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1.  FIAU: From reporter gene imaging to imaging of bacterial proliferation 
The radioiodinated thymidine analogue, FIAU, is a tracer that has been developed for reporter gene, for cells that were transfected with herpes simplex virus thymidine kinase, HSV-TK. FIAU is also a specific substrate of bacterial TK due to the homology between viral and bacterial TK. In this issue of AJNMMI (http://www.ajnmmi.us), Pullamb-hatla et al. reported that the accumulation of 125I-FIAU in pulmonary infectious foci correlated with the bacterial burden in the lungs. 125I-FIAU could be used to monitor the efficacy of anti-microbial therapy in mice. Potentially 124I-FIAU PET could be used to discriminate microbial from sterile inflammation in patients with prosthetic implants.
PMCID: PMC3477741  PMID: 23133817
Infection; inflammation; reporter gene imaging; positron emission tomography (PET)
2.  18F-FDG PET/CT: timing for evaluation of response to therapy remains a clinical challenge 
Utilizing novel imaging modalities for defining response and predicting long-term outcome after treatment may have a significant impact on cancer patient management. 18F-FDG PET/CT has great potential for use in early assessment of response to cancer therapy. However, the lack of a general consensus on a specific set of response criteria makes adoption of PET difficult for the oncology community. The optimal time after initiating therapy for assessing response to treatment also has yet to be clearly determined.
PMCID: PMC3477715  PMID: 23133796
18F-FDG; PET/CT; Therapeutic response; Cancer
4.  PET/MR imaging of atherosclerosis: initial experience and outlook 
Hybrid scanners such as PET/CT have in the past emerged as a valuable modality in clinical routine as well as an important research tool. Recently, the newly developed fully integrated PET/MR scanners were introduced to the market, raising high expectations especially due to the excellent soft tissue contrast and functional imaging capabilities of MRI. In this issue of the American Journal of Nuclear Medicine and Molecular Imaging, initial experiences using a hybrid PET/MR scanner for carotid artery imaging in a group of patients with increased risk for atherosclerosis are described. This represents a proof-of-principle study, which could stimulate future applications of this powerful modality in atherosclerotic plaque imaging.
PMCID: PMC3784802  PMID: 24116347
PET/MR; PET/CT; hybrid imaging; atherosclerosis; FDG
5.  Molecular MRI of VEGFR-2 reveals intra-tumor and inter-tumor heterogeneity 
Non-invasive and quantitative imaging of vascular endothelial growth factor receptor-2 (VEGFR-2) expression levels is highly important in cancer diagnosis, prognosis, and patient management. Although various literature reports have investigated the tumor expression levels of VEGFR-2 using imaging techniques such as positron emission tomography, single-photon emission computed tomography, targeted ultrasound, etc., accurate evaluation of the dynamic microdistribution of VEGFR-2 in vivo with good spatial and temporal resolution remains a major challenge. In this issue of the American Journal of Nuclear Medicine and Molecular Imaging, He at al. reported the use of a VEGFR-2 targeted probe for magnetic resonance imaging (MRI) of VEGFR-2 in two glioma models in rats (i.e. C6 and RG2). The heterogeneity of VEGFR-2 expression was non-invasively imaged with MRI and validated with various in vitro, in vivo, and ex vivo experiments. Not only was heterogeneous expression of VEGFR-2 found in different glioma tumors, it was also observed in different regions within the same tumor (e.g. tumor periphery, peri-necrotic area, and tumor interior). This report highlights the complex nature of gliomas, which may offer invaluable insights into tumor heterogeneity and potential clinical management of glioma patients. These patients have dismal clinical outcomes and are in urgent need of better tools to improve brain tumor treatment.
PMCID: PMC3715775  PMID: 23900733
Molecular MRI (mMRI); glioma; tumor angiogenesis; VEGFR-2; molecular imaging
6.  “Kit like” 18F labeling method for synthesis of RGD peptide-based PET probes 
Positron Emission Tomography (PET) has become a popular imaging technique widely used for diagnostic purposes. To date, much attention has been devoted to 18F-fluoride because of the characteristics of its nuclear decay, as well as its relative ease of preparation from 18O-water. However, with a half-life of 110 minutes, swift and efficient incorporation of 18F-fluorine into biomolecules is necessary to minimize loss of activity. Therefore, the discovery of rapid and reliable incorporation of 18F-fluorine atoms into biomolecules would be highly beneficial, especially if these protocols can be carried out directly in irradiated 18O-water. In the study published in the American Journal of Nuclear Medicine and Molecular Imaging, cyclo-RGD-18F-aryltrifluoroborate conjugates were prepared based on one-step and one-pot-two-step methods. This paper represents recent efforts on the design and development of novel PET tracers based on the “Kit like” 18F labeling method.
PMCID: PMC3545367  PMID: 23342304
Positron emission tomography (PET); 18F; RGD; integrin αvβ3; molecular imaging
7.  Ready for prime time? Dual tracer PET and SPECT imaging 
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.
PMCID: PMC3484417  PMID: 23145358
Dualisotope; dual tracer; positron emission tomography (PET); single photon emission tomography (SPECT); quantitative imaging
9.  In a “nutshell”: intrinsically radio-labeled quantum dots 
Quantum dots (QDs) have many intriguing properties suitable for biomedical imaging applications. The poor tissue penetration of optical imaging in general, including those using QDs, has motivated the development of various QD-based dual-modality imaging agents. In this issue of AJNMMI (http://www.ajnmmi.us), Sun et al. reported the synthesis and in vitro/in vivo characterization of intrinsically radio-labeled QDs (r-QDs), where 109Cd was incorporated into the core/shell of QDs of various compositions. These r-QDs emit in the near-infrared range, have long circulation half-life, are quite stable with low cytotoxicity, exhibit small size and low accumulation in the reticuloendothelial system, and can allow for accurate measurement of their biodistribution in mice. With these desirable features demonstrated in this study, future development and optimization will further enhance the biomedical potential of intrinsically radio-labeled QDs.
PMCID: PMC3477731  PMID: 23133808
Quantum-dots (QDs); nanoparticle; positron emission tomography (PET); single-photon emission computed tomography (SPECT); near-infrared (NIR); optical imaging
10.  PET imaging of metabotropic glutamate receptor subtype 5 (mGluR5) 
Metabotropic glutamate receptors (mGluRs) belong to a family of G-protein coupled receptors involved in the modulation of fast excitatory transmission. In particular, the subtype-5 receptor (mGluR5) was found to be an attractive target for the treatment and diagnosis of variety of psychiatric and neurological disease including anxiety, depression, epilepsy, drug addiction, and Parkinson's disease. Positron emission tomography (PET) is a highly sensitive imaging technique that holds great potential for the diagnosis of a brain disorder. In the study published in the American Journal of Nuclear Medicine and Molecular Imaging, a 18F labelled PET probe was developed targeting mGluR5. This paper represents the efforts and challenges on the design and development of novel PET tracers for mGluR5 imaging.
PMCID: PMC3478119  PMID: 23133800
mGluR5; positron emission tomography (PET); 18F; 11C; molecular imaging

Results 1-12 (12)