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Brain-infiltrating leukocytes contribute to multiple sclerosis (MS) and autoimmune encephalomyelitis and likely play a role in traumatic brain injury, seizure, and stroke. Brain-infiltrating leukocytes are also primary targets for MS disease-modifying therapies. However, no method exists for noninvasively visualizing these cells in a living organism. 1-(2′-deoxy-2′-(18)F-fluoroarabinofuranosyl) cytosine ((18)F-FAC) is a PET radiotracer that measures deoxyribonucleoside salvage and accumulates preferentially in immune cells. We hypothesized that (18)F-FAC PET could noninvasively image brain-infiltrating leukocytes. Methods: Healthy mice were imaged with (18)F-FAC PET to quantify if this radiotracer crosses the blood–brain barrier (BBB). Experimental autoimmune encephalomyelitis (EAE) is a mouse disease model with brain-infiltrating leukocytes. To determine whether (18)F-FAC accumulates in brain-infiltrating leukocytes, EAE mice were analyzed with (18)F-FAC PET, digital autoradiography, and immunohistochemistry, and deoxyribonucleoside salvage activity in brain-infiltrating leukocytes was analyzed ex vivo. Fingolimod-treated EAE mice were imaged with (18)F-FAC PET to assess if this approach can monitor the effect of an immunomodulatory drug on brain-infiltrating leukocytes. PET scans of individuals injected with 2-chloro-2′-deoxy-2′-(18)F-fluoro-9-β-d-arabinofuranosyl-adenine ((18)F-CFA), a PET radiotracer that measures deoxyribonucleoside salvage in humans, were analyzed to evaluate whether (18)F-CFA crosses the human BBB. Results: (18)F-FAC accumulates in the healthy mouse brain at levels similar to (18)F-FAC in the blood (2.54 ± 0.2 and 3.04 ± 0.3 percentage injected dose per gram, respectively) indicating that (18)F-FAC crosses the BBB. EAE mice accumulate (18)F-FAC in the brain at 180% of the levels of control mice. Brain (18)F-FAC accumulation localizes to periventricular regions with significant leukocyte infiltration, and deoxyribonucleoside salvage activity is present at similar levels in brain-infiltrating T and innate immune cells. These data suggest that (18)F-FAC accumulates in brain-infiltrating leukocytes in this model. Fingolimod-treated EAE mice accumulate (18)F-FAC in the brain at 37% lower levels than control-treated EAE mice, demonstrating that (18)F-FAC PET can monitor therapeutic interventions in this mouse model. (18)F-CFA accumulates in the human brain at 15% of blood levels (0.08 ± 0.01 and 0.54 ± 0.07 SUV, respectively), indicating that (18)F-CFA does not cross the BBB in humans. Conclusion: (18)F-FAC PET can visualize brain-infiltrating leukocytes in a mouse MS model and can monitor the response of these cells to an immunomodulatory drug. Translating this strategy into humans will require exploring additional radiotracers.

Quantitative monitoring of brain neurochemistry is aimed at an accurate measurement of chemical basal levels and dynamics defining neuronal activities. Analytical tools must be endowed with high selectivity, sensitivity, and spatiotemporal resolution to tackle this task. On one hand, in vivo electroanalysis combined with miniature electrodes has evolved into a minimally invasive method for probing transient events during neural communication and metabolism. On the other hand, noninvasive imaging techniques have been widely adopted in visualizing the neural structure and processes within a population of neurons in two or three dimensions. This perspective will give a concise review of the inspiring frontiers at the interface of neurochemistry and electrochemistry (microvoltammetry, nanoamperometry, galvanic redox potentiometry and ion transport-based sensing) or imaging (super-resolution single nanotube tracking, deep multiphoton microscopy, and free animal imaging). Potential opportunities with these methods and their combinations for multimodal brain analysis will be discussed, intending to draw a brief picture for future neuroscience research.

Non-invasive monitoring of tumor therapy response helps in developing personalized treatment strategies. Here, we performed sequential positron emission tomography (PET) and diffusion-weighted magnetic resonance imaging (DW-MRI) to evaluate changes induced by a FOLFOX-like combination chemotherapy in colorectal cancer (CRC) xenografts, to identify the cellular and molecular determinants of these imaging biomarkers. Methods: Tumor bearing CD1 nude mice, engrafted with FOLFOX-sensitive Colo205 CRC xenografts, were treated with FOLFOX (5 fluorouracil, leucovorin and oxaliplatin) in weekly intervals. On d1, d2, d6, d9 and d13 of therapy, tumors were assessed by in vivo imaging and ex vivo analyses. In addition, HCT116 xenografts, which did not respond to the FOLFOX treatment, were imaged on d1 of therapy. Results: In Colo205 xenografts, FOLFOX induced a profound increase in uptake of the proliferation PET tracer 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT), which was accompanied by increases in markers for proliferation (Ki67, TK1) and for activated DNA damage response (DDR; γH2AX), whereas the effect on cell death was minimal. As tracer uptake was unaltered in the HCT116 model, these changes appear to be specific for tumor response. Conclusion: We demonstrate that [18F]FLT PET can non-invasively monitor molecular alterations induced by a cancer treatment, including thymidine metabolism and DDR. The cellular or imaging changes may not, however, be directly related to therapy response as assessed by volumetric measurements.

Introduction We describe a simple fixture that can be added to the imaging bed of a small-animal PET scanner that allows for automated counting of multiple organ or tissue samples from mouse-sized animals and counting of injection syringes prior to administration of the radiotracer. The combination of imaging and counting capabilities in the same machine offers advantages in certain experimental settings. Methods A polyethylene block of plastic, sculpted to mate with the animal imaging bed of a small-animal PET scanner, is machined to receive twelve 5-ml containers, each capable of holding an entire organ from a mouse-sized animal. In addition, a triangular cross-section slot is machined down the centerline of the block to secure injection syringes from 1-ml to 3-ml in size. The sample holder is scanned in PET whole-body mode to image all samples or in one bed position to image a filled injection syringe. Total radioactivity in each sample or syringe is determined from the reconstructed images of these objects using volume re-projection of the coronal images and a single region-of-interest for each. We tested the accuracy of this method by comparing PET estimates of sample and syringe activity with well counter and dose calibrator estimates of these same activities. Results PET and well counting of the same samples gave near identical results (in MBq, R 2 =0.99, slope=0.99, intercept=0.00-MBq). PET syringe and dose calibrator measurements of syringe activity in MBq were also similar ( R 2 =0.99, slope=0.99, intercept=− 0.22-MBq). Conclusion A small-animal PET scanner can be easily converted into a multi-sample and syringe counting device by the addition of a sample block constructed for that purpose. This capability, combined with live animal imaging, can improve efficiency and flexibility in certain experimental settings.

Rationale: Despite its widespread use in oncology, the PET radiotracer 18F-FDG is ineffectivefor improving early detection of pancreatic ductal adenocarcinoma (PDAC). An alternative strategy for early detection of pancreatic cancer involves visualisation of high-grade pancreatic intraepithelial neoplasias (PanIN-3), generally regarded as the non-invasive precursors of PDAC. The DNA damage response is known to be hyper-activated in late-stage PanINs. Therefore, we investigated whether the SPECT imaging agent, 111In-anti-γH2AX-TAT, allows visualisation of the DNA damage repair marker γH2AX in PanIN-3s in an engineered mouse model of PDAC, to facilitate early detection of PDAC. Methods: Genetically engineered KPC mice (KRasLSL.G12D/+; p53LSL.R172H/+; PdxCre) were imaged with 18F-FDG and 111In-anti-γH2AX-TAT. PanIN/PDAC presence visualised by histology was compared with autoradiography and immunofluorescence. Separately, the survival of KPC mice imaged with 111In-anti-γH2AX-TAT was evaluated. Results: In KPC mouse pancreata, γH2AX expression was increased in high-grade PanINs, but not in PDAC, corroborating earlier results obtained from human pancreas sections. Uptake of 111In-anti-γH2AX-TAT, but not 111In-IgG-TAT or 18F-FDG, within the pancreas was positively correlated with the age of KPC mice, which was correlated with the number of highgrade PanINs. 111In-anti-γH2AX-TAT localises preferentially in high-grade PanIN lesions, but not in established PDAC. Younger, non-tumour-bearing KPC mice that show uptake of 111Inanti-γH2AX-TAT in the pancreas survive significantly shorter than mice with physiological 111In-anti-γH2AX-TAT uptake. Conclusion: 111In-anti-γH2AX-TAT imaging allows non-invasive detection of DNA damage repair signalling upregulation in pre-invasive PanIN lesions and is a promising new tool to aid in the early detection and staging of pancreatic cancer.

Preclinical PET/CT is a well-established noninvasive imaging tool for studying disease development/progression and the development of novel radiotracers and pharmaceuticals for clinical applications. Despite this pivotal role, standardization of preclinical PET/CT protocols, including CT absorbed dose guidelines, is essentially nonexistent. This study (1) quantitatively assesses the variability of current preclinical PET/CT acquisition and reconstruction protocols routinely used across multiple centers and scanners; and (2) proposes acquisition and reconstruction PET/CT protocols for standardization of multicenter data, optimized for routine scanning in the preclinical PET/CT laboratory. Methods: Five different commercial preclinical PET/CT scanners in Europe and the United States were enrolled. Seven different PET/CT phantoms were used for evaluating biases on default/general scanner protocols, followed by developing standardized protocols. PET, CT, and absorbed dose biases were assessed. Results: Site default CT protocols were the following: greatest extracted Hounsfield units (HU) were 133 HU for water and −967 HU for air; significant differences in all tissue equivalent material (TEM) groups were measured. The average CT absorbed doses for mouse and rat were 72 mGy and 40 mGy, respectively. Standardized CT protocol were the following: greatest extracted HU were −77 HU for water and −990 HU for air; TEM precision improved with a reduction in variability for each tissue group. The average CT absorbed dose for mouse and rat decreased to 37 mGy and 24 mGy, respectively. Site default PET protocols were the following: uniformity was substandard in one scanner, recovery coefficients (RCs) were either over- or underestimated (maximum of 43%), standard uptake values (SUVs) were biased by a maximum of 44%. Standardized PET protocols were the following: scanner with substandard uniformity improved by 36%, RC variability decreased by 13% points, and SUV accuracy improved to 10%. Conclusion: Data revealed important quantitative biases in preclinical PET/CT and absorbed doses with default protocols. Standardized protocols showed improvements in measured PET/CT accuracy and precision with reduced CT absorbed dose across sites. Adhering to standardized protocols generates reproducible and consistent preclinical imaging datasets, thus augmenting translation of research findings to the clinic.

Cell death is an important target for imaging the early response of tumors to treatment. We describe here validation of a phosphatidylserine-binding agent for detecting tumor cell death in vivo based on the C2A domain of Synaptotagmin-I. Methods: The capability of near infrared fluorophore-labeled and 99mTechnetium- and 111Indium-labeled derivatives of C2Am for imaging tumor cell death, using planar near infrared fluorescence (NIRF) imaging and single photon computed tomography (SPECT) respectively, was evaluated in implanted and genetically engineered mouse models of lymphoma and in a human colorectal xenograft. Results: The fluorophore labeled C2Am derivative showed predominantly renal clearance and high specificity and sensitivity for detecting low levels of tumor cell death (2-5%). There was a significant correlation (R>0.9, P

F-18-FDG PET imaging is routinely used to investigate brown adipose tissue (BAT) thermogenesis, which requires mitochondrial uncoupling protein 1 (UCP1). It remains uncertain, however, whether BAT F-18-FDG uptake is a reliable surrogate measure of UCP1-mediated heat production. Methods: UCP1 knockout (KO) and wild-type (WT) mice housed at thermoneutrality were treated with the selective beta 3 adrenergic receptor agonist CL 316, 243 and under-went metabolic cage, infrared thermal imaging and F-18-FDG PET/MRI experiments. Primary brown adipocytes were additionally examined for their bioenergetics by extracellular flux analysis as well as their uptake of 2-deoxy-H-3-glucose. Results: In response to CL 316, 243 treatments, oxygen consumption, and BAT thermogenesis were diminished in UCP1 KO mice, but BAT F-18-FDG uptake was fully retained. Isolated UCP1 KO brown adipocytes exhibited defective induction of uncoupled respiration whereas their glycolytic flux and 2-deoxy-H-3-glucose uptake rates were largely unaffected. Conclusion: Adrenergic stimulation can increase BAT F-18-FDG uptake independently of UCP1 thermogenic function.

PURPOSE: Lung cancer heterogeneity makes response to therapy extremely hard to predict. Patient-derived xenografts (PDXs) represent a reliable preclinical model that closely recapitulates the main characteristics of the primary tumor and could represent a useful asset to test new therapies. Here, using PET imaging, we verify how lung cancer PDXs reproduce the metabolic features of the corresponding primary tumors. METHODS: We performed longitudinal [18F]FDG-PET studies on nine different PDXs, obtained by implants of primary cancer fragments harvested from patients. Max [18F]FDG uptake values of the lesion for each group were calculated and compared to corresponding patient's uptake. RESULTS: Different PDXs showed variable tumor growth rate and [18F]FDG uptake confirming the preservation of individual characteristics. A good intra-group reproducibility of PET measurements was observed. Furthermore, the subgroup of PDXs originating from primary tumors with higher metabolic rate displayed a rank order of [18F]FDG uptake similar to that of patients' original SUV. CONCLUSION: PDXs reproduced the original glucose metabolism of primary lesions and represent therefore a promising preclinical model also for the early assessment of therapy efficacy.

Owing to diverse functionalities and metal binding abilities, proteins have been proven to be promising ligands in the synthesis of gold nanoclusters (Au NCs). In this work, we explored β-lactoglobulin (β-Lg), a protein byproduct generated during cheese processing, as a biotemplate for fabrication of Au NCs by a facile and green method for the first time. The as-prepared Au NCs are water soluble and highly fluorescent and exhibit high sensitivity and selectivity for Hg2+ detection in aqueous solution. Interestingly, we found that the fluorescence of these Au NCs is stable either in a variety of complex matrixes or over a broad pH range (5.0–13.0) and therefore can be explored as a cell and animal imaging agent. More importantly, we demonstrated that the β-lactoglobulin-stabilized Au NCs (β-Lg–Au NCs) could serve as a sensor for the detection and quantification of Hg2+ in beverages, urine, and serum with high sensitivity.

Precise quantitative delineation of tumor hypoxia is essential in radiation therapy treatment planning to improve the treatment efficacy by targeting hypoxic sub-volumes. We developed a combined imaging system of positron emission tomography (PET) and electron para-magnetic resonance imaging (EPRI) of molecular oxygen to investigate the accuracy of PET imaging in assessing tumor hypoxia. The PET/EPRI combined imaging system aims to use EPRI to precisely measure the oxygen partial pressure in tissues. This will evaluate the validity of PET hypoxic tumor imaging by (near) simultaneously acquired EPRI as ground truth. The combined imaging system was constructed by integrating a small animal PET scanner (inner ring diameter 62 mm and axial field of view 25.6 mm) and an EPRI subsystem (field strength 25 mT and resonant frequency 700 MHz). The compatibility between the PET and EPRI subsystems were tested with both phantom and animal imaging. Hypoxic imaging on a tumor mouse model using $^{18}$F-fluoromisonidazole radio-tracer was conducted with the developed PET/EPRI system. We report the development and initial imaging results obtained from the PET/EPRI combined imaging system., Comment: 12 pages, 6 figures

The aim of this work was to explore 132La as a PET imaging surrogate for 225Ac using a DOTA-based, tumor-targeting alkylphosphocholine (NM600). Methods:132La was produced on a biomedical cyclotron. For in vivo experiments, mice bearing 4T1 tumors were administered 132La-NM600, and PET/CT scans were acquired up to 24 h after injection. After the last time point, the ex vivo tissue distribution was measured to corroborate the in vivo PET data. The ex vivo tissue distribution in mice was determined at 4 and 24 h after injection of 225Ac-NM600. Results: PET/CT images showed elevated, persistent 132La-NM600 uptake in the tumor. Low bone accumulation confirmed the in vivo stability of the conjugate. Ex vivo biodistribution studies validated the image-derived quantitative data, and the comparison of the 132La-NM600 and 225Ac-NM600 tissue distributions revealed a similar biodistribution for the 2 radiotracers. Conclusion: These findings suggest that 132La is a suitable imaging surrogate to probe the in vivo biodistribution of 225Ac radiotherapeutics.

Positron Emission Tomography (PET) imaging with 18F-FDG followed by mathematical modelling of the pulmonary uptake rate (Ki) is the gold standard for assessment of pulmonary inflammation in experimental studies of acute respiratory distress syndrome (ARDS). However, dynamic PET requires long imaging and only allows the assessment of one cranio-caudal field of view (~15 cm). We investigated whether static 18F-FDG-PET/CT and analysis of standard uptake values (SUV) or standard uptake ratios (SURstat, uptake time corrected ratio of 18F-FDG-concentration in lung tissue and blood plasma) might be an alternative to dynamic 18F-FDG-PET/CT and Patlak analysis for quantification of pulmonary inflammation in experimental ARDS. METHODS: ARDS was induced by saline lung lavage followed by injurious mechanical ventilation in fourteen anesthetized pigs (29.5-40.0 kg). PET/CT imaging sequences were acquired before and after 24 h of mechanical ventilation. Ki and the apparent volume of distribution (Vdist) were calculated from dynamic 18F-FDG-PET/CT scans using the Patlak analysis. Static 18F-FDG-PET/CT scans were obtained immediately after dynamic PET/CT and used for calculations of SUV and SURstat. Mean Ki values of the whole imaged field of view and of five ventro-dorsal lung regions were compared with corresponding SUV and SURstat values, respectively, by means of linear regression and concordance analysis. The variability of the 18F-FDG concentration in blood plasma (arterial input function) was analyzed. RESULTS: Both for the whole imaged field of view and ventro-dorsal subregions, Ki were linearly correlated with SURstat (r2 ≥ 0.84), while Ki-SUV correlations were worse (r2 ≤ 0.75). The arterial input function exhibited an essentially invariant shape across all animals and time points and can be described by an inverse power law. Compared to Ki, SURstat and SUV tracked the same direction of change in regional lung inflammation in 98.6 % and 84.3 % of measurements, respectively. CONCLUSION: The Ki-SURstat correlation was considerably stronger than the Ki-SUV correlation. The good Ki-SURstat correlation suggests that static 18F-FDG-PET/CT and SURstat analysis provides an alternative to dynamic 18F-FDG-PET/CT and Patlak analysis, allowing the assessment of inflammation of whole lungs, repeated measurements within the period of 18F-FDG decay, and faster data acquisition.

The study of animal models remains a cornerstone of preclinical cancer research. Recent advances in technology have led to the proliferation of animal imaging devices that are now integral to the study of cancer biology. Imaging is routinely used for the development and characterization of animal tumor models, measuring response to anticancer therapy, and for the detailed examination of individual molecular pathways within neoplastic tissue. The purpose of this chapter will be to provide an introduction to the most common imaging modalities used in contemporary oncologic investigation in order to help the reader determine if an imaging approach may complement their research goals.

International audience; Rationale: PET imaging using radiolabeled high-affinity substrates of P-glycoprotein (ABCB1) has convincingly revealed the role of this major efflux transporter in limiting the influx of its substrates from blood into the brain across the blood-brain barrier (BBB). Many drugs, such as metoclopramide, are weak ABCB1 substrates and distribute into the brain even when ABCB1 is fully functional. In this study, we used kinetic modeling and validated simplified methods to highlight and quantify the impact of ABCB1 on the BBB influx and efflux of $^{11}$C-metoclopramide, as a model weak ABCB1 substrate, in non-human primates. Methods: The regional brain kinetics of a tracer dose of $^{11}$C-metoclopramide (298 ± 44 MBq) were assessed in baboons using PET without (n = 4) or with intravenous co-infusion of the ABCB1 inhibitor tariquidar (4 mg/kg/h, n = 4). Metabolite-corrected arterial input functions were generated to estimate the regional volume of distribution (V$_T$) as well as the influx (K$_1$) and efflux (k$_2$) rate constants, using a one-tissue compartment model. Modeling outcome parameters were correlated with image-derived parameters, i.e. area under the curve AUC$_{0-30}$$_{min}$ and AUC$_{30-60min}$ (SUV.min) as well as the elimination slope (k$_E$; min$^{-1}$) from 30 to 60 min of the regional time-activity curves. Results: Tariquidar significantly increased the brain distribution of $^{11}$C-metoclopramide (V$_T$ = 4.3 ± 0.5 mL/cm$^3$ and 8.7 ± 0.5 mL/cm$^3$ for baseline and ABCB1 inhibition conditions, respectively, P

Chaemin Lim,1,* Yu Seok Youn,2,* Kyung Soo Lee,1 Ngoc Ha Hoang,1 Taehoon Sim,1 Eun Seong Lee,3 Kyung Taek Oh1 1Department of Pharmaceutical Sciences, College of Pharmacy, Chung-Ang University, Seoul, 2Department of Pharmaceutical Sciences, School of Pharmacy, Sungkyunkwan University, Suwon, 3Division of Biotechnology, The Catholic University of Korea, Gyeonggi-do, South Korea *These authors contributed equally tothis work Abstract: A polyelectrolyte ionomer complex (PIC) composed of cationic and anionic polymers was developed for nanomedical applications. Here, a poly(ethylene glycol)–poly(lactic acid)–poly(ethylene imine) triblock copolymer (PEG–PLA–PEI) and a poly(aspartic acid) (P[Asp]) homopolymer were synthesized. These polyelectrolytes formed stable aggregates through electrostatic interactions between the cationic PEI and the anionic P(Asp) blocks. In particular, the addition of a hydrophobic PLA and a hydrophilic PEG to triblock copolyelectrolytes provided colloidal aggregation stability by forming a tight hydrophobic core and steric hindrance on the surface of PIC, respectively. The PIC showed different particle sizes and zeta potentials depending on the ratio of cationic PEI and anionic P(Asp) blocks (C/A ratio). The doxorubicin (dox)-loaded PIC, prepared with a C/A ratio of 8, demonstrated pH-dependent behavior by the deprotonation/protonation of polyelectrolyte blocks. The drug release and the cytotoxicity of the dox-loaded PIC (C/A ratio: 8) increased under acidic conditions compared with physiological pH, due to the destabilization of the formation of the electrostatic core. In vivo animal imaging revealed that the prepared PIC accumulated at the targeted tumor site for 24 hours. Therefore, the prepared pH-sensitive PIC could have considerable potential as a nanomedicinal platform for anticancer therapy. Keywords: polyelectrolyte ionomer complex, PEG–PLA–PEI, nanomedicine, pH-sensitive, animal imaging

The real-time monitoring of key biospecies in the living systems has received thrusting attention during the past decades. Specifically, fluorescent detection based on near-infrared (NIR) fluorescent probes is highly favorable for live cells, live tissues, and even animal imaging, owing to the substantial merits of the NIR window, such as minimal phototoxicity, deep penetration into tissues, and low autofluorescence background. Nevertheless, developing potent NIR fluorescent probes still poses serious challenges to the chemists because traditional NIR fluorophores are less tunable than visible-wavelength fluorophores. To address this issue, here we report a set of novel NIR hybrid fluorophores, namely, the hybrid chromenylium-cyanine fluorophore (CC-Fluor), in which both the fluorescence intensity and the emission wavelength can be easily adjusted by the conformational changes and substitution groups. Compared to known NIR fluorophores, the new CC-Fluors are substantially advantageous for NIR probe development: (1) CC-Fluors display tunable and moderate Stokes shifts and quantum yields; (2) the fluorophores are stable at physiological conditions after long-term incubation; (3) the absorption maxima of CC-Fluors coincide with the common laser spectral lines in mainstream in vivo imaging systems; (4) most importantly, CC-Fluors can be easily modified to prepare NIR probes targeting various biospecies. To fully demonstrate the practical utility of CC-Fluors, we report two innovative NIR probes, a ratiometric pH probe and a turn-on Hg(2+) probe, both are successfully employed in live animal imaging. Hence, the detailed studies allow us to confirm that CC-Fluors can work as an excellent platform for developing NIR probes for the detection of species in living systems.

Fibrillary tau aggregates in Alzheimer’s disease (AD) and allied neurodegenerative disorders have been visualized in-vivo by positron emission tomography (PET), while mechanistic links between PET-detectable tau deposits and neurotoxicity remain elusive. Here, we took advantage of transgenic mouse models of tauopathies to evaluate associations between PET and postmortem measures of tau probe binding and their relation to neuronal loss.Methods:PET with a tau probe,11C-PBB3 (2-((1E,3E)-4-(6-(11C-methylamino)pyridine-3-yl)buta-1,3-dienyl)benzo[d]thiazol-6-ol), and volumetric magnetic resonance imaging (MRI) were performed for rTg4510 and non-transgenic mice. Binding of11C-PBB3 and its blockade by another tau binding compound, AV-1451 (-(6-fluoropyridine-3-yl)-5H-pyrido[4,3-b]indole), in homogenized brains of tauopathy patients and rTg4510 and PS19 mice were quantified, and PBB3-positive and phosphorylated tau lesions in sectioned brains of these mice were assessed.Results:In-vivo11C-PBB3 binding to the rTg4510 neocortex/hippocampus was increased relative to controls, and was correlated with local atrophy. In-vitro11C-PBB3 binding in the neocortex/hippocampus was also well correlated with in-vivo radioligand binding and regional atrophy in the same individual rTg4510 mice. By contrast, in-vitro11C-PBB3 binding was elevated in the brainstem but not hippocampus of PS19 mice, despite a pronounced loss of neurons in the hippocampus rather than brainstem. Finally, PBB3 and AV-1451 showed similar binding properties between mouse models and tauopathy patients.Conclusion:The present findings support the distinct utilities of11C-PBB3-PET along with MRI of rTg4510 and PS19 mice for quantitatively pursuing mechanisms connecting PET-detectable and PET-undetectable tau aggregations to neuronal death, which recapitulate two different modes of tau-provoked neurotoxicity.

General anesthesia has been performed reliably for nearly 170 years even though its exact mechanism is still unknown. To date, almost all small animal studies to investigate the effects of general anesthesia have been done under anesthesia and it prevents the quantitative analysis because of anesthesia itself effects the neurofunctional parameters under study. Here we have used an awake animal imaging method to study and compare cerebral glucose utilization in the awake and anesthetized states. We have shown that the general anesthesia has a profound effect on rat brain and it depends on the type and the dose of anesthetic drug.

Objective: Although Iodine-125 (125I) has been widely used for in vitro studies because of its relatively long half-life (60.1 days), 125I imaging is limited because of its low energy (27 - 35 keV), even in an animal-dedicated system. In this study, imaging characteristics of 125I were assessed using a small animal-dedicated imaging system and clinical scanner. Methods: Using the Siemens Inveon and Siemens Symbia TruePoint systems, imaging characteristics such as resolution, sensitivity, and image quality were compared. Mouse high resolution (MHR-0.5), mouse general purpose (MGP-1.0), and mouse high sensitivity (MHS-2.0) collimators were used for the Inveon scanner, and low energy high-resolution (LEHR) and low energy all-purpose (LEAP) collimators were used for the Symbia TruePoint. For animal imaging, 16.8 MBq of 125I was administered to BALB/c mice intravenously, and the planar image and single-photon emission computed tomography (SPECT) were obtained using both scanners. Results: The resolution of 125I for the Inveon scanner was 3.98 mm full width at half maximum (FWHM) at a 30-mm distance with the MHR-0.5 collimator, and the value of Symbia scanner was 8.72 mm FWHM at a 30-mm distance with the LEHR collimator. The sensitivity of 125I for the Inveon scanner was 21.87 cps/MBq, and the value for the clinical scanner was 30.55 cps/MBq. The planar images of mice were successfully obtained at the level of evaluating specific binding in both scanners. Conclusion: 125I small animal imaging can be achieved with a clinical scanner. This result may enhance the utilization of 125I small animal imaging using a clinical scanner.

Rationale: Neuroinflammation has been associated with different neurological diseases including Alzheimer's disease (AD). In AD, the translocator protein 18kDa (TSPO) is overexpressed in the activated microglia that surround the β-amyloid plaques. In the current longitudinal study, using a mouse model of AD, we evaluated the association between β-amyloid deposition and neuroinflammation in AD. Methods: To monitor the longitudinal changes in β-amyloid deposition and neuroinflammation, we used in vivo PET imaging and ex vivo autoradiography with 11C-PIB and a TSPO tracer, 18F-GE-180, in the APP23 mouse model of AD. We also applied immunohistochemistry to study β-amyloid and activated microglia in the mouse brain tissue. Results: From 17 to 26 months of age, the mice showed robust increased binding of 11C-PIB with aging in the frontal cortex, parietotemporal cortex, hippocampus, and thalamus while the increase in 18F-GE-180 binding with aging was minimal in areas of early amyloidosis such as frontal cortex and hippocampus. A clear positive correlation between β-amyloid deposition and neuroinflammation was detected with 11C-PIB, and 18F-GE-180 was obtained only in the parietotemporal cortex and thalamus. Conclusion: The neuroinflammation increase detected with 18F-GE-180 is less than the increase in amyloidosis detected with 11C-PIB. Furthermore, the binding of 18F-GE-180 plateaus at an earlier stage of pathogenesis whereas the amyloidosis continues to increase. We suggest that TSPO can be a good marker for early pathogenesis detection but not for tracking long-term disease progression.

3-[18F]fluoro-4-aminopyridine, [18F]3F4AP, is a radiofluorinated analog of the FDA-approved drug for multiple sclerosis 4-aminopyridine (4AP). This compound is currently under investigation as a PET tracer for demyelination. We recently described a novel chemical reaction to produce metafluorinated pyridines consisting of direct fluorination of a pyridine N-oxide and the utilization of this reaction for the radiochemical synthesis of [18F]3F4AP. In this article, we demonstrate how to produce this tracer using an automated synthesizer and an in-house made flow hydrogenation reactor. We also show the standard quality control procedures performed before releasing the radiotracer for preclinical animal imaging studies. This semi-automated procedure may serve as the basis for future production of [18F]3F4AP for clinical studies.

Amyloidosis is a protein-misfolding disorder characterized by the extracellular deposition of amyloid, a complex matrix composed of protein fibrils, hyper-sulphated glycosaminoglycans and serum amyloid P component (SAP). Accumulation of amyloid in visceral organs results in the destruction of tissue architecture leading to organ dysfunction and failure. Early differential diagnosis and disease monitoring are critical for improving patient outcomes; thus, whole body amyloid imaging would be beneficial in this regard. Non-invasive molecular imaging of systemic amyloid is performed in Europe by using iodine-123-labelled SAP; however, this tracer is not available in the US. Therefore, we evaluated synthetic, poly-basic peptides, designated p5 and p5+14, as alternative radiotracers for detecting systemic amyloidosis. Herein, we perform a comparative effectiveness evaluation of radiolabelled peptide p5+14 with p5 and SAP, in amyloid-laden mice, using dual-energy SPECT imaging and tissue biodistribution measurements. All three radiotracers selectively bound amyloid in vivo; however, p5+14 was significantly more effective as compared to p5 in certain organs. Moreover, SAP bound principally to hepatosplenic amyloid, whereas p5+14 was broadly distributed in numerous amyloid-laden anatomic sites, including the spleen, liver, pancreas, intestines and heart. These data support clinical validation of p5+14 as an amyloid radiotracer for patients in the US.

Background Preclinical neuroimaging allows for the assessment of brain anatomy, connectivity and function in laboratory animals, such as mice and rats. Most of these studies are performed under anesthesia to avoid movement during the scanning sessions. Method Due to the limitations associated with anesthetized imaging, recent efforts have been made to conduct rodent imaging studies in awake animals, habituated to the restraint systems used in these instances. As of now, only one such system is commercially available for mouse scanning (Animal Imaging Research, Boston, MA, USA) integrating the radiofrequency coil electronics with the restraining element, an approach which, although effective in reducing head motion during awake imaging, has some limitations. In the current report, we present a novel mouse restraining system that addresses some of these limitations. Results/Comparison to other methods The effectiveness of the restraining system was evaluated in terms of three-dimensional linear head movement across two consecutive functional MRI scans (total 20 min) in 33 awake mice. Head movement was minimal, recorded in roughly 12% of the time-series. Respiration rate during the acclimation procedure dropped while the bolus count remained unchanged. Body movement during functional acquisitions did not have a significant effect on magnetic field (B0) homogeneity. Conclusion/novelty Compared to the commercially available system, the benefit of the current design is two-fold: 1) it is compatible with a range of commercially-available coils, and 2) it allows for the pairing of neuroimaging with other established techniques involving intracranial cannulation (i.e. microinfusion and optogenetics).

During the past ten years significant advances have been achieved in quantum dot (QD) research field. The new synthetic methods and the discovery of new types of QDs have enabled a variety of new applications of QDs for bioimaging and biosensing. This review will focus on the most recent progress of QDs for biomedical applications. Ample examples will be given in this review on newly developed synthetic methods of QDs, non-toxic QDs, QDs for biomolecule detection, cell and animal imaging, and disease therapy.

Functional MRI in awake rats involves acclimatization to restraint to minimize motion. We designed a study to examine the effects of an acclimatization protocol (5 days of restraint, 60 min per day) on the emission of 22-kHz ultrasonic vocalizations and performance in a forced swim test (FST). Our results showed that USV calls are reduced significantly by days 3, 4 and 5 of acclimatization. Although the rats showed less climbing activity (and more immobility) in FST on day 5 compared to the 1st day of restraint acclimatization, the difference was not detected once the animals were given a 2-week hiatus. Overall, we showed that animals adapt to the restraint over a five-day period; however, restraint may introduce confounding behavioral outcomes that may hinder the interpretation of results derived from awake rat imaging. The present data warrants further testing of the effects of MRI restraint on behavior.

Creation of an animal imaging center is rarely as simple as purchasing a system, placing it in a room somewhere, and turning people loose to use it. There are very few imaging devices that are appropriate to place on a laboratory bench top and use right out of the box without further integration, for example, a microscope. Most systems require training of users and a specialized environment for handling data and animals. Use of animals requires approval of physical spaces, imaging systems, and protocols by the Institutional Animal Care and Use Committee (IACUC), radiation use requires approval from the Radiation Safety Officer (RSO), local institutional veterinary considerations may apply, and usually biosafety approval is required. There may also be other environmental health and safety (EHS) issues to consider, such as magnetic field safety and airflow requirements. The process of comprehensive planning and oversight is now commonplace to house, use, and experiment with animals (Stout et al. 2005; Klaunberg and Davis 2008).