13Deoxyglucose) are positron emitters and decay by emitting high-energy gamma
rays that need a PET scanner to generate images. The extent of monitoring of
the stem cells using this technique is time limited and depends on the half-life
of the radionuclide. In general the time available for imaging is the lesser of the
physical and biological half-life of the radionuclide. Radionuclide imaging has
been used successfully to label and image stem cells in cardiac applications and
imaging of myocardial infarction [ 28 , 29 ]. The major advantage of using
SPECT or PET imaging is the their ability to detect very low quantities of
radiotracer. As low as nano and femto-molar concentrations can be detected
respectively by these modalities. However these modalities are limited by rela-
tively low spatial resolution when compared to MRI. Combining PET and
SPECT with CT has helped remove overlapping anatomy but spatial resolution
remains inherently poor.
Reporter gene imaging using SPECT and PET has also been successfully
employed in the past [ 30 , 31 ]. A reporter gene can also be incorporated in a stem
cell that produces a substrate (either a cell receptor or enzyme), which can bind with
an exogenous probe containing the radiotracer. This allows non-invasive imaging,
longitudinal monitoring and study of stem cell biology with high sensitivity. Several
Fig. 1.4 Comparison of 18F–FDG PET (upper row) and 18F-FDG-labeled MSCs (middle row) in
a rabbit myocardial infarction model. Three days after ligation at the left anterior descending artery
near the apical region, 1.110718F-FDG-labeled MSCs were injected directly into the left ventricle.
The PET scan was performed 3.5 h after injection. In the fusion images (lower row), 18F-FDG-
labeled MSCs were found to be distributed into the peri-infarcted zone of the myocardium (arrow).
(Courtesy, Wu C et al. In vivo cell tracking via^18 F–fluorodeoxyglucose labeling: a review of the
preclinical and clinical applications in cell-based diagnosis and therapy. Clin Imaging. 2013
Jan-Feb;37(1):28–36)
1 Current Indications and Overview of Molecular Imaging Techniques...