Automated analysis of FDG PET as a tool for single-subject probabilistic prediction and detection of Alzheimer's disease dementia.

PURPOSE: To introduce, evaluate and validate a voxel-based analysis method of ¹8F-FDG PET imaging for determining the probability of Alzheimer's disease (AD) in a particular individual. METHODS: The subject groups for model derivation comprised 80 healthy subjects (HS), 36 patients with mild cognitive impairment (MCI) who converted to AD dementia within 18 months, 85 non-converter MCI patients who did not convert within 24 months, and 67 AD dementia patients with baseline FDG PET scan were recruited from the AD Neuroimaging Initiative (ADNI) database. Additionally, baseline FDG PET scans from 20 HS, 27 MCI and 21 AD dementia patients from our institutional cohort were included for model validation. The analysis technique was designed on the basis of the AD-related hypometabolic convergence index adapted for our laboratory-specific context (AD-PET index), and combined in a multivariable model with age and gender for AD dementia detection (AD score). A logistic regression analysis of different cortical PET indexes and clinical variables was applied to search for relevant predictive factors to include in the multivariable model for the prediction of MCI conversion to AD dementia (AD-Conv score). The resultant scores were stratified into sixtiles for probabilistic diagnosis. RESULTS: The area under the receiver operating characteristic curve (AUC) for the AD score detecting AD dementia in the ADNI database was 0.879, and the observed probability of AD dementia in the six defined groups ranged from 8% to 100% in a monotonic trend. For predicting MCI conversion to AD dementia, only the posterior cingulate index, Mini-Mental State Examination (MMSE) score and apolipoprotein E4 genotype (ApoE4) exhibited significant independent effects in the univariable and multivariable models. When only the latter two clinical variables were included in the model, the AUC was 0.742 (95% CI 0.646 - 0.838), but this increased to 0.804 (95% CI 0.714 - 0.894, bootstrap p=0.027) with the addition of the posterior cingulate index (AD-Conv score). Baseline clinical diagnosis of MCI showed 29.7% of converters after 18 months. The observed probability of conversion in relation to baseline AD-Conv score was 75% in the high probability group (sixtile 6), 34% in the medium probability group (merged sixtiles 4 and 5), 20% in the low probability group (sixtile 3) and 7.5% in the very low probability group (merged sixtiles 1 and 2). In the validation population, the AD score reached an AUC of 0.948 (95% CI 0.625 - 0.969) and the AD-Conv score reached 0.968 (95% CI 0.908 - 1.000), with AD patients and MCI converters included in the highest probability categories. CONCLUSION: Posterior cingulate hypometabolism, when combined in a multivariable model with age and gender as well as MMSE score and ApoE4 data, improved the determination of the likelihood of patients with MCI converting to AD dementia compared with clinical variables alone. The probabilistic model described here provides a new tool that may aid in the clinical diagnosis of AD and MCI conversion.

The nigrostriatal system in the presymptomatic and symptomatic stages in the MPTP monkey model: a PET, histological and biochemical study.

Parkinson's disease (PD) is diagnosed when striatal dopamine (DA) loss exceeds a certain threshold and the cardinal motor features become apparent. The presymptomatic compensatory mechanisms underlying the lack of motor manifestations despite progressive striatal depletion are not well understood. Most animal models of PD involve the induction of a severe dopaminergic deficit in an acute manner, which departs from the typical, chronic evolution of PD in humans. We have used 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administered to monkeys via a slow intoxication protocol to produce a more gradual development of nigral lesion. Twelve control and 38 MPTP-intoxicated monkeys were divided into four groups. The latter included monkeys who were always asymptomatic, monkeys who recovered after showing mild parkinsonian signs, and monkeys with stable, moderate and severe parkinsonism. We found a close correlation between cell loss in the substantia nigra pars compacta (SNc) and striatal dopaminergic depletion and the four motor states. There was an overall negative correlation between the degree of parkinsonism (Kurlan scale) and in vivo PET ((18)F-DOPA K(i) and (11)C-DTBZ binding potential), as well as with TH-immunoreactive cell counts in SNc, striatal dopaminergic markers (TH, DAT and VMAT2) and striatal DA concentration. This intoxication protocol permits to establish a critical threshold of SNc cell loss and dopaminergic innervation distinguishing between the asymptomatic and symptomatic parkinsonian stages. Compensatory changes in nigrostriatal dopaminergic activity occurred in the recovered and parkinsonian monkeys when DA depletion was at least 88% of control, and accordingly may be considered too late to explain compensatory mechanisms in the early asymptomatic period. Our findings suggest the need for further exploration of the role of non-striatal mechanisms in PD prior to the development of motor features.

Quantitative volumetric analysis of gliomas with sequential MRI and ¹¹C-methionine PET assessment: patterns of integration in therapy planning.

PURPOSE: The aim of the study was to evaluate the volumetric integration patterns of standard MRI and (11)C-methionine positron emission tomography (PET) images in the surgery planning of gliomas and their relationship to the histological grade. METHODS: We studied 23 patients with suspected or previously treated glioma who underwent preoperative (11)C-methionine PET because MRI was imprecise in defining the surgical target contour. Images were transferred to the treatment planning system, coregistered and fused (BrainLAB). Tumour delineation was performed by (11)C-methionine PET thresholding (vPET) and manual segmentation over MRI (vMRI). A 3-D volumetric study was conducted to evaluate the contribution of each modality to tumour target volume. All cases were surgically treated and histological classification was performed according to WHO grades. Additionally, several biopsy samples were taken according to the results derived either from PET or from MRI and analysed separately. RESULTS: Fifteen patients had high-grade tumours [ten glioblastoma multiforme (GBM) and five anaplastic), whereas eight patients had low-grade tumours. Biopsies from areas with high (11)C-methionine uptake without correspondence in MRI showed tumour proliferation, including infiltrative zones, distinguishing them from dysplasia and radionecrosis. Two main PET/MRI integration patterns emerged after analysis of volumetric data: pattern vMRI-in-vPET (11/23) and pattern vPET-in-vMRI (9/23). Besides, a possible third pattern with differences in both directions (vMRI-diff-vPET) could also be observed (3/23). There was a statistically significant association between the tumour classification and integration patterns described above (p < 0.001, κ = 0.72). GBM was associated with pattern vMRI-in-vPET (9/10), low-grade with pattern vPET-in-vMRI (7/8) and anaplastic with pattern vMRI-diff-vPET (3/5). CONCLUSION: The metabolically active tumour volume observed in (11)C-methionine PET differs from the volume of MRI by showing areas of infiltrative tumour and distinguishing from non-tumour lesions. Differences in (11)C-methionine PET/MRI integration patterns can be assigned to tumour grades according to the WHO classification. This finding may improve tumour delineation and therapy planning for gliomas.

Preparation, radiolabeling with 99mTc and 67Ga and biodistribution studies of albumin nanoparticles covered with polymers. / Preparación, radiomarcaje con 99mTc y 67Ga y estudios de biodistribución de nanopartículas de albúmina con recubrimientos poliméricos.

OBJECTIVE: To optimize radiolabeling with 99mTc and 67Ga of albumin nanoparticles coated with 4 differents synthetic polymers and to evaluate their stability in vivo and in vitro, as well as their biodistribution in vivo after intravenous administration. MATERIAL AND METHODS: The nanoparticles were prepared using albumin and NOTA-modified albumin by the desolvation method and coated with 4 different polymers; HPMC, GMN2, GPM2 and GTM2. They were purified, lyophilized and characterized. Radiolabelling with 99mTc was perfomed with 74 MBq of 99mTc sodium pertechnetate, previously reduced with and acid solution of tin chloride at different concentrations (0.003, 0.005, 0.007, 0.01, 0.05 and 0.1mg/ml) and at different times (5, 10, 15, 30 and 60minutes) and temperatures (room temperature, 40°C and 60°C). Radiolabelling with 67Ga was perfomed by incubation of the nanoparticles with 37 MBq of 67Gallium chloride (obtained from commercial gallium-67 citrate) at different times (10 and 30minutes) and temperatures (room temperature, 30°C and 60°C), and posterior purification with microconcentrators. The radiochemical purity was evaluated by TLC. Stability studies of radiolabeled nanoparticles in physiological serum and blood plasma were perfomed. Biodistribution studies of nanoparticles coated with GPM2 polymer were carried out in Wistar rats after intravenous administration of the nanoparticles. Control animals were carried out with 99mTc sodium pertechnetate and 67Ga chloride. To do so, the animals were killed and activity in organs was measured in a gamma counter. RESULTS: 99mTc labeling was carried out optimally with a tin concentration of 0.007mg/ ml for the GPM2 nanoparticles and 0.005mg / ml for the rest of the formulations, with a radiolabelling time of 10minutes at room temperature. In the case of 67Ga the label was optimized at 30° C temperature and 30minutes of incubation. In both cases the radiochemical purity obtained was greater than 97%. The nanoparticles showed high stability in vitro after 48hours of labeling (70% nanoparticles labeled with 99mTc and 90% those labeled with 67Ga). Biodistribution studies of nanoparticles 99mTc -GPM2 and 67Ga -NOTA-GPM2 showed a high accumulation of activity in the liver at 2 and 24hours after intravenous administration. CONCLUSION: The labeling procedure with 99mTc and 67Ga of albumin and albumin modified with NOTA nanoparticles allows obtaining nanoparticles with high labeling yields and adequate in vitro stability, allowing their use for in vivo studies.

PET imaging of thymidine kinase gene expression in the liver of non-human primates following systemic delivery of an adenoviral vector.

Non-invasive in vivo imaging of transgene expression is currently providing very important means to optimize gene therapy regimes. Results in non-human primates are considered the most predictive models for the outcome in patients. In this study, we have documented that tumour and primary cell lines from human and non-human primates are comparably gene-transduced in vitro by serotype 5 adenovirus expressing HSV1-thymidine kinase. Transgene expression can be quantified in human and monkey cultured cells by positron emission tomography (PET) imaging when transduced cells are incubated with a fluoride-18 labelled penciclovir analogue. In our hands, PET images of cell cultures estimate the number of transduced cells rather than intensity of transgene expression once a threshold of TK per cell is reached. Interestingly, in vivo systemic administration of a clinical grade recombinant adenovirus expressing TK into macaques gives rise to an intense retention of the radiotracer in the liver parenchyma, providing an experimental system to visualize transgene expression that ought to be similar in human and macaques. Such imaging methodology might contribute to improve strategies based on adenoviral vectors.

New MRI, 18F-DOPA and 11C-(+)-alpha-dihydrotetrabenazine templates for Macaca fascicularis neuroimaging: advantages to improve PET quantification.

Normalization of neuroimaging studies to a stereotaxic space allows the utilization of standard volumes of interest (VOIs) and voxel-based analysis (SPM). Such spatial normalization of PET and MRI studies requires a high quality template image. The aim of this study was to create new MRI and PET templates of (18)F-DOPA and (11)C-(+)-alpha-dihydrotetrabenazine ((11)C-DTBZ) of the Macaca fascicularis brain, an important animal model of Parkinson's disease. MRI template was constructed as a smoothed average of the scans of 15 healthy animals, previously transformed into the space of one representative MRI. In order to create the PET templates, (18)F-DOPA and (11)C-DTBZ PET of the same subjects were acquired in a dedicated small animal PET scanner and transformed to the created MRI template space. To validate these templates for PET quantification, parametric values obtained with a standard VOI-map applied after spatial normalization to each template were statistically compared to results computed using individual VOIs drawn for each animal. The high correlation between both procedures validated the utilization of all the templates, improving the reproducibility of PET analysis. To prove the utility of the templates for voxel-based quantification, dopamine striatal depletion in a representative monkey treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was assessed by SPM analysis of (11)C-DTBZ PET. A symmetric reduction in striatal (11)C-DTBZ uptake was detected in accordance with the induced lesion. In conclusion, templates of M. fascicularis brain have been constructed and validated for reproducible and automated PET quantification. All templates are electronically available via the internet.

High prevalence of asthma and allergic diseases in children aged 6 to [corrected] 7 years from the Canary Islands. [corrected].

OBJECTIVE: To investigate the prevalence of bronchial asthma and allergic diseases in schoolchildren from the Canary Islands, Spain. METHODS: Cross-sectional study following the methodology of ISAAC (International Study of Asthma and Allergies in Childhood), which uses standardized and validated questionnaires. The study participants were children aged between 6 and 7 years attending schools in Las Palmas de Gran Canaria, Canary Islands, Spain. RESULTS: Of the 3108 questionnaires distributed, 1883 were answered, and 1871 were evaluable (60.6%). Gender distribution was similar (51.8% boys vs 48.2% girls). Current prevalence of asthma was 18.4% (95% confidence interval [CI], 16.7-20.2), rhinitis 40.3% (95% CI, 38-42.3), and atopic dermatitis 35.8% (95% CI, 33.6-37.9). The highest prevalence of rhinitis was recorded during the autumn months (P<.005). Asthma was more frequent in boys than in girls (P<.05), but there were no statistical differences for the other allergic diseases. CONCLUSIONS: The prevalence of asthma and allergic diseases in children aged 6-7 years in the Canary Islands is higher than in other areas of Spain where the ISAAC study has been performed. Male gender is an important risk factor in children, especially for asthma symptoms.

Preclinical safety of topically administered nanostructured lipid carriers (NLC) for wound healing application: biodistribution and toxicity studies.

Re-activation of the healing process is a major challenge in the field of chronic wound treatment. For that purpose, lipid-nanoparticles, especially nanostructured lipid carriers (NLC), possess extremely useful characteristics such as biodegradability, biocompatibility and long-term stability, besides being suitable for drug delivery. Moreover, they maintain wound moisture due to their occlusive properties, which have been associated with increased healing rates. In the light of above, NLC have been extensively used topically for wound healing; but to date, there are no safety-preclinical studies concerning such type of application. Thus, in this work, biodistribution studies were performed in rats with the NLC previously developed by our research group, using technetium-99 m (99mTc-NLC) as radiomarker, topically administered on a wound. 99mTc-NLC remained on the wound for 24 h and systemic absorption was not observed after administration. In addition, toxicological studies were performed to assess NLC safety after topical administration. The results obtained demonstrated that NLC were non-cytotoxic, non-sensitizing and non-irritant/corrosive. Overall, it might be concluded that developed NLC remained at the administration area, potentially exerting a local effect, and were safe after topical administration on wounds.

[Quick and simple synthesis of (11)C-(+)-alpha-dihydrotetrabenazine to be used as a PET radioligand of vesicular monoamine transporters]. / Síntesis rápida y simplificada de C-(+)-alpha-dihidrotetrabenazina para su utilización como radioligando PET de los transportadores vesiculares de monoaminas.

UNLABELLED: Dihydrotetrabenazine (2-hydroxy-3-isobutyl-9,10-dimethoxy-1,3,4,6,7-hexahydro-11bH-benzo[a]-quinolizine, DTBZ) has become the ideal radioligand for the presynaptic vesicular monoamine transporter VMAT2 based on its high binding affinity and optimal lipophilicity. OBJECTIVE: To develop an automatic procedure for labelling DTBZ with carbon-11, which has been shown to be a highly effective marker for in vivo studies of neuronal losses in animal models with Parkinson's disease using positron emission tomography (PET). MATERIALS AND METHODS: We have developed a new fully automated synthesis procedure to obtain 11C-(+)DTBZ quickly and simply through labelling the precursor -(+)desmethyldihy-drotetrabenazine- at room temperature in the presence of dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH), using 11CH3I as primary precursor. The final purification was carried out by solid phase extraction using commercially available cartridges and the residual solvents (DMSO and ethyl ether) were eliminated by evaporation. RESULTS: The whole procedure was automated, and after 54 syntheses, an average production of 1.94 GBq of sterile, pyrogen-free 11C-(+)DTBZ with a radiochemical purity > 99 % was obtained with 5 minutes irradiation and 6 minutes of synthesis after 11CH3I production. 11C-(+)DTBZ binding to presynaptic dopamine nerve terminals has been demonstrated by MicroPET studies in Wistar rats and M. Fascicularis monkeys. CONCLUSIONS: This new synthesis procedure is quick and simple, due to optimised techniques, which have allowed elimination of residual solvents based on their polarity for the final purification. It is also applicable to other automatic syntheses for obtaining compounds labelled by methylation reactions.

[Use of 11C-(+)-alpha -dihydrotetrabenazine for the assessment of dopaminergic innervation in animal models of Parkinson's disease]. / Utilización de la 11C-(+)-alpha -dihidrotetrabenazina para la evaluación de la inervación dopaminérgica en modelos animales de la enfermedad de Parkinson.

AIM: This study evaluates the utility of (11)C-(+)-alpha -dihydrotetrabenazine ((11)C-(+)DTBZ) in the quantification of dopaminergic innervation by positron emission tomography (PET) in rat and monkey, two animal species used as animal models of Parkinson's disease. MATERIAL AND METHODS: Healthy control animals (n = 10) and the effect of 6-hydroxidopamine (6-OHDA) neurotoxic were studied in rats. (18)F-DOPA PET studies and digital quantitative autoradiography were also carried out. Studies with Macaca fascicularis were performed in control and 1-methyl 4-phenyl 1, 2, 3, 6-tetrahydropyridine (MPTP) treated animals. RESULTS: In both species high quality images were generated in which clear uptake of (11)C-(+)DTBZ was found in the striatum. (11)C-(+)DTBZ uptake quantification was estimated by creating parametric images and binding potential (BP) calculation. BP in control rats was 1.10 +/- 0.16 (mean +/- standard deviation [SD], whereas 6-OHDA produced a decrease in the uptake depending on the lesion degree. Images obtained with (18)F-DOPA were not adequate for the analysis as they did not discriminate the stratum whereas digital quantitative autoradiography studies confirmed the high affinity of striatum by (11)C-(+)DTBZ. In monkeys, final BP values were 1.31 and 1.06 and MPTP treatment reduced uptake by 40 %. CONCLUSIONS: The quality of PET images and the decrease of uptake in 6-OHDA and MPTP lesions show that (11)C-(+)DTBZ is an adequate radiotracer for the study of dopaminergic innervation in these animal models.

18F-FDG metabolism in a rat model of chronic infarction: a 17-sector semiquantitative analysis.

UNLABELLED: Strategies to establish the functional benefit of cell therapy in cardiac regeneration and the potential mechanism are needed. AIMS: Development of a semi-quantitative method for non invasive assessment of cardiac viability and function in a rat model of myocardial infarction (MI) based on the use of microPET. ANIMALS, METHODS: Ten rats were subjected to myocardial imaging 2, 7, 14, 30, 60 and 90 days after left coronary artery ligation. Intravenous 18F-fluoro-2-deoxy-2-D-glucose (18F-FDG) was administered and regional 18F activity concentrations per unit area were measured in 17 regions of interest (ROIs) drawn on cardiac polar maps. By comparing the differences in 18F uptake between baseline and each of the follow up time points, parametric polar maps of statistical significance (PPMSS) were calculated. Left ventricular ejection fraction (LVEF) was blindly assessed echocardiographically. All animals were sacrificed for histopathological analysis after 90 days. RESULTS: The diagnostic quality of 18F-FDG microPET images was excellent. PPMSS demonstrated a statistically significant decrease in 18F concentrations as early as 48 hours after MI in 4 of the 17 ROIs (segments 7, 13, 16 and 17; p < 0.05) that persisted throughout the study. Semiquantitative analysis of 18F-FDG uptake correlated with echocardiographic decrease in LVEF (p < 0.001). CONCLUSION: The use of PPMSS based on 18F-FDG-microPET provides valuable semi-quantitative information of heart glucose metabolism allowing for non-invasive follow up thus representing a useful strategy for assessment of novel therapies in cardiac regeneration.

Position statement on radiopharmaceutical production for clinical trials.

The EU regulation 536/2014 aims to facilitate the experimental use of diagnostic radiopharmaceuticals in particular for GMP requirements and needs to be applied in EU countries. As definitely clarified by this survey, the application is still far from being completed due to national restrictions that are conflicting with the content of the above EU regulation. Although the nuclear medicine centers are obliged to be compliant with national regulatory, national authorities have to be required to work towards full application of the regulation. On the other hand, an update of 536/2014 that includes therapeutic radiopharmaceuticals would also be beneficial to a rational and safe advance of nuclear medicine.

Study of the neutron field in the vicinity of an unshielded PET cyclotron.

The neutron field in the proximity of an unshielded PET cyclotron was investigated during 18F radioisotope production with an 18 MeV proton beam. Thermoluminescent detector (TLD) models TLD600 and TLD700 as well as Bonner moderating spheres were irradiated at different positions inside the vault room where the cyclotron is located to determine the thermal neutron flux, neutron spectrum and dose equivalent. Furthermore, from a combination of measurements and Monte Carlo simulations the neutron source intensity at the target was estimated. The resulting intensity is in good agreement with the IAEA recommendations. Neutron doses derived from the measured spectra were found to vary between 7 and 320 mSv per 1 microA h of proton-integrated current. Finally, gamma doses were determined from TLD700 readings and amounted to around 10% of the neutron doses.

Radiation dosimetry and biodistribution in non-human primates of the sodium/iodide PET ligand [(18)F]-tetrafluoroborate.

BACKGROUND: [(18)F]-tetrafluoroborate is a PET radiotracer taken up by the sodium/iodide symporter (NIS). Albeit the in vivo behavior in rodents is similar to the (99m)Tc-pertechnetate, no studies exist in primates or in humans. The aims of this study were to evaluate the biodistribution of [(18)F]-tetrafluoroborate in non-human primates with PET and to estimate the absorbed dose in organs. METHODS: Whole-body PET imaging was done in a Siemens ECAT HR+ scanner in two male Macaca fascicularis monkeys. After an i.v. injection of 24.93 ± 0.05 MBq/kg of [(18)F]-tetrafluoroborate, prepared by isotopic exchange of sodium tetrafluoroborate with [(18)F]-fluoride under acidic conditions, eight sequential images from the head to the thigh (five beds) were collected for a total duration of 132 min. The whole-body emission scan was reconstructed applying attenuation and scatter corrections. After image reconstruction, three-dimensional volumes of interest (VOIs) were hand-drawn on the PET transaxial or coronal slices of the frame where the organ was most conspicuous. Time-activity curves for each VOI were obtained, and the organ residence times were calculated by integration of the time-activity curves. Human absorbed doses were estimated using the OLINDA/EXM software and the standard human model. RESULTS: [(18)F]-tetrafluoroborate was able to discriminate clearly the thyroid gland with an excellent signal-to-noise ratio. Most of the radiotracers (residence time) are localised in the organs that express NIS (stomach wall, salivary glands, thyroid, olfactory mucosa), are involved in excretion (kidneys and bladder), or reflect the vascular phase (heart and lungs). Considering the OLINDA source organs, the critical organs were the stomach wall, thyroid and bladder wall, with absorbed doses lower than 0.078 mGy/MBq. The effective dose was 0.025 mSv/MBq. CONCLUSIONS: [(18)F]-tetrafluoroborate is a very useful radiotracer for PET thyroid imaging in primates, with a characteristic biodistribution in organs expressing NIS. It delivers an effective dose slightly higher than the dose produced by (99m)Tc-pertechnetate but much lower than that produced by radioiodine in the form of (131)INa, (123)INa, or (124)INa.

Three-dimensional clinical PET in lung cancer: validation and practical strategies.

UNLABELLED: The feasibility of 3-dimensional acquisition mode for semiquantitative analysis in thoracic PET studies was compared to the conventional 2-dimensional mode. Several practical considerations were analyzed to propose an optimized scanning protocol for clinical use. METHODS: Twenty-one patients with focal thoracic abnormalities were evaluated with FDG PET. The acquisition consisted of 3 consecutive static scans for a single bed position: 3-dimensional (10 min), 2-dimensional (15 min), and 3-dimensional (5 min). On the basis of the average and maximum activity values per region of interest, standardized uptake value (SUV) normalized for total body weight (TBW), lean body mass (LBM), body surface area (BSA), and blood glucose level (PGL) were evaluated. The effect of the delay between tracer injection and PET scanning on the SUV, as well as on the relative error of the activity distribution, was studied from 40-134 min after tracer injection. RESULTS: A strong positive correlation was observed among SUVs from 2-dimensional and both 3-dimensional acquisitions. The mean SUV percentage differences between both acquisition modes were about 17%, differences that were not statistically significant when time postinjection was addressed in the analysis of covariance. SUVs provided the greatest variability and differences among studies on experimental periods up to 70 min postinjection. Indeed, the variability of 20% observed on the SUVs from 2 PET scans 13 min apart was reduced to 9% when the acquisitions started at least 70 min after tracer injection. In addition, a two-fold reduction in the relative error of the activity distribution was observed over this period of time. The reproducibility coefficient was increased from 0.87 to 0.95 before and after 70 min postinjection, respectively. No correlation was found between different normalization procedures of SUV and LBM, BSA, TBW, or height, whereas a weak correlation was found between SUV and PGL. CONCLUSION: 18F-FDG 3-dimensional PET is a realistic alternative to the gold standard 2-dimensional for clinical nonkinetic studies. A short, 5-min 3-dimensional acquisition at 70 min postinjection is proposed as the best protocol for the clinical evaluation of thoracic pathologies.

cAMP activates transcription of the human glucocorticoid receptor gene promoter.

Glucocorticoids and cAMP regulate, either in a synergistic or additive fashion, the transcription of multiple genes, although some antagonistic effects of dexamethasone on cAMP-activated transcription have been described. The increased glucocorticoid receptor (GR) mediated response of some cell types, as a result of augmented cAMP, has been considered to be mainly due to an increased stability of GR mRNA, although other plausible explanations should not be ruled out. We studied the possibility that GR transcription itself could be affected by cAMP levels. HeLa cells were transfected with human GR (hGR) promoter constructs and their transcriptional activity determined after inducing a cAMP increase with forskolin. We found that forskolin almost doubled the transcriptional activity of the promoter construct spanning -2995 to +38 of the hGR, whereas no significant variations were observed with shorter chimeras containing sequences downstream -979. Shift mobility showed binding of CREB in vitro to a putative cAMP responsive element located at -1000, suggesting that hGR may be upregulated by cAMP at the transcriptional level, thus adding a new mechanism ascribable to this second messenger, which in conjunction with the cAMP-induced GR mRNA increased stability, would lead to a more precise control of the amount of GR protein within the cell.

[Use of a cyclotron in the production of positron emitting radionuclides]. / Utilización de un ciclotrón para la producción de radionucleidos emisores de positrones.

The experience acquired by our center during the first two years of using cyclotron 18/9 (IBA) dedicated to the production of clinical positron emission radionuclides is described. The cyclotron performance characteristics, production yields, quality control and synthesized radiotracers are analyzed. Cyclotron makes it possible to produce up to 3,300 mCi of 18F-, 270 mCi of 18F2, 3,100 mCi of 11C, 502 mCi of 13N (in 120, 60, 35 and 20 minutes respectively) and 540 mCi/min of 15O. In our center, about 85% of the PET studies are performed with 18F-FDG, whereas the remaining are done with 15O-water, 11C-bicarbonate, 11C-methionine, 13N-ammonia or 18F-. Cyclotron is included in the Radiopharmacy Unit of our PET facility and is subjected to a global quality control program. Follow-up of the bombardment parameters and periodic verifications of the cyclotron performance have made it possible to prevent equipment functioning problems, increase mean time between stoppage and decrease downtime. We conclude that cyclotron has high production capabilities and allows enough flexibility for a clinical and research positron emission tomography center; furthermore, it can also be used for regional distribution of 18F-FDG to satellite PET centers.

[Positron emission tomography with F-18-FDG: a new tool in the evaluation of patients with head and neck tumors]. / Tomografía de emisión de positrones con F-18-FDG: una nueva técnica en la evaluación de pacientes con neoplasias de cabeza y cuello.

INTRODUCTION: Positron emission tomography using fluoro-deoxyglucose (PET-FDG) imaging has been shown to be effective in detecting and staging malignancies based on tumor glucose metabolism. The aim of the study was to evaluate the use of PET-FDG for the detection of metastatic lesions as well as early recurrence in patients with head and neck tumors. MATERIAL AND METHODS: Eleven patients were examined with PET-FDG to study the reliability of PET in assessing regional nodal status and in identifying distant metastasis (group I) and 37 patients who had previously received curative treatment and who presented differential diagnostic problems were imaged to differentiate between scar and residual or recurrent cancer (group II). PET-FDG studies were compared to results of computed tomography (CT) in 35 patients, magnetic resonance imaging (MRI) in 4 patients and both techniques in 6 patients. RESULTS: All PET-FDG studies were positive in group I, while CT failed to detect metastatic lesions in three patients. In group II PET-FDG accurately detected recurrent disease in 22/25 patients, while CT/MRI were negative in 4 cases and equivocal in 6 cases. However, there was a false positive PET study with equivocal CT in a patient with local infection. CONCLUSION: PET-FDG was highly effective in detecting metastatic cervical lymph nodes in head and neck tumours. It was most helpful in differentiating residual or recurrent tumour from scar sequelae and it enhanced the diagnostic accuracy when CT and MRI were equivocal due to anatomical distortions.