Yu AS, Hirayama BA, Timbol G, Liu J, Diez-Sampedro A, Kepe V, Satyamurthy N, Huang SC, Wright EM, Barrio JR. Regional distribution of SGLT activity in rat brain in vivo. Am J Physiol Cell Physiol. 2013 Feb 1;304(3):C240-7. doi: 10.1152/ajpcell.00317.2012. Epub 2012 Nov 14.

Abstract

Na(+)-glucose cotransporter (SGLT) mRNAs have been detected in many organs of the body, but, apart from kidney and intestine, transporter expression, localization, and functional activity, as well as physiological significance, remain elusive. Using a SGLT-specific molecular imaging probe, α-methyl-4-deoxy-4-[(18)F]fluoro-D-glucopyranoside (Me-4-FDG) with ex vivo autoradiography and immunohistochemistry, we mapped in vivo the regional distribution of functional SGLTs in rat brain. Since Me-4-FDG is not a substrate for GLUT1 at the blood-brain barrier (BBB), in vivo delivery of the probe into the brain was achieved after opening of the BBB by an established procedure, osmotic shock. Ex vivo autoradiography showed that Me-4-FDG accumulated in regions of the cerebellum, hippocampus, frontal cortex, caudate nucleus, putamen, amygdala, parietal cortex, and paraventricular nucleus of the hypothalamus. Little or no Me-4-FDG accumulated in the brain stem. The regional accumulation of Me-4-FDG overlapped the distribution of SGLT1 protein detected by immunohistochemistry. In summary, after the BBB is opened, the specific substrate for SGLTs, Me-4-FDG, enters the brain and accumulates in selected regions shown to express SGLT1 protein. This localization and the sensitivity of these neurons to anoxia prompt the speculation that SGLTs may play an essential role in glucose utilization under stress such as ischemia. The expression of SGLTs in the brain raises questions about the potential effects of SGLT inhibitors under development for the treatment of diabetes.

http://www.ncbi.nlm.nih.gov/pubmed/23151803

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Teng E, Kepe V, Frautschy SA, Liu J, Satyamurthy N, Yang F, Chen PP, Cole GB, Jones MR, Huang SC, Flood DG, Trusko SP, Small GW, Cole GM, Barrio JR.  [F-18]FDDNP microPET imaging correlates with brain Aβ burden in a transgenic rat model of Alzheimer disease: effects of aging, in vivo blockade, and anti-Aβ antibody treatment. Neurobiol Dis. 2011 Sep;43(3):565-75. doi: 10.1016/j.nbd.2011.05.003. Epub 2011 May 13.

Abstract

In vivo detection of Alzheimer's disease (AD) neuropathology in living patients using positron emission tomography (PET) in conjunction with high affinity molecular imaging probes for β-amyloid (Aβ) and tau has the potential to assist with early diagnosis, evaluation of disease progression, and assessment of therapeutic interventions. Animal models of AD are valuable for exploring the in vivo binding of these probes, particularly their selectivity for specific neuropathologies, but prior PET experiments in transgenic mice have yielded conflicting results. In this work, we utilized microPET imaging in a transgenic rat model of brain Aβ deposition to assess [F-18]FDDNP binding profiles in relation to age-associated accumulation of neuropathology. Cross-sectional and longitudinal imaging demonstrated that [F-18]FDDNP binding in the hippocampus and frontal cortex progressively increases from 9 to 18months of age and parallels age-associated Aβ accumulation. Specificity of in vivo [F-18]FDDNP binding was assessed by naproxen pretreatment, which reversibly blocked [F-18]FDDNP binding to Aβ aggregrates. Both [F-18]FDDNP microPET imaging and neuropathological analyses revealed decreased Aβ burden after intracranial anti-Aβ antibody administration. The combination of this non-invasive imaging method and robust animal model of brain Aβ accumulation allows for future longitudinal in vivo assessments of potential therapeutics for AD that target Aβ production, aggregation, and/or clearance. These results corroborate previous analyses of [F-18]FDDNP PET imaging in clinical populations.

http://www.ncbi.nlm.nih.gov/pubmed/21605674

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Khoja S, Lambert J, Nitzahn M, Eliav A, Zhang Y, Tamboline M, Le CT, Nasser E, Li Y, Patel P, Zhuravka I, Lueptow LM, Tkachyova I, Xu S, Nissim I, Schulze A, Lipshutz GS.  Gene therapy for guanidinoacetate methyltransferase deficiency restores cerebral and myocardial creatine while resolving behavioral abnormalities. Mol Ther Methods Clin Dev. 2022 Mar 28;25:278-296. doi: 10.1016/j.omtm.2022.03.015. eCollection 2022 Jun 9.

Abstract

Creatine deficiency disorders are inborn errors of creatine metabolism, an energy homeostasis molecule. One of these, guanidinoacetate N-methyltransferase (GAMT) deficiency, has clinical characteristics that include features of autism, self-mutilation, intellectual disability, and seizures, with approximately 40% having a disorder of movement; failure to thrive can also be a component. Along with low creatine levels, guanidinoacetic acid (GAA) toxicity has been implicated in the pathophysiology of the disorder. Present-day therapy with oral creatine to control GAA lacks efficacy; seizures can persist. Dietary management and pharmacological ornithine treatment are challenging. Using an AAV-based gene therapy approach to express human codon-optimized GAMT in hepatocytes, in situ hybridization, and immunostaining, we demonstrated pan-hepatic GAMT expression. Serial collection of blood demonstrated a marked early and sustained reduction of GAA with normalization of plasma creatine; urinary GAA levels also markedly declined. The terminal time point demonstrated marked improvement in cerebral and myocardial creatine levels. In conjunction with the biochemical findings, treated mice gained weight to nearly match their wild-type littermates, while behavioral studies demonstrated resolution of abnormalities; PET-CT imaging demonstrated improvement in brain metabolism. In conclusion, a gene therapy approach can result in long-term normalization of GAA with increased creatine in guanidinoacetate N-methyltransferase deficiency and at the same time resolves the behavioral phenotype in a murine model of the disorder. These findings have important implications for the development of a new therapy for this abnormality of creatine metabolism.

https://pubmed.ncbi.nlm.nih.gov/35505663/

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Hsu JJ, Lu J, Umar S, Lee JT, Kulkarni RP, Ding Y, Chang C, Hsiai TK, Hokugo A, Gkouveris I, Tetradis S, Nishimura I, Demer LL, Tintut Y. Changes in microarchitecture of atherosclerotic calcification assessed by 18F-NaF PET and CT after a progressive exercise regimen in hyperlipidemic mice. J. Nucl. Cardiol. 2020 Jan 02; 28;2207–2214 (2021)

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Hsu JJ, Fong F, Patel R, Qiao R, Lo K, Soundia A, Chang C, Le V, Tseng C, Demer LL, Tintut Y. Changes in microarchitecture of atherosclerotic calcification assessed by 18F-NaF PET and CT after a progressive exercise regimen in hyperlipidemic mice. J. Nucl. Cardiol. 2020 Jan 02; 28;2207–2214 (2021)

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Xian JZ, Lu M, Qiao R, Patel NR, Abeydeera D, Iriana S, Demer LL, Tintut Y. Statin Effects on Vascular Calcification. ATVB. 2021 Jan; 41:e185–e192.

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Hsu JJ, Lu J, Umar S, Lee JT, Kulkarni RP, Ding Y, Chang CC, Hsiai T, Hokugo A, Gkouveris I, Tetradis S, Nishimura I, Demer LL, Tintut Y. Effects of bone anabolic therapy on progression of calcific aortic vasculopathy in Apoe-/- mice. Am J Physiol Heart Circ Physiol. 2018 Feb 16. PMC6032086

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Pillai ICL, Li S, Romay M, Lam L, Lu Y, Huang J, Dillard N, Zemanova M, Rubbi L, Wang Y, Lee JT, Xia M, Liang O, Xie YH, Pellegrini M, Lusis AJ and Deb A. Cardiac Fibroblasts Adopt Osteogenic Fates and Can Be Targeted to Attenuate Pathological Heart Calcification. Cell Stem Cell. 2017 Feb; 20(2):1–15. PMCID: PMC5291784

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Xu S, Zhou T, Doh HM, Trinh R, Catapang A, Lee JT, Braas D, Bayley NA, Yamada RE, Vasuthasawat A, Sasine JP, Timmerman JM, Larson SM, Kim Y, MacLeod AR, Morrison SL, Herschman HR. An HK2 antisense oligonucleotide induces synthetic lethality in HK1-HK2+ multiple myeloma. Cancer Res. 2019 March 18. doi:10.1158/0008-5472.CAN-18-2799. PMID: 30885978

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Xu S, Catapang A, Braas D, Stiles L, Doh HM, Lee JT, Graeber TG, Damoiseaux R, Shirihai O, Herschman HR. A precision therapeutic strategy for hexokinase 1-null, hexokinase 2-positive cancers. Cancer Metab. 2018 Jun 28;6:7. doi: 10.1186/s40170-018-0181-8. eCollection 2018. PMC6022704

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Liu X, Lin P, Perrett I, Lin J, Liao YP, Chang CH, Jiang J, Wu N, Donahue T, Wainberg Z, Nel AE, Meng H. Tumor-penetrating peptide enhances transcytosis of silicasome-based chemotherapy for pancreatic cancer. J Clin Invest. 2017 May 1;127:2007-2018. PMC5409788

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Liu X, Situ A, Kang Y, Villabroza KR, Liao Y, Chang CH, Donahue T, Nel AE, Meng H. Irinotecan Delivery by Lipid-Coated Mesoporous Silica Nanoparticles Shows Improved Efficacy and Safety over Liposomes for Pancreatic Cancer. ACS Nano. 2016 Feb 23;10:2702-15. PMC4851343

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Murphy JM, Armijo AL, Nomme J, Lee CH, Smith QA, Li Z, Campbell DO, Liao HI, Nathanson DA, Austin WR, Lee JT, Darvish R, Wei L, Wang J, Su Y, Damoiseaux R, Sadeghi S, Phelps ME, Herschman HR, Czernin J, Alexandrova AN, Jung ME, Lavie A, Radu CG. Development of new deoxycytidine kinase inhibitors and noninvasive in vivo evaluation using positron emission tomography. J Med Chem. 2013 Sep 12;56(17):6696-708. doi: 10.1021/jm400457y. Epub 2013 Aug 15.

Abstract

Combined inhibition of ribonucleotide reductase and deoxycytidine kinase (dCK) in multiple cancer cell lines depletes deoxycytidine triphosphate pools leading to DNA replication stress, cell cycle arrest, and apoptosis. Evidence implicating dCK in cancer cell proliferation and survival stimulated our interest in developing small molecule dCK inhibitors. Following a high throughput screen of a diverse chemical library, a structure-activity relationship study was carried out. Positron Emission Tomography (PET) using (18)F-L-1-(2'-deoxy-2'-FluoroArabinofuranosyl) Cytosine ((18)F-L-FAC), a dCK-specific substrate, was used to rapidly rank lead compounds based on their ability to inhibit dCK activity in vivo. Evaluation of a subset of the most potent compounds in cell culture (IC50 = ∼1-12 nM) using the (18)F-L-FAC PET pharmacodynamic assay identified compounds demonstrating superior in vivo efficacy.

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Lee JH, Chen KJ, Noh SH, Garcia MA, Wang H, Lin WY, Jeong H, Kong BJ, Stout DB, Cheon J, Tseng HR. On-demand drug release system for in vivo cancer treatment through self-assembled magnetic nanoparticles. Angew Chem Int Ed Engl. 2013 Apr 15;52(16):4384-8. doi: 10.1002/anie.201207721. Epub 2013 Mar 20.

Abstract

On-demand drug release: Magnetothermally responsive drug-encapsulated supramolecular nanoparticles for on-demand drug release in vivo have been developed. The remote application of an alternative magnetic field heats the magnetic particles that effectively trigger the release of the drug. An acute drug concentration can be delivered to the tumor in vivo, resulting in an improved therapeutic outcome.

http://www.ncbi.nlm.nih.gov/pubmed/23519915

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Maynard HD, Gelb MB, Messina KMM, Vinciguerra D, Ko JH, Collins J, Tamboline M, Xu S, Ibarrondo J, Maynard HD. Poly(trehalose methacrylate) as an Excipient for Insulin Stabilization: Mechanism and Safety. ACS Publications. 2022 Aug 14;2022, 14, 33, 37410–37423. doi: 10.1021/acsami.2c09301.

Abstract

Insulin, the oldest U.S. Food and Drug Administration (FDA)-approved recombinant protein and a World Health Organization (WHO) essential medicine for treating diabetes globally, faces challenges due to its storage instability. One approach to stabilize insulin is the addition of poly(trehalose methacrylate) (pTrMA) as an excipient. The polymer increases the stability of the peptide to heat and mechanical agitation and has a low viscosity suitable for injection and pumps. However, the safety and stabilizing mechanism of pTrMA is not yet known and is required to understand the potential suitability of pTrMA as an insulin excipient. Herein is reported the immune response, biodistribution, and insulin plasma lifetime in mice, as well as investigation into insulin stabilization. pTrMA alone or formulated with ovalbumin did not elicit an antibody response over 3 weeks in mice, and there was no observable cytokine production in response to pTrMA. Micropositron emission tomography/microcomputer tomography of 64Cu-labeled pTrMA showed excretion of 78–79% ID/cc within 24 h and minimal liver accumulation at 6–8% ID/cc when studied out to 120 h. Further, the plasma lifetime of insulin in mice was not altered by added pTrMA. Formulating insulin with 2 mol equiv of pTrMA improved the stability of insulin to standard storage conditions: 46 weeks at 4 °C yielded 87.0% intact insulin with pTrMA present as compared to 7.8% intact insulin without the polymer. The mechanism by which pTrMA-stabilized insulin was revealed to be a combination of inhibiting deamidation of amino acid residues and preventing fibrillation, followed by aggregation of inactive and immunogenic amyloids all without complexing insulin into its hexameric state, which could delay the onset of insulin activity. Based on the data reported here, we suggest that pTrMA stabilizes insulin as an excipient without adverse effects in vivo and is promising to investigate further for the safe formulation of insulin.

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Vuong HE, Coley EJL, Kazantsev M, Cooke ME, Rendon TK, Paramo J, Hsiao EY. Interactions between maternal fluoxetine exposure, the maternal gut microbiome and fetal neurodevelopment in mice. Behavioral Brain Research. 2021 July 23;410:113353. doi:10.1016/j.bbr.2021.113353

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Khoja S, Lambert J, Nitzahn M, Eliav A, Zhang Y, Tamboline M, Le CT, Nasser E, Li Y, Patel P, Zhuravka I, Lueptow LM, Tkachyova I, Xu S, Nissim I, Schulze A, Lipshutz GS. Gene therapy for guanidinoacetate methyltransferase deficiency restores cerebral and myocardial creatine while resolving behavioral abnormalities. Mol Ther Methods Clin Dev. 2022 Mar 28;25:278-296. doi: 10.1016/j.omtm.2022.03.015. eCollection 2022 Jun 9.

https://pubmed.ncbi.nlm.nih.gov/35505663/

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Zhao X, Chen G, Zhao Y, Nashalian A, Xu J, Tat T, Song Y, Libanori A, Xu S, Li S, Chen J. Giant Magnetoelastic Effect Enabled Stretchable Sensor for Self-Powered Biomonitoring. ACS Nano. 2022 Apr 13. doi: 10.1021/acsnano.1c11350.

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Wang J, Rios A, Lisova K, Slavik R, Chatziioannou AF, van Dam RM. High-throughput radio-TLC analysis. Nuclear Medicine and Biology. 2020; 82-83:41-48. doi: 10.1016/j.nucmedbio.2019.12.003.

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Jones J, Ha NS, Barajas AG, Chatziioannou AF, van Dam RM. Integration of high-resolution radiation detector for hybrid microchip electrophoresis (hybrid-MCE). Analytical Chemistry 92(4): 3483-3491, 2020. DOI: 10.1021/acs.analchem.9b04827

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Gu Z, Taschereau R, Vu NT, Prout DL, Lee J, Chatziioannou AF. Performance evaluation of HiPET, a high sensitivity and high resolution preclinical PET tomograph. Phys Med Biol. 2020 Feb 12; 65(4):045009. doi: 10.1088/1361-6560/ab6b44

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Prout DL, Gu Z, Shustef M, Chatziioannou AF. A digital phoswich detector using time-over-threshold for depth of interaction in PET. Phys Med Biol. 2020 Dec 15; 65(24):245017. doi: 10.1088/1361-6560/abcb21

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Wang H, Han Y, Chen Z, Hu R, Chatziioannou AF, Zhang B. Prediction of major torso organs in low-contrast micro-CT images of mice using a two-stage deeply supervised fully convolutional network. Phys Med Biol. 2019 Dec 19; 64(24):245014. doi: 10.1088/1361-6560/ab59a4.

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Gu Z, Taschereau R, Vu N, Prout DL, Silverman RW, Lee JT, Chatziioannou AF. Performance evaluation of G8, a high sensitivity benchtop preclinical PET/CT tomograph. J Nucl Med. 2018 Jun 14. doi: 10.2967/jnumed.118.208827. [Epub ahead of print]. PMC6354226.

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Gu Z, Prout DL, Silverman RW, Herman H, Dooraghi A, Chatziioannou AF. A DOI Detector With Crystal Scatter Identification Capability for High Sensitivity and High Spatial Resolution PET Imaging. IEEE Trans Nucl Sci. 2015; 62:740-747. PMC4608445

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Shin YS, Kim J, Johnson D, Dooraghi AA, Mai WX, Ta L, Chatziioannou AF, Phelps ME, Nathanson DA, Heath JR. Quantitative assessments of glycolysis from single cells. Technology (Singap World Sci). 2015 Jun 1;3:172-178. PMC4728151.

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Wang H, Stout DB, Chatziioannou AF. A deformable atlas of the laboratory mouse. Mol Imaging Biol. 2015 Feb;17(1):18-28. doi: 10.1007/s11307-014-0767-7.

Abstract

PURPOSE: This paper presents a deformable mouse atlas of the laboratory mouse anatomy. This atlas is fully articulated and can be positioned into arbitrary body poses. The atlas can also adapt body weight by changing body length and fat amount.

PROCEDURES: A training set of 103 micro-CT images was used to construct the atlas. A cage-based deformation method was applied to realize the articulated pose change. The weight-related body deformation was learned from the training set using a linear regression method. A conditional Gaussian model and thin-plate spline mapping were used to deform the internal organs following the changes of pose and weight.

RESULTS: The atlas was deformed into different body poses and weights, and the deformation results were more realistic compared to the results achieved with other mouse atlases. The organ wights of this atlas matched well with the measurements of real mouse organ weights. This atlas can also be converted into voxelized images with labeled organs, pseudo CT images and tetrahedral mesh for phantom studies.

CONCLUSIONS: With the unique ability of articulated pose and weight changes, the deformable laboratory mouse atlas can become a valuable tool for preclinical image analysis.

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Gu Z, Taschereau R, Vu NT, Wang H, Prout DL, Silverman RW, Bai B, Stout DB, Phelps ME, Chatziioannou AF. NEMA NU-4 performance evaluation of PETbox4, a high sensitivity dedicated PET preclinical tomograph. Phys Med Biol. 2013 Jun 7;58(11):3791-814. doi: 10.1088/0031-9155/58/11/3791. Epub 2013 May 10.

Abstract

PETbox4 is a new, fully tomographic bench top PET scanner dedicated to high sensitivity and high resolution imaging of mice. This manuscript characterizes the performance of the prototype system using the National Electrical Manufacturers Association NU 4-2008 standards, including studies of sensitivity, spatial resolution, energy resolution, scatter fraction, count-rate performance and image quality. The PETbox4 performance is also compared with the performance of PETbox, a previous generation limited angle tomography system. PETbox4 consists of four opposing flat-panel type detectors arranged in a box-like geometry. Each panel is made by a 24 × 50 pixelated array of 1.82 × 1.82 × 7 mm bismuth germanate scintillation crystals with a crystal pitch of 1.90 mm. Each of these scintillation arrays is coupled to two Hamamatsu H8500 photomultiplier tubes via a glass light guide. Volumetric images for a 45 × 45 × 95 mm field of view (FOV) are reconstructed with a maximum likelihood expectation maximization algorithm incorporating a system model based on a parameterized detector response. With an energy window of 150-650 keV, the peak absolute sensitivity is approximately 18% at the center of FOV. The measured crystal energy resolution ranges from 13.5% to 48.3% full width at half maximum (FWHM), with a mean of 18.0%. The intrinsic detector spatial resolution is 1.5 mm FWHM in both transverse and axial directions. The reconstructed image spatial resolution for different locations in the FOV ranges from 1.32 to 1.93 mm, with an average of 1.46 mm. The peak noise equivalent count rate for the mouse-sized phantom is 35 kcps for a total activity of 1.5 MBq (40 µCi) and the scatter fraction is 28%. The standard deviation in the uniform region of the image quality phantom is 5.7%. The recovery coefficients range from 0.10 to 0.93. In comparison to the first generation two panel PETbox system, PETbox4 achieves substantial improvements on sensitivity and spatial resolution. The overall performance demonstrates that the PETbox4 scanner is suitable for producing high quality images for molecular imaging based biomedical research.

http://www.ncbi.nlm.nih.gov/pubmed/23666034

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Lu Y, Machado HB, Bao Q, Stout D, Herschman H, Chatziioannou AF. In vivo mouse bioluminescence tomography with radionuclide-based imaging validation. Mol Imaging Biol. 2011 Feb;13(1):53-8. doi: 10.1007/s11307-010-0332-y.

Abstract

INTRODUCTION: Bioluminescence imaging, especially planar bioluminescence imaging, has been extensively applied in in vivo preclinical biological research. Bioluminescence tomography (BLT) has the potential to provide more accurate imaging information due to its 3D reconstruction compared with its planar counterpart.

METHODS: In this work, we introduce a positron emission tomography (PET) radionuclide imaging-based strategy to validate the BLT results. X-ray computed tomography, PET, spectrally resolved bioluminescence imaging, and surgical excision were performed on a tumor xenograft mouse model expressing a bioluminescent reporter gene.

SULTS: With different spectrally resolved measured data, the BLT reconstructions were acquired based on the third-order simplified spherical harmonics (SP3) approximation and the diffusion approximation (DA). The corresponding tomographic images were obtained for validation of bioluminescence source reconstruction.

CONCLUSION: Our results show the strength of PET imaging compared with other validation methods for BLT and improved source localization accuracy based on the SP(3) approximation compared with the diffusion approximation

http://www.ncbi.nlm.nih.gov/pubmed/20464517

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Amarasekera B, Marchis PD, Bobinski KP, Radu CG, Czernin J, Barrio JR, van Dam RM. High-pressure, compact, modular radiosynthesizer for production of positron emitting biomarkers. Applied Radiation and Isotopes, vol. 78, pp. 88–101, Aug. 2013.

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Liu K, Lepin EJ, Wang MW, Guo F, Lin WY, Chen YC, Sirk SJ, Olma S, Phelps ME, Zhao XZ, Tseng HR, van Dam RM, Wu AM, and Shen CKF. Microfluidic-based 18F-Labeling of Biomolecules for Immuno-Positron Emission Tomography. Mol. Imag., vol. 10, no. 3, pp. 168–176, 2011.

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Sadeghi S, Liang V, Cheung S, Woo S, Wu C, Ly J, Deng Y, Eddings M, van Dam RM.Reusable electrochemical cell for rapid separation of [¹⁸F]fluoride from [¹⁸O]water for flow-through synthesis of ¹⁸F-labeled tracers. Applied Radiation and Isotopes, vol. 75, pp. 85–94, May 2013.

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Claggett SB, Quinn KM, Lazari M, Moore MD,van Dam RM. Simplified programming and control of automated radiosynthesizers through unit operations. EJNMMI Research, vol. 3, no. 1, p. 53, Jul. 2013.

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Dooraghi AA, Keng PY, Chen S, Javed MR, Kim CJ, Chatziioannou AF, van Dam RM. Optimization of microfluidic PET tracer synthesis with Cerenkov imaging. Analyst, vol. 138, no. 19, pp. 5654–5664, Aug. 2013.

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Chen S, Javed MR, Kim HK, Lei J, Lazari M, Shah GJ, van Dam RM, Keng PY, Kim CJ. Radiolabelling diverse positron emission tomography (PET) tracers using a single digital microfluidic reactor chip. Lab Chip 14: 902-910, 2014.

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Javed MR, Chen S, Lei J, Collins J, Sergeev M, Kim HK, Kim CJ, van Dam RM, Keng PY. High yield and high specific activity synthesis of [¹⁸F]fallypride in a batch microfluidic reactor for micro-PET imaging. Chem. Commun., vol. 50, no. 10, pp. 1192–1194, 2014.

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Tseng WY and van Dam RM. Compact microfluidic device for rapid concentration of PET tracers. Lab Chip, vol. 14, no. 13, p. 2293, 2014.

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Javed MR, Chen S, Kim K, Wei L, Czernin J, Kim CJ, van Dam RM, Keng PY.Efficient radiosynthesis of 3'-deoxy-3'-18F-fluorothymidine using electrowetting-on-dielectric digital microfluidic chip. J Nucl Med, vol. 55, no. 2, pp. 321–328, Feb. 2014.

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Cheung S, Ly J, Lazari M, Sadeghi S, Keng PY, van Dam RM. The separation and detection of PET tracers via capillary electrophoresis for chemical identity and purity analysis. Journal of Pharmaceutical and Biomedical Analysis, vol. 94, pp. 12–18, Jun. 2014.

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Lazari M, Collins J, Shen B, Farhoud M, Yeh D, Maraglia B, Chin FT, Nathanson DA, Moore M, van Dam RM. Fully Automated Production of Diverse ¹⁸F-Labeled PET Tracers on the ELIXYS Multireactor Radiosynthesizer Without Hardware Modification. J. Nucl. Med. Technol., vol. 42, no. 3, pp. 203–210, Sep. 2014.

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Lazari M, Lyashchenko SK, Burnazi EM, Lewis JS, van Dam RM, Murphy JM. Fully-automated synthesis of 16β-¹⁸F-Fluoro-5α-dihydrotestosterone (FDHT) on the ELIXYS radiosynthesizer. Applied Radiation and Isotopes 103: 9–14, 2015. https://doi.org/10.1016/j.apradiso.2015.05.010

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Keng PY and van Dam RM. Digital microfluidics: A new paradigm for radiochemistry. Molecular Imaging 14: 579-594, 2015.

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Lazari M, Irribarren J, Zhang S, van Dam RM. Understanding temperatures and pressures during short radiochemical reactions. Applied Radiation and Isotopes 108: 82-91, 2016.

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Ha NS, Ly J, Jones J, Cheung S, van Dam RM. Novel volumetric method for highly repeatable injection in microchip electrophoresis. Analytica Chimica Acta 985: 129-140, 2017.

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Wang J, Chao PH, Hanet S, van Dam RM. Performing multi-step chemical reactions in microliter-sized droplets by leveraging a simple passive transport mechanism. Lab Chip 17: 4342 – 4355, 2017.

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Ha NS, Sadeghi S, van Dam RM. Recent Progress Toward Microfluidic Quality Control Testing of Radiopharmaceuticals. Micromachines 8(11): 337, 2017. DOI: 10.3390/mi8110337.

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Ly J, Ha NS, Cheung S, van Dam Rm. Toward miniaturized analysis of chemical identity and purity of radiopharmaceuticals via microchip electrophoresis. Analytical and Bioanalytical Chemistry 410(9): 2423-2436, 2018.

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Chao PH, Lazari Mark, Hanet S, Narayanam MK, Murphy JM, van Dam RM. Automated concentration of [¹⁸F]fluoride into microliter volumes. Applied Radiation and Isotopes 141: 138-148, 2018.

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Schopf E, Waldmann CM, Collins J, Drake C, Slavik R, van Dam RM. Automation of a Positron-emission Tomography (PET) Radiotracer Synthesis Protocol for Clinical Production. Journal of Visualized Experiments 140: e58428, 2018. DOI: 10.3791/58428.

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Wang J, Chao PH, van Dam RM. Ultra-compact, automated microdroplet radiosynthesizer. Lab on a Chip 19: 2415 - 2424, 2019. DOI: 10.1039/C9LC00438F.

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Rios A, Wang J, Chao PH, van Dam RM. A novel multi-reaction microdroplet platform for rapid radiochemistry optimization. RSC Advances 9: 20370-20374, 2019. DOI: 10.1039/C9RA03639C

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Kim HK, Javed MR, Chen S, Zettlitz KA, Collins J, Wu AM, Kim CJ, van Dam Rm, Keng PY. On-demand radiosynthesis of N-succinimidyl-4-[¹⁸F]fluorobenzoate ([¹⁸F]SFB) on an electrowetting-on-dielectric microfluidic chip for ¹⁸F-labeling of protein. RSC Advances 9: 32175-32183 (2019). DOI: 10.1039/C9RA06158D

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Lisova K, Chen BY, Wang J, Fong KMM, Clark PM,van Dam RM. Rapid, efficient, and economical synthesis of PET tracers in a droplet microreactor: application to O-(2-([¹⁸F]fluoroethyl)-L-tyrosine ([¹⁸F]FET). EJNMMI Radiopharmacy and Chemistry 5: 1, 2020.

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Wang J, Rios A, Lisova K, Slavik R, Chatziioannou AF, van Dam RM. High-throughput radio-TLC analysis. Nuclear Medicine and Biology. 2020; 82-83:41-48. doi: 10.1016/j.nucmedbio.2019.12.003.

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Wang J, Holloway T, Lisova K, van Dam RM. Green and efficient synthesis of the radiopharmaceutical [¹⁸F]FDOPA using a microdroplet reactor. Reaction Chemistry & Engineering 5: 320-329, 2020. DOI: 10.1039/C9RE00354A

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Jones J, Ha NS, Barajas AG, Chatziioannou AF, van Dam RM. Integration of high-resolution radiation detector for hybrid microchip electrophoresis (hybrid-MCE). Analytical Chemistry 92(4): 3483-3491, 2020. DOI: 10.1021/acs.analchem.9b04827

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Wang J, Chao PH, Slavik R, van Dam RM. Multi-GBq production of the radiotracer [¹⁸F]fallypride in a droplet microreactor. RSC Advances 10: 7828-7838, 2020. DOI: https://doi.org/10.1039/D0RA01212B

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Wang J, van Dam RM. High-efficiency production of radiopharmaceuticals via droplet radiochemistry: a review of recent progress. Molecular Imaging 19: 1-21, 2020. https://doi.org/10.1177/1536012120973099

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Lisova K, Wang J, Chao PH, van Dam RM. A simple and efficient automated microvolume radiosynthesis of [¹⁸F]Florbetaben. EJNMMI Radiopharmacy and Chemistry 5: 30, 2020.

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van Dam RM, Chatziioannou AF. Cerenkov luminescence imaging in the development and production of radiopharmaceuticals. Frontiers in Physics 9: 632056, 2021. DOI: 10.3389/fphy.2021.632056

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Rios A, Holloway TS, Wang J, van Dam RM. Optimization of Radiochemical Reactions using Droplet Arrays. J. Vis. Exp. 168: e62056, 2021. DOI: 10.3791/62056

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Lisova K*, Wang J*, Hajagos TJ, Lu Y, Hsiao A, Elizarov A, van Dam RM. Economical droplet-based microfluidic production of [¹⁸F]FET and [¹⁸F]Florbetaben suitable for human use. Scientific Reports 11: 20636, 2021.

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Sergeev ME, Lazari M, Morgia F, Collins J, Javed MR, Sergeeva O, Jones J, Phelps ME, Lee JT, Keng PY, van Dam RM. Performing radiosynthesis in microvolumes to maximize molar activity of tracers for positron emission tomography. Comm Chemistry. 2018 Mar 22; 1(10). [Epub ahead of print].

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Collins J, Waldmann CM, Drake C, Slavik R, Ha NS, Sergeev M, Lazari M, Shen B, Chin FT, Moore M, Sadeghi S, Phelps ME, Murphy JM, van Dam RM. Production of diverse PET probes with limited resources: 2418F-labeled compounds prepared with a single radiosynthesizer. Proc Natl Acad Sci U S A. 2017 Oct 24;114:11309-11314. PMC5664529

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Chao P, Collins J, Argus J, Tseng W-Y, Lee JT, van Dam RM. Automatic concentration and reformulation of PET tracers via microfluidic membrane distillation. Lab on a Chip. 2017 May 16;17(10):1802-1816. PMCID: PMC5497730.

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Dooraghi AA, Carroll L, Collins J, van Dam RM, Chatziioannou AF. ARAS: an automated radioactivity aliquoting system for dispensing solutions containing positron-emitting radioisotopes. EJNMMI Res. 2016 Dec 1;6:22. PMC4783308

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Herman H, Flores G, Quinn K, Eddings M, Olma S, Moore MD, Ding H, Bobinski KP, Wang M, Williams D, Wiliams D, Shen CK, Phelps ME, Michael van Dam R. Plug-and-play modules for flexible radiosynthesis. Appl Radiat Isot. 2013 Aug;78:113-24. doi: 10.1016/j.apradiso.2013.04.023. Epub 2013 Apr 25.

Abstract

We present a plug-and-play radiosynthesis platform and accompanying computer software based on modular subunits that can easily and flexibly be configured to implement a diverse range of radiosynthesis protocols. Modules were developed that perform: (i) reagent storage and delivery, (ii) evaporations and sealed reactions, and (iii) cartridge-based purifications. The reaction module incorporates a simple robotic mechanism that removes tubing from the vessel and replaces it with a stopper prior to sealed reactions, enabling the system to withstand high pressures and thus provide tremendous flexibility in choice of solvents and temperatures. Any number of modules can rapidly be connected together using only a few fluidic connections to implement a particular synthesis, and the resulting system is controlled in a semi-automated fashion by a single software interface. Radiosyntheses of 2-[(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG), 1-[(18)F]fluoro-4-nitrobenzene ([(18)F]FNB), and 2'-deoxy-2'-[(18)F]fluoro-1-β-d-arabinofuranosyl cytosine (d-[(18)F]FAC) were performed to validate the system and demonstrate its versatility.

http://www.ncbi.nlm.nih.gov/pubmed/23702795

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Lazari M, Quinn KM, Claggett SB, Collins J, Shah GJ, Herman HE, Maraglia B, Phelps ME, Moore MD, van Dam RM. ELIXYS - a fully automated, three-reactor high-pressure radiosynthesizer for development and routine production of diverse PET tracers. EJNMMI Res. 2013 Jul 12;3(1):52. doi: 10.1186/2191-219X-3-52.

Abstract

BACKGROUND: Automated radiosynthesizers are vital for routine production of positron-emission tomography tracers to minimize radiation exposure to operators and to ensure reproducible synthesis yields. The recent trend in the synthesizer industry towards the use of disposable kits aims to simplify setup and operation for the user, but often introduces several limitations related to temperature and chemical compatibility, thus requiring reoptimization of protocols developed on non-cassette-based systems. Radiochemists would benefit from a single hybrid system that provides tremendous flexibility for development and optimization of reaction conditions while also providing a pathway to simple, cassette-based production of diverse tracers.

METHODS: We have designed, built, and tested an automated three-reactor radiosynthesizer (ELIXYS) to provide a flexible radiosynthesis platform suitable for both tracer development and routine production. The synthesizer is capable of performing high-pressure and high-temperature reactions by eliminating permanent tubing and valve connections to the reaction vessel. Each of the three movable reactors can seal against different locations on disposable cassettes to carry out different functions such as sealed reactions, evaporations, and reagent addition. A reagent and gas handling robot moves sealed reagent vials from storage locations in the cassette to addition positions and also dynamically provides vacuum and inert gas to ports on the cassette. The software integrates these automated features into chemistry unit operations (e.g., React, Evaporate, Add) to intuitively create synthesis protocols. 2-Deoxy-2-[¹⁸F]fluoro-5-methyl-β-l-arabinofuranosyluracil (l-[¹⁸F]FMAU) and 2-deoxy-2-[¹⁸F]fluoro-β-d-arabinofuranosylcytosine (d-[¹⁸F]FAC) were synthesized to validate the system.

RESULTS: l-[¹⁸F]FMAU and d-[¹⁸F]FAC were successfully synthesized in 165 and 170 min, respectively, with decay-corrected radiochemical yields of 46% ± 1% (n = 6) and 31% ± 5% (n = 6), respectively. The yield, repeatability, and synthesis time are comparable to, or better than, other reports. d-[¹⁸F]FAC produced by ELIXYS and another manually operated apparatus exhibited similar biodistribution in wild-type mice.

CONCLUSION: The ELIXYS automated radiosynthesizer is capable of performing radiosyntheses requiring demanding conditions: up to three reaction vessels, high temperatures, high pressures, and sensitive reagents. Such flexibility facilitates tracer development and the ability to synthesize multiple tracers on the same system without customization or replumbing. The disposable cassette approach simplifies the transition from development to production.

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Keng PY, Chen S, Ding H, Sadeghi S, Shah GJ, Dooraghi A, Phelps ME, Satyamurthy N, Chatziioannou AF, Kim CJ, van Dam RM. Micro-chemical synthesis of molecular probes on an electronic microfluidic device. Proc Natl Acad Sci U S A. 2012 Jan 17;109(3):690-5. doi: 10.1073/pnas.1117566109. Epub 2011 Dec 30.

Abstract

We have developed an all-electronic digital microfluidic device for microscale chemical synthesis in organic solvents, operated by electrowetting-on-dielectric (EWOD). As an example of the principles, we demonstrate the multistep synthesis of [(18)F]FDG, the most common radiotracer for positron emission tomography (PET), with high and reliable radio-fluorination efficiency of [(18)F]FTAG (88 ± 7%, n = 11) and quantitative hydrolysis to [(18)F]FDG (> 95%, n = 11). We furthermore show that batches of purified [(18)F]FDG can successfully be used for PET imaging in mice and that they pass typical quality control requirements for human use (including radiochemical purity, residual solvents, Kryptofix, chemical purity, and pH). We report statistical repeatability of the radiosynthesis rather than best-case results, demonstrating the robustness of the EWOD microfluidic platform. Exhibiting high compatibility with organic solvents and the ability to carry out sophisticated actuation and sensing of reaction droplets, EWOD is a unique platform for performing diverse microscale chemical syntheses in small volumes, including multistep processes with intermediate solvent-exchange steps.

http://www.ncbi.nlm.nih.gov/pubmed/22210110

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Cho JS, Taschereau R, Olma S, Liu K, Chen YC, Shen CK, van Dam RM, Chatziioannou AF. Cerenkov radiation imaging as a method for quantitative measurements of beta particles in a microfluidic chip. Phys Med Biol. 2009 Nov 21;54(22):6757-71. doi: 10.1088/0031-9155/54/22/001. Epub 2009 Oct 21.

Abstract

It has been observed that microfluidic chips used for synthesizing (18)F-labeled compounds demonstrate visible light emission without nearby scintillators or fluorescent materials. The origin of the light was investigated and found to be consistent with the emission characteristics from Cerenkov radiation. Since (18)F decays through the emission of high-energy positrons, the energy threshold for beta particles, i.e. electrons or positrons, to generate Cerenkov radiation was calculated for water and polydimethylsiloxane (PDMS), the most commonly used polymer-based material for microfluidic chips. Beta particles emitted from (18)F have a continuous energy spectrum, with a maximum energy that exceeds this energy threshold for both water and PDMS. In addition, the spectral characteristics of the emitted light from (18)F in distilled water were also measured, yielding a broad distribution from 300 nm to 700 nm, with higher intensity at shorter wavelengths. A photograph of the (18)F solution showed a bluish-white light emitted from the solution, further suggesting Cerenkov radiation. In this study, the feasibility of using this Cerenkov light emission as a method for quantitative measurements of the radioactivity within the microfluidic chip in situ was evaluated. A detector previously developed for imaging microfluidic platforms was used. The detector consisted of a charge-coupled device (CCD) optically coupled to a lens. The system spatial resolution, minimum detectable activity and dynamic range were evaluated. In addition, the calibration of a Cerenkov signal versus activity concentration in the microfluidic chip was determined. This novel method of Cerenkov radiation measurements will provide researchers with a simple yet robust quantitative imaging tool for microfluidic applications utilizing beta particles.

http://www.ncbi.nlm.nih.gov/pubmed/19847018

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Xu S, Herschman HR. Comparison of the Efficacy and Sensitivity of Alternative PET Reporter Gene/PET Reporter Probe Systems That Minimize Biological Variables. Cell Tracking 2123: 177-190, 2020. doi: 10.1007/978-1-0716-0364-2_16.

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Narayanam MK, Lai BT, Loredo JM, Wilson JA, Eliasen AM, LaBerge NA, Nason M, Cantu AL, Luton BK, Xu S, Agnew HD, Murphy JM. Positron Emission Tomography Tracer Design of Targeted Synthetic Peptides via ¹⁸F-Sydnone Alkyne Cycloaddition. Bioconjugate Chemistry 32 (9): 2073-2082, 2021. doi: 10.1021/acs.bioconjchem.1c00379.

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Sergeev ME, Morgia F, Wang C Jr, van Dam R.M. Titania-catalyzed radiofluorination of tosylated precursors in highly aqueous medium. J. Am. Chem. Soc. 137: 5686−5694, 2015. doi: 10.1021/jacs.5b02659.

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Hoover AJ, Lazari M, Ren H, Narayanam MK, Murphy JM, van Dam R.M, Hooker JM, Ritter T. A Transmetalation Reaction Enables the Synthesis of [¹⁸F]5-Fluorouracil from [¹⁸F]Fluoride for Human PET Imaging. Organometallics 35 (7): 1008–1014, 2016. doi: 10.1021/acs.organomet.6b00059.

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Zettlitz KA, Tavare R, Tsai WK, Yamada RE, Ha NS, Collins J, van Dam R.M, Timmerman JM, Wu AM. ¹⁸F-labeled anti-human CD20 cys-diabody for same-day immunoPET in a model of aggressive B cell lymphoma in human CD20 transgenic mice. EJNMMI 46(2): 489-500, 2018. doi: 10.1007/s00259-018-4214-x.

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Waldmann CM, Stuparu AD, van Dam R.M, Slavik R. The Search for an Alternative to [⁶⁸Ga]Ga-DOTA-TATE in Neuroendocrine Tumor Theranostics: Current State of ¹⁸F-labeled Somatostatin Analog Development. Theranostics 9(5):1336-1347, 2019. doi: 10.7150/thno.31806.

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Kannan P, Furedi A, Dizdarevic S, Wanek T, Mairinger S, Collins J, Falls T, van Dam R.M, Maheshwari D, Lee JT, Szakacs G, Langer. In vivo characterization of [¹⁸F]AVT-011 as a radiotracer for PET imaging of multidrug resistance. European Journal of Nuclear Medicine and Medical Imaging. 2019. doi: 10.1007/s00259-019-04589-w.

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Zoller S, Park H, Olafsen T, Zamilpa C, Burke ZD, Blumstein G, Sheppard WL, Hamad CD, Hori KR, Tseng JC, Czupryna J, McMannus C, Lee JT, Bispo M, Pastrana FR, Raineri EJM, Miller LS, Dijl JM, Francis KP, Bernthal NM. Multimodal Imaging Guides Surgical Management in a Preclinical Spinal Implant Infection Model. JCI Insight. 2019 Feb 7;4(3):e124813. doi: 10.1172/jci.insight.124813. PMC6413782

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Salas JR, Chen BY, Wong A, Duarte S, Angarita SAK, Lipshutz GS, Witte ON, Clark PM. Noninvasive Imaging of Drug-Induced Liver Injury with 18F-DFA PET. J Nucl Med. 2018 Aug;59:1308-1315. PMC6071498

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Lisova K, Sergeev M, Evans-Axelsson S, Stuparu AD, Beykan S, Collins J, Jones J, Lassmann M, Herrmann K, Perrin D, Lee JT, Slavik R, van Dam M. Microfluidic radiosynthesis, preclinical imaging and dosimetry study of [18F]AMBF3-TATE: a potential PET tracer for clinical imaging of somatostatin receptors. Nucl Med Biol. 2018 Apr 20;61:36-44. PMCID: PMC6015542

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Gonzalez C, Sanchez A, Collins J, Lisova K, Lee JT, van Dam RM, Barbieri MA, Ramanchandran C, Wnuk SF. The 4-N-Acyl and 4-N-Alkyl Gemcitabine Analogues with Silicon-Fluoride-Acceptor: Application to 18F-Radiolabeling. Eur J Med Chem. 2018 Mar 25;148:314-324. [Epub ahead of print]. PMCID: PMC5841594

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Radiochemistry on electrodes: synthesis of an 18F-labelled and in vivo-stable COX-2 inhibitor

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Lee JT, Zhang H, Moroz MA, Likar Y, Shenker L, Sumzin N, Lobo J, Zurita J, Collins J, van Dam RM, Ponomarev V. Comparative Analysis of Human Nucleoside Kinase-Based Reporter Systems for PET Imaging. Mol Imaging Biol. 2017 Feb;19(1):100-108. PMCID: PMC5345744.

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Lee JT*, Boschi S*, Beykan S, Slavik R, Wei L, Spick C, Eberlein U, Buck AK, Lodi F, Cicoria G, Czernin J, Lassmann M, Fanti S, Herrmann K. Synthesis and preclinical evaluation of an Al18F radiofluorinated GLU-UREA-LYS(AHX)-HBED-CC PSMA ligand. Eur J Nucl Med Mol Imaging. 2016 Nov; 43(12):2122-2130. PMC5050145. *contributed equally to this work.

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Hou S, Choi JS, Garcia MA, Xing Y, Chen KJ, Chen YM, Jiang ZK, Ro T, Wu L, Stout DB, Tomlinson JS, Wang H, Chen K, Tseng HR, Lin WY. Pretargeted Positron Emission Tomography Imaging That Employs Supramolecular Nanoparticles with in Vivo Bioorthogonal Chemistry. ACS Nano. 2016 Jan 26;10:1417-24. PMC4893318

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Mosessian S, Duarte-Vogel SM, Stout DB, Roos KP, Lawson GW, Jordan MC, Ogden A, Matter C, Sadeghi S, Mills GQ, Schelbert HR, Shu CG, Czernin J, Couto M, Phelps ME. INDs for PET molecular imaging probes-approach by an academic institution. Mol Imaging Biol. 2014 Aug;16(4):441-8. doi: 10.1007/s11307-014-0735-2.

Abstract

We have developed an efficient, streamlined, cost-effective approach to obtain Investigational New Drug (IND) approvals from the Food and Drug Administration (FDA) for positron emission tomography (PET) imaging probes (while the FDA uses the terminology PET drugs, we are using "PET imaging probes," "PET probes," or "probes" as the descriptive terms). The required application and supporting data for the INDs were collected in a collaborative effort involving appropriate scientific disciplines. This path to INDs was successfully used to translate three [(18) F]fluoro-arabinofuranosylcytosine (FAC) analog PET probes to phase 1 clinical trials. In doing this, a mechanism has been established to fulfill the FDA regulatory requirements for translating promising PET imaging probes from preclinical research into human clinical trials in an efficient and cost-effective manner.

http://www.ncbi.nlm.nih.gov/pubmed/24733693

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Clark PM, Flores G, Evdokimov NM, Clark MN, Chai T, Nair-Gill E, O'Mahony F, Beaven SW, Faull KF, Phelps ME, Jung ME, Witte ON. Positron emission tomography probe demonstrates a striking concentration of ribose salvage in the liver. Proc Natl Acad Sci U S A. 2014 Jul 15;111(28):E2866-74. doi: 10.1073/pnas.1410326111. Epub 2014 Jun 30.

Abstract

PET is a powerful technique for quantifying and visualizing biochemical pathways in vivo. Here, we develop and validate a novel PET probe, [(18)F]-2-deoxy-2-fluoroarabinose ([(18)F]DFA), for in vivo imaging of ribose salvage. DFA mimics ribose in vivo and accumulates in cells following phosphorylation by ribokinase and further metabolism by transketolase. We use [(18)F]DFA to show that ribose preferentially accumulates in the liver, suggesting a striking tissue specificity for ribose metabolism. We demonstrate that solute carrier family 2, member 2 (also known as GLUT2), a glucose transporter expressed in the liver, is one ribose transporter, but we do not know if others exist. [(18)F]DFA accumulation is attenuated in several mouse models of metabolic syndrome, suggesting an association between ribose salvage and glucose and lipid metabolism. These results describe a tool for studying ribose salvage and suggest that plasma ribose is preferentially metabolized in the liver.

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Gil JS, Machado HB, Campbell DO, Clark M, Shu C, Witte ON, Herschman HR. Application of a rapid, simple, and accurate adenovirus-based method to compare PET reporter gene/PET reporter probe systems. Mol Imaging Biol. 2013 Jun;15(3):273-81. doi: 10.1007/s11307-012-0596-5.

Abstract

PURPOSE: This study aims to use a simple, quantitative method to compare the HSV1sr39TK/(18) F-FHBG PET reporter gene/PET reporter probe (PRG/PRP) system with PRGs derived from human nucleoside kinases.

PROCEDURES: The same adenovirus vector is used to express alternative PRGs. Equal numbers of vectors are injected intravenously into mice. After PRP imaging, quantitative hepatic PET signals are normalized for transduction by measuring hepatic viral genomes.

RESULTS: The same adenovirus vector was used to express equivalent amounts of HSV1sr39TK, mutant human thymidine kinase 2 (TK2-DM), and mutant human deoxycytidine kinase (dCK-A100VTM) in mouse liver. HSV1sr39TK expression was measured with (18) F-FHBG, TK2-DM and dCK-A100VTM with (18) F-L-FMAU. TK2-DM/(18) F-L-FMAU and HSV1sr39TK/(18) F-FHBG had equivalent sensitivities; dCK-A100VTM/(18) F-L-FMAU was twice as sensitive as HSV1sr39TK/(18) F-FHBG.

CONCLUSIONS: The human PRG/PRP sensitivities are comparable and/or better than HSV1sr39TK/(18) F-FHBG. However, for clinical use, identification of the best PRP substrate for each enzyme, characterization of probe distribution, and consequences of overexpressing nucleoside kinases must be evaluated.

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Campbell DO, Campbell SS, Su Y, Lee JT, Auerbach MS, Herschman H, Satyamurthy N, Czernin J, Lavie A, Shu CG. Structure-guided engineering of human thymidine kinase 2 as a positron emission tomography reporter gene for enhanced phosphorylation of non-natural thymidine analog reporter probe. J Biol Chem. 2012 Jan 2;287(1):446-54. doi: 10.1074/jbc.M111.314666. Epub 2011 Nov 9.

Abstract

Positron emission tomography (PET) reporter gene imaging can be used to non-invasively monitor cell-based therapies. Therapeutic cells engineered to express a PET reporter gene (PRG) specifically accumulate a PET reporter probe (PRP) and can be detected by PET imaging. Expanding the utility of this technology requires the development of new non-immunogenic PRGs. Here we describe a new PRG-PRP system that employs, as the PRG, a mutated form of human thymidine kinase 2 (TK2) and 2'-deoxy-2'-¹⁸F-5-methyl-1-β-L-arabinofuranosyluracil (L-¹⁸F-FMAU) as the PRP. We identified L-¹⁸F-FMAU as a candidate PRP and determined its biodistribution in mice and humans. Using structure-guided enzyme engineering, we generated a TK2 double mutant (TK2-N93D/L109F) that efficiently phosphorylates L-¹⁸F-FMAU. The N93D/L109F TK2 mutant has lower activity for the endogenous nucleosides thymidine and deoxycytidine than wild type TK2, and its ectopic expression in therapeutic cells is not expected to alter nucleotide metabolism. Imaging studies in mice indicate that the sensitivity of the new human TK2-N93D/L109F PRG is comparable with that of a widely used PRG based on the herpes simplex virus 1 thymidine kinase. These findings suggest that the TK2-N93D/L109F/L-¹⁸F-FMAU PRG-PRP system warrants further evaluation in preclinical and clinical applications of cell-based therapies.

http://www.ncbi.nlm.nih.gov/pubmed/22074768

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Shu CJ, Campbell DO, Lee JT, Tran AQ, Wengrod JC, Witte ON, Phelps ME, Satyamurthy N, Czernin J, Shu CG. Novel PET probes specific for deoxycytidine kinase. J Nucl Med. 2010 Jul;51(7):1092-8. doi: 10.2967/jnumed.109.073361. Epub 2010 Jun 16.

Abstract

Deoxycytidine kinase (dCK) is a rate-limiting enzyme in the deoxyribonucleoside salvage pathway and a critical determinant of therapeutic activity for several nucleoside analog prodrugs. We have previously reported the development of 1-(2'-deoxy-2'-(18)F-fluoro-beta-D-arabinofuranosyl)cytosine ((18)F-FAC), a new probe for PET of dCK activity in immune disorders and certain cancers. The objective of the current study was to develop PET probes with improved metabolic stability and specificity for dCK. Toward this goal, several candidate PET probes were synthesized and evaluated in vitro and in vivo.

METHODS: High-pressure liquid chromatography was used to analyze the metabolic stability of (18)F-FAC and several newly synthesized analogs with the natural D-enantiomeric sugar configuration or the corresponding unnatural L-configuration. In vitro kinase and uptake assays were used to determine the affinity of the (18)F-FAC L-nucleoside analogs for dCK. The biodistribution of selected L-analogs in mice was determined by small-animal PET/CT.

RESULTS: Candidate PET probes were selected using the following criteria: low susceptibility to deamination, high affinity for purified recombinant dCK, high uptake in dCK-expressing cell lines, and biodistribution in mice reflective of the tissue-expression pattern of dCK. Among the 10 newly developed candidate probes, 1-(2'-deoxy-2'-(18)F-fluoro-beta-L-arabinofuranosyl)cytosine (L-(18)F-FAC) and 1-(2'-deoxy-2'-(18)F-fluoro-beta-L-arabinofuranosyl)-5-methylcytosine (L-(18)F-FMAC) most closely matched the selection criteria. The selection of L-(18)F-FAC and L-(18)F-FMAC was validated by showing that these two PET probes could be used to image animal models of leukemia and autoimmunity.

CONCLUSION: Promising in vitro and in vivo data warrant biodistribution and dosimetry studies of L-(18)F-FAC and L-(18)F-FMAC in humans.

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Yong J, Rasooly J, Dang H, Lu Y, Middleton B, Zhang Z, Hon L, Namavari M, Stout DB, Atkinson MA, Tian J, Gambhir SS, Kaufman DL. Multimodality imaging of β-cells in mouse models of type 1 and 2 diabetes. Diabetes. 2011 May;60(5):1383-92. doi: 10.2337/db10-0907. Epub 2011 Mar 25.

Abstract

OBJECTIVE: β-Cells that express an imaging reporter have provided powerful tools for studying β-cell development, islet transplantation, and β-cell autoimmunity. To further expedite diabetes research, we generated transgenic C57BL/6 "MIP-TF" mice that have a mouse insulin promoter (MIP) driving the expression of a trifusion (TF) protein of three imaging reporters (luciferase/enhanced green fluorescent protein/HSV1-sr39 thymidine kinase) in their β-cells. This should enable the noninvasive imaging of β-cells by charge-coupled device (CCD) and micro-positron emission tomography (PET), as well as the identification of β-cells at the cellular level by fluorescent microscopy.

RESEARCH DESIGN AND METHODS: MIP-TF mouse β-cells were multimodality imaged in models of type 1 and type 2 diabetes.

RESULTS: MIP-TF mouse β-cells were readily identified in pancreatic tissue sections using fluorescent microscopy. We show that MIP-TF β-cells can be noninvasively imaged using microPET. There was a correlation between CCD and microPET signals from the pancreas region of individual mice. After low-dose streptozotocin administration to induce type 1 diabetes, we observed a progressive reduction in bioluminescence from the pancreas region before the appearance of hyperglycemia. Although there have been reports of hyperglycemia inducing proinsulin expression in extrapancreatic tissues, we did not observe bioluminescent signals from extrapancreatic tissues of diabetic MIP-TF mice. Because MIP-TF mouse β-cells express a viral thymidine kinase, ganciclovir treatment induced hyperglycemia, providing a new experimental model of type 1 diabetes. Mice fed a high-fat diet to model early type 2 diabetes displayed a progressive increase in their pancreatic bioluminescent signals, which were positively correlated with area under the curve-intraperitoneal glucose tolerance test (AUC-IPGTT).

CONCLUSIONS: MIP-TF mice provide a new tool for monitoring β-cells from the single cell level to noninvasive assessments of β-cells in models of type 1 diabetes and type 2 diabetes.
http://www.ncbi.nlm.nih.gov/pubmed/21441442

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Wilks MQ, Knowles SM, Wu AM, Huang SC. Improved modeling of in vivo kinetics of slowly diffusing radiotracers for tumor imaging. J Nucl Med. 2014 Sep;55(9):1539-44. doi: 10.2967/jnumed.114.140038. Epub 2014 Jul 3.

Abstract

Large-molecule tracers, such as labeled antibodies, have shown success in immuno-PET for imaging of specific cell surface biomarkers. However, previous work has shown that localization of such tracers shows high levels of heterogeneity in target tissues, due to both the slow diffusion and the high affinity of these compounds. In this work, we investigate the effects of subvoxel spatial heterogeneity on measured time-activity curves in PET imaging and the effects of ignoring diffusion limitation on parameter estimates from kinetic modeling.

METHODS: Partial differential equations (PDE) were built to model a radially symmetric reaction-diffusion equation describing the activity of immuno-PET tracers. The effects of slower diffusion on measured time-activity curves and parameter estimates were measured in silico, and a modified Levenberg-Marquardt algorithm with Bayesian priors was developed to accurately estimate parameters from diffusion-limited data. This algorithm was applied to immuno-PET data of mice implanted with prostate stem cell antigen-overexpressing tumors and injected with (124)I-labeled A11 anti-prostate stem cell antigen minibody.

RESULTS: Slow diffusion of tracers in linear binding models resulted in heterogeneous localization in silico but no measurable differences in time-activity curves. For more realistic saturable binding models, measured time-activity curves were strongly dependent on diffusion rates of the tracers. Fitting diffusion-limited data with regular compartmental models led to parameter estimate bias in an excess of 1,000% of true values, while the new model and fitting protocol could accurately measure kinetics in silico. In vivo imaging data were also fit well by the new PDE model, with estimates of the dissociation constant (Kd) and receptor density close to in vitro measurements and with order of magnitude differences from a regular compartmental model ignoring tracer diffusion limitation.

CONCLUSION: Heterogeneous localization of large, high-affinity compounds can lead to large differences in measured time-activity curves in immuno-PET imaging, and ignoring diffusion limitations can lead to large errors in kinetic parameter estimates. Modeling of these systems with PDE models with Bayesian priors is necessary for quantitative in vivo measurements of kinetics of slow-diffusion tracers.

http://www.ncbi.nlm.nih.gov/pubmed/24994929

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Wong KP, Zhang X, Huang SC. Improved derivation of input function in dynamic mouse [¹⁸F]FDG PET using bladder radioactivity kinetics. Mol Imaging Biol. 2013 Aug;15(4):486-96. doi: 10.1007/s11307-013-0610-6.

Abstract

PURPOSE: Accurate determination of the plasma input function (IF) is essential for absolute quantification of physiological parameters in positron emission tomography (PET). However, it requires an invasive and tedious procedure of arterial blood sampling that is challenging in mice because of the limited blood volume. In this study, a hybrid modeling approach is proposed to estimate the plasma IF of 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) in mice using accumulated radioactivity in urinary bladder together with a single late-time blood sample measurement.

METHODS: Dynamic PET scans were performed on nine isoflurane-anesthetized male C57BL/6 mice after a bolus injection of [¹⁸F]FDG at the lateral caudal vein. During a 60- or 90-min scan, serial blood samples were taken from the femoral artery. Image data were reconstructed using filtered backprojection with computed tomography-based attenuation correction. Total accumulated radioactivity in the urinary bladder at late times was fitted to a renal compartmental model with the last blood sample and a one-exponential function that described the [¹⁸F]FDG clearance in blood. Multiple late-time blood sample estimates were calculated by the blood [¹⁸F]FDG clearance equation. A sum of four-exponentials was assumed for the plasma IF that served as a forcing function to all tissues. The estimated plasma IF was obtained by simultaneously fitting the [¹⁸F]FDG model to the time-activity curves (TACs) of liver and muscle and the forcing function to early (0-1 min) left-ventricle data (corrected for delay, dispersion, partial-volume effects, and erythrocyte uptake) and the late-time blood estimates. Using only the blood sample collected at the end of the study to estimate the IF and the use of liver TAC as an alternative IF were also investigated.

RESULTS: The area under the plasma IFs calculated for all studies using the hybrid approach was not significantly different from that using all blood samples. [¹⁸F]FDG uptake constants in brain, myocardium, skeletal muscle, and liver computed by the Patlak analysis using estimated and measured plasma IFs were in excellent agreement (slope∼1; R2>0.983). The IF estimated using only the last blood sample drawn at the end of the study and the use of liver TAC as the plasma IF provided less reliable results.

CONCLUSIONS: The estimated plasma IFs obtained with the hybrid method agreed well with those derived from arterial blood sampling. Importantly, the proposed method obviates the need of arterial catheterization, making it possible to perform repeated dynamic [¹⁸F]FDG PET studies on the same animal. Liver TAC is unsuitable as an input function for absolute quantification of [¹⁸F]FDG PET data.

http://www.ncbi.nlm.nih.gov/pubmed/23322346

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Sha W, Ye H, Iwamoto KS, Wong KP, Wilks MQ, Stout D, McBride W, Huang SC. Factors affecting tumor (18) F-FDG uptake in longitudinal mouse PET studies. EJNMMI Res. 2013 Jul 10;3:51. doi: 10.1186/2191-219X-3-51. eCollection 2013.

Abstract

BACKGROUND: Many biological factors of 2-[(18) F]fluoro-2-deoxy-d-glucose ((18) F-FDG) in blood can affect (18) F-FDG uptake in tumors. In this study, longitudinal (18) F-FDG positron emission tomography (PET) studies were performed on tumor-bearing mice to investigate the effect of blood glucose level and tumor size on (18) F-FDG uptake in tumors.

METHODS: Six- to eight-week-old severe combined immunodeficiency mice were implanted with glioblastoma U87 (n = 8) or adenocarcinoma MDA-MB-231 (MDA) (n = 11) in the shoulder. When the tumor diameter was approximately 2.5 mm, a 60-min dynamic (18) F-FDG PET scan was performed weekly until the tumor diameter reached 10 mm. Regions of interests were defined in major organs and tumor. A plasma curve was derived based on a modeling method that utilizes the early heart time-activity curve and a late-time blood sample. The (18) F-FDG uptake constant K i was calculated using Patlak analysis on the tumors without an apparent necrotic center shown in the PET images. For each tumor type, the measured K i was corrected for partial volume (PV), and multivariate regression analysis was performed to examine the effects of blood glucose level ([Glc]) and tumor growth. Corrected Akaike's information criterion was used to determine the best model.

RESULTS: The regression model that best fit the PV-corrected K i for U87 data was K i /RC = (1/[Glc]) × (0.27 ± 0.027) mL/min/mL (where [Glc] is in mmol/L), and for MDA, it was K i /RC = (0.04 ± 0.005) mL/min/mL, where K i /RC denotes the PV-corrected K i using an individual recovery coefficient (RC). The results indicated that (18) F-FDG K i /RC for U87 was inversely related to [Glc], while [Glc] had no effect on (18) F-FDG K i /RC of MDA. After the effects of PV and [Glc] were accounted for, the data did not support any increase of (18) F-FDG K i as the tumor (of either type) grew larger in size.

CONCLUSIONS: The effect of [Glc] on the tumor (18) F-FDG K i was tumor-dependent. PV- and [Glc]-corrected (18) F-FDG K i did not show significant increase as the tumor of either type grew in size.

http://www.ncbi.nlm.nih.gov/pubmed/23841937

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Kreissl MC, Stout DB, Wong KP, Wu HM, Caglayan E, Ladno W, Zhang X, Prior JO, Reiners C, Huang SC, Schelbert HR. Influence of dietary state and insulin on myocardial, skeletal muscle and brain [F]-fluorodeoxyglucose kinetics in mice. EJNMMI Res. 2011 Jul 6;1:8. doi: 10.1186/2191-219X-1-8.

Abstract

BACKGROUND: We evaluated the effect of insulin stimulation and dietary changes on myocardial, skeletal muscle and brain [(18)F]-fluorodeoxyglucose (FDG) kinetics and uptake in vivo in intact mice.

METHODS: Mice were anesthetized with isoflurane and imaged under different conditions: non-fasted (n = 7; "controls"), non-fasted with insulin (2 IU/kg body weight) injected subcutaneously immediately prior to FDG (n = 6), fasted (n = 5), and fasted with insulin injection (n = 5). A 60-min small-animal PET with serial blood sampling and kinetic modeling was performed.

RESULTS: We found comparable FDG standardized uptake values (SUVs) in myocardium in the non-fasted controls and non-fasted-insulin injected group (SUV 45-60 min, 9.58 ± 1.62 vs. 9.98 ± 2.44; p = 0.74), a lower myocardial SUV was noted in the fasted group (3.48 ± 1.73; p < 0.001). In contrast, the FDG uptake rate constant (K(i)) for myocardium increased significantly by 47% in non-fasted mice by insulin (13.4 ± 3.9 ml/min/100 g vs. 19.8 ± 3.3 ml/min/100 g; p = 0.030); in fasted mice, a lower myocardial K(i) as compared to controls was observed (3.3 ± 1.9 ml/min/100 g; p < 0.001). Skeletal muscle SUVs and K(i) values were increased by insulin independent of dietary state, whereas in the brain, those parameters were not influenced by fasting or administration of insulin. Fasting led to a reduction in glucose metabolic rate in the myocardium (19.41 ± 5.39 vs. 3.26 ± 1.97 mg/min/100 g; p < 0.001), the skeletal muscle (1.06 ± 0.34 vs. 0.34 ± 0.08 mg/min/100 g; p = 0.001) but not the brain (3.21 ± 0.53 vs. 2.85 ±0.25 mg/min/100 g; p = 0.19).

CONCLUSIONS: Changes in organ SUVs, uptake rate constants and metabolic rates induced by fasting and insulin administration as observed in intact mice by small-animal PET imaging are consistent with those observed in isolated heart/muscle preparations and, more importantly, in vivo studies in larger animals and in humans. When assessing the effect of insulin on the myocardial glucose metabolism of non-fasted mice, it is not sufficient to just calculate the SUV - dynamic imaging with kinetic modeling is necessary.

http://www.ncbi.nlm.nih.gov/pubmed/21841971

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Wong KP, Sha W, Zhang X, Huang SC. Effects of administration route, dietary condition, and blood glucose level on kinetics and uptake of ¹⁸F-FDG in mice. J Nucl Med. 2011 May;52(5):800-7. doi: 10.2967/jnumed.110.085092. Epub 2011 Apr 15.

Abstract

The effects of dietary condition and blood glucose level on the kinetics and uptake of (18)F-FDG in mice were systematically investigated using intraperitoneal and tail-vein injection.

METHODS: Dynamic PET was performed for 60 min on 23 isoflurane-anesthetized male C57BL/6 mice after intravenous (n = 11) or intraperitoneal (n = 12) injection of (18)F-FDG. Five and 6 mice in the intravenous and intraperitoneal groups, respectively, were kept fasting overnight (18 ± 2 h), and the others were fed ad libitum. Serial blood samples were collected from the femoral artery to measure (18)F-FDG and glucose concentrations. Image data were reconstructed using filtered backprojection with CT-based attenuation correction. The standardized uptake value (SUV) was estimated from the 45- to 60-min image. The metabolic rate of glucose (MRGlu) and (18)F-FDG uptake constant (K(i)) were derived by Patlak graphical analysis.

RESULTS: In the brain, SUV and K(i) were significantly higher in fasting mice with intraperitoneal injection, but MRGlu did not differ significantly under different dietary states and administration routes. Cerebral K(i) was inversely related to elevated blood glucose levels, irrespective of administration route or dietary state. In myocardium, SUV, K(i), and MRGlu were significantly lower in fasting than in nonfasting mice for both routes of injection. Myocardial SUV and K(i) were strongly dependent on the dietary state, and K(i) did not correlate with the blood glucose level. Similar results were obtained for skeletal muscle, although the differences were not as pronounced.

CONCLUSION: Intraperitoneal injection is a valid alternative route, providing pharmacokinetic data equivalent to data from tail-vein injection for small-animal (18)F-FDG PET. Cerebral K(i) varies inversely with blood glucose level, but the measured cerebral MRGlu does not correlate with blood glucose level or dietary condition. Conversely, the K(i) values of the myocardium and skeletal muscle are strongly dependent on dietary condition but not on blood glucose level. In tissue in which (18)F-FDG uptake declines with increasing blood glucose, correction for blood glucose level will make SUV a more robust outcome measure of MRGlu.

http://www.ncbi.nlm.nih.gov/pubmed/21498533

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