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Am J Nucl Med Mol Imaging 2012;2(4):415-417
Invited Perspective
Ready for prime time? Dual tracer PET and SPECT imaging
Georges El Fakhri
Center for Advanced Radiological Sciences, Harvard Medical School; Division of Nuclear Medicine & Molecular Imaging, Radiology,
Massachusetts General Hospital, Boston, MA, USA.
Received October 14, 2012; Accepted October 18, 2012; Epub October 15, 2012; Published October 30, 2012
Abstract: Dual isotope single photon emission computed tomography (SPECT) and dual tracer positron emission tomography
(PET) imaging have great potential in clinical and molecular applications in the pediatric as well as the adult populations in many
areas of brain, cardiac, and oncologic imaging as it allows the exploration of different physiological and molecular functions (e.g.,
perfusion, neurotransmission, metabolism, apoptosis, angiogenesis) under the same physiological and physical conditions. This is
crucial when the physiological functions studied depend on each other (e.g., perfusion and metabolism) hence requiring
simultaneous assessment under identical conditions, and can reduce greatly the quantitation errors associated with physical factors
that can change between acquisitions (e.g., human subject or animal motion, change in the attenuation map as a function of time)
as is detailed in this editorial. The clinical potential of simultaneous dual isotope SPECT, dual tracer PET and dual SPECT/PET
imaging are explored and summarized. In this issue of AJNMMI (http://www.ajnmmi.us), Chapman et al. explore the feasibility of
simultaneous and sequential SPECT/PET imaging and conclude that down-scatter and crosstalk from 511 keV photons preclude
obtaining useful SPECT information in the presence of PET radiotracers. They report on an alternative strategy that consists of
performing sequential SPECT and PET studies in hybrid microPET/SPECT/CT scanners, now widely available for molecular
imaging. They validate their approach in a phantom consisting of a 96-well plate with variable 99mTc and 18F concentrations and
illustrate the utility of such approaches in two sequential SPECT-PET/CT studies that include 99mTc-MAA/18F-NaF and
99mTc-Pentetate/18F-NaF. These approaches will need to be proven reproducible, accurate and robust to variations in the
experimental conditions before they can be accepted by the molecular imaging community and be implemented in routine molecular
microPET and microSPECT explorations. Although currently not accepted as standard procedures in the molecular imaging
community, such approaches have the potential to open the way to new SPECT/PET explorations that allow studying molecular
mechanisms and pathways in the living animal under similar physiological conditions. Although still premature for the clinical
setting, these approaches can be extended to clinical research once proven accurate and precise in vivo in small and large animal
models. (ajnmmi1210002).
Keywords: Dualisotope, dual tracer, positron emission tomography (PET), single photon emission tomography (SPECT),
quantitative imaging
Address all correspondence to:
Dr. Georges El Fakhri
DABR, Center for Advanced Radiological Sciences
Radiology Department, Massachusetts General Hospital
White 427, 55 Fruit Street
Boston, MA 02114, USA.
E-mail: elfakhri@pet.mgh.harvard.edu
Invited Perspective
Ready for prime time? Dual tracer PET and SPECT imaging
Georges El Fakhri
Center for Advanced Radiological Sciences, Harvard Medical School; Division of Nuclear Medicine & Molecular Imaging, Radiology,
Massachusetts General Hospital, Boston, MA, USA.
Received October 14, 2012; Accepted October 18, 2012; Epub October 15, 2012; Published October 30, 2012
Abstract: Dual isotope single photon emission computed tomography (SPECT) and dual tracer positron emission tomography
(PET) imaging have great potential in clinical and molecular applications in the pediatric as well as the adult populations in many
areas of brain, cardiac, and oncologic imaging as it allows the exploration of different physiological and molecular functions (e.g.,
perfusion, neurotransmission, metabolism, apoptosis, angiogenesis) under the same physiological and physical conditions. This is
crucial when the physiological functions studied depend on each other (e.g., perfusion and metabolism) hence requiring
simultaneous assessment under identical conditions, and can reduce greatly the quantitation errors associated with physical factors
that can change between acquisitions (e.g., human subject or animal motion, change in the attenuation map as a function of time)
as is detailed in this editorial. The clinical potential of simultaneous dual isotope SPECT, dual tracer PET and dual SPECT/PET
imaging are explored and summarized. In this issue of AJNMMI (http://www.ajnmmi.us), Chapman et al. explore the feasibility of
simultaneous and sequential SPECT/PET imaging and conclude that down-scatter and crosstalk from 511 keV photons preclude
obtaining useful SPECT information in the presence of PET radiotracers. They report on an alternative strategy that consists of
performing sequential SPECT and PET studies in hybrid microPET/SPECT/CT scanners, now widely available for molecular
imaging. They validate their approach in a phantom consisting of a 96-well plate with variable 99mTc and 18F concentrations and
illustrate the utility of such approaches in two sequential SPECT-PET/CT studies that include 99mTc-MAA/18F-NaF and
99mTc-Pentetate/18F-NaF. These approaches will need to be proven reproducible, accurate and robust to variations in the
experimental conditions before they can be accepted by the molecular imaging community and be implemented in routine molecular
microPET and microSPECT explorations. Although currently not accepted as standard procedures in the molecular imaging
community, such approaches have the potential to open the way to new SPECT/PET explorations that allow studying molecular
mechanisms and pathways in the living animal under similar physiological conditions. Although still premature for the clinical
setting, these approaches can be extended to clinical research once proven accurate and precise in vivo in small and large animal
models. (ajnmmi1210002).
Keywords: Dualisotope, dual tracer, positron emission tomography (PET), single photon emission tomography (SPECT),
quantitative imaging
Address all correspondence to:
Dr. Georges El Fakhri
DABR, Center for Advanced Radiological Sciences
Radiology Department, Massachusetts General Hospital
White 427, 55 Fruit Street
Boston, MA 02114, USA.
E-mail: elfakhri@pet.mgh.harvard.edu
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