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Glucose transport rates are estimated noninvasively in physiological and pathological states by kinetic imaging using PET. The glucose analog most often used is [.sup.18]F-labeled 2FDG. Compared with glucose, 2FDG is poorly transported by intestine and kidney. We examined the possible use of 6FDG as a tracer of glucose transport. Lacking a hydroxyl at its 6th position, 6FDG cannot be phosphorylated as 2FDG is. Prior studies have shown that 6FDG competes with glucose for transport in yeast and is actively transported by intestine. Its uptake by muscle has been reported to be unresponsive to insulin, but that study is suspect. We found that insulin stimulated 6FDG uptake 1.6-fold in 3T3-L1 adipocytes and azide stimulated the uptake 3.7-fold in Clone 9 cells. Stimulations of the uptake of 3OMG, commonly used in transport assays, were similar, and the uptakes were inhibited by cyclochalasin B. Glucose transport is by GLUT1 and GLUT4 transporters in 3T3-L1 adipocyte and by the GLUT1 transporter in Clone 9 cells. Cytochalasin B inhibits those transporters. Rats were also imaged in vivo by PET using 6[sup.18]FDG. There was no excretion of [sup.18]F into the urinary bladder unless phlorizin, an inhibitor of active renal transport, was also injected. [sup.18]F activity in brain, liver, and heart over the time of scanning reached a constant level, in keeping with the 6FDG being distributed in body water. In contrast, [sup.18]F from 2[sup.18]FDG was excreted in relatively large amounts into the bladder, and [sup.18]F activity rose with time in heart and brain in accord with accumulation of 2[sup.18]FDG-6-P in those organs. We conclude that 6FDG is actively transported by kidney as well as intestine and is insulin responsive. In trace quantity, it appears to be distributed in body water unchanged. These results provide support for its use as a valid tracer of glucose transport. imaging; 2-fluoro-2-deoxy-D-glucose; positron emission tomography; renal transport doi:10.1152/ajpendo.00022.2007

Three-dimensional (3-D) positron emission tomography (PET) imaging of inhaled radiolabeled aerosol in the nasal or pulmonary regions provides an in vivo measurement of drug distribution using the drug itself as the tracer. Repeated or dynamic PET scans over the time after inhalation provides us with further information about the fate of the deposited drug. These quantitative measurements are sufficient to describe the performance of a drug or device and they are obtained in a noninvasive fashion, which cannot be achieved by using any other methods. Using this PET-imaging paradigm, we conducted a sequence of drug studies to evaluate the performance of aerosol drugs and delivery devices; to compare the performance of similar drugs from different manufacturers; to assess the similarity between different formulations and propellants for the same drug; to appraise delivery devices such as spacers and nebulizers, etc. This paper reviews only the imaging and data analysis techniques developed for the above-mentioned studies that include multi-modality image registration, region definition and region-based data analysis, and nonregion-based data analysis. We separated the techniques into nasal and pulmonary studies because of the uniqueness of each group. Specific drugs or devices are not identified and no result about drug performance is given because the imaging and data analysis methodology, which is the focus of this paper, applies to all these studies regardless of the drugs or their delivery devices. The quantitative data are used as the scientific basis for evaluation although we also developed visualization techniques to enhance the results drawn from the data. Index Terms--Aerosol deposition, multi-modality imaging, nasal inhalation, positron emission tomography (PET) quantification, pulmonary inhalation, three-dimensional (3-D) visualization.

Neural progenitor cell expansion is critical for normal brain development and an appropriate response to injury. During the brain growth spurt, exposures to general anesthetics, which either block the N-methyl-D-aspartate receptor or enhance the g-aminobutyric acid receptor type A can disturb neuronal transduction. This effect can be detrimental to brain development. Until now, the effects of anesthetic exposure on neural progenitor cell expansion in vivo had seldom been reported. Here, minimally invasive micro positron emission tomography (microPET) coupled with 30-deoxy-30 [18F] fluoro-l-thymidine ([18F]FLT) was utilized to assess the effects of sevoflurane exposure on neural progenitor cell proliferation. FLT, a thymidine analog, is taken up by proliferating cells and phosphorylated in the cytoplasm, leading to its intracellular trapping. Intracellular retention of [18F]FLT, thus, represents an observable in vivo marker of cell proliferation. Here, postnatal day 7 rats (n=11/group)were exposed to 2.5% sevoflurane or room air for 9 h. For up to 2 weeks following the exposure, standard uptake values (SUVs) for [18F]-FLT in the hippocampal formation were significantly attenuated in the sevoflurane-exposed rats (p <0.0001), suggesting decreased uptake and retention of [18F]FLT (decreased proliferation) in these regions. Four weeks following exposure, SUVs for [18F]FLT were comparable in the sevoflurane-exposed rats and in controls. Co-administration of 7-nitroindazole (30 mg/kg, n=5), a selective inhibitor of neuronal nitric oxide synthase, significantly attenuated the SUVs for [18F]FLT in both the air-exposed (p =0.00006) and sevoflurane-exposed rats (p =0.0427) in the first week following the exposure. These findings suggested that microPET in couple with [18F]FLT as cell proliferation marker could be used as a non-invasive modality to monitor the sevoflurane-induced inhibition of neural progenitor cell proliferation in vivo. [ABSTRACT FROM AUTHOR]

Background. The inhalation anesthetics nitrous oxide (N2O) and isoflurane (ISO) are used in surgical procedures for human infants. Injury to the central nervous system is often accompanied by localization of activated microglia or astrocytosis at the site of injury. The tracer that targets to the peripheral benzodiazepine receptor (PBR), [18F]N-2-(2-fluoroethoxy)benzyl)- N-(4-phenoxypyridin-3-yl)acetamide ([18F]-FEPPA), has been reported as a sensitive biomarker for the detection of neuronal damage/inflammation. Methods. On postnatal day (PND) 5 or 6 rhesus monkey neonates were exposed to a mixture of N2O/oxygen and ISO for 8 hours and control monkeys were exposed to room air. MicroPET/CT images with [18F]-FEPPA were obtained for each monkey 1 day, one week, three weeks, and 6 months after the anesthetic exposure. Results. The radiotracer quickly distributed into the brains of both treated and control monkeys on all scan days. One day after anesthetic exposure, the uptake of [18F]-FEPPA was significantly increased in the temporal lobe. One week after exposure, the uptake of [18F]-FEPPA in the frontal lobe of treated animals was significantly greater than that in controls. Conclusions. These findings suggest that microPET imaging is capable of dynamic detection of inhaled anesthetic-induced brain damage in different brain regions of the nonhuman primate. [ABSTRACT FROM AUTHOR]

Variation in the rate at which drugs reach the brain influences many different drug effects and is also thought to influence liability to addiction. For example, rapid intravenous delivery of cocaine and nicotine is more effective in producing hedonic effects, tolerance, psychomotor sensitization, and in inducing gene expression. Smoking is thought to result in an especially rapid rate of rise of nicotine in the brain, but whether this is true has never been adequately addressed. Thus, in this study, we sought to determine the true rate of rise of smoked nicotine in human brain and compare this with previous intravenous nicotine delivery. Positron emission tomography scans of lung and brain regions and arterial and venous blood curves were obtained in human subjects after single puffs from cigarettes formulated with [11C]nicotine. The rise of nicotine concentration following a single puff was rapid, reaching more than 50% of maximum brain levels within 15 s of bolus arrival in the brain in most subjects. This rate of rise was considerably faster than that seen in previous studies using intravenous administration. Uptake in human brain from a single inhalation was sufficiently rapid that it is plausible that fast rate-of-rise contributes to nicotine dependence in smokers. [ABSTRACT FROM AUTHOR]

It has been reported that suppression of N-methyl-D-aspartate (NMDA) receptor function by ketamine may trigger apoptosis of neurons when given repeatedly during the brain growth spurt period. Because microPET scans can provide in vivo molecular imaging at sufficient resolution, it has been proposed as a minimally invasive method for detecting apoptosis using the tracer 18F-labeled annexin V. In this study, the effect of ketamine on the metabolism and integrity of the rat brain were evaluated by investigating the uptake and retention of 18F-fluorodeoxyglucose (FDG) and 18F-annexin V using microPET imaging. On postnatal day (PND) 7, rat pups in the experimental group were exposed to six injections of ketamine (20 mg/kg at 2-h intervals) and control rat pups received six injections of saline. On PND 35, 37 MBq (1 mCi) of 18F-FDG or 18F-annexin V was injected into the tail vein of treated and control rats, and static microPET images were obtained over 1 (FDG) and 2 h (annexin V) following the injection. No significant difference was found in 18F-FDG uptake in the regions of interest (ROIs) in the brains of ketamine-treated rats compared with saline-treated controls. The uptake of 18F-annexin V, however, was significantly increased in the ROI of ketamine-treated rats. Additionally, the duration of annexin V tracer washout was prolonged in the ketamine-treated animals. These results demonstrate that microPET imaging is capable of distinguishing differences in retention of 18F-annexin V in different brain regions and suggests that this approach may provide a minimally invasive biomarker of neuronal apoptosis in rats. [ABSTRACT FROM PUBLISHER]

Describes the use of three-dimensional positron emission tomography (PET) imaging of inhaled radiolabeled aerosol in the nasal or pulmonary regions. Description of the performance of a drug or device; Comparison of the performance of similar drugs from different manufacturers; Assessment of the similarity between different formulations and propellants for the same drug.