18F-FDG PET in drug-resistant epilepsy due to focal cortical dysplasia type 2: additional value of electroclinical data and coregistration with MRI.

PURPOSE: To assess the localizing value of 18F-FDG PET in patients operated on for drug-resistant epilepsy due to focal cortical dysplasia type 2 (FCD2). METHODS: We analysed 18F-FDG PET scans from 103 consecutive patients (52 males, 7-65 years old) with histologically proven FCD2. PET and MRI data were first reviewed by visual analysis blinded to clinical information and FCD2 location. The additional value of electroclinical data and PET/MRI coregistration was assessed by comparison with pathological results and surgical outcomes. RESULTS: Visual analysis of PET scans showed focal or regional hypometabolism corresponding to the FCD2 in 45 patients (44%), but the findings were doubtful or misleading in 37 patients and negative in 21. When considering electroclinical data, positive localization was obtained in 73 patients, and this increased to 85 (83%) after coregistration of PET and MRI data. Under the same conditions, MRI was positive in 61 patients (59%), doubtful in 15 and negative in 27. The additional value of PET was predominant in patients negative or doubtful on MRI, localizing the FCD2 in 35 patients (83%). Interobserver agreement correlated with the grade of hypometabolism: it was good in patients with mild to severe hypometabolism (82-95%), but moderate in those with subtle/doubtful hypometabolism (45%). The main factors influencing positive PET localization were the grade of hypometabolism and the size of the FCD2 (P < 0.0001). Misleading location (nine patients) was associated with a small FCD2 in the mesial frontal and central regions. Following limited cortical resection mainly located in extratemporal areas (mean follow-up 5.6 years), a seizure-free outcome was achieved in 94% of patients, including Engel's class IA in 72%. CONCLUSION: In this series, 18F-FDG PET contributed to the localization of FCD2 in 83% of patients. This high localizing value was obtained by integration of electroclinical data and PET/MRI coregistration. This approach may help improve the surgical outcome in extratemporal epilepsy, even in patients negative on MRI.

Correction to: 18F-FDG PET in drug-resistant epilepsy due to focal cortical dysplasia type 2: additional value of electroclinical data and coregistration with MRI.

The original version of this article has added numbers in the text which are unnecessary. Correct line should be: "We also performed PET/MRI based surgical resections in an increasing number of MRI negative/ doubtful cases with favourable outcome."

Diagnostic value of combining ¹¹C-choline and ¹8F-FDG PET/CT in hepatocellular carcinoma.

PURPOSE: In this prospective study, our goal was to emphasize the diagnostic value of combining (11)C-choline and (18)F-FDG PET/CT for hepatocellular carcinoma (HCC) in patients with chronic liver disease. METHODS: Thirty-three consecutive patients were enrolled. All patients were suspected to have HCC based on CT and/or MRI imaging. A final diagnosis was obtained by histopathological examination or by imaging alone according to American Association for the Study of Liver Disease criteria. All patients underwent PET/CT with both tracers within a median of 5 days. All lesions showing higher tracer uptake than normal liver were considered positive for HCC. We examined how tracer uptake was related to biological (serum α-fetoprotein levels) and pathological (differentiation status, peritumoral capsule and vascular invasion) prognostic markers of HCC, as well as clinical observations at 6 months (recurrence and death). RESULTS: Twenty-eight HCC, four cholangiocarcinomas and one adenoma were diagnosed. In the HCC patients, the sensitivity of (11)C-choline, (18)F-FDG and combined (11)C-choline and (18)F-FDG PET/CT for the detection of HCC was 75 %, 36 % and 93 %, respectively. Serum α-fetoprotein levels >200 ng/ml were more frequent among patients with (18)F-FDG-positive lesions than those with (18)F-FDG-negative lesions (p < 0.05). Early recurrence (n=2) or early death (n=5) occurred more frequently in patients with (18)F-FDG-positive lesions than in those with (18)F-FDG-negative lesions (p < 0.05). CONCLUSION: The combined use of (11)C-choline and (18)F-FDG PET/CT detected HCC with high sensitivity. This approach appears to be of potential prognostic value and may facilitate the selection of patients for surgical resection or liver transplantation.

Determinants of brain metabolism changes in mesial temporal lobe epilepsy.

OBJECTIVE: To determine the main factors influencing metabolic changes in mesial temporal lobe epilepsy (MTLE) due to hippocampal sclerosis (HS). METHODS: We prospectively studied 114 patients with MTLE (62 female; 60 left HS; 15- to 56-year-olds) with (18) F-fluorodeoxyglucose-positron emission tomography and correlated the results with the side of HS, structural atrophy, electroclinical features, gender, age at onset, epilepsy duration, and seizure frequency. Imaging processing was performed using statistical parametric mapping. RESULTS: Ipsilateral hypometabolism involved temporal (mesial structures, pole, and lateral cortex) and extratemporal areas including the insula, frontal lobe, perisylvian regions, and thalamus, more extensively in right HS (RHS). A relative increase of metabolism (hypermetabolism) was found in the nonepileptic temporal lobe and in posterior areas bilaterally. Voxel-based morphometry detected unilateral hippocampus atrophy and gray matter concentration decrease in both frontal lobes, more extensively in left HS (LHS). Regardless of the structural alterations, the topography of hypometabolism correlated strongly with the extent of epileptic networks (mesial, anterior-mesiolateral, widespread mesiolateral, and bitemporal according to the ictal spread), which were larger in RHS. Notably, widespread perisylvian and bitemporal hypometabolism was found only in RHS. Mirror hypermetabolism was grossly proportional to the hypometabolic areas, coinciding partly with the default mode network. Gender-related effect was significant mainly in the contralateral frontal lobe, in which metabolism was higher in female patients. Epilepsy duration correlated with the contralateral temporal metabolism, positively in LHS and negatively in RHS. Opposite results were found with age at onset. High seizure frequency correlated negatively with the contralateral metabolism in LHS. SIGNIFICANCE: Epileptic networks, as assessed by electroclinical correlations, appear to be the main determinant of hypometabolism in MTLE. Compensatory mechanisms reflected by a relative hypermetabolism in the nonepileptic temporal lobe and in extratemporal areas seem more efficient in LHS and in female patients, whereas long duration, late onset of epilepsy, and high seizure frequency may reduce these adaptive changes.

Resting state FDG-PET functional connectivity as an early biomarker of Alzheimer's disease using conjoint univariate and independent component analyses.

Imaging cerebral glucose metabolism with positron emission tomography (PET) in Alzheimer's disease (AD) has allowed for improved characterisation of this pathology. Such patterns are typically analysed using either univariate or multivariate statistical techniques. In this work we combined voxel-based group analysis and independent component analysis to extract differential characteristic patterns from PET data of glucose metabolism in a large cohort of normal elderly controls and patients with AD. The patterns were used in conjunction with a support vector machine to discriminate between subjects with mild cognitive impairment (MCI) at risk or not of converting to AD. The method was applied to baseline fluoro-deoxyglucose (FDG)-PET images of subjects from the ADNI database. Our approach achieved improved early detection and differentiation of typical versus pathological metabolic patterns in the MCI population, reaching 80% accuracy (85% sensitivity and 75% specificity) when using selected regions. The method has the potential to assist in the advance diagnosis of Alzheimer's disease, and to identify early in the development of the disease those individuals at high risk of rapid cognitive decline who could be candidates for new therapeutic approaches.

Ultra-low-dose in brain 18F-FDG PET/MRI in clinical settings.

We previously showed that the injected activity could be reduced to 1 MBq/kg without significantly degrading image quality for the exploration of neurocognitive disorders in 18F-FDG-PET/MRI. We now hypothesized that injected activity could be reduced ten-fold. We simulated a 18F-FDG-PET/MRI ultra-low-dose protocol (0.2 MBq/Kg, PETULD) and compared it to our reference protocol (2 MBq/Kg, PETSTD) in 50 patients with cognitive impairment. We tested the reproducibility between PETULD and PETSTD using SUVratios measurements. We also assessed the impact of PETULD for between-group comparisons and for visual analysis performed by three physicians. The intra-operator agreement between visual assessment of PETSTD and PETULD in patients with severe anomalies was substantial to almost perfect (kappa > 0.79). For patients with normal metabolism or moderate hypometabolism however, it was only moderate to substantial (kappa > 0.53). SUV ratios were strongly reproducible (SUVratio difference ± SD = 0.09 ± 0.08). Between-group comparisons yielded very similar results using either PETULD or PETSTD. 18F-FDG activity may be reduced to 0.2 MBq/Kg without compromising quantitative measurements. The visual interpretation was reproducible between ultra-low-dose and standard protocol for patients with severe hypometabolism, but less so for those with moderate hypometabolism. These results suggest that a low-dose protocol (1 MBq/Kg) should be preferred in the context of neurodegenerative disease diagnosis.

Brain perfusion SPECT correlates with CSF biomarkers in Alzheimer's disease.

PURPOSE: Our aim was to study the correlations between cerebrospinal fluid (CSF) biomarker levels such as beta-amyloid 42 (Abeta(42)), total and phosphorylated tau protein (T-tau and P-tau) and brain perfusion SPECT in Alzheimer's disease (AD) using a voxel-based methodology. METHODS: Patients (n = 31) with clinical features of AD (n = 25) or amnestic mild cognitive impairment (aMCI) (n = 6) were retrospectively included. All subjects underwent the same clinical, neuropsychological and neuroimaging tests. They had a lumbar puncture and a brain perfusion ((99m)Tc-ECD) SPECT within a time interval of 10 (+/-26) days. Correlations between CSF biomarker concentrations and perfusion were studied using SPM2 software. Individual normalised regional activity values were extracted from the eligible clusters for calculation of correlation coefficients. RESULTS: No significant correlation was found between Abeta(42) concentrations and brain perfusion. A significant correlation (p < 0.01, corrected) was found between T-tau or P-tau concentrations and perfusion in the left parietal cortex. CONCLUSION: Our results suggest a strong correlation between T-tau and P-tau levels and decreased brain perfusion in regions typically affected by neuropathological changes in AD.

Distribution of ventilation/perfusion ratios in pulmonary embolism: an adjunct to the interpretation of ventilation/perfusion lung scans.

UNLABELLED: Diagnosis of pulmonary embolism (PE) by visual interpretation of ventilation/perfusion (V/Q) scans is limited by the high percentages of patients classified in the intermediate- and low-probability categories. This study proposes a quantitative analysis of the distribution of V/Q ratios to better identify patients with PE. METHODS: We studied 99 consecutive patients who underwent dual-isotope (81m)Kr/(99m)Tc-macroaggregate V/Q scanning and arterial blood gas analysis within 48 h. The 8-view V/Q scans were visually analyzed by 2 observers according to the revised criteria of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) (normal scan or low, intermediate, or high probability of PE). Quantitative analysis of the posterior-view distribution histogram of V/Q ratios was performed using dedicated software. Briefly, regions of interest were drawn around the lungs on the matched V/Q images, smooth filtering was applied, normalized regional V/Q ratios were calculated within each pixel, and a distribution histogram was built. RESULTS: Patients with normal scans (n = 16) had a predominance of V/Q ratios (63.3% +/- 13.0%) between 0.8 and 1.2. They had only 9.8% +/- 5.8% of ratios > 1.2, and the remaining 26.9% +/- 7.5% of ratios were <0.8. By contrast, patients with PE (n = 34) were characterized by a significant increase (15.5 +/- 10.0%, P = 0.04) in high V/Q ratios (>1.2) and a significant increase (34.5% +/- 8.2%, P = 0.003) in low V/Q ratios (<0.8). Interestingly, a similar pattern was found in patients with a high PIOPED probability of PE, 21.3% +/- 11.0% and 37.5% +/- 9.2%, respectively. Within the nondiagnostic group (intermediate- + low-probability scans, n = 58), 17 patients were finally diagnosed with PE. Analysis of the distribution histogram in this group allowed the identification of 5 patients with PE (specificity, 78%). CONCLUSION: A quantitative approach to lung scan interpretation, based on the distribution histogram of V/Q ratios, may be helpful for categorizing patients with suspected PE.

Ultrasound, elastography, and fluorodeoxyglucose positron emission tomography/computed tomography imaging in Riedel's thyroiditis: report of two cases.

BACKGROUND: Riedel's thyroiditis (RT) is a rare disease characterized by a chronic inflammatory lesion of the thyroid gland with invasion by a dense fibrosis. Publications of the imaging features of RT are scarce. To our knowledge, ultrasound elastography (USE) findings have not been previously reported. Therefore, we describe two patients with RT who were imaged with ultrasonography (US), USE, and fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT). SUMMARY: Two women were referred for a large, hard goiter with compressive symptoms (dyspnea and dysphagia); in one patient, the goiter was associated with retroperitoneal fibrosis. In both cases, RT was confirmed by surgical biopsy with pathological examination. Thyroid US imaging was performed with a US scan and a 10-13 MHz linear transducer. The hardness of the tissues was analyzed using transient USE (ShearWave, Aixplorer-SuperSonic Imagine). PET/CT scanning was performed with a Philips Gemini GXL camera (GE Medical Systems). In the first patient, US examination revealed a compressive multinodular goiter with large solid hypoechoic and poorly vascularized areas adjacent to the nodules. The predominant right nodule was hypoechoic with irregular margins. The second patient had a hypoechoic goiter with large bilateral hypoechoic areas. In both cases, an unusual feature was observed: the presence of tissue surrounding the primitive carotid artery, associated with thrombi of the internal jugular vein. Further, USE showed heterogeneity in the stiffness values of the thyroid parenchyma varying between 21 kPa and 281 kPa. FDG-PET/CT imaging showed uptake foci in the thyroid gland. In both cases, US showed a decrease in the thyroid gland volume and the disappearance of encasement of the neck vasculature in response to corticosteroid treatment. In contrast, the FDG-PET/CT features remained unchanged. CONCLUSIONS: US features, such as vascular encasement and improvement under corticosteroid treatment, seem to be specific to this rare disease. For the first time, USE documents the hardness of RT tissues. Apart from the FDG-PET/CT findings that merit further investigation, US and USE prove useful tools in the assessment of such a rare disease.