazole (18F-FMISO)Rapid tumor growth leads to underdeveloped new vascularization, which creates hypoxia. 18F-FMISO takes advantage of increased tracer retention in hypoxic tissues with partial pressure of oxygen < 10 mm Hg.
    Apoptosis18F-fluorobenzyl triphenylphosphonium cation (18F-FBnTP)Apoptosis involves permanent collapse of mitochondrial membrane electrochemical potential. 18F-FBnTP is voltage-sensitive probe.
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