The value of combined MRI, enhanced CT and 18F-FDG PET/CT in the diagnosis of recurrence and metastasis after surgery for ovarian cancer.

OBJECTIVE: The purpose of this article was to investigate the value of combined MRI, enhanced CT and 18F-FDG PET/CT in the diagnosis of recurrence and metastasis after surgery for ovarian cancer. METHODS: Ninety-five ovarian cancer patients were selected as the study subjects, all of them underwent surgical treatment, and MRI, enhanced CT and 18F-FDG PET/CT were performed on all of them in the postoperative follow-up, and the pathological results after the second operation were used as the diagnostic "gold standard". The diagnostic value (sensitivity, specificity, accuracy, negative predictive value and positive predictive value) of the three examination methods alone or in combination for the diagnosis of postoperative recurrence and metastasis of ovarian cancer was compared, and the detection rate was calculated when the lesion was the unit of study, so as to compare the efficacy of the three methods in the diagnosis of postoperative recurrent metastatic lesions of ovarian cancer. RESULTS: The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of the combined group were higher than those of MRI and enhanced CT for recurrence and metastasis of ovarian cancer after surgery, and the specificity, accuracy and positive predictive value of the combined group were higher than those of the 18F-FDG PET/CT group, and those of the 18F-FDG PET/CT group were higher than those of the enhanced CT group (all P < 0.05). When the postoperative recurrent metastatic lesions of ovarian cancer were used as the study unit, the detection rate of lesions in the combined group was higher than that of the three examinations detected individually, and the detection rate of lesions in 18F-FDG PET/CT was higher than that of enhanced CT and MRI (P < 0.05). CONCLUSION: The combination of MRI, enhanced CT and 18F-FDG PET/CT can accurately diagnose recurrence and metastasis of ovarian cancer after surgery, detect recurrent metastatic lesions as early as possible, and improve patients' prognosis.

PCA and logistic regression in 2-[18F]FDG PET neuroimaging as an interpretable and diagnostic tool for Alzheimer's disease.

Objective.to develop an optimization and training pipeline for a classification model based on principal component analysis and logistic regression using neuroimages from PET with 2-[18F]fluoro-2-deoxy-D-glucose (FDG PET) for the diagnosis of Alzheimer's disease (AD).Approach.as training data, 200 FDG PET neuroimages were used, 100 from the group of patients with AD and 100 from the group of cognitively normal subjects (CN), downloaded from the repository of the Alzheimer's Disease Neuroimaging Initiative (ADNI). Regularization methods L1 and L2 were tested and their respective strength varied by the hyperparameter C. Once the best combination of hyperparameters was determined, it was used to train the final classification model, which was then applied to test data, consisting of 192 FDG PET neuroimages, 100 from subjects with no evidence of AD (nAD) and 92 from the AD group, obtained at the Centro de Diagnóstico por Imagem (CDI).Main results.the best combination of hyperparameters was L1 regularization andC≈ 0.316. The final results on test data were accuracy = 88.54%, recall = 90.22%, precision = 86.46% and AUC = 94.75%, indicating that there was a good generalization to neuroimages outside the training set. Adjusting each principal component by its respective weight, an interpretable image was obtained that represents the regions of greater or lesser probability for AD given high voxel intensities. The resulting image matches what is expected by the pathophysiology of AD.Significance.our classification model was trained on publicly available and robust data and tested, with good results, on clinical routine data. Our study shows that it serves as a powerful and interpretable tool capable of assisting in the diagnosis of AD in the possession of FDG PET neuroimages. The relationship between classification model output scores and AD progression can and should be explored in future studies.

Impact of 18F-FDG PET/CT in the management decisions of breast cancer board on early-stage breast cancer.

PURPOSE: Breast cancer is the most common malignancy accounting for 11.7% of all cancer cases, with a rising incidence rate. Various diagnostic methods, including 18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT), play a crucial role in breast cancer diagnosis and staging. However, the unnecessary use of advanced imaging techniques such as PET/CT in early-stage breast cancer can have negative effects on both economics and patients. We aimed to investigate the impact of PET/CT on the management decisions of early-stage breast cancer patients by the breast cancer tumor board. METHODS: A retrospective analysis was performed on a cohort of 81 patients with early-stage breast cancer who were evaluated by breast cancer tumor board from January 2015 to December 2020. Demographic, clinical, and radiographic data, along with surgical procedures and treatment options, were documented and analyzed. RESULTS: The results showed that 18F-FDG PET/CT had a moderate impact on treatment decisions of breast cancer tumor board, as only treatment decisions were changed in 14,86% of the patients. The surgical procedure decision of breast cancer tumor board changed in 12.35% of patients, while 87.65% of patients had consistent decisions before and after PET/CT. Pathological assessments revealed invasive ductal carcinoma as the most prevalent tumor type, and molecular subtypes were predominantly luminal B. PET/CT use had limited impact on surgical procedures and did not significantly alter treatment decisions of breast cancer tumor board in this early-stage breast cancer cohort. CONCLUSIONS: In conclusion, this study highlights the importance of adherence to the guidelines and appropriate use of PET/CT in early-stage breast cancer management. PET/CT should be reserved for cases where it is clinically warranted, considering the potential economic burden and minimal impact on treatment decisions of breast cancer tumor board in this patient population.

Detection of Liver Lesions in Colorectal Cancer Patients Using 18F-FDG PET/CT Dual-Time-Point Scan Imaging.

OBJECTIVE: The aim of this study was to evaluate the diagnostic performance of dual-time-point fluorine-18-fluorodeoxyglucose positron emission computed tomography/computed tomography (18F-FDG PET/CT) compared to conventional early imaging for detecting colorectal liver metastases (CRLM) in colorectal cancer (CRC) patients. METHODS: One hundred twenty-four consecutive CRC patients underwent dual-time-point imaging scans on a retrospective basis. Histopathological confirmation and/or clinical follow-up were accepted as the gold standard. Standard uptake values (SUV), signal-to-noise ratio (SNR), retention index (RI), tumor-to-normal liver ratio (TNR), and lesion sizes were measured for early and delayed PET scans. The diagnostic performance of early and delayed images was calculated on a per-patient basis and compared using McNemar's test. RESULTS: Among the 124 patients, 57 (46%) had CRLM, 6 (4.8%) had benign lesions, and 61 (49.2%) had no concerning lesions detected. Smaller CRLM lesions (<5 cm3) showed significantly higher uptake in the delayed scans relative to early imaging (p < 0.001). The SUV and TNR increased significantly in delayed imaging of all metastatic lesions (p < 0.001). The retention index of all CRLM was high (40.8%), especially for small lesions (54.8%). A total of 177 lesions in delayed images and 124 in standard early images were identified. In a per-patient analysis, delayed imaging had significantly higher sensitivity (100% vs. 87.7%) and specificity (91.0% vs. 94.0%) compared to early imaging (p-value = 0.04). CONCLUSIONS: The detection of liver lesions using dual-time-point PET/CT scan improves the sensitivity and specificity for the detection of colorectal liver metastasis.

Semiquantitative analysis of cerebral [18F]FDG-PET uptake in pediatric patients.

BACKGROUND: Glycolytic metabolism in the brain of pediatric patients, imaged with [18F]  fluorodeoxyglucose-positron emission tomography (FDG-PET) is incompletely characterized. OBJECTIVE: The purpose of the current study was to characterize [18F]FDG-PET brain uptake in a large sample of pediatric patients with non-central nervous system diseases as an alternative to healthy subjects to evaluate changes at different pediatric ages. MATERIALS AND METHODS: Seven hundred ninety-five [18F]FDG-PET examinations from children < 18 years of age without central nervous system diseases were included. Each brain image was spatially normalized, and the standardized uptake value (SUV) was obtained. The SUV and the SUV relative to different pseudo-references were explored as a function of age. RESULTS: At all evaluated ages, the occipital lobe showed the highest [18F]FDG uptake (0.27 ± 0.04 SUV/year), while the parietal lobe and brainstem had the lowest uptake (0.17 ± 0.02 SUV/year, for both regions). An increase [18F]FDG uptake was found for all brain regions until 12 years old, while no significant uptake differences were found between ages 13 (SUV = 5.39) to 17 years old (SUV = 5.52) (P < 0.0001 for the whole brain). A sex dependence was found in the SUVmean for the whole brain during adolescence (SUV 5.04-5.25 for males, 5.68-5.74 for females, P = 0.0264). Asymmetries in [18F]FDG uptake were found in the temporal and central regions during infancy. CONCLUSIONS: Brain glycolytic metabolism of [18F]FDG, measured through the SUVmean, increased with age until early adolescence (< 13 years old), showing differences across brain regions. Age, sex, and brain region influence [18F]FDG uptake, with significant hemispheric asymmetries for temporal and central regions.

Anthracycline cardiotoxicity: current methods of diagnosis and possible role of 18F-FDG PET/CT as a new biomarker.

Despite advances in chemotherapy, the drugs used in cancer treatment remain rather harmful to the cardiovascular system, causing structural and functional cardiotoxic changes. Positron-emission tomography associated with computed tomography (PET/CT) has emerged like a promising technique in the early diagnosis of these adverse drug effects as the myocardial tissue uptake of fluorodeoxyglucose labeled with fluorine-18 (18F-FDG), a glucose analog, is increased after their use. Among these drugs, anthracyclines are the most frequently associated with cardiotoxicity because they promote heart damage through DNA breaks, and induction of an oxidative, proinflammatory, and toxic environment. This review aimed to present the scientific evidence available so far regarding the use of 18F-FDG PET/CT as an early biomarker of anthracycline-related cardiotoxicity. Thus, it discusses the physiological basis for its uptake, hypotheses to justify its increase in the myocardium affected by anthracyclines, importance of 18F-FDG PET/CT findings for cardio-oncology, and primary challenges of incorporating this technique in standard clinical oncology practice.

Characterization of the anticonvulsant effect of dapsone on metabolic activity assessed by [18F]FDG -PET after kainic acid-induced status epilepticus in rats.

BACKGROUND: Development of effective drugs for epilepsy are needed, as nearly 30 % of epileptic patients, are resistant to current treatments. This study is aimed to characterize the anticonvulsant effect of dapsone (DDS), in the kainic acid (KA)-induced Status Epilepticus (SE) by recording the brain metabolic activity with an [18F]FDG-PET analysis. METHODS: Wistar rats received KA (10 mg/kg, i.p., single dose) to produce sustained seizures. [18F]FDG-PET and electroencephalographic (EEG) studies were then performed. DDS or vehicle were administered 30 min before KA. [18F]FDG uptake and EEG were evaluated at baseline, 2 and 25 h after KA injection. Likewise, caspase-8, 3 hippocampal activities and Fluoro-Jade B neuronal degeneration and Hematoxylin-eosin staining were measured 25 h after KA. RESULTS: PET data evaluated at 2 h showed hyper-uptake of [18F]FDG in the control group, which was decreased by DDS. At 25 h, hypo-uptake was observed in the control group and higher values due to DDS effect. EEG spectral power was increased 2 h after KA administration in the control group during the generalized tonic-clonic seizures, which was reversed by DDS, correlated with [18F]FDG-PET uptake changes. The values of caspases-8 activity decreased 48 and 43 % vs control group in the groups treated with DDS (12.5 y 25 mg/kg respectively), likewise; caspase-3 activity diminished by 57 and 53 %. Fewer degenerated neurons were observed due to DDS treatments. CONCLUSIONS: This study pinpoints the anticonvulsant therapeutic potential of DDS. Given its safety and effectiveness, DDS may be a viable alternative for patients with drug-resistant epilepsy.

Role of molecular imaging in the diagnosis of prosthetic aortic valve endocarditis by Bacillus licheniformis: a case report.

Background: Infective endocarditis is a challenging diagnosis that usually requires cardiovascular image confirmation as part of the approach. 18F-Fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) is an imaging technique more sensible for the diagnosis of prosthetic valve endocarditis (PVE) when echocardiography is inconclusive. Case summary: We present the case of a 35-year-old man who had a previous Bentall-De Bono procedure 4 years prior that included biological, national institute of cardiology (INC)-type, locally manufactured aortic valve replacement and woven Dacron tube graft implantation in the ascending aorta. He was admitted because of dyspnoea, oedema, fever, and syncope. A complete auriculoventricular blockade was diagnosed, requiring cardiac pacing. Also, infective endocarditis (IE) was suspected. Blood cultures showed the isolation of Bacillus licheniformis. Transthoracic echocardiography, transoesophageal echocardiography, and CT angiography were inconclusive for IE. Treatment was initiated with intravenous (IV) antibiotic therapy, and an extensive protocol for IE, including molecular imaging modalities, was ordered. 99mTc-Ubiquicidin scintigraphy was acquired without abnormal findings. Images of 18F-FDG-PET/CT revealed abnormally intense heterogeneous uptake in the prosthetic aortic annulus in a classic pattern. Applying the modified 2015 Duke criteria for PET/CT, PVE was confirmed. Discussion: Although the other imaging modalities were negative, the high clinical suspicion made it mandatory to continue the study protocol, remarking on the utility of 18F-FDG-PET/CT on patients categorized as having 'possible' endocarditis, as in our patient.

Recurrent thyroid carcinoma in a dog - diagnosis by 18F-fluorodeoxyglucose positron emission tomography

Background: Thyroid tumor is a common endocrine tumor that accounts for up to 3.8% of all tumors in dogs. Most of them are malignant and usually nonfunctional in dogs. 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) is an imaging modality that detects intracellular accumulation of radioactive deoxyglucose administered in the body and is used in combination with computed tomography to provide functional information with exact anatomical localization. It is used in human medicine to detect residual or recurrent head and neck neoplasm after treatments, such as surgical resection. This report describes the first case of diagnosing recurrent thyroid carcinoma (TC) through FDG-PET in a dog. Case: A 9-year-old castrated male Maltese dog presented with a palpable mobile mass in the right ventral cervical region. Radiography and ultrasonography (US) showed a radiopaque mass adjacent to the trachea, and the right thyroid gland was enlarged on computed tomography. The surgically excised mass was encapsulated and measured to be 2.3 × 1.0 × 3.4 cm (width x length x height) in size. Histopathologically, the mass was diagnosed as differentiated follicular TC, and gross and vascular invasions were observed. To prevent recurrence, postoperative carboplatin chemotherapy was performed for 5 months. Two months after completion of chemotherapy, a nodule of approximately 7 mm in diameter was detected in the thyroidectomy bed by US. FDG-PET scanning was performed as an effective means of evaluating the malignancy, local recurrence, and metastasis of differentiated follicular TC. The nodule had the dimensions of 2.8 × 5.9 × 8.6 mm, a maximum standardized uptake value (SUV) of 8.49, and a mean SUV of 5.6. The results of FDG-PET suggested the recurrence of TC; therefore, the second chemotherapy protocol using toceranib was applied for 16 months. After initiation of the 2nd chemotherapy, follow-up examinations were conducted approximately every 4 months. On the 134th day, although the nodule was not palpated, its size was observed to have increased to 5.0 × 3.8 × 13.6 mm on cervical US on the 232nd day, showing heterogeneous and hypoechoic parenchyma. On the 405th day, the tumor was enlarged to a size of 13.4 × 12.9 × 22 mm and identified as a lobular, amorphous shape, and its heterogeneity was increased. Moreover, 2 pulmonary nodules with well-defined margins were found on radiography in the left caudal lung lobe (9 × 10 mm and 12 × 12 mm [width × length]); thus, lung metastasis was suspected. On the 536th day, anorexia and lethargy occurred, and the dog was lost to follow-up. Discussion: In the present case, local recurrence of TC was suspected based on cervical US. Although US was useful as a screening tool, additional examinations were necessary for evaluating local invasiveness, malignancy, and nodal/distant metastasis. FDG-PET can detect recurrence at an early stage because it can sense increased tumor metabolism through physiologic absorption of FDG, even before the beginning of anatomic change in the lesion. Therefore, FDG-PET can assist in treatment planning and provide better prognosis. In humans, focal FDG uptake and a high maximum SUV in the thyroid gland on FDG-PET were associated with a higher risk of cancer. Because there was no evidence of neoplasia except the thyroid lesion during the FDG-PET examination, the tumor showed an increasingly malignant pattern of the thyroid gland on US during the follow-up period, and the metastatic pulmonary nodules were identified on the 650th day after the thyroidectomy, the present case was diagnosed as recurrent TC. This report describes the use of FDG-PET for diagnosing local recurrence of TC, pointing to FDG-PET as a potential strategy to evaluate loco-regional recurrence and distant metastasis of TC.

Tumor glycolytic profiling through 18F-FDG PET/CT predicts immune checkpoint inhibitor efficacy in advanced NSCLC.

Background: A significant proportion of patients with non-small-cell lung cancer (NSCLC) do not respond to immune checkpoint inhibitors (ICIs). Since metabolic reprogramming with increased glycolysis is a hallmark of cancer and is involved in immune evasion, we used 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) to evaluate the baseline glycolytic parameters of patients with advanced NSCLC submitted to ICIs, and assessed their predictive value. Methods: 18F-FDG PET/CT results in the 3 months before ICIs treatment were included. Maximum standardized uptake values, whole metabolic tumor volume (wMTV), and whole-body total lesion glycolysis (wTLG) were evaluated. Cutoff values for high or low glycolytic categories were determined using receiver-operating characteristic curves. Progression-free survival (PFS) and overall survival (OS) were evaluated. Patients with a complete response and a matching group with resistance to ICIs underwent immunohistochemistry analysis. An unsupervised k-means clustering model integrating programmed cell death ligand 1 (PD-L1) expression, glycolytic parameters, and ICIs therapy was performed. Results: In all, 98 patients were included. Lower baseline 18F-FDG PET/CT parameters were associated with responses to ICIs. Patients with low wMTV or wTLG had improved PFS and OS. High wTLG, strong tumor expression of glucose transporter-1, and lack of responses were significantly associated. Patients with low glycolytic parameters benefited from ICIs, regardless of chemotherapy. Conversely, those with high parameters benefited from the addition of chemotherapy. Patients with higher wTLG and lower PD-L1 were associated with progression and worse survival to ICIs monotherapy. Conclusions: Glycolytic metabolic profiles established through baseline 18F-FDG PET/CT are useful biomarkers for evaluating ICI therapy in advanced NSCLC.

Propolis induces cardiac metabolism changes in 6-hydroxydopamine animal model: A dietary intervention as a potential cardioprotective approach in Parkinson's disease.

While there is sustained growth of the older population worldwide, ageing is a consistent risk factor for neurodegenerative diseases, such as Parkinson's-disease (PD). Considered an emblematic movement disorder, PD comprises a miscellany of non-motor symptoms, for which effective management remains an unfulfilled need in clinical practice. Highlighted are the cardiovascular abnormalities, that cause significant burden in PD patients. Evidence suggests that key biological processes underlying PD pathophysiology can be modulated by diet-derived bioactive compounds, such as green propolis, a natural functional food with biological and pharmacological properties. The effects of propolis on cardiac affection associated to PD have received little coverage. In this study, a metabolomics approach and Positron Emission Tomography (PET) imaging were used to assess the metabolic response to diet supplementation with green propolis on heart outcomes of rats with Parkinsonism induced by 6-hydroxydopamine (6-OHDA rats). Untargeted metabolomics approach revealed four cardiac metabolites (2-hydroxybutyric acid, 3-hydroxybutyric acid, monoacylglycerol and alanine) that were significantly modified between animal groups (6-OHDA, 6-OHDA + Propolis and sham). Propolis-induced changes in the level of these cardiac metabolites suggest beneficial effects of diet intervention. From the metabolites affected, functional analysis identified changes in propanoate metabolism (a key carbohydrate metabolism related metabolic pathway), glucose-alanine cycle, protein and fatty acid biosynthesis, energy metabolism, glutathione metabolism and urea cycle. PET imaging detected higher glucose metabolism in the 17 areas of the left ventricle of all rats treated with propolis, substantially contrasting from those rats that did not consume propolis. Our results bring new insights into cardiac metabolic substrates and pathways involved in the mechanisms of the effects of propolis in experimental PD and provide potential novel targets for research in the quest for future therapeutic strategies.

Assessment of Cardiac Sarcoidosis: FDG PET and BMIPP SPECT.

PURPOSE OF REVIEW: Cardiac sarcoidosis (CS) is an inflammatory disease of unknown etiology that can lead to life-threatening arrhythmias, heart failure, and death. Advanced cardiac imaging modalities have improved the clinician's ability to detect this disease. The purpose of this review is to discuss the recent evidence of cardiac metabolic imaging as assessed by [18F]FDG PET and [123I]BMIPP SPECT in the evaluation of CS patients. RECENT FINDINGS: [18F]FDG PET is the gold standard to identify myocardial inflammation. [123I]BMIPP SPECT can uncover early myocardial damage as well as advanced stages of CS when fibrosis prevails. In presence of inflammation, myocardial [18F]FDG uptake is increased, but in contrast, BMIPP myocardial uptake is reduced or even suppressed. Thus, a complementary role of cardiac metabolic imaging by [18F]FDG PET and BMIPP SPECT has been proposed to detect the whole spectrum of CS. [18F]FDG PET is considered an important tool to improve the diagnosis and optimize the management of CS. The role of [123I]BMIPP SPECT in diagnosing CS is still under investigation. Further studies are needed to evaluate the clinical utility of combined cardiac metabolic imaging in the diagnosis, prognosis, and for selecting treatments in CS patients.

Nandrolone Supplementation Promotes AMPK Activation and Divergent 18[FDG] PET Brain Connectivity in Adult and Aged Mice.

Decreased anabolic androgen levels are followed by impaired brain energy support and sensing with loss of neural connectivity during physiological aging, providing a neurobiological basis for hormone supplementation. Here, we investigated whether nandrolone decanoate (ND) administration mediates hypothalamic AMPK activation and glucose metabolism, thus affecting metabolic connectivity in brain areas of adult and aged mice. Metabolic interconnected brain areas of rodents can be detected by positron emission tomography using 18FDG-mPET. Albino CF1 mice at 3 and 18 months of age were separated into 4 groups that received daily subcutaneous injections of either ND (15 mg/kg) or vehicle for 15 days. At the in vivo baseline and on the 14th day, brain 18FDG-microPET scans were performed. Hypothalamic pAMPKT172/AMPK protein levels were assessed, and basal mitochondrial respiratory states were evaluated in synaptosomes. A metabolic connectivity network between brain areas was estimated based on 18FDG uptake. We found that ND increased the pAMPKT172/AMPK ratio in both adult and aged mice but increased 18FDG uptake and mitochondrial basal respiration only in adult mice. Furthermore, ND triggered rearrangement in the metabolic connectivity of adult mice and aged mice compared to age-matched controls. Altogether, our findings suggest that ND promotes hypothalamic AMPK activation, and distinct glucose metabolism and metabolic connectivity rearrangements in the brains of adult and aged mice.

Cannabidiol Treatment Improves Glucose Metabolism and Memory in Streptozotocin-Induced Alzheimer's Disease Rat Model: A Proof-of-Concept Study.

An early and persistent sign of Alzheimer's disease (AD) is glucose hypometabolism, which can be evaluated by positron emission tomography (PET) with 18F-2-fluoro-2-deoxy-D-glucose ([18F]FDG). Cannabidiol has demonstrated neuroprotective and anti-inflammatory properties but has not been evaluated by PET imaging in an AD model. Intracerebroventricular (icv) injection of streptozotocin (STZ) is a validated model for hypometabolism observed in AD. This proof-of-concept study evaluated the effect of cannabidiol treatment in the brain glucose metabolism of an icv-STZ AD model by PET imaging. Wistar male rats received 3 mg/kg of STZ and [18F]FDG PET images were acquired before and 7 days after STZ injection. Animals were treated with intraperitoneal cannabidiol (20 mg/kg-STZ-cannabidiol) or saline (STZ-saline) for one week. Novel object recognition was performed to evaluate short-term and long-term memory. [18F]FDG uptake in the whole brain was significantly lower in the STZ-saline group. Voxel-based analysis revealed a hypometabolism cluster close to the lateral ventricle, which was smaller in STZ-cannabidiol animals. The brain regions with more evident hypometabolism were the striatum, motor cortex, hippocampus, and thalamus, which was not observed in STZ-cannabidiol animals. In addition, STZ-cannabidiol animals revealed no changes in memory index. Thus, this study suggests that cannabidiol could be an early treatment for the neurodegenerative process observed in AD.

Clozapine induces astrocyte-dependent FDG-PET hypometabolism.

PURPOSE: Advances in functional imaging allowed us to visualize brain glucose metabolism in vivo and non-invasively with [18F]fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) imaging. In the past decades, FDG-PET has been instrumental in the understanding of brain function in health and disease. The source of the FDG-PET signal has been attributed to neuronal uptake, with hypometabolism being considered as a direct index of neuronal dysfunction or death. However, other brain cells are also metabolically active, including astrocytes. Based on the astrocyte-neuron lactate shuttle hypothesis, the activation of the glutamate transporter 1 (GLT-1) acts as a trigger for glucose uptake by astrocytes. With this in mind, we investigated glucose utilization changes after pharmacologically downregulating GLT-1 with clozapine (CLO), an anti-psychotic drug. METHODS: Adult male Wistar rats (control, n = 14; CLO, n = 12) received CLO (25/35 mg kg-1) for 6 weeks. CLO effects were evaluated in vivo with FDG-PET and cortical tissue was used to evaluate glutamate uptake and GLT-1 and GLAST levels. CLO treatment effects were also assessed in cortical astrocyte cultures (glucose and glutamate uptake, GLT-1 and GLAST levels) and in cortical neuronal cultures (glucose uptake). RESULTS: CLO markedly reduced in vivo brain glucose metabolism in several brain areas, especially in the cortex. Ex vivo analyses demonstrated decreased cortical glutamate transport along with GLT-1 mRNA and protein downregulation. In astrocyte cultures, CLO decreased GLT-1 density as well as glutamate and glucose uptake. By contrast, in cortical neuronal cultures, CLO did not affect glucose uptake. CONCLUSION: This work provides in vivo demonstration that GLT-1 downregulation induces astrocyte-dependent cortical FDG-PET hypometabolism-mimicking the hypometabolic signature seen in people developing dementia-and adds further evidence that astrocytes are key contributors of the FDG-PET signal.

Characterization of metabolic activity induced by kainic acid in adult rat whole brain at the early stage: A 18FDG-PET study.

OBJECTIVE: Brain metabolic processes are not fully characterized in the kainic acid (KA)-induced Status Epilepticus (KASE). Thus, we evaluated the usefulness of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) as an experimental strategy to evaluate in vivo, in a non-invasive way, the glucose consumption in several brain regions, in a semi-quantitative study to compare and to correlate with data from electroencephalography and histology studies. METHODS: Sixteen male Wistar rats underwent FDG-PET scans at basal state and after KA injection. FDG-PET images were normalized to an MRI-based atlas and segmented to locate regions. Standardized uptake values (SUV) were obtained at several time points. EEGs and cell viability by histological analysis, were also evaluated. RESULTS: FDG-PET data showed changes in regions such as: amygdala, hippocampus, accumbens, entorhinal cortex, motor cortex and hypothalamus. Remarkably, hippocampal hypermetabolism was found (mean SUV = 2.66 ± 0.057) 2 h after KA administration, while hypometabolism at 24 h (mean SUV = 1.83 ± 0.056) vs basal values (mean SUV = 2.19 ± 0.057). EEG showed increased spectral power values 2 h post-KA administration. Hippocampal viable-cell counting 24 h after KA was decreased, while Fluoro-Jade B-positive cells were increased, as compared to control rats, coinciding with the hypometabolism detected in the same region by semi-quantitative FDG-PET at 24 h after KASE. CONCLUSIONS: PET is suitable to measure metabolic brain changes in the rat model of status epilepticus induced by KA (KASE) at the first 24 h, compared to that of EEG; PET data may also be sensitive to cell viability.

Prognostic value of 18F-FDG PET/CT parameters and histopathologic variables in head and neck cancer / Valor prognóstico de parâmetros de PET/TC com 18F-FDG e variáveis histopatológicas em câncer de cabeça e pescoço

Abstract Introduction 18F-fluorodeoxyglucose positron emission tomography/computed tomography parameters such as; maximum standardized uptake values, standard metabolic tumor volume and otal lesion glycosis are important prognostic biomarkers in cancers. Objective To investigate the prognostic value of these parameters in patients with head and neck cancers. Methods We performed a retrospective study including 47 patients with head and neck cancer who underwent18F-fluorodeoxyglucose positron emission tomography/computed tomography prior to treatment. Standard metabolic tumor volume, otal lesion glycosis and standardized uptake were measured for each patient. The prognostic value of quantitative 18F-fluorodeoxyglucose positron emission tomography/computed tomography parameters and clinicopathologic variables on disease free survival and overall survival were analyzed. Results The median (range) standard metabolic tumor volume and otal lesion glycosis and standardized uptake were 7.63 cm3 (0.6-34.3), 68.9 g (2.58-524.5 g), 13.89 (4.89-33.03 g/mL), respectively. Lymph node metastases and tumour differentiation were significant variables for disease free survival and overall survival, however, all 18F-fluorodeoxyglucose positron emission tomography/computed tomography parameters were not associated with disease- free survival and overall survival. Conclusion Pretreatment quantities positron emission tomography parameters did not predict survival in head and neck cancer.

Resumo Introdução Os parâmetros da tomografia por emissão de pósitrons/tomografia computadorizada com 18F-fluordesoxiglicose, como os máximos valores de captação padronizados, o volume metabólico tumoral padrão e a glicólise total da lesão são importantes biomarcadores prognósticos de câncer. Objetivo Investigar o valor prognóstico desses parâmetros em pacientes com câncer de cabeça e pescoço. Método Fizemos um estudo retrospectivo que incluiu 47 pacientes com câncer de cabeça e pescoço e que foram submetidos à tomografia por emissão de pósitrons/tomografia computadorizada com 18F-fluordesoxiglicose antes do tratamento. Volume metabólico tumoral, glicólise total da lesão e valores de captação padronizados foram aferidos em cada paciente. O valor prognóstico de parâmetros quantitativos da tomografia por emissão de pósitrons/tomografia computadorizada com 18F-fluordesoxiglicose e das variáveis clínico-patológicas sobre a sobrevida livre de doença e a sobrevida geral foi analisado. Resultados A média (intervalo) de volume metabólico tumoral e glicólise total da lesão e valores de captação padronizados foram 7,63 cm3 (0,6-34,3), 68,9 g (2,58-524,5) e 13,89 g/mL (4,89-33,03), respectivamente. Metástase nos nódulos linfáticos e diferenciação tumoral foram variáveis significativas de sobrevida livre de doença e sobrevida geral; contudo, nenhum parâmetro da tomografia por emissão de pósitrons/tomografia computadorizada com 18F-fluordesoxiglicose estava associado a sobrevida livre de doença e sobrevida geral. Conclusão As quantidades dos parâmetros da tomografia por emissão de pósitrons pré-tratamento não previram a sobrevida em câncer de cabeça e pescoço.

PET/CT F18-FDG with soft tissue plasmacytomas in multiple myeloma.

Multiple myeloma is characterized by malignant proliferation of clonal plasma cells. Usually, appears as a generalized disease but it can present as solitary bone plasmacytoma or a solitary soft tissue mass or extramedullary plasmacytoma. In the case of extramedullary involvement, it could present as soft tissue plasmacytomas and the prognosis is poor. The 18F-FDG PET/CT could be a valuable tool for characterization of the medullary and extramedullary involvement. We present a case of F18-FDG PET/CT with extramedullary involvement with soft tissue plasmacytomas in the setting of MM.

Imágenes en endocarditis infecciosa: no todo es ecocardiografía / Imaging in infective endocarditis: not all is ultrasonography

Resumen La endocarditis infecciosa (EI) es una enfermedad de alta mortalidad, caracterizada por una infección endocárdica y frecuentes complicaciones multiorgánicas, que requiere un diagnóstico rápido y preciso, y un manejo agresivo, ya sea médico o quirúrgico. Su diagnóstico se realiza tomando en cuenta criterios bacteriológicos, clínicos y ecocardiográficos. Es objetivo de este artículo realizar una actualización del estudio imagenológico en paciente con EI, con especial énfasis en aquellos exámenes no ecocardiográficos disponibles en nuestro medio. En los últimos años, estudios de imagen avanzados han adquirido un rol creciente en su estudio inicial, particularmente la tomografía computada multicorte (TCMC) cardiaca y el positron emission tomography/computed tomography (PET/CT), y han sido recomendados como criterios diagnósticos en las guías recientes para el manejo de esta entidad. La TCMC cardiaca proporciona información anatómica detallada de las válvulas cardiacas y tejido perivalvular, identificando pseudoaneurismas, abscesos y dehiscencias valvulares. El PET/CT con F18-fluorodeoxiglucosa (F18-FDG) permite aumentar la sensibilidad en la detección de EI, y pesquisar con alta eficiencia fenómenos embólicos sistémicos, de elevada frecuencia en esta población. Ambos métodos prestan particular utilidad en EI de válvula protésica, donde la ecocardiografía presenta menor rendimiento diagnóstico. La resonancia magnética (RM) cerebral es el mejor método de imagen para descartar eventos isquémicos/embólicos del sistema nervioso central.

Abstract Infective endocarditis (IE) is an entity characterized by endocardial infection and frequent multiorgan complications, resulting in high mortality. It requires a rapid and accurate diagnosis, and a medical or surgical aggressive treatment. Currently, IE diagnosis rests on bacterial, clinical and ultrasonographic criteria. The objective of this article is to update the imaging study in patients with IE, with special emphasis on those non-echocardiographic examinations available in our environment. Last years, advanced imaging had achieved a growing role in IE diagnosis, especially cardiac multislice computed tomography (MSCT) and positron emission tomography/computed tomography (PET/CT), which have been recommended in recent clinical guidelines to be included as part of diagnostic criteria. Cardiac MSCT provides detailed anatomic information of cardiac valves and perivalve tissue, allowing identification of pseudoaneurysm, abscess and valve dehiscence. F18-FDG PET/CT increases sensitivity for IE detection and shows high accuracy in searching for extracranial systemic embolic events. Both MSCT and PET/CT have particular utility in cases of prosthetic valve endocarditis, where cardiac ultrasonography shows lower performance. Brain magnetic resonance imaging (MRI) is the best imaging method for evaluating ischemic/embolic events of central nervous system.

Neurobehavioral Characteristics of FDG-PET Defined Right-Dominant Semantic Dementia: A Longitudinal Study.

INTRODUCTION: Semantic dementia (SD) is characterized by fluent speech, anomia, and loss of word and object knowledge with varying degrees of right and left anterior-medial temporal lobe hypometabolism on [18F] fluorodeoxyglucose (FDG)-PET. We assessed neurobehavioral features in SD patients across 3 FDG-PET-defined metabolic patterns and investigated progression over time. METHODS: Thirty-four patients with SD who completed FDG-PET were classified into a left- and right-dominant group based on the degree of hypometabolism in each temporal lobe. The left-dominant group was further subdivided depending on whether hypometabolism in the right temporal lobe was more or less than 2 standard deviations from controls (left+ group). Neurobehavioral characteristics determined using the Neuropsychiatric Inventory Questionnaire (NPI-Q) were compared across groups. Progression of NPI-Q scores and FDG-PET hypometabolism was assessed in 14 patients with longitudinal follow-up. RESULTS: The right-dominant group performed worse on the NPI-Q and had a greater frequency of abnormal behaviors and more severe disinhibition compared to the left-dominant group. Performance on the NPI-Q and severity of disinhibition correlated with right medial and lateral, but not left, temporal lobe hypometabolism. Severity of abnormal behaviors worsened over time in most left-dominant and left+ patients but appeared to improve in the 2 right-dominant patients with longitudinal follow-up. All groups showed progressive worsening of metabolism in both temporal lobes over time, with hypometabolism spreading from anteromedial to posterior temporal regions. However, the degree of temporal lobe asymmetry remained relatively constant over time. CONCLUSION: In SD, neurobehavioral features, especially disinhibition, are associated with right medial and lateral temporal lobe hypometabolism and commonly develop over time even in patients that present with left-dominant patterns of hypometabolism.