Search

This study evaluated the MRI-derived fat fraction (FF), from a Cooling-reheating protocol, for estimating the cold-induced brown adipose tissue (BAT) metabolic rate of glucose (MRglu) and changes in lipid content, perfusion and arterial blood volume (VA) within cervical-supraclavicular fat (sBAT). Twelve volunteers underwent PET/MRI at baseline, during cold exposure and reheating. For each temperature condition, perfusion and VA were quantified with dynamic [15O]water-PET, and FF, with water-fat MRI. MRglu was assessed with dynamic [18F]fluorodeoxyglucose-PET during cold exposure. sBAT was defined using anatomical criteria, and its subregion sBATHI, by MRglu > 11 μmol/100 cm3/min. For all temperature conditions, sBAT-FF correlated negatively with sBAT-MRglu (ρ ≤ − 0.87). After 3 h of cold, sBAT-FF decreased (− 2.13 percentage points) but tended to normalize during reheating although sBATHI-FF remained low. sBAT-perfusion and sBAT-VA increased during cold exposure (perfusion: + 5.2 ml/100 cm3/min, VA: + 4.0 ml/100 cm3). sBAT-perfusion remained elevated and sBAT-VA normalized during reheating. Regardless of temperature condition during the Cooling-reheating protocol, sBAT-FF could predict the cold-induced sBAT-MRglu. The FF decreases observed after reheating were mainly due to lipid consumption, but could potentially be underestimated due to intracellular lipid replenishment. The influence of perfusion and VA, on the changes in FF observed during cold exposure, could not be ruled out.

2-Deoxy-2-(18)F-fluoro-d-glucose (2-FDG) with PET is undeniably useful in the clinic, being able, among other uses, to monitor change over time using the 2-FDG SUV metric. This report suggests some potentially serious caveats for this and related roles for 2-FDG PET. Most critical is the assumption that there is an exact proportionality between glucose metabolism and 2-FDG metabolism, called the lumped constant, or LC. This report describes that LC is not constant for a specific tissue and may be variable before and after disease treatment. The purpose of this work is not to deny the clinical value of 2-FDG PET; it is a reminder that when one extends the use of an appropriately qualified imaging method, new observations may arise and further validation would be necessary. The current understanding of glucose-based energetics in vivo is based on the quantification of glucose metabolic rates with 2-FDG PET, a method that permits the noninvasive assessment of various human disorders. However, 2-FDG is a good substrate only for facilitated-glucose transporters (GLUTs), not for sodium-dependent glucose cotransporters (SGLTs), which have recently been shown to be distributed in multiple human tissues. Thus, the GLUT-mediated in vivo glucose utilization measured by 2-FDG PET would be masked to the potentially substantial role of functional SGLTs in glucose transport and use. Therefore, under these circumstances, the 2-FDG LC used to quantify in vivo glucose utilization should not be expected to remain constant. 2-FDG LC variations have been especially significant in tumors, particularly at different stages of cancer development, affecting the accuracy of quantitative glucose measures and potentially limiting the prognostic value of 2-FDG, as well as its accuracy in monitoring treatments. SGLT-mediated glucose transport can be estimated using α-methyl-4-deoxy-4-(18)F-fluoro-d-glucopyranoside (Me-4FDG). Using both 2-FDG and Me-4FDG should provide a more complete picture of glucose utilization via both GLUT and SGLT transporters in health and disease states. Given the widespread use of 2-FDG PET to infer glucose metabolism, it is relevant to appreciate the potential limitations of 2-FDG as a surrogate for glucose metabolic rate and the potential reasons for variability in LC. Even when the readout for the 2-FDG PET study is only an SUV parameter, variability in LC is important, particularly if it changes over the course of disease progression (e.g., an evolving tumor).

Author(s): Nozawa, Asae; Rivandi, Ali Hosseini; Kanematsu, Masayuki; Hoshi, Hiroaki; Piccioni, David; Kesari, Santosh; Hoh, Carl K | Abstract: BackgroundStandardized uptake values (SUVs) of fluorine-18 fluorodeoxyglucose PET ((18)F-FDG PET) are used widely to differentiate residual or recurrent high-grade gliomas from post-treatment changes in patients with brain tumors. The aim of this study is to assess the accuracy of SUV corrected by blood glucose level (SUV(gluc)) compared with various quantitative methods in this role.Materials and methodsIn 55 patients with dynamic F-FDG PET scans, there were 97 glioma lesions: glioblastoma (n=60), grade III gliomas (n=22), grade III or IV gliomas (n=6), grade I/II (n=7), and prebiopsy lesions (n=2). The final actual diagnosis was made on the basis of pathology (n=33) and clinical outcome (n=64). Dynamic F-FDG PET scans were processed to generate parametric images of SUV(gluc), SUV(max), and glucose metabolic rate (GMR). Lesion to cerebellum ratios (SUV(Rc)) and contralateral white matter ratios (SUV(Rw)) were also measured. The SUV(gluc) was calculated as SUV(max)×blood glucose level/100.ResultsUsing the thresholds of SUV(max)g4.6, SUV(Rc)g0.9, SUV(Rw)g1.8, SUV(gluc)g4.3, and GMRg12.2 μmol/min/100 g to represent positivity for viable tumors, the accuracies were the same for the SUV(gluc) and SUV(Rw) (80%) and were higher than the conventional SUV(max) (72%). The area under the receiver operating characteristic curve for the SUV(gluc) (0.8933) was better than that for the SUV(max) (0.8266) (Pl0.01) and was similar to those of the GMR (0.8622), SUV(Rc) (0.8606), and SUV(Rw) (0.8981).ConclusionThese results suggest that SUV(gluc) may aid in the differentiation of residual or recurrent high-grade tumor from post-treatment changes in patients with abnormal blood glucose levels. The simplicity of the SUV(gluc) avoids the complexity of kinetic analysis or the requirement of a reference tissue.

The relationships of unconscious aggression (according to the Hand Test) with regional glucose metabolic rates in the brain (estimated using positron emission tomography) have been analyzed in patients with multiple sclerosis. It has been shown that an increased proneness to open aggression (unconscious aggression) in patients with multiple sclerosis is mainly related to reduced functioning of different areas of the frontal lobes of the brain on the left and with changes in glucose metabolic rate in the structures of the limbic system of the left and right hemispheres. An enhanced unconscious aggression is accompanied by a decrease in the glucose metabolic rate in some areas of Broca’s convolution and the middle frontal gyrus on the left.

Contains fulltext : 179634.pdf (Publisher’s version ) (Closed access) Purpose To assess whether dynamic fluorine 18 (18F) fluorodeoxyglucose (FDG) positron emission tomography (PET) has added value over static 18F-FDG PET for tumor delineation in non-small cell lung cancer (NSCLC) radiation therapy planning by using pathology volumes as the reference standard and to compare pharmacokinetic rate constants of 18F-FDG metabolism, including regional variation, between NSCLC histologic subtypes. Materials and Methods The study was approved by the institutional review board. Patients gave written informed consent. In this prospective observational study, 1-hour dynamic 18F-FDG PET/computed tomographic examinations were performed in 35 patients (36 resectable NSCLCs) between 2009 and 2014. Static and parametric images of glucose metabolic rate were obtained to determine lesion volumes by using three delineation strategies. Pathology volume was calculated from three orthogonal dimensions (n = 32). Whole tumor and regional rate constants and blood volume fraction (VB) were computed by using compartment modeling. Results Pathology volumes were larger than PET volumes (median difference, 8.7-25.2 cm3; Wilcoxon signed rank test, P < .001). Static fuzzy locally adaptive Bayesian (FLAB) volumes corresponded best with pathology volumes (intraclass correlation coefficient, 0.72; P < .001). Bland-Altman analyses showed the highest precision and accuracy for static FLAB volumes. Glucose metabolic rate and 18F-FDG phosphorylation rate were higher in squamous cell carcinoma (SCC) than in adenocarcinoma (AC), whereas VB was lower (Mann-Whitney U test or t test, P = .003, P = .036, and P = .019, respectively). Glucose metabolic rate, 18F-FDG phosphorylation rate, and VB were less heterogeneous in AC than in SCC (Friedman analysis of variance). Conclusion Parametric images are not superior to static images for NSCLC delineation. FLAB-based segmentation on static 18F-FDG PET images is in best agreement with pathology volume and could be useful for NSCLC autocontouring. Differences in glycolytic rate and VB between SCC and AC are relevant for research in targeting agents and radiation therapy dose escalation. (c) RSNA, 2016 Online supplemental material is available for this article.

Reviews of imaging studies assessing the brain effects of vascular risk factors typically include a substantial number of studies with subjects with a history of symptomatic cardiovascular or cerebrovascular disease and/or events, limiting our ability to disentangle the primary brain effects of vascular risk factors from those of resulting brain and cardiac damage. The objective of this study was to perform a systematic review of brain changes from imaging studies in patients with vascular risk factors but without clinically manifest cardiovascular or cerebrovascular disease or events. The 77 studies included in this review demonstrate that in persons without symptomatic cardiovascular, cerebrovascular, or peripheral vascular disease, the vascular risk factors of hypertension, diabetes mellitus, obesity, hyperlipidemia, and smoking are all independently associated with brain imaging changes before the clinical manifestation of cardiovascular or cerebrovascular disease. We conclude that the identification of brain changes associated with vascular risk factors, before the manifestation of clinically significant cerebrovascular damage, presents a window of opportunity wherein adequate treatment of these modifiable vascular risk factors may prevent the development of irreversible deleterious brain changes and potentially alter patients’ clinical course.

The mechanism of the development of cognitive impairments in multiple sclerosis (MS) was investigated by studying glucose metabolism at the level of the brain by positron emission tomography (PET). A total of 61 patients with different types of MS were studied. Correlation analysis identified a relationship between cognitive impairments and regional glucose metabolic rate. The authors believe that this may be evidence for an important role for metabolic abnormalities in the gray matter of the brain in the pathogenesis of cognitive impairments in MS.

Diabetes is an incurable disease where the body is not able to maintain the blood sugar level as the glucose in the blood is not utilize due to the destruction of the beta pancreatic cell of the liver. Blood sugar level of body is a very important factor for health and it should be maintain within the desired level or else this would result in complications and often serious damage to the body. Therefore treatment must be provided in case of high or low blood sugar level. In case of high blood sugar level, insulin must be injected and in case of low blood sugar level we should inject glucagon into the body. This paper is concerned on advanced method of simulation that can be used to implement a real insulin and glucagon pump that can work in real time to prevent the fatal effects of diabetes on body. This system also covers all the safety critical system aspect required to build a system that has a direct effect on human life. To provide better insulin and glucagon management and to reduce the need for human supervision, we have implement a control algorithm for the insulin and glucagon pump to automate the delivery process. The control algorithm adapts the glucose metabolic rate and determine the appropriate amount of insulin or glucagon to be delivered into the body. Method that is followed is effective and efficient in maintaining the blood sugar level. The Graphical User Interface (GUI) of the system is very easy and user friendly that makes it easier for the patient and doctor to use. Different sets of testing were used to insure the safety and efficiency of the insulin pump simulation.

Es vergeht kaum eine Woche, in der nicht neue Befunde zu Hirnstorungen bei Zwang in Fachzeitschriften veroffentlicht werden. Die ermittelten Zusammenhange zwischen Gehirn und Zwang entlasten einige Betroffene (»It’s not me – it’s my OCD«, zu Deutsch etwa: »Das bin nicht ich, sondern mein Zwang«). Wiederum andere resignieren aufgrund dieser Resultate, da der Irrglaube besteht, bei Zwang liege ein irreparabler Defekt vor – wie bei einem kaputten Auto. Diese Annahme beruht auf einer falschen Vorstellung uber die Funktionsweise unseres Gehirns, wie im folgenden Abschnitt gezeigt werden soll.

Since its inception, positron emission tomography (PET) has emerged as a non-invasive imaging modality that allows, in different fields (neurology, cardiology and oncology), in vivo quantitative assessment of molecular and physiological biomarkers in healthy and disease states [1–4]. Quantitative analysis makes it possible to establish a direct relationship between the time-varying activity concentration in organs/tissues of interest and the functional parameters representing the underlying biological processes at the cellular level [5–8]. It should, however, be emphasized that the term quantification has often been used inappropriately in the medical imaging literature to indicate different measurement approaches such as [5]: (1) semi-quantification (a contradiction in terms) or relative quantification (e.g., measurement of SUV), (2) absolute quantification of activity concentration, usually incorporating careful corrections for physical degrading factors (e.g., measurement of tracer uptake in MBq), and (3) proper physiological quantification, where the absolute activity concentration [obtained in (2)] is converted into molecular parameters of interest [e.g., glucose metabolic rate (rGMCglc) expressed as mol/100 g/min]. The concentration of tracers in organs/tissues of interest depends on their specific kinetic properties, i.e., various factors including, but not limited to, the rate of delivery through circulation, the biochemical reactions involved in the specific biological process under examination, biological clearance, and so on. Furthermore, the measurement of radioactivity in volumes of interest must take into account the physical half-life of the radionuclide employed for the pharmaceutical labeling. These physiological and physical factors must be fully taken into consideration if quantitative PET is to realize its full potential, and thus allow assessment of the physiological and molecular characteristics of the cells and organs/tissues under examination. Using these approaches, it is possible to quantify a number of processes, including the rate of glucose utilization, receptor binding, receptor occupancy, and so on. The resulting estimates can then be linked to clinical outcomes (e.g., disease evolution, response to treatment, survival) so that disease activity can be assessed and related to the underlying pathological states. Moreover, these quantitative measures can provide surrogate endpoints in therapy trials. The major challenges to quantitative preclinical PET imaging, when the aim is to quantify biological or pharmacokinetic processes, can be categorized in five classes [9, 10]

P-glycoprotein (Pgp, ABCB1) is one of the active efflux pumps that are able to extrude a large variety of chemotherapeutic drugs from the cells, causing the phenomenon of multidrug resistance. It has been shown earlier that the combined application of a class of Pgp modulators (e.g. cyclosporine A and SDZ PSC 833) used at low concentrations and UIC2 antibody is a novel, specific, and effective way of blocking Pgp function (Goda et al., 2007). In the present work we study the UIC2 antibody mediated Pgp inhibition in more detail measuring the accumulation of tumor diagnostic radiotracers, 2-[(18)F]fluoro-2-deoxy-d-glucose ((18)FDG) and [(99m)Tc]hexakis-2-methoxybutyl isonitrile ((99m)Tc-MIBI), into Pgp(+) (A2780AD) and Pgp(-) (A2780) human ovarian carcinoma cells. Co-incubation of cells with UIC2 and cyclosporine A (CSA, 2μM) increased the binding of UIC2 more than 3-fold and reverted the rhodamine 123 (R123), daunorubicin (DNR) and (99m)Tc-MIBI accumulation of the Pgp(+) 2780AD cells to approx. the same level as observed in Pgp(-) cells. Similarly, 50μM paclitaxel (Pacl) increased UIC2 binding, and consequently reinstated the uptake of R123, DNR and (99m)Tc-MIBI into the Pgp(+) cells. Blocking Pgp by combined treatments with CSA+UIC2 or Pacl+UIC2 also decreased the glucose metabolic rate of the A2780AD Pgp(+) cells measured in (18)FDG accumulation experiments suggesting that the maintenance of Pgp activity requires a considerable amount of energy. Similar treatments of the A2780 Pgp(-) cells did not result in significant change in the R123, DNR, (99m)Tc-MIBI and (18)FDG accumulation demonstrating that the above effects are Pgp-specific. Thus, combined treatment with the UIC2 antibody and Pgp modulators can completely block the function of Pgp in human ovarian carcinoma cells and this effect can be followed in vitro by using tumor-diagnostic radiotracers, (99m)Tc-MIBI and (18)FDG.

We review research on the neural efficiency hypothesis of intelligence, stating that brighter individuals display lower (more efficient) brain activation while performing cognitive tasks [Haier, R.J., Siegel, B.V., Nuechterlein, K.H., Hazlett, E., Wu, J.C., Paek, J., Browning, H.L., Buchsbaum, M.S., 1988. Cortical glucose metabolic rate correlates of abstract reasoning and attention studied with positron emission tomography. Intelligence 12, 199-217]. While most early studies confirmed this hypothesis later research has revealed contradictory evidence or has identified some moderating variables like sex, task type, task complexity or brain area. Neuroscientific training studies suggest that neural efficiency also seems to be a function of the amount and quality of learning. From integrating this evidence we conclude that neural efficiency might arise when individuals are confronted with tasks of (subjectively) low to moderate task difficulty and it is mainly observable for frontal brain areas. This is true for easier novel cognitive tasks or after sufficient practice allowing participants to develop appropriate (efficient) strategies to deal with the task. In very complex tasks more able individuals seem to invest more cortical resources resulting in positive correlations between brain usage and cognitive ability. Based on the reviewed evidence we propose future empirical approaches in this field.

Pet with 18F-FDG provides a noninvasive quantitative approach to measuring the glucose utilization rates in various brain regions in vivo (1–3). Quantitative studies in rodents have been improved with the aid of better image resolutions of small-animal PET in recent years (∼1.3-mm full width at half maximum [FWHM] at the center of the field of view) (4). The quantification of cMRglc requires either dynamic imaging with an input function (i.e., using the kinetic model fitting or the Patlak analysis) or static imaging with the input function (i.e., using the operational equations) (5–8). The latter also needs the typical values of 18F-FDG rate constants (K1*,k2*,k3*, and k4*). In mouse studies, the 18F-FDG rate constants of mouse cerebral cortex have not been reported; therefore, the constants estimated from the rat brain have been usually used in the operational equation (9). An input function is required by both of the dynamic and static imaging methods. The blood samples are usually collected manually from the femoral artery of a rodent (10). The total blood volume of a mouse is approximately 2 mL (e.g., ∼7.5% of the body weight of a mouse) (11). Up to 10% (e.g., ∼0.2 mL for an adult mouse) of the total blood volume can be taken from a mouse without altering significantly the physiologic conditions (12). To minimize blood loss and to overcome the procedural difficulty in sampling blood from a mouse during a dynamic small-animal PET scan, a microfluidic blood sampler was developed previously. The amount of blood loss in a quantitative study with this device was less than 5% of the total blood volume in the animal (13). Because of the technical difficulty involved in arterial catheterization for taking blood samples from a mouse, the liver time–activity curve derived from small-animal PET dynamic images is sometimes used as a surrogate input function based on the assumption that the liver is a large blood pool and has relatively low 18F-FDG retention (14,15). Without the need of arterial catheterization, the derivation of the input function from a liver time–activity curve is highly desirable for longitudinal studies. In this study, we performed dynamic 18F-FDG PET studies in 13 mice and, for each study, took blood samples using the microfluidic blood sampler to estimate the mouse cerebral 18F-FDG rate constants K1*−k4*. A noninvasive-image-derived input function from the liver for estimating cMRglc by various quantification methods was also evaluated. The merits and the limitations of various quantification approaches for calculating cMRglc were discussed.

Trivalent chromium (Cr+3) is an essential trace mineral for fish bio-physiological functions. Researches on Cr+3 in the form of organic compound indicated that the mineral affected the bio-activity of insulin, the blood glucose influx, and subsequently the blood glucose metabolic rate. By increasing the blood glucose metabolism, dietary carbohydrate will be more efficiently used as a main energy source, thereby, dietary protein couldbe efficiently retained as for somatic growth. Researches on various feeding habits of fish (e.g. gouramy-herbivorous fish, tilapia-omnivorous fish, and catfish-carnivorous fish) showed that dietary Cr+3 in certain amount increased diet utilization and the fish growth.

This study compared brain glucose metabolism during sevoflurane anaesthesia and propofol anaesthesia using positron emission tomography (PET) in the same eight human volunteers. All the volunteers were anaesthetized twice, with a 1-week interval. Half of the volunteers received sevoflurane on the first occasion and propofol on the second; the other half received the two anaesthetics in the reverse order. PET scans using 18F-fluorodeoxyglucose were performed after sevoflurane or propofol anaesthesia. The relative glucose metabolic rate (rGMR) in the brain was assessed with statistical parametric mapping. Propofol suppressed the rGMR of the neocortex area more than sevoflurane, and sevoflurane suppressed the rGMR of the paleocortex and telencephalon more than propofol. These findings suggest that these two anaesthetics act via different mechanisms and may provide an important clue to the relationship between anaesthesia and the brain.

Objective The authors examined the relationship between impaired insight regarding cognitive and functional deficits and frontal cortex hypometabolism in 41 patients with Alzheimer disease (AD). Methods Regional cerebral glucose metabolism was determined with 18F fluorodeoxyglucose and positron emission tomography. Level of insight was measured with the clinician-rated Neurobehavioral Rating Scale, and severity of global cognitive impairment was determined with the Mini-Mental State Exam. Results Inaccurate insight was correlated with glucose metabolic rate in the right lateral frontal cortex (Brodmann areas 6 and 45, and the lateral aspect of Brodmann areas 8 and 9) after controlling for global cognitive dysfunction. Conclusions The findings from this study help to further elucidate the neurobiological mechanisms underlying impaired insight in AD, indicating a link between this important clinical phenomenon and dysmetabolism in a focal region of the right prefrontal cortex.

The aim of this study was to determine whether the apparent loss of overall gray-white matter contrast (GM/WM) seen on FDG-PET imaging reflects the differential changes of glucose metabolic rate (CMRglc) in cortical gray mater (GM) and subcortical white mater (WM) following TBI. The clinical significance of the CMRglc GM-to-WM ratio was also evaluated. Nineteen normal volunteers and 14 TBI patients were studied. Each subject had a quantitative FDG-PET, a quantitative H215O-PET and a MR scan acutely following TBI. Stabilities of the global and regional FDG lumped constants (LC) were studied. Parametric images (pixel unit: mg/min/100g) of FDG uptake rate (CURFDG) and CMRglc were generated. The changes of CMR(glc) in whole brain, GM and WM were studied separately by using a MRI-segmentation-based technique. The GM-to-WM ratios of both CURFDG and CMRglc images were significantly (p0.001) decreased (31%) in TBI patients. The global LC value reduced significantly (p0.01) in TBI patients. The CMRglc decreased significantly (p0.001) in GM but not in WM (p0.1). Kinetic analysis revealed significant (p0.001) decrease of GM hexokinase activity in TBI patients. The GM-to-WM ratios of CMRglc correlated (r = 0.64) with the initial Glasgow Coma Score (GCS) of TBI patients. The patients with higher CMRglc GM-to-WM ratios (1.54) showed good recovery 12 months after TBI. There was a selective CMRglc reduction in cortical GM following TBI. The pathophysiological basis for the reduction in GM-to-WM CMRglc ratio seen on FDG-PET imaging following TBI remains to be determined.

The purpose of this investigation was to 1) evaluate the relative accuracy of the Sokoloff and Patlak tracer kinetic models in estimating glucose metabolic rate (GMR) in the presence and absence of insulin; 2) evaluate the effect of nutritional state on the lumped constant (LC); and 3) compare the kinetics of 2-fluoro-2-deoxy-d-[14C]glucose (FDG) and 2-deoxy-d-[3H]glucose (DG) membrane transport and phosphorylation. The experimental preparation was the isolated, red blood cell-albumin-perfused rabbit heart. Our results showed that both tracer kinetic models provided GMR estimates that correlated well with the Fick method (for FDG, R = 0.84 and 0.91 for the Sokoloff and Patlak models, respectively); nutritional state did not affect the LC; and FDG and DG have different transport and/or phosphorylation parameters. We also observed that 1) the addition of a fourth compartment to the Sokoloff model reduced the mean squared error between measured and modeled data by a factor of 7.4; 2) a longer time (21.8 min) was required to obtain a linear phase of the Patlak plot than is allowed in clinical studies; and 3) accurate GMR estimates were obtained only by using different LCs reflecting insulin’s presence or absence. Our results indicate potential sources of error in the use of FDG and positron emission tomography to quantify GMR in patients.

We have previously reported the use of simultaneous emission and transmission (SET) scanning in whole body PET and the technique may also be applicable in kinetic studies. However, there are potential sources of bias, particularly at low emission count rates, which may affect the accuracy of parameter estimates. We investigated these potential sources of bias and their effect on parameter estimation in oncological PET studies. The sources of bias considered include: (i) variation in transmission spillover (into the emission window) throughout the field of view, (ii) increased scatter arising from the rod sources, and (iii) inaccurate dead time correction. Net bias was calculated as a function of emission count rate and used to predict distortion in FDG tissue curves simulating normal and metastatic liver. The distortion was characterised by spectral analysis and the effect on parameter estimates was assessed by compartmental modelling. Variation in spillover was found to be a negligible source of bias in SET measurements. Scatter and dead time errors work in opposing directions and approximately cancel during the early part of the study when count rate is maximal. The resulting distortion causes apparently decreased tracer clearance, particularly in tumours, which mainly affects estimates of k/sub 4/ and volume of distribution. Estimates of K/sub 1/-k/sub 3/ were relatively unaffected, while bias in glucose metabolic rate was +8% and +2% for normal liver and tumour respectively.

We investigated the effect of whole-body exposure to 915-MHz radiofrequency identification (RFID) on rat cortical glucose metabolism by using (18)F-deoxyglucose positron emission tomography (FDG-PET).Male Sprague-Dawley rats were divided into three groups: Cage-control, sham-exposed and RFID-exposed groups. Rats were exposed to the 915-MHz RFID for 8 h daily, 5 days per week, for 2 or 16 weeks. The whole-body average specific absorption rate (SAR) was 4 W/kg for the field of the 915 MHz RFID signal. FDG-PET images were obtained the day after RFID exposure, using micro-PET with a FDG tracer. With a Xeleris functional imaging workstation, absolute values in regions of interest (ROI) in the frontal, temporal and parietal cortexes and cerebellum were measured. Cortical ROI values were normalized to the cerebellar value and compared.The data showed that the relative cerebral glucose metabolic rate was unchanged in the frontal, temporal and parietal cortexes of the 915 MHz RFID-exposed rats, compared with rats in cage-control and sham-exposed groups.Our results suggest that 915 MHz RFID radiation exposure did not cause a significant long lasting effect on glucose metabolism in the rat brain.

Positron emission tomography of cerebral glucose metabolism in adult human subjects was used to investigate amygdaloid complex (AC) activity associated with the storage of long-term memory for emotionally arousing events. Subjects viewed two videos (one in each of two separate positron emission tomography sessions, separated by 3-7 days) consisting either of 12 emotionally arousing film clips ("E" film session) or of 12 relatively emotionally neutral film clips ("N" film session), and rated their emotional reaction to each film clip immediately after viewing it. Three weeks after the second session, memory for the videos was assessed in a free recall test. As expected, the subjects' average emotional reaction to the E films was higher than that for the N films. In addition, the subjects recalled significantly more E films than N films. Glucose metabolic rate of the right AC while viewing the E films was highly correlated with the number of E films recalled. AC activity was not significantly correlated with the number of N films recalled. The findings support the view derived from both animal and human investigations that the AC is selectively involved with the formation of enhanced long-term memory associated with emotionally arousing events.

Brain size and cerebral glucose metabolic rate (GMR) were determined with magnetic resonance imaging (MRI) and positron emission tomography (PET) in individuals with mild mental retardation (MR), individuals with Down syndrome (DS) without dementia and in matched controls. The MRI data showed that the MR and the DS groups both had brain volumes of about 80% of controls; variance was greatest within the MR group. PET was obtained with [18F]-fluorodeoxyglucose (FDG) as the tracer during a test of attention (Continuous Performance Test; CPT). Whole brain cortex GMR was higher than the controls in both the MR and the DS groups. For all subjects combined, the correlation between brain size and IQ was .65 (p

Positorn emission tomgraphy (PET) has been used and studied in patients with various kinds of neoplasms in a few decades. We have studied PET using Fluorine-18-fluorodeoxyglucose (FDG) in malignant lymphoma. and some findings have been dis-coverd. FDG uptake of lymphoma closely revealed the glucose metabolic rate. The uptake was higher than normal soft tissue. Especially, high-grade or aggressive lymphoma likely showed higher FDG uptake. FDG-PET may be useful for tumor-seeking, grading and predicting the prognosis in lymphoma.