A systems-level analysis highlights microglial activation as a modifying factor in common epilepsies.

AIMS: The causes of distinct patterns of reduced cortical thickness in the common human epilepsies, detectable on neuroimaging and with important clinical consequences, are unknown. We investigated the underlying mechanisms of cortical thinning using a systems-level analysis. METHODS: Imaging-based cortical structural maps from a large-scale epilepsy neuroimaging study were overlaid with highly spatially resolved human brain gene expression data from the Allen Human Brain Atlas. Cell-type deconvolution, differential expression analysis and cell-type enrichment analyses were used to identify differences in cell-type distribution. These differences were followed up in post-mortem brain tissue from humans with epilepsy using Iba1 immunolabelling. Furthermore, to investigate a causal effect in cortical thinning, cell-type-specific depletion was used in a murine model of acquired epilepsy. RESULTS: We identified elevated fractions of microglia and endothelial cells in regions of reduced cortical thickness. Differentially expressed genes showed enrichment for microglial markers and, in particular, activated microglial states. Analysis of post-mortem brain tissue from humans with epilepsy confirmed excess activated microglia. In the murine model, transient depletion of activated microglia during the early phase of the disease development prevented cortical thinning and neuronal cell loss in the temporal cortex. Although the development of chronic seizures was unaffected, the epileptic mice with early depletion of activated microglia did not develop deficits in a non-spatial memory test seen in epileptic mice not depleted of microglia. CONCLUSIONS: These convergent data strongly implicate activated microglia in cortical thinning, representing a new dimension for concern and disease modification in the epilepsies, potentially distinct from seizure control.

Repeatability and reproducibility of ADC measurements: a prospective multicenter whole-body-MRI study.

OBJECTIVES: Multicenter oncology trials increasingly include MRI examinations with apparent diffusion coefficient (ADC) quantification for lesion characterization and follow-up. However, the repeatability and reproducibility (R&R) limits above which a true change in ADC can be considered relevant are poorly defined. This study assessed these limits in a standardized whole-body (WB)-MRI protocol. METHODS: A prospective, multicenter study was performed at three centers equipped with the same 3.0-T scanners to test a WB-MRI protocol including diffusion-weighted imaging (DWI). Eight healthy volunteers per center were enrolled to undergo test and retest examinations in the same center and a third examination in another center. ADC variability was assessed in multiple organs by two readers using two-way mixed ANOVA, Bland-Altman plots, coefficient of variation (CoV), and the upper limit of the 95% CI on repeatability (RC) and reproducibility (RDC) coefficients. RESULTS: CoV of ADC was not influenced by other factors (center, reader) than the organ. Based on the upper limit of the 95% CI on RC and RDC (from both readers), a change in ADC in an individual patient must be superior to 12% (cerebrum white matter), 16% (paraspinal muscle), 22% (renal cortex), 26% (central and peripheral zones of the prostate), 29% (renal medulla), 35% (liver), 45% (spleen), 50% (posterior iliac crest), 66% (L5 vertebra), 68% (femur), and 94% (acetabulum) to be significant. CONCLUSIONS: This study proposes R&R limits above which ADC changes can be considered as a reliable quantitative endpoint to assess disease or treatment-related changes in the tissue microstructure in the setting of multicenter WB-MRI trials. KEY POINTS: • The present study showed the range of R&R of ADC in WB-MRI that may be achieved in a multicenter framework when a standardized protocol is deployed. • R&R was not influenced by the site of acquisition of DW images. • Clinically significant changes in ADC measured in a multicenter WB-MRI protocol performed with the same type of MRI scanner must be superior to 12% (cerebrum white matter), 16% (paraspinal muscle), 22% (renal cortex), 26% (central zone and peripheral zone of prostate), 29% (renal medulla), 35% (liver), 45% (spleen), 50% (posterior iliac crest), 66% (L5 vertebra), 68% (femur), and 94% (acetabulum) to be detected with a 95% confidence level.

Sonographic and radiographic evaluation of the extensor tendons in early postoperative period after total knee arthroplasty.

OBJECTIVE: To prospectively assess the early changes in the quadriceps and patellar tendons before and after total knee arthroplasty using ultrasound, shear wave elastography, and X-rays. MATERIALS AND METHODS: Radiographs, ultrasound, and shear wave elastography were performed on 23 patients (16 women; aged 51-85, mean 66 ± 9 years) before and after surgery at 6 weeks and on 11 patients at 3 months. Patellar position and patellar tendon lengths were evaluated by radiography; joint effusion or synovitis, quadriceps and patellar tendon lengths, and thicknesses, echogenicity, vascularity, and stiffness were assessed with ultrasound and shear wave elastography. RESULTS: In the early postoperative period, 87% of the patients had joint effusion, and 43% had signs of synovitis. There was a significant thickening of the quadriceps tendon in 51.5% (p < .0001) and of the patellar tendon in 93.8% (p < .0001) of patients with a significant shortening of the patellar tendon in 7.8% (p < .0001). A hypoechoic defect on the medial aspect of the quadriceps tendon was found in 87% of the patients. There was a significant increase in Young's modulus in the quadriceps tendon (p = .0006) but not in the patellar tendon. CONCLUSION: The following should not be considered to be pathological findings at early postoperative imaging: joint effusion, synovitis, increasing of stiffness and thickening of quadriceps tendons by more than 50%, thickening of patellar tendon by more than 90%, focal defect through the medial aspect of the quadriceps tendon, and shortening of the patellar tendon by 8%.

The central vein sign in multiple sclerosis patients with vascular comorbidities.

BACKGROUND: The central vein sign (CVS) is an imaging biomarker able to differentiate multiple sclerosis (MS) from other conditions causing similar appearance lesions on magnetic resonance imaging (MRI), including cerebral small vessel disease (CSVD). However, the impact of vascular risk factors (VRFs) for CSVD on the percentage of CVS positive (CVS+) lesions in MS has never been evaluated. OBJECTIVE: To investigate the association between different VRFs and the percentage of CVS+ lesions in MS. METHODS: In 50 MS patients, 3T brain MRIs (including high-resolution 3-dimensional T2*-weighted images) were analyzed for the presence of the CVS and MRI markers of CSVD. A backward stepwise regression model was used to predict the combined predictive effect of VRF (i.e. age, hypertension, diabetes, obesity, ever-smoking, and hypercholesterolemia) and MRI markers of CSVD on the CVS. RESULTS: The median frequency of CVS+ lesions was 71% (range: 35%-100%). In univariate analysis, age (p < 0.0001), hypertension (p < 0.001), diabetes (p < 0.01), obesity (p < 0.01), smoking (p < 0.05), and the presence of enlarged-perivascular-spaces on MRI (p < 0.005) were all associated with a lower percentage of CVS+ lesions. The stepwise regression model showed that age and arterial hypertension were both associated with the percentage of CVS+ lesions in MS (adjusted R2 = 0.46; p < 0.0001 and p = 0.01, respectively). CONCLUSION: The proportion of CVS+ lesions significantly decreases in older and hypertensive MS patients. Although this study was conducted in patients with an already established MS diagnosis, the diagnostic yield of the previously proposed 35% CVS proportion-based diagnostic threshold appears to be not affected. Overall these results suggest that the presence of VRF for CSVD should be taken into account during the CVS assessment.

Network-based atrophy modeling in the common epilepsies: A worldwide ENIGMA study.

Epilepsy is increasingly conceptualized as a network disorder. In this cross-sectional mega-analysis, we integrated neuroimaging and connectome analysis to identify network associations with atrophy patterns in 1021 adults with epilepsy compared to 1564 healthy controls from 19 international sites. In temporal lobe epilepsy, areas of atrophy colocalized with highly interconnected cortical hub regions, whereas idiopathic generalized epilepsy showed preferential subcortical hub involvement. These morphological abnormalities were anchored to the connectivity profiles of distinct disease epicenters, pointing to temporo-limbic cortices in temporal lobe epilepsy and fronto-central cortices in idiopathic generalized epilepsy. Negative effects of age on atrophy further revealed a strong influence of connectome architecture in temporal lobe, but not idiopathic generalized, epilepsy. Our findings were reproduced across individual sites and single patients and were robust across different analytical methods. Through worldwide collaboration in ENIGMA-Epilepsy, we provided deeper insights into the macroscale features that shape the pathophysiology of common epilepsies.

Multi-atlas segmentation of the skeleton from whole-body MRI-Impact of iterative background masking.

PURPOSE: To improve multi-atlas segmentation of the skeleton from whole-body MRI. In particular, we study the effect of employing the atlas segmentations to iteratively mask tissues outside of the region of interest to improve the atlas alignment and subsequent segmentation. METHODS: An improved atlas registration scheme is proposed. Starting from a suitable initial alignment, the alignment is refined by introducing additional stages of deformable registration during which the image sampling is limited to the dilated atlas segmentation label mask. The performance of the method was demonstrated using leave-one-out cross-validation using atlases of 10 whole-body 3D-T1 images of prostate cancer patients with bone metastases and healthy male volunteers, and compared to existing state of the art. Both registration accuracy and resulting segmentation quality, using four commonly used label fusion strategies, were evaluated. RESULTS: The proposed method showed significant improvement in registration and segmentation accuracy with respect to the state of the art for all validation criteria and label fusion strategies, resulting in a Dice coefficient of 0.887 (STEPS label fusion). The average Dice coefficient for the multi-atlas segmentation showed over 11% improvement with a decrease of false positive rate from 28.3% to 13.2%. For this application, repeated application of the background masking did not lead to significant improvement of the segmentation result. CONCLUSIONS: A registration strategy, relying on the use of atlas segmentations as mask during image registration was proposed and evaluated for multi-atlas segmentation of whole-body MRI. The approach significantly improved registration and final segmentation accuracy and may be applicable to other structures of interest.

Assessment of cardiac-driven liver movements with filtered harmonic phase image representation, optical flow quantification, and motion amplification.

PURPOSE: To characterize cardiac-driven liver movements using a harmonic phase image representation (HARP) with an optical flow quantification and motion amplification method. The method was applied to define the cardiac trigger delay providing minimal signal losses in liver DWI images. METHODS: The 16-s breath-hold balanced-SSFP time resolved 20 images/s were acquired at 3T in coronal and sagittal orientations. A peripheral pulse unit signal was recorded. Cardiac-triggered DWI images were acquired after different peripheral pulse unit delays. A steerable pyramid decomposition with multiple orientations and spatial frequencies was applied. The liver motion field-map was derived from temporal variations of the HARP representation filtered around the cardiac frequency. Liver displacements were quantified with an optical flow method; moreover the right liver motion was amplified. RESULTS: The largest displacements were observed in the left liver (feet-head:3.70 ± 1.06 mm; anterior-posterior: 2.35 ± 0.51 mm). Displacements were statistically significantly weaker in the middle right liver (0.47 ± 0.11 mm; P = 0.0156). The average error was 0.013 ± 0.022 mm (coronal plane) and 0.021 ± 0.041 mm (sagittal plane). The velocity field demonstrated opposing movements of the right liver extremities during the cardiac cycle. DWI signal loss was minimized in regions and instants of smallest amplitude of both velocity and velocity gradient. CONCLUSION: Cardiac-driven liver movements were quantified with combined cardiac frequency-filtered HARP and optical flow methods. A motion phase opposition between right liver extremities was demonstrated. Displacement amplitude and velocity were larger in the left liver especially along the vertical direction. Motion amplification visually emphasized cardiac-driven right liver displacements. The optimal cardiac timing minimizing signal loss in liver DWI images was derived.

Value of dual-energy CT angiography in patients with treated intracranial aneurysms.

PURPOSE: To evaluate the ability of dual-energy CT angiography (DECTA) in metal artifact reduction in patients with treated intracranial aneurysms by comparing DECTA-based virtual monoenergetic extrapolations (VMEs) and mixed images (MI). METHODS: Thirty-five patients underwent prospectively a dual-source DECTA (Somatom Force, Siemens Medical Solutions, Forchheim, Germany) after aneurysm repair. A total number of 40 aneurysms (23 treated by coil embolization and 17 treated by surgical clipping) were analyzed. Mixed images (equivalent to a conventional single-energy CT angiography) were compared to VMEs at 75, 95, and 115 keV. Artifact severity was assessed quantitatively by measuring the mean attenuation value and standard deviation within regions of interest placed in the most hypodense coil or clip artifact area. Artifact severity score and contrast vessel score were also assessed qualitatively by two independent blinded readers. RESULTS: In those aneurysms treated by surgical clipping, quantitative and qualitative analyses showed significant reduction of artifacts on VMEs compared to MI with the best compromise being obtained at 95 keV in order to keep an optimal vessel contrast in the adjacent vessel. In those aneurysms treated by coil embolization, there was no significant reduction of artifacts both on quantitative and qualitative analyses. CONCLUSION: Dual-source DECTA was helpful in order to reduce clip artifacts on VMEs with the optimal adjacent vessel visualization obtained at 95 keV, whereas this technique was not helpful in aneurysms treated by coiling.

Assessment of response to chemotherapy in pancreatic ductal adenocarcinoma: Comparison between diffusion-weighted MR quantitative parameters and RECIST.

PURPOSE: To prospectively assess chemotherapy-induced changes in pancreatic ductal adenocarcinoma (PDA) with diffusion-weighted (DW)-MR quantitative metrics, including apparent diffusion coefficient (ADC) and histogram-derived parameters, compared with RECIST 1.1. METHODS: 24 patients underwent DW-MR at baseline, week-2 and week-8 after chemotherapy initiation. Tumour diameter was assessed on T2-weighted images. Regions-of-interest (ROI) were drawn on ADC map for ROI-ADC. Volume segmentation (b = 1000 s/mm2 images) provided DW-volume and histogram-derived diffusion parameters (H-ADC, H-D and H-PF). All variables and their relative change were compared to baseline or between responders and non-responders. Discriminant analysis was performed. RESULTS: 15/24 patients were responders. RECIST 1.1 correctly characterized 6/15 responders at week-8. At week-2, in responders DW-volume decreased (P = .002); ROI-ADC mean H-D increased (P = .047; P = .048;). The 25th percentile H-D increased in responders and decreased in non-responders (P = .016; P = .048). At week-8 in responders DW-volume decreased and ROI-ADC mean, 25th, 50th, 75th percentiles of H-ADC and H-D increased (P < .05). No changes were observed in non-responders (P > .05). At week-2, 25th percentile of H-D and H-PF relative change correctly classified 20/24 patients (P = .003); at week-8, DW-volume relative change correctly classified 22/24 patients (P < .0001). CONCLUSIONS: ROI-ADC, DW-volume and histogram-derived diffusion parameters are more accurate to categorize responding and non-responding PDA patients treated with chemotherapy compared with RECIST 1.1.

Structural brain abnormalities in the common epilepsies assessed in a worldwide ENIGMA study.

Progressive functional decline in the epilepsies is largely unexplained. We formed the ENIGMA-Epilepsy consortium to understand factors that influence brain measures in epilepsy, pooling data from 24 research centres in 14 countries across Europe, North and South America, Asia, and Australia. Structural brain measures were extracted from MRI brain scans across 2149 individuals with epilepsy, divided into four epilepsy subgroups including idiopathic generalized epilepsies (n =367), mesial temporal lobe epilepsies with hippocampal sclerosis (MTLE; left, n = 415; right, n = 339), and all other epilepsies in aggregate (n = 1026), and compared to 1727 matched healthy controls. We ranked brain structures in order of greatest differences between patients and controls, by meta-analysing effect sizes across 16 subcortical and 68 cortical brain regions. We also tested effects of duration of disease, age at onset, and age-by-diagnosis interactions on structural measures. We observed widespread patterns of altered subcortical volume and reduced cortical grey matter thickness. Compared to controls, all epilepsy groups showed lower volume in the right thalamus (Cohen's d = -0.24 to -0.73; P < 1.49 × 10-4), and lower thickness in the precentral gyri bilaterally (d = -0.34 to -0.52; P < 4.31 × 10-6). Both MTLE subgroups showed profound volume reduction in the ipsilateral hippocampus (d = -1.73 to -1.91, P < 1.4 × 10-19), and lower thickness in extrahippocampal cortical regions, including the precentral and paracentral gyri, compared to controls (d = -0.36 to -0.52; P < 1.49 × 10-4). Thickness differences of the ipsilateral temporopolar, parahippocampal, entorhinal, and fusiform gyri, contralateral pars triangularis, and bilateral precuneus, superior frontal and caudal middle frontal gyri were observed in left, but not right, MTLE (d = -0.29 to -0.54; P < 1.49 × 10-4). Contrastingly, thickness differences of the ipsilateral pars opercularis, and contralateral transverse temporal gyrus, were observed in right, but not left, MTLE (d = -0.27 to -0.51; P < 1.49 × 10-4). Lower subcortical volume and cortical thickness associated with a longer duration of epilepsy in the all-epilepsies, all-other-epilepsies, and right MTLE groups (beta, b < -0.0018; P < 1.49 × 10-4). In the largest neuroimaging study of epilepsy to date, we provide information on the common epilepsies that could not be realistically acquired in any other way. Our study provides a robust ranking of brain measures that can be further targeted for study in genetic and neuropathological studies. This worldwide initiative identifies patterns of shared grey matter reduction across epilepsy syndromes, and distinctive abnormalities between epilepsy syndromes, which inform our understanding of epilepsy as a network disorder, and indicate that certain epilepsy syndromes involve more widespread structural compromise than previously assumed.

Absence of clinical cerebellar syndrome after serial injections of more than 20 doses of gadoterate, a macrocyclic GBCA: a monocenter retrospective study.

Sound evidence of gadolinium accumulation in brain has been recently provided after repeated administrations of linear gadolinium-based contrast agents (GBCAs), especially at the cerebellum level. Although data regarding brain accumulation of macrocyclic GBCAs are more reassuring, there is now a genuine concern ("gadolinium-phobia") about possible long-term consequences of gadolinium deposits, especially in terms of cerebellar sequelae. We, therefore, questioned about the clinical impact of serial administration of gadoterate meglumine, a macrocyclic GBCA. In this retrospective study (2000-2016) of medical files of patients who received more than 20 administrations of gadoterate, we searched for cerebellar symptoms and signs developing during the regular follow-up. We reviewed medical files of ten patients (mean age 34.4 ± 20.8 years; 4 males, 6 females) who received 28.2 ± 5.3 doses of gadoterate (average total dose of GBCA 518 ± 226 ml; range 185-785 ml). Patients were examined by at least two medical specialists depending on initial diagnosis, and at least once by a neurosurgeon. Mean follow-up time was 91 months (range 49-168) and six out of ten patients experienced new symptoms or signs. No clinician reported the appearance of a rising cerebellar syndrome, nor newly appeared symptoms or signs suggested cerebellar toxicity. This retrospective clinical study shows no de novo clinical cerebellar syndrome following repeated administrations of gadoterate. Our results argue against a cerebellar toxicity of this macrocyclic agent. Still, confirmation in a larger number of subjects is required, as well as clinical studies concerning linear GBCAs whose structure and in vivo stability are distinct.

Added value of diffusion-weighted magnetic resonance imaging for the detection of pancreatic fluid collection infection.

OBJECTIVES: To investigate the added value of diffusion-weighted (DW) magnetic resonance (MR) imaging in the detection of infection in pancreatic fluid collections (PFC). METHODS: Forty-patients with PFC requiring endoscopic-transmural drainage underwent conventional-MR and DW-MR imaging (b = 1000 s/mm2) before endoscopy. MR images were divided into two sets (set1, conventional-MR; set2, conventional-MR, DW-MR and ADC maps) and randomized. Two independent readers performed qualitative and quantitative (apparent diffusion coefficient, ADC) image analysis. Bacteriological analysis of PFC content was the gold standard. Non-parametric tests were used for comparisons. Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV) and accuracy were calculated for the two sets for both readers. Receiver operating characteristic curves (ROC) were drawn to assess quantitative DW-MR imaging diagnostic performance. RESULTS: For both readers, sensitivity, specificity, NPV, PPV and accuracy for infected PFCs were higher for set2 (P > .05). ADC were lower in infected versus non-infected PFCs (P ≤ .031). Minimum ADC cut-off: 1,090×10-3 mm2/s for reader 1 and 1,012×10-3 mm2/s for reader 2 (sensitivity and specificity 67 % and 96 % for both readers). CONCLUSION: Qualitative information provided by DW-MR may help to assess PFCs infection. Infected PFCs show significantly lower ADCs compared to non-infected ones. KEY POINTS: • DW improves MR diagnostic accuracy to detect infection of PFC • Infected PFCs show lower ADC compared to non-infected ones (P < .031) • DW-MR images are easy to interpret especially for non-experienced radiologist.

Neural correlates of correct and failed response inhibition in heavy versus light social drinkers: an fMRI study during a go/no-go task by healthy participants.

The ability to suppress responses that are inappropriate, as well as the mechanisms monitoring the accuracy of actions in order to compensate for errors, is central to human behavior. Neural alterations that prevent stopping an inaccurate response, combined with a decreased ability of error monitoring, are considered to be prominent features of alcohol abuse. Moreover, (i) alterations of these processes have been reported in heavy social drinkers (i.e. young healthy individuals who do not yet exhibit a state of alcohol dependence); and (ii) through longitudinal studies, these alterations have been shown to underlie subsequent disinhibition that may lead to future alcohol use disorders. In the present functional magnetic resonance imaging study, using a contextual Go/No-Go task, we investigated whether different neural networks subtended correct inhibitions and monitoring mechanisms of failed inhibitory trials in light versus heavy social drinkers. We show that, although successful inhibition did not lead to significant changes, neural networks involved in error monitoring are different in light versus heavy drinkers. Thus, while light drinkers exhibited activations in their right inferior frontal, right middle cingulate and left superior temporal areas; heavy drinkers exhibited activations in their right cerebellum, left caudate nucleus, left superior occipital region, and left amygdala. These data are functionally interpreted as reflecting a "visually-driven emotional strategy" vs. an "executive-based" neural response to errors in heavy and light drinkers, respectively. Such a difference is interpreted as a key-factor that may subtend the transition from a controlled social heavy consumption to a state of clinical alcohol dependence.

Quantifying brain volumes for Multiple Sclerosis patients follow-up in clinical practice - comparison of 1.5 and 3 Tesla magnetic resonance imaging.

INTRODUCTION: There is emerging evidence that brain atrophy is a part of the pathophysiology of Multiple Sclerosis (MS) and correlates with several clinical outcomes of the disease, both physical and cognitive. Consequently, brain atrophy is becoming an important parameter in patients' follow-up. Since in clinical practice both 1.5Tesla (T) and 3T magnetic resonance imaging (MRI) systems are used for MS patients follow-up, questions arise regarding compatibility and a possible need for standardization. METHODS: Therefore, in this study 18 MS patients were scanned on the same day on a 1.5T and a 3T scanner. For each scanner, a 3D T1 and a 3D FLAIR were acquired. As no atrophy is expected within 1 day, these datasets can be used to evaluate the median percentage error of the brain volume measurement for gray matter (GM) volume and parenchymal volume (PV) between 1.5T and 3T scanners. The results are obtained with MSmetrix, which is developed especially for use in the MS clinical care path, and compared to Siena (FSL), a widely used software for research purposes. RESULTS: The MSmetrix median percentage error of the brain volume measurement between a 1.5T and a 3T scanner is 0.52% for GM and 0.35% for PV. For Siena this error equals 2.99%. When data of the same scanner are compared, the error is in the order of 0.06-0.08% for both MSmetrix and Siena. CONCLUSIONS: MSmetrix appears robust on both the 1.5T and 3T systems and the measurement error becomes an order of magnitude higher between scanners with different field strength.

Liver apparent diffusion coefficient repeatability with individually predetermined optimal cardiac timing and artifact elimination by signal filtering.

PURPOSE: To prospectively assess liver ADC (apparent diffusion coefficient) repeatability from cardiac-triggered diffusion-weighted images obtained with an individually predetermined optimal cardiac time window minimizing cardiac-related effects and to evaluate a signal filtering method aimed at artifact elimination. MATERIALS AND METHODS: After Institutional Review Board approval and written informed consent, eight healthy volunteers underwent four repetitions of respiratory-triggered diffusion-weighted sequences (3T, b: 0,150,500 s/mm(2) ) without (RTnoCT, 51 sec) and with individually optimized cardiac triggering (RTCT, 306 sec). The optimal cardiac delay was individually predetermined using a 5-second breath-hold sequence. Monoexponential liver ADC and left-to-right-liver ADC ratio were computed from region of interest (ROI) signal measurements (two independent readers). A filtering method, excluding signal intensities lower than the mean intensity at fixed b-value, provided ADC recalculation. Limits-of-agreement (LOAs) from 95% confidence intervals for differences across the four repetitions provided the variability range. RESULTS: For Reader 1 (Reader 2), left-to-right-liver ADC ratios were significantly higher in RTnoCT 1.51 (1.52) than in RTCT 1.12 (1.15), P = 0.012 (P = 0.017). Respectively for RTnoCT and RTCT: left liver LOAs were ±835 (±775), ± 315 (±369) 10(-6) mm(2) /s; right liver LOAs were ±392 (±445), ± 172 (±140) 10(-6) mm(2) /s: LOAs were larger in the left than in the right lobe (both P < 0.001). After filtering, left liver ADC LOAs narrowed to ±650 (±367) 10(-6) mm(2) /s, P = 0.17 (P < 0.001); ± 152 (±208) 10(-6) mm(2) /s (both P < 0.002) and left-to-right-liver ADC ratio decreased to 1.28 (1.20), P = 0.017 (P = 0.012); 1.09 (1.08), P = 0.106 (P = 0.105). CONCLUSION: Compared to noncardiac-triggered acquisitions, individually optimized cardiac-triggered acquisitions improved ADC repeatability in both liver lobes and reduced ADC differences between left and right liver. Left liver ADC repeatability was further improved after signal filtering.

Focal liver lesions detection: Comparison of respiratory-triggering, triggering and tracking navigator and tracking-only navigator in diffusion-weighted imaging.

PURPOSE: To compare low b value (10s/mm(2)) spin-echo echo-planar (SE-EP) diffusion-weighted imaging (DWI) acquired with respiratory-triggering (RT), triggering and tracking navigator (TT), tracking only navigator (TRON) techniques for image quality and focal liver lesions (FLL) detection in non-cirrhotic patients. MATERIAL AND METHODS: This bi-centric study was approved by the institutional review boards; informed consent was obtained. Eighty-three patients were prospectively included and SE-EP-DWI with RT, TT and TRON techniques were performed. DWI sequences were randomized and independently analyzed by two readers. The qualitative evaluation was based on a 3-point score for axial artifacts (motion, ghost, susceptibility artifacts and distortion) and stair-step artifacts. Sensitivity of FLL detection was calculated for all lesions together and after lesion size stratification (≤ 10 mm, >10-20mm and >20mm). The standard of reference consisted of a retrospective reading of the conventional MRI, the three DWI sequences and by follow-up (12 months): a total of 409 FLL were detected. Data between sequences was compared with non-parametric tests. Cohen's kappa coefficient was used for inter-observer agreement. RESULTS: Image quality was comparable for RT and TT. TRON showed statistically significantly more axial artifacts for the two readers (p<0.05). Stair-step artifacts were not statistically significantly different between DWI sequences. Overall sensitivities for RT, TT, TRON were 85%, 86%, 82% and 86%, 89% 83%, respectively, for readers 1 and 2. The inter-observer agreement was very good. CONCLUSION: Image quality was better for RT and TT compared to TRON. Overall sensitivities for FLL detection were comparable between techniques and readers.

Structural asymmetries in motor and language networks in a population of healthy preterm neonates at term equivalent age: a diffusion tensor imaging and probabilistic tractography study.

In this MRI study, we aimed to provide new in vivo structural markers of asymmetry in motor and language networks in a population of healthy preterm neonates scanned at term equivalent age. Using diffusion tensor imaging and probabilistic tractography, we showed that, besides volume and microstructural asymmetries in the parieto-temporal part of the superior longitudinal fasciculus (SLF) and a trend towards microstructural asymmetry in the corticospinal tract (CST), volume asymmetry in the motor part of the superior thalamic radiations (STR) and a trend towards volume asymmetry in the CST are already present in the neonatal period. No asymmetry was found in the sensory part of the STR, the anterior thalamic radiations (ATR), and posterior thalamic radiations (PTR) neither in the fronto-parietal part of the SLF. These results suggest that structural asymmetries in the motor and language networks are present in healthy preterm neonates at term equivalent age, well before the development of speech and hand preference.