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The aim of this study was to present an overview of variations of the hepatic artery from the origin to the segmental branching.Abdominal Computed Tomography performed on consecutive patients in our tertiary center between 2019 and 2020 were analyzed. Hepatic arterial branching and its relationship to the portal veins were reported.Out of 500 imaging, 16 anatomic patterns were found for the origin of hepatic artery, with 65.6% conventional origin at celiac axis (n = 328); 10 patterns for the left hepatic artery, 23 for segment IV artery, and more than 21 for the right hepatic artery (RHA), with conventional branching in respectively 66.8%, 39.6% and in 46.4% of patients. Conventional anatomy from celiac axis to segmental branching was found in 10.4% of patients.Dedicated thin-section imaging appears to be essential for preoperative planning in liver surgery, given the high variability of arterial distribution and their surgical implications.

Patients with Crohn’s disease can develop intestinal strictures, containing various degrees of inflammation and fibrosis. Differentiation of the main component of a stricturing lesion is the key for defining the therapeutic management. We assessed for the first time the accuracy of magnetic resonance elastography in detecting intestinal fibrosis and predicting clinical course in patients with Crohn’s disease. This was a prospective study of adult patients with Crohn’s disease and magnetic resonance imaging examination, including magnetic resonance elastography, between April 2019 and February 2020. The association between the bowel stiffness value and the degree of fibrosis was evaluated. The relationship between the stiffness value and the occurrence of clinical events was also investigated. A total of 69 patients were included. The stiffness value measured by magnetic resonance elastography was correlated with the degree of fibrosis (p

International audience; installation which might be impossible in some cases (e.g. pregnant women in lateral position, utilization of a tight flexible coil), and allows monitoring of only respiratory and heart activities. Moreover, being designed for clinical use, they offer no control over data acquisition and post-processing, which can be critical for some applications. For example, standard ECG processing can lead to incorrect QRS detection in case of steep gradient waveforms; no control over respiratory belt signal gain and offset (to avoid signal saturation) is available. Thus, often, accessory devices are thirdparty systems, which offer more flexibility, however have no communication interface with the MR system, or limited ones. Dedicated computer and electronics systems, as well as communication interfaces, are needed for use in either realtime/online applications or retrospective/offline applications. In the following we review several exemplary applications with the aim to derive typical requirements for such systems. Example applications that require real-time processing and communication include ECG denoising (7-10) and detection of the QRS complex (11-13), in order to trigger the MR sequence to the heart rate prospectively. The trigger is provided to the MR system by a TTL signal. The delays introduced by the real-time processing system, as defined by the latency (mean delay) and jitter (standard deviation of the delay), should be significantly lower that the temporal resolution of cardiac MR imaging, which is typically above 20 ms. Real-time display of the denoised ECG is also desired during anesthesia, cardiac stress MRI, or interventional MRI. Prospective motion correction (14) using external devices also relies on a real-time setup to modulate the MRI pulses (RF and magnetic field gradient pulses) in order to compensate for the effect of patient motion during spatial encoding. Low latency is also desired, ideally to be equal to the repetition time (TR) of the sequence or lower, i.e. 3 to 5 ms, though in practice it is limited by the time needed to process video images, e.g. 60 to 150 ms in (15). Software communication interfaces need to be defined with the vendor-dependent pulse sequence program in order to provide certain motion parameters (e.g. translations, rotations).

The study of articulatory gestures has a wide spectrum of applications, notably in speech production and recognition. Sets of phonemes, as well as their articulation, are language-specific; however, existing MRI databases mostly include English speakers. In our present work, we introduce a dataset acquired with MRI from 10 healthy native French speakers. A corpus consisting of synthetic sentences was used to ensure a good coverage of the French phonetic context. A real-time MRI technology with temporal resolution of 20 ms was used to acquire vocal tract images of the participants speaking. The sound was recorded simultaneously with MRI, denoised and temporally aligned with the images. The speech was transcribed to obtain phoneme-wise segmentation of sound. We also acquired static 3D MR images for a wide list of French phonemes. In addition, we include annotations of spontaneous swallowing., Measurement(s)Vocal tract images • SpeechTechnology Type(s)Magnetic Resonance Imaging • Microphone DeviceSample Characteristic - OrganismHomo sapiens Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.16404453

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International audience; Magnetic resonance has become a backbone of medical imaging but suffers from inherently low sensitivity. This can be alleviated by improved radio frequency (RF) coils. Multi-turn multi-gap coaxial coils (MTMG-CCs) introduced in this work are flexible, form-fitting RF coils extending the concept of the single-turn single-gap CC by introducing multiple cable turns and/or gaps. It is demonstrated that this enables free choice of the coil diameter, and thus, optimizing it for the application to a certain anatomical site, while operating at the self-resonance frequency. An equivalent circuit for MTMG-CCs is modeled to predict their resonance frequency. Possible configurations regarding size, number of turns and gaps, and cable types for different B 0 field strengths are calculated. Standard copper wire loop coils (SCs) and flexible CCs made from commercial coaxial cable were fabricated as receive-only coils for 3 T and transmit/receive coils at 7 T with diameters between 4 and 15 cm. Electromagnetic simulations are used to investigate the currents on MTMG-CCs, and demonstrate comparable specific absorption rate of 7 T CCs and SCs. Signal-to-noise ratio (SNR), transmit efficiency, and active detuning performance of CCs were compared in bench tests and MR experiments. For the form-fitted receive-only CCs at 3 T no significant SNR degradation was found as compared to flat SCs on a balloon phantom. Form-fitted transmit/receive CCs at 7 T showed higher transmit efficiency and SNR. MTMG-CCs can be sized to optimize sensitivity, are flexible and lightweight, and could therefore enable the fabrication of wearable coils with improved patient comfort.

International audience; Introduction: T1-based method is considered as the gold standard for extracellular volume fraction (ECV) mapping. This technique requires at least a 10 min delay after injection to acquire the post injection T1 map. Quantitative analysis of Dynamic Contrast Enhancement (DCE) images could lead to an earlier estimation of an ECV like parameter (2 min). The purpose of this study was to design a quantitative pixel-wise DCE analysis workflow to assess the feasibility of an early estimation of ECV.Methods: Fourteen patients with mitral valve prolapse were included in this study. The MR protocol, performed on a 3 T MR scanner, included MOLLI sequences for T1 maps acquisition and a standard SR-turboFlash sequence for dynamic acquisition. DCE data were acquired for at least 120 s. We implemented a full DCE analysis pipeline with a pre-processing step using an innovative motion correction algorithm (RC-REG algorithm) and a post-processing step using the extended Tofts Model (ECVETM). Estimated ECVETM maps were compared to standard T1-based ECV maps (ECVT1) with both a Pearson correlation analysis and a group-wise analysis.Results: Image and map quality assessment showed systematic improvements using the proposed workflow. Strong correlation was found between ECVETM, and ECVT1 values (r-square = 0.87).Conclusion: A DCE analysis workflow based on RC-REG algorithm and ETM analysis can provide good quality parametric maps. Therefore, it is possible to extract ECV values from a 2 min-long DCE acquisition that are strongly correlated with ECV values from the T1 based method.

International audience; Electrocardiogram (ECG) acquisition is required during catheter treatment of cardiac arrhythmias. The remote magnetic navigation technology allows the catheter to be moved automatically inside the heart chambers using large external magnets. Each change of position of the catheter requires fast motion of the magnets, therefore magnetic fluxes are created through the ECG cables, causing large distortions of the ECG signals. In this study a novel ECG sensor is proposed for reducing such distortions. The sensor uses short cables to connect the electrodes to the amplification and optical conversion circuit, using a technology similar to that used for magnetic resonance imaging. The proposed sensor was compared to the conventional 12-lead ECG device during various operation modes of the magnets. Quantitative morphological analysis of the different waves of the ECG was performed in two healthy subjects and on a conductivity phantom reproducing various cardiac pathologies. In healthy subjects the beat-to-beat correlation coefficients were improved with the proposed sensor for the PR interval (80-93% vs. 49-89%), QRS complex (93-96% vs. 74-94%), ST segment + T wave (95-98% vs. 67-99%), and whole PQRST wave (82-97% vs. 55-96%). Similar observations were made with the conductive gel in the whole PQRST wave in the pathological morphologies of the ECG for the VT (99% vs. 56-98%), AT (95% vs. 26-89%), STE (96-97% vs. 20-91%) and STD (96% vs. 28-90%). The new sensor might be used for better (uninterrupted) monitoring of the patient during catheter interventions using remote magnetic navigation. It has the potential to improve the robustness and/or duration of certain clinical procedures such as ventricular tachycardia ablation.

Background The relative modification of the myocardial volume between end-systole and end-diastole ([Formula: see text]) has already been assessed with different methods and falls in a range of 0.9–0.97 (mean value = 0.93). Purpose To estimate [Formula: see text] from the three longitudinal ([Formula: see text], circumferential ([Formula: see text]), and radial ([Formula: see text]) strains of the left ventricle using the formula: [Formula: see text] and to test whether this estimate of [Formula: see text] can be used as a marker of the echocardiography quality. Material and Methods Two hundred manuscripts, including a total of 34,690 patients or healthy volunteers, were identified in the Medline database containing values of [Formula: see text], [Formula: see text], and [Formula: see text] measured from echocardiography. Results The median value of was 0.93, in accordance with the literature, with no significant difference between patients or healthy volunteers ( P = 0.38). The proportion of studies with [Formula: see text] was 79%. When only considering groups of healthy volunteers, the studies failing this test had higher standard deviations for the three individual strains: 0.038 vs. 0.029 ( P = 0.02) for [Formula: see text]; 0.060 vs. 0.034 ( P –6) for [Formula: see text], and 0.243 vs. 0.101 ( P –14) for [Formula: see text]. Conclusion The median ratio of the left ventricular myocardial volumes between end-systole and end-diastole in the investigated studies was [Formula: see text]. The formula [Formula: see text] could be used to detect studies with inaccurate strain measurements.

International audience; Worker exposure to electromagnetic fields (EMF) is a growing concern of international commissions. A European directive from 2013 (2013/35/EU) recommend to estimate or measure EMF exposure of all exposed workers. Magnetic resonance imaging (MRI) workers are specially concerned by this point because they work all day long in the vicinity of a very strong magnet (generally 1.5 or 3 T), which cannot be turned off. Setting up a magnetic field monitoring device on these workers would therefore be a good way to ensure their security. European directive threshold adequacy could then be verified. But this verification does not ensure a complete analysis of the worker exposure. Such an analysis based on quality control charts and exposure time's metrics has been described in this paper. The proposed magnetic field exposure analysis has additionally been tested on a long-term exposure follow-up of 18 MRI workers during 2 months.

Aims Our study assesses the value of electrograms (EGMs) characteristics to identify a ventricular tachycardia (VT) isthmus entrance in patients with post-infarct VT. Post-infarct VTs are mostly due to a re-entrant circuit. A pacemapping (PM) approach is able to localize the VT isthmus during sinus rhythm. Limited data are available about the role of local EGMs in defining VT isthmus location. Methods and results Twenty consecutive patients (70% male) referred for post-infarct VT catheter ablation were included in the present study. The VT isthmus was defined according to the PM method. At each recording site, 10 characteristics of the local EGM were assessed to predict the location of the VT isthmus entrance. In total, 924 EGMs were acquired, of which 127 were located in the VT isthmus entrance. Logistic regression analysis showed that bipolar voltage, number of EGM positive peaks, and sQRS interval were independently associated with VT isthmus entrance location. The ROC curve best fitted the model at the cut-off 0.1641 (sensitivity 72%, specificity 75.2%, positive predictive value 31.3%, negative predictive value 94.4%, area under the curve 0.78, P Conclusion Our study suggests that three EGM characteristics: bipolar voltage, number of positive peaks, and sQRS interval can successfully identify a VT isthmus entrance in post-infarct patients.

International audience; Objective: A novel method is developed to identify ablation targets for the catheter treatment of ventricular tachycardia (VT). Methods: The method is based on pace-mapping, which is a validated technique to determine the catheter ablation targets. Conventionally, it consists of stimulating the heart ventricle from various sites and comparing the resulting activation pathways to that of a clinical VT by the analysis of surface electrocardiograms (ECG). In this paper, a novel pace-mapping method is presented, which does not require a reference ECG recording of the VT. A three-dimensional correlation gradient map is reconstructed by semiautomatic analysis of ECG morphological changes within the network of pace-mapping sites. In these maps, abnormal points are identified by high correlation gradient values (i.e., corresponding to slow propagation of the electric influx, as in the core of the reentrant VT circuit). The relation between the conventional and reference-less method is described theoretically and evaluated in a retrospective study including 24 VT ablation procedures. Results: The “reference-less” method was able to identify normal points with a high accuracy (negative predictive value: NPV = 97%), and to detect more abnormal points, as predicted by the theory. Correlation gradients computed by the proposed method were significantly higher in ablation zones than in other zones of the ventricle (p

International audience; Purpose: Current electrocardiography (ECG) devices in MRI use non-conventional electrode placement, have a narrow bandwidth, and suffer from signal distortions including magnetohydrodynamic (MHD) effects and gradient-induced artifacts. In this work a system is proposed to obtain a high-quality 12-lead ECG.Methods: A network of N electrically independent MR-compatible ECG sensors was developed (N = 4 in this study). Each sensor uses a safe technology - short cables, preamplification/digitization close to the patient, and optical transmission - and provides three bipolar voltage leads. A matrix combination is applied to reconstruct a 12-lead ECG from the raw network signals. A subject-specific calibration is performed to identify the matrix coefficients, maximizing the similarity with a true 12-lead ECG, acquired with a conventional 12-lead device outside the scan room. The sensor network was subjected to radiofrequency heating phantom tests at 3T. It was then tested in four subjects, both at 1.5T and 3T.Results: Radiofrequency heating at 3T was within the MR-compatibility standards. The reconstructed 12-lead ECG showed minimal MHD artifacts and its morphology compared well with that of the true 12-lead ECG, as measured by correlation coefficients above 93% (respectively, 84%) for the QRS complex shape during steady-state free precession (SSFP) imaging at 1.5T (respectively, 3T).Conclusion: High-quality 12-lead ECG can be reconstructed by the proposed sensor network at 1.5T and 3T with reduced MHD artifacts compared to previous systems. The system might help improve patient monitoring and triggering and might also be of interest for interventional MRI and advanced cardiac MR applications.

Increasing numbers of patients with active implantable medical devices (AIMDs) require magnetic resonance (MR) examinations. The manufacturers are continuing to improve the MR compatibility of their AIMDs. To this end, a variety of measurement methods and numerical simulations are used to evaluate the risks associated with magnetic resonance imaging (MRI). In this article, test methods used to investigate interactions between AIMDs with radio frequency fields and time-varying magnetic gradient fields are reviewed. A literature review of known test methods for radio frequency and gradient field exposure of AIMDs with leads, in particular for neurostimulators, cochlear implants, and implanted infusion pumps, is presented. The state of the art and promising methods are discussed. ISO/TS 10974 describes the design of high frequency and gradient injection setups to test conductive materials. A large number of sensor designs have been published to measure the induced voltages and currents through radio frequency and gradient fields and for monitoring AIMDs during MR examinations in in vitro tests. The test methods should be planned to be as conservative as possible to cover the worst case scenario. However, in vitro measurements and computer simulation are far from being able to cover all possible configurations in their complexity and uniqueness. For safer MR examinations, current research recommends in vivo testing prior to MR, parallel radiofrequency transmission techniques, and new sequences with reduced energy input in the presence of AIMDs.

International audience; Objective: Despite being routinely acquired during MRI examinations for triggering or monitoring purposes, electrocardiogram (ECG) signal recording and analysis remain challenging due to the inherent magnetic environment of an MRI scanner. The ECG signals are particularly distorted by the induction of electrical fields in the body by the MRI gradients. In this study, we propose a new hardware and software solution for the acquisition of ECG signal during MRI up to 3 T.Approach: Instead of restricting the sensor bandwidth to limit these gradient artifacts, the new sensor architecture has a higher bandwidth, higher sampling frequency and larger input dynamics, in order to acquire the ECG signals and the gradient artifacts more precisely. Signal processing based on a novel detection algorithm and blanking are then applied for improved artifact suppression.Main results: The proposed sensor allows the gradient artifacts to be acquired more precisely, and these artifacts are recorded with peak-to-peak amplitudes two orders of magnitude larger than for QRS complexes. The proposed method outperforms a state-of-the-art approach both in terms of signal quality (+9% 'SNR') and accuracy of QRS detection (+11%).Significance: The proposed hardware and software solutions open the way for the acquisition of high-quality of ECG gating in MRI, and improved diagnostic quality of ECG signals in MRI.

International audience; Purpose: To quantitatively evaluate a superresolution technique for 3D, one-millimeter isotropic diffusion-weighted imaging (DWI) of the whole breasts.Methods: Isotropic 3D DWI datasets are obtained using a combination of (i) a readout-segmented diffusion-weighted-echo-planar imaging (DW-EPI) sequence (rs-EPI), providing high in-plane resolution, and (ii) a superresolution (SR) strategy, which consists of acquiring 3 datasets with thick slices (3 mm) and 1-mm shifts in the slice direction, and combining them into a 1 × 1 × 1-mm3 dataset using a dedicated reconstruction. Two SR reconstruction schemes were investigated, based on different regularization schemes: conventional Tikhonov or Beltrami (an edge-preserving constraint). The proposed SR strategy was compared to native 1 × 1 × 1-mm3 acquisitions (i.e. with 1-mm slice thickness) in 8 healthy subjects, in terms of signal-to-noise ratio (SNR) efficiency, using a theoretical framework, Monte Carlo simulations and region-of-interest (ROI) measurements, and image sharpness metrics. Apparent diffusion coefficient (ADC) values in normal breast tissue were also compared.Results: The SR images resulted in an SNR gain above 3 compared to native 1 × 1 × 1-mm3 using the same acquisition duration (acquisition gain 3 and reconstruction gain >1). Beltrami-SR provided the best results in terms of SNR and image sharpness. The ADC values in normal breast measured from Beltrami-SR were preserved compared to low-resolution images (1.91 versus 1.97 ×10-3 mm2 /s, P = .1).Conclusion: A combination of rs-EPI and SR allows 3D, 1-mm isotropic breast DWI data to be obtained with better SNR than a native 1-mm isotropic acquisition. The proposed DWI protocol might be of interest for breast cancer monitoring/screening without injection.

International audience; Isotropic three-dimensional (3D) acquisition is a challenging task in magnetic resonance imaging (MRI). Particularly in cardiac MRI, due to hardware and time limitations, current 3D acquisitions are limited by low-resolution, especially in the through-plane direction, leading to poor image quality in that dimension. To overcome this problem, super-resolution (SR) techniques have been proposed to reconstruct a single isotropic 3D volume from multiple anisotropic acquisitions. Previously, local regularization techniques such as total variation have been applied to limit noise amplification while preserving sharp edges and small features in the images. In this paper, inspired by the recent progress in patch-based reconstruction, we propose a novel isotropic 3D reconstruction scheme that integrates non-local and self-similarity information from 3D patch neighborhoods. By grouping 3D patches with similar structures, we enforce the natural sparsity of MR images, which can be expressed by a low-rank structure, leading to robust image reconstruction with high signal-to-noise ratio efficiency. An Augmented Lagrangian formulation of the problem is proposed to efficiently decompose the optimization into a low-rank volume denoising and a SR reconstruction. Experimental results in simulations, brain imaging and clinical cardiac MRI, demonstrate that the proposed joint SR and self-similarity learning framework outperforms current state-of-the-art methods. The proposed reconstruction of isotropic 3D volumes may be particularly useful for cardiac applications, such as myocardial infarction scar assessment by late gadolinium enhancement MRI.

4. Conclusions: Combined respiratory and cardiac triggering improves the localization accuracy and spectral quality in cardiac1H-MRS dramatically leading to substantially increased spectral reproducibility. The best practical realization of double triggering turned out to be the use of the ECG amplitude when making use of the fact that it is modulated by respiration. In spite of the spectral quality achieved in most subjects, we still fail to record satisfactory spectra in a minority of subjects. The reasons for this are not understood at present but must be some particulars of either a given subject or the experimental setup. The cardiac1H-MR spectra contain quantifiable contributions from creatine, TMA, lipids, and probably taurine. It is possible that the spectral contributions of creatine are subject to dipolar coupling similar to the observations for skeletal muscle

Few studies have addressed the interaction between instruction content and saccadic eye movement control. To assess the impact of instructions on top-down control, we instructed 20 healthy volunteers to deliberately delay saccade triggering, to make inaccurate saccades or to redirect saccades--i.e. to glimpse towards and then immediately opposite to the target. Regular pro- and antisaccade tasks were used for comparison. Bottom-up visual input remained unchanged and was a gap paradigm for all instructions. In the inaccuracy and delay tasks, both latencies and accuracies were detrimentally impaired by either type of instruction and the variability of latency and accuracy was increased. The intersaccadic interval (ISI) required to correct erroneous antisaccades was shorter than the ISI for instructed direction changes in the redirection task. The word-by-word instruction content interferes with top-down saccade control. Top-down control is a time consuming process, which may override bottom-up processing only during a limited time period. It is questionable whether parallel processing is possible in top-down control, since the long ISI for instructed direction changes suggests sequential planning.

International audience; Respiratory motion is a source of artifacts in multimodality imaging such as PET/MR. Solutions include retrospective or prospective gating. They have however found limited use in clinical practice, since their increased overall acquisition duration to maintain overall image quality. More elaborate methods consist of using 4D MR datasets to extract spatial deformations in order to correct for the respiratory motion in PET. The main drawbacks of such approaches is the relatively long acquisition times associated with 4D MR imaging which is often incompatible with clinical PET/MR protocols. The objective of this work was to overcome these limitations by exploiting a generalized reconstruction by inversion of coupled systems (GRICS) approach. The methodology is based on a joint estimation of motion during the MR image reconstruction process, providing internal structure motion and associated deformation matrices for retrospective use in PET respiratory motion correction. This method was first validated on four MR volunteers and two PET/MR patient datasets by comparing GRICS generated MR images to 4D MR series obtained by retrospective gating. In a second step 4D PET datasets corresponding to acquired 4D MR images were simulated using the GATE Monte Carlo simulation platform. GRICS generated deformation matrices were subsequently used to correct respiratory motion in comparison to the 4D MR image based deformations both for the simulated and the two 4D PET/MR patient datasets. Results confirm that GRICS synchronized MR images correlate well with the acquired 4D MR series. Similarly, the use of GRICS for respiratory motion correction allows an equivalent percentage improvement on lesion contrast, position and size, considering the PET simulated tumors as well as PET real tumors. This work demonstrates the potential interest of using GRICS for PET respiratory motion correction in combined PET/MR using shorter duration acquisitions without the need for 4D MRI and associated specific MR sequences.

To evaluate the function of an active implantable medical device (AIMD) during magnetic resonance imaging (MRI) scans. The induced voltages caused by the switching of magnetic field gradients and rectified radio frequency (RF) pulse were measured, along with the AIMD stimulations. An MRI-compatible voltage probe with a bandwidth of 0–40 kHz was designed. Measurements were carried out both on the bench with an overvoltage protection circuit commonly used for AIMD and with a pacemaker during MRI scans on a 1.5 T (64 MHz) MR scanner. The sensor exhibits a measurement range of ± 15 V with an amplitude resolution of 7 mV and a temporal resolution of 10 µs. Rectification was measured on the bench with the overvoltage protection circuit. Linear proportionality was confirmed between the induced voltage and the magnetic field gradient slew rate. The pacemaker pacing was recorded successfully during MRI scans. The characteristics of this low-frequency voltage probe allow its use with extreme RF transmission power and magnetic field gradient positioning for MR safety test of AIMD during MRI scans.

International audience; Objective: We describe a new real-time filter to reduce artefacts on electrocardiogram (ECG) due to magnetic field gradients during MRI. The proposed filter is a least mean square (LMS) filter able to continuously adapt its step size according to the gradient signal of the ongoing MRI acquisition.Materials and methods: We implemented this filter and compared it, within two databases (at 1.5 and 3 T) with over 6000 QRS complexes, to five real-time filtering strategies (no filter, low pass filter, standard LMS, and two other filters optimized within the databases: optimized LMS, and optimized Kalman filter).Results: The energy of the remaining noise was significantly reduced (26 vs. 68%, p < 0.001) with the new filter vs. standard LMS. The detection error of our ventricular complex (QRS) detector was: 11% with our method vs. 25% with raw ECG, 35% with low pass filter, 17% with standard LMS, 12% with optimized Kalman filter, and 11% with optimized LMS filter.Conclusion: The adaptive step size LMS improves ECG denoising during MRI. QRS detection has the same F1 score with this filter than with filters optimized within the database.

Eye movement behaviour during visual exploration of 24 patients with probable Alzheimer's disease and 24 age-matched controls was compared in a clock reading task. Controls were found to focus exploration on distinct areas at the end of each clock hand. The sum of these two areas of highest fixation density was defined as the informative region of interest (ROI). In Alzheimer's disease patients, visual exploration was less focused, with fewer fixations inside the ROI, and the time until the first fixation was inside the ROI was significantly delayed. Changes of fixation distribution correlated significantly with the ability to read the clock correctly, but did not correlate with dementia severity. In Alzheimer's disease patients, fixations were longer and saccade amplitudes were smaller. The altered visual exploration in Alzheimer's disease might be related to parietal dysfunction or to an imbalance between a degraded occipito-parietal and relatively preserved occipito-temporal visual network.

International audience; Purpose: Segmentation of cardiac cine MRI data is routinely used for the volumetric analysis of cardiac function. Conventionally, 2D contours are drawn on short-axis (SAX) image stacks with relatively thick slices (typically 8 mm). Here, an acquisition/reconstruction strategy is used for obtaining isotropic 3D cine datasets; reformatted slices are then used to optimize the manual segmentation workflow.Methods: Isotropic 3D cine datasets were obtained from multiple 2D cine stacks (acquired during free-breathing in SAX and long-axis (LAX) orientations) using nonrigid motion correction (cine-GRICS method) and super-resolution. Several manual segmentation strategies were then compared, including conventional SAX segmentation, LAX segmentation in three views only, and combinations of SAX and LAX slices. An implicit B-spline surface reconstruction algorithm is proposed to reconstruct the left ventricular cavity surface from the sparse set of 2D contours.Results: All tested sparse segmentation strategies were in good agreement, with Dice scores above 0.9 despite using fewer slices (3-6 sparse slices instead of 8-10 contiguous SAX slices). When compared to independent phase-contrast flow measurements, stroke volumes computed from four or six sparse slices had slightly higher precision than conventional SAX segmentation (error standard deviation of 5.4 mL against 6.1 mL) at the cost of slightly lower accuracy (bias of -1.2 mL against 0.2 mL). Functional parameters also showed a trend to improved precision, including end-diastolic volumes, end-systolic volumes, and ejection fractions).Conclusion: The postprocessing workflow of 3D isotropic cardiac imaging strategies can be optimized using sparse segmentation and 3D surface reconstruction. Magn Reson Med 79:2665-2675, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

International audience; Objective: The objective of our study was to evaluate the diagnostic performance of qualitative 3-T proton MR spectroscopy (1H-MRS) for the characterization of musculoskeletal neoplasms.Subjects and methods: Proton MRS studies of 74 patients (76 lesions) with a histologically confirmed musculoskeletal neoplasm or neoplasms were prospectively included in this study. All studies were performed using a 3-T MRI scanner. Spectra were analyzed with conventional MRI software provided by the fabricant and with dedicated independent MRS software. Spectra were evaluated visually for the presence or absence of a choline peak at 3.2 ppm. The presence of a choline peak was considered indicative of malignancy. The influences of tumor origin and spectral quality on diagnostic performance were considered.Results: Diagnostic performance was similar with both software used (κ = 0.97). Qualitative 1H-MRS failed to differentiate benign from malignant bone tumors regardless of the application of quality criteria (best sensitivity and specificity, 50.0% and 61.5%, respectively). Diagnostic performance was better with soft-tissue lesions, but the specificity remained low (best sensitivity and specificity, 82.4% and 64.3%, respectively). The application of spectral quality criteria for the evaluation of soft-tissue tumors led to the exclusion of 35.4% of the evaluated spectra.Conclusion: Qualitative 3-T 1H-MRS cannot be used to characterize bone tumors. This technique has good sensitivity but poor specificity for the characterization of soft-tissue lesions.

International audience; To evaluate the added value of ULTRAFAST-MR sequence to an abbreviated FAST protocol in comparison with FULL protocol to distinguish benign from malignant lesions in a population of women, regardless of breast MR imaging indication. Materials and methods: From March 10th to September 22th, 2014, we retrospectively included a total of 70 consecutive patients with 106 histologically proven lesions (58 malignant and 48 benign) who underwent breast MR imaging for preoperative breast staging (n = 38), high-risk screening (n = 7), problem solving (n = 18), and nipple discharge (n = 4) with 12 time resolved imaging of contrast kinetics (TRICKS) acquisitions during contrast inflow interleaved in a regular high-resolution dynamic MRI protocol (FULL protocol). Two readers scored MR exams as either positive or negative and described significant lesions according to Bi-RADS lexicon with a TRICKS images (ULTRAFAST), an abbreviated protocol (FAST) and all images (FULL protocol). Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for each protocol and compared with McNemar's test. Results: For all readers, the combined FAST-ULTRAFAST protocol significantly improved the reading with a specificity of 83.3% and 70.8% in comparison with FAST protocol or FULL protocol, respectively, without change in sensitivity. By adding ULTRAFAST protocol to FAST protocol, readers 1 and 2 were able to correctly change the diagnosis in 22.9% (11/48) and 10.4% (5/48) of benign lesions, without missing any malignancy, respectively. Both interpretation and image acquisition times for combined FAST-ULTRAFAST protocol and FAST protocol were shorter compared to FULL protocol (p < 0.001). Conclusion: Compared to FULL protocol, adding ULTRAFAST to FAST protocol improves specificity, mainly in correctly reclassifying benign masses and reducing interpretation and acquisition time, without decreasing sensitivity.

International audience; OBJECTIVE:To study the effects of calcium on the choline peak measurements with 1H MR spectroscopy.MATERIAL AND METHODS:The thigh muscles of two cadaveric specimens were prospectively evaluated on a 3 T MR unit before and after the injection of calcium carbonate (up to 0.4322 g). The choline peaks of 147 spectra from 10 different anatomic locations were quantitatively evaluated. The influence of the calcium concentration and its disposition with respect to the main magnetic field were considered. B0 phase maps were used to evaluate field inhomogeneities.RESULTS:The presence of calcium led to a 43 % underestimation of the choline peak and the choline concentration (p = 0.0002 and 0.0036). The mean choline concentrations before and after CaCO3 injection were 3.53 ± 1.72 mmol/l and 1.58 ± 0.63 mmol/l. The influence of calcium carbonate on the choline peak estimations was proportional to the calcium concentration. There was a significant position-dependent difference in the estimation of the choline peak amplitude (p

International audience; This study was designed retrospectively to assess the value of myocardial T2 to detect or predict ongoing acute heart rejection, in heart transplant patients, with a 1.5-T MRI magnet. One hundred and ninety-six myocardial T2 quantifications were performed on sixty consecutive heart transplant patients during routine follow- up. T2 values were assessed (i) with regard to the results of concomitant biopsies and (ii) with a Cox multivariate model for the prediction of subsequent rejections, defined by a ≥ grade 2 at biopsy or highly suspected in the absence of biopsy (>10% drop in ejection fraction with subsequent reversibility under treatment). T2 values were proposed as main covariate, after logit transformation andadjustment for other confounding parameters such as delay since graft surgery and delay before biopsy. T2 values were strongly linked (i) to the presence of rejection on concomitant biopsy (P < 0.0001) and (ii) to the risk of subsequent rejection on Cox multivariate model (P < 0.001). T2 values above 60 ms were associated with relative risk of rejection higher than 2.0 and rapidly increasing. In conclusion, myocardial T2 yields a high diagnostic and prognostic value for graft rejection in heart transplant patients.

Introduction Evaluate the capability of different Computed Tomography scanners to determine urinary stone compositions based on CT attenuation values and to evaluate potential differences between each model. Methods 241 human urinary stones were obtained and their biochemical composition determined. Four different CT scanners (Siemens, Philips, GEMS and Toshiba) were evaluated. Mean CT-attenuation values and the standard deviation were recorded separately and compared with a t-paired test. Results For all tested CT scanners, when the classification of the various types of stones was arranged according to the mean CT-attenuation values and to the confidence interval, large overlappings between stone types were highlighted. The t-paired test showed that most stone types could not be identified. Some types of stones presented mean CT attenuation values significantly different from one CT scanner to another. At 80 kV, the mean CT attenuation values obtained with the Toshiba Aquilion were significantly different from those obtained with the Siemens Sensation. On the other hand, mean values obtained with the Philips Brilliance were all significantly equal to those obtained with the Siemens Sensation and with the Toshiba Aquilion. At 120 kV mean CT attenuation values of uric acid, cystine and struvite stones obtained with the Philips model are significantly different from those obtained with the Siemens and the Toshiba but equal to those obtained with the GE 64. Conclusions According to our study, there is a great variability when different brands and models of scanners are compared directly. Furthermore, the CT scan analysis and HU evaluation appears to gather insufficient information in order to characterize and identify the composition of renal stones.

International audience; Age estimation of living individuals aged less than 13, 18 or 21 years, which are some relevant legal ages in most European countries, is currently problematic in the forensic context. Thus, numerous methods are available for legal authorities, although their efficiency can be discussed. For those reasons, we aimed to propose a new method, based on the biometric analysis of hand bones. 451 hand radiographs of French individuals under the age of 21 were retrospectively analyzed. This total sample was divided into three subgroups bounded by the relevant legal ages previously mentioned: 0–13, 13–18 and 18–21 years. On these radiographs, we numerically applied the osteometric board method used in anthropology, by including each metacarpal and proximal phalange of the five hand rays in the smallest rectangle possible. In that we can access their length and width information thanks to a measurement protocol developed precisely for our treatment with the ORS Visual 1 software. Then, a statistical analysis was performed from these biometric data: a Linear Discriminant Analysis (LDA) evaluated the probability for an individual to belong to one of the age group (0–13, 13–18 or 18–21); and several multivariate regression models were tested for the establishment of age estimation formulas for each of these age groups. The mean Correlation Coefficient between chronological age and both lengths and widths of hand bones is equal to 0.90 for the total sample. Repeatability and reproducibility were assessed. The LDA could more easily predict the belonging to the 0–13 age group. Age can be estimated with a mean standard error which never exceeds 1 year for the 95% confidence interval. Finally, compared to the literature, we can conclude that estimating an age from the biometric information of metacarpals and proximal phalanges is promising.

To evaluate the impact of a novel postprocessing denoising technique on accuracy and precision in myocardial TThis study introduces a fast and robust denoising method developed for magnetic resonance TSimulations on synthetic phantom showed signal-to-noise ratio and sharpness improvement with the proposed method in comparison with conventional denoising. In vivo results demonstrated that our method preserves accuracy, as no difference in mean TThe proposed denoising method preserves accuracy and improves precision in myocardial T3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1377-1388.

International audience; Purpose: To compare three widely used methods for myocardial infarct (MI) sizing on late gadolinium-enhanced (LGE) magnetic resonance (MR) images: manual delineation and two semiautomated techniques (full-width at half-maximum [FWHM] and n-standard deviation [SD]).Materials and methods: 3T phase-sensitive inversion-recovery (PSIR) LGE images of 114 patients after an acute MI (2-4 days and 6 months) were analyzed by two independent observers to determine both total and core infarct sizes (TIS/CIS). Manual delineation served as the reference for determination of optimal thresholds for semiautomated methods after thresholding at multiple values. Reproducibility and accuracy were expressed as overall bias ± 95% limits of agreement.Results: Mean infarct sizes by manual methods were 39.0%/24.4% for the acute MI group (TIS/CIS) and 29.7%/17.3% for the chronic MI group. The optimal thresholds (ie, providing the closest mean value to the manual method) were FWHM30% and 3SD for the TIS measurement and FWHM45% and 6SD for the CIS measurement (paired t-test; all P > 0.05). The best reproducibility was obtained using FWHM. For TIS measurement in the acute MI group, intra-/interobserver agreements, from Bland-Altman analysis, with FWHM30%, 3SD, and manual were -0.02 ± 7.74%/-0.74 ± 5.52%, 0.31 ± 9.78%/2.96 ± 16.62% and -2.12 ± 8.86%/0.18 ± 16.12, respectively; in the chronic MI group, the corresponding values were 0.23 ± 3.5%/-2.28 ± 15.06, -0.29 ± 10.46%/3.12 ± 13.06% and 1.68 ± 6.52%/-2.88 ± 9.62%, respectively. A similar trend for reproducibility was obtained for CIS measurement. However, semiautomated methods produced inconsistent results (variabilities of 24-46%) compared to manual delineation.Conclusion: The FWHM technique was the most reproducible method for infarct sizing both in acute and chronic MI. However, both FWHM and n-SD methods showed limited accuracy compared to manual delineation. J. Magn. Reson. Imaging 2016;44:1206-1217.

International audience; Objectives: To assess cardiac and vascular adaptations in long-distance male triathletes and the influence of an increased training volume on these parameters. Design: Case-control study using long-distance male triathletes (Tri) (n = 12) and an age-matched cohort of sedentary volunteers (Ctrl). Methods: All participants gave an informed consent and underwent a Cardiovascular Magnetic Resonance imaging (CMR) exam to measure left and right ventricle functional parameters, and aortic parameters (surface, strain, compliance, pulse wave velocity). This exam was repeated in the triathletes' group after an increased training volume of at least 2 h/week for six weeks. Results: Compared to control volunteers, triathletes presented at baseline a typical pattern of athlete's heart (higher end-diastolic, end-systolic and stroke volumes index, p ≤ 0.009, and lower cardiac rate, p = 0.015) but similar vascular characteristics except a trend towards an enlarged ascending aorta (surface 942 ± 106 vs 812 ± 127 mm 2 , p = 0.058). Between the two visits, the triathletes increased their weekly training time from 9.67 ± 2.43 (Tri1) to 12.15 ± 3.01 h (Tri2): no modifications were found regarding cardiac parameters, but compliance and distensibility of the ascending aorta increased, from 2.60 to 3.34 mm 2 /mmHg (p = 0.028) and from 3.36 to 4.40 × 10 −3 mmHg −1 (p = 0.048) respectively. Conclusions: Using CMR, we showed that vascular characteristics of the ascending aorta may vary along the sport season in endurance athletes. This remodelling could be considered as a physiological adaptation, but could eventually lead to an adverse vascular remodelling.

International audience; Background: With ablation, the follow-up of preexcitation syndrome now is difficult to assess. The purpose was to collect data of children with a preexcitation syndrome studied on two separate occasions within a minimal interval of 1 year.Methods: This is a retrospective chart review of 47 children initially aged 12 ± 4 years, who underwent two or more invasive electrophysiological studies (EPS) within 1-25 years of one another (6.3 ± 4.8) for occurrence of symptoms or new evaluation.Results: Among initially symptomatic children (n = 25), four (19%) became asymptomatic and one presented life-threatening arrhythmia. Among asymptomatic children (n = 22), five became symptomatic (22.7%). Anterograde conduction disappeared in seven of 23 children with initially long accessory pathway-effective refractory period, but four of six had still induced atrioventricular reentrant tachycardia (AVRT). AVRT was induced at second EPS in three of 13 asymptomatic preexcitation syndrome with negative initial EPS. There were no spontaneous adverse events in the five children with criteria of malignancy at initial EPS; signs of malignancy disappeared in two. At multivariate analysis, AVRT at initial EPS was the only independent factor of symptomatic AVRT during follow-up. Absence of induced AVRT at initial EPS was the only factor of absence of symptoms and a negative study at the second EPS.Conclusions: There were no significant changes of data in children after 6.3 ± 4.8 years of follow-up. Most children with spontaneous/inducible AVRTs at initial EPS had still inducible AVRT at second EPS. Induced AF conducted with high rate has a relatively low prognostic value for the prediction of adverse events.

International audience

International audience; Goal: A novel magnetic resonance (MR) compatible accelerometer for respiratory motion sensing (MARMOT) is developed as a surrogate of the vendors' pneumatic belts. We aim to model and correct respiratory motion for free-breathing thoracic-abdominal MR imaging and to simplify patient installation.Methods: MR compatibility of MARMOT sensors was assessed in phantoms and its motion modeling/correction efficacy was demonstrated on 21 subjects at 3 T. Respiration was modeled and predicted from MARMOT sensors and pneumatic belts, based on real-time images and a regression method. The sensor accuracy was validated by comparing motion errors in the liver/kidney. Sensor data were also exploited as inputs for motion-compensated reconstruction of free-breathing cardiac cine MR images. Multiple and single sensor placement strategies were compared.Results: The new sensor is compatible with the MR environment. The average motion modeling and prediction errors with MARMOT sensors and with pneumatic belts were comparable (liver and kidney) and were below 2 mm with all tested configurations (belts, multiple/single MARMOT sensor). Motion corrected cardiac cine images were of improved image quality, as assessed by an entropy metric (p < 10-6), with all tested configurations. Expert readings revealed multiple MARMOT sensors were the best (p < 0.03) and the single MARMOT sensor was similar to the belts (nonsignificant in two of the three readers).Conclusion: The proposed sensor can model and predict respiratory motion with sufficient accuracy to allow free-breathing MR imaging strategy.Significance: It provides an alternative sensor solution for the respiratory motion problem during MR imaging and may improve the convenience of patient setup.

The motion of the vestibulo-cochlear nerve (VCN) was quantified at the level of the cerebello-pontine angle in 28 healthy volunteers enrolled in a prospective study performed on a 3 T MRI scanner. A phase contrast MRI (PCMRI) sequence was used. The VCN was divided into a cisternal part and a meatic part, both of which were measured for motion in the cranio-caudal (CC) and antero-posterior (AP) directions. Motion was cardiac-cycle-dependent in these two directions. The meatic VCN motion was delayed compared to the cisternal VCN motion. In the CC direction, the mean amplitude of the cisternal VCN motion was twice larger than the mean amplitude of the meatic VCN motion (0.37 +/− 0.14 mm versus 0.17 +/− 0.08 mm). In the AP direction, the mean amplitude of the cisternal VCN was 0.19 +/− 0.08 mm versus 0.16 +/− 0.14 mm for the meatic VCN. We used an “oscillating string” to explain the VCN motion. Reproducibility tests have shown small variations in measurements of the CC motion. PCMRI can be used to assess the VCN motion at the level of the cerebello-pontine angle.

Purpose: To assess cardiac function by means of a novel free-breathing cardiac magnetic resonance imaging (MRI) strategy. Materials and Methods: A stack of ungated 2D steady-state free precession (SSFP) slices was acquired during free breathing and reconstructed as cardiac cine imaging based on the generalized reconstruction by inversion of coupled systems (GRICS). A motion-compensated sliding window approach allows reconstructing cine movies with most motion artifacts cancelled. The proposed reconstruction uses prior knowledge from respiratory belts and electrocardiogram recordings and features a piecewise linear model that relates the electrocardiogram signal to cardiac displacements. The free-breathing protocol was validated in six subjects against a standard breath-held protocol. Results: Image sharpness, as assessed by the image gradient entropy, was comparable to that of breath-held images and significantly better than in uncorrected images. Volumetric parameters of cardiac function in the left ventricle (LV) and right ventricle (RV) were similar, including end-systolic volumes, end-diastolic volumes and mass, stroke volumes, and ejection fractions (with differences of 3% ± 2.4 in the LV and 2.9% ± 4.4 in the RV). The duration of the free-breathing protocol was nearly the same as the breath-held protocol. Conclusion: Free-breathing cine-GRICS enables accurate assessment of volumetric parameters of cardiac function with efficient correction of motion. J. Magn. Reson. Imaging 2012;340-351. © 2011 Wiley Periodicals, Inc.

BACKGROUND Hypertension is strongly associated with cognitive decline and a promising target for dementia prevention. Our aim was to investigate the association between different antihypertensive treatments and cognitive performance in elderly hypertensive patients presenting with subjective memory complaints. PATIENTS AND METHODS Three hundred and seventy-eight elderly hypertensive patients more than 60 years (mean age 70.4 ± 6.3 years) treated with at least one antihypertensive agent and presenting with subjective memory complaints but without dementia were prospectively recruited and underwent a combination of neuropsychological tests, brain magnetic resonance imaging with semiquantification of white matter hyperintensities, carotid echotracking, brachial endothelial function, and ambulatory blood pressure assessments. RESULTS None of the three composite scores (memory score, verbal fluency, and visual memory capacity) was found associated with blood pressure levels. On the other hand, age-adjusted and sex-adjusted analyses showed a significant and positive association between memory score and use of calcium channel blockers (CCBs) (users: +0.14 ± 0.09 versus nonusers: -0.12 ± 0.06; P = 0.016). Multivariate analyses also revealed that CCB use was significantly associated with a better memory score, independently of age, male sex, white matter hyperintensities, and carotid wall cross-sectional area, all of which were associated with worse memory scores. CONCLUSION In elderly hypertensive treated patients with subjective memory complaints, CCB use was associated with better memory performance independently of blood pressure level and macrovascular and microvascular alterations, suggesting a specific neuroprotective effect of this pharmacological class. Interventional controlled trials are required to confirm the specific protective effect of CCBs on cognitive decline.

Background: We have recently shown that vascular abnormalities are associated with cognitive impairment as well as with white matter hyperintensities (WMH) in elderly hypertensive patients presenting with subjective memory complaints (SMC), a population at high risk of developing dementia. The aim of the present study was to identify genetic variants associated with the degree of cognitive impairment and the severity of WMH in the same study population, focusing on genes involved in vascular alterations. Methods: 50 gene polymorphisms known to be associated with vascular alterations (blood pressure regulation, lipid and homocysteine metabolism, thrombosis and inflammation) were genotyped using a multilocus genotyping assay in 369 elderly treated hypertensive patients >60 years of age and presenting with SMC but no dementia. The patients underwent a combination of neuropsychological tests and brain magnetic resonance imaging with semiquantification of WMH. Results: None of the tested polymorphisms were found to be associated with age- and gender-adjusted memory score, visual capacity, body-mass-index-adjusted verbal fluency score or the age-adjusted WMH Fazekas score. Conclusion: Our results suggest that the associations between arterial factors and cognitive decline or WMH are not genetically driven by the genes we investigated, at least at this early stage of cognitive decline.

Background and Purpose— Arterial stiffening and thickening and endothelial dysfunction may be associated with cognitive decline or white matter hyperintensities (WMH) independently of blood pressure level. We aimed to investigate, using an integrative approach, the relative contributions of structural and functional vascular factors to the degree of cognitive impairment (primary outcome) and the severity of WMH (secondary outcome) in elderly hypertensive patients with subjective memory complaints, a group prone to dementia. Methods— A prospective, dedicated, cross-sectional population of 198 elderly hypertensive patients (mean age 69.3±6.2 years) with subjective memory complaints underwent a full set of cognitive function assessments, brain MRI with semiquantification of WMH, carotid ultrasonography, carotid–femoral pulse wave velocity, brachial endothelial function, and plasma von Willebrand Factor measurements. Results— After adjustment for the usual cardiovascular risk factors, increased arterial stiffness (as assessed by pulse wave velocity) was significantly and independently associated with memory impairment in men. The severity of WMH was independently associated with increased carotid intima media thickness and stiffness (as assessed by augmentation index) as well as with increased age and plasma levels of von Willebrand Factor, a biomarker of endothelial dysfunction. Conclusions— Our data suggest that vascular abnormalities, independently of blood pressure levels, may play a role in the setting of subjective memory complaints as well as of WMH in elderly hypertensive patients. Arterial thickness and stiffness as well as endothelial function should be assessed simultaneously and may represent additional targets for the prevention of subjective memory complaints and WMH.

A reconstruction strategy is proposed for physiological motion correction, which overcomes many limitations of existing techniques. The method is based on a general framework allowing correction for arbitrary motion–nonrigid or affine, making it suitable for cardiac or abdominal imaging, in the context of multiple coil, arbitrarily sampled acquisition. A model is required to predict motion in the field of view at each sample time point, based on prior knowledge provided by external sensors. A theoretical study is carried out to analyze the influence of motion prediction errors. Small errors are shown to propagate linearly in that reconstruction algorithm, and thus induce a reconstruction residue that is bounded (stability). Furthermore, optimization of the motion model is proposed in order to minimize this residue. This leads to reformulating reconstruction as two inverse problems which are coupled: motion-compensated reconstruction (known motion) and model optimization (known image). A fixed-point multiresolution scheme is described for inverting these two coupled systems. This framework is shown to allow fully autocalibrated reconstructions, as coil sensitivities and motion model coefficients are determined directly from the corrupted raw data. The theory is validated with real cardiac and abdominal data from healthy volunteers, acquired in free-breathing. Magn Reson Med 60:146–157, 2008. © 2008 Wiley-Liss, Inc.

International audience; OBJECTIVE:To evaluate the performance of quantitative diffusion-weighted imaging (DWI) correlated with T2 signal in differentiating non-fatty benign from malignant tumors.MATERIAL AND METHODS:A total of 76 patients with a histologically confirmed non-fatty soft tissue tumors (46 benign and 30 malignant) were prospectively included in this ethics committee approved study. All patients signed an informed consent and underwent MRI with DWI with two b values (0 and 600). ADC values from the solid components of these tumors were obtained and were correlated with the lesion's signal intensity on T2-weighted fat-saturated sequences. ADC values were obtained from adjacent normal muscle to allow calculation of tumor/muscle ADC ratios.RESULTS:There were 58 hyperintense and 18 iso or hypointense lesions. All hypointense lesions were benign. The mean ADC values for benign and malignant tumors were 1.47 ± 0.54 × 10(-3) and 1.17 ± 0.38 × 10(-3) mm(2)/s respectively (p

International audience; OBJECTIVES:Blood pressure (BP) and its changes with antihypertensive therapy are key parameters when monitoring left ventricular (LV) remodeling. This dual cross-sectional and longitudinal MRI study aimed to determine whether this monitoring is enhanced by aortic stroke volume (SV) values provided by a phase-contrast sequence.METHODS:The study involved 334 MRI examinations from 247 study participants who had no significant cardiac disease (18-85 years old, 40% with hypertension) and among whom 48 had a 2-4-year MRI follow-up. Left ventricular hypertrophy and concentric geometry were: respectively assessed according to LV mass indexed to body surface area (g/m) and mass/end-diastolic volume ratio (concentric remodeling index); and correlated with vascular parameters involving BP and the indexed SV (ml/m) determined in the ascending aorta with a phase-contrast sequence.RESULTS:Stroke volume was highly variable, ranging from 22 to 74 ml/m. The best cross-sectional correlates were: mean BP × SV product, reflecting cardiac work, for LV mass (r = 0.21); and mean BP/SV ratio, reflecting arterial load, for concentric geometry (r = 0.29). These two SV-derived parameters led to more than two-fold enhancements in cross-sectional predictions compared with BP parameters alone, whereas their longitudinal changes over time paralleled those of concentric geometry (P = 0.003 for mean BP/SV) and LV mass (P = 0.006 for mean BP × SV), suggesting direct links with cardiac remodeling.CONCLUSION:The determination of aortic SV with a phase-contrast sequence leads to a significant enhancement in the characterization and monitoring of cardiac remodeling.

Summary Objectives: To review past and present challenges and ongoing trends in numerical simulation for MRI (Magnetic Resonance Imaging) safety evaluation of medical devices. Methods: A wide literature review on numerical and analytical simulation on simple or complex medical devices in MRI electromagnetic fields shows the evolutions through time and a growing concern for MRI safety over the years. Major issues and achievements are described, as well as current trends and perspectives in this research field. Results: Numerical simulation of medical devices is constantly evolving, supported by calculation methods now well-established. Implants with simple geometry can often be simulated in a computational human model, but one issue remaining today is the experimental validation of these human models. A great concern is to assess RF heating on implants too complex to be traditionally simulated, like pacemaker leads. Thus, ongoing researches focus on alternative hybrids methods, both numerical and experimental, with for example a transfer function method. For the static field and gradient fields, analytical models can be used for dimensioning simple implants shapes, but limited for complex geometries that cannot be studied with simplifying assumptions. Conclusions: Numerical simulation is an essential tool for MRI safety testing of medical devices. The main issues remain the accuracy of simulations compared to real life and the studies of complex devices; but as the research field is constantly evolving, some promising ideas are now under investigation to take up the challenges.

International audience; Objective: Assess the use of a volumetric simulation tool for the evaluation of radiology resident MR and CT interpretation skills.Material and methods: Forty-three participants were evaluated with a software allowing the visualisation of multiple volumetric image series. There were 7 medical students, 28 residents and 8 senior radiologists among the participants. Residents were divided into two sub-groups (novice and advanced). The test was composed of 15 exercises on general radiology and lasted 45 min. Participants answered a questionnaire on their experience with the test using a 5-point Likert scale. This study was approved by the dean of the medical school and did not require ethics committee approval.Results: The reliability of the test was good with a Cronbach alpha value of 0.9. Test scores were significantly different in all sub-groups studies (p < 0.0225). The relation between test scores and the year of residency was logarithmic (R2 = 0.974). Participants agreed that the test reflected their radiological practice (3.9 ± 0.9 on a 5-point scale) and was better than the conventional evaluation methods (4.6 ± 0.5 on a 5-point scale).Conclusion: This software provides a high quality evaluation tool for the assessment of the interpretation skills in radiology residents.Key points: • This tool allows volumetric image analysis of MR and CT studies. • A high reliability test could be created with this tool. • Test scores were strongly associated with the examinee expertise level. • Examinees positively evaluated the authenticity and usability of this tool.

Exploiting redundancies between multiple images of an MRI examination can be formalized as the joint reconstruction of these images. The anatomy is preserved indeed so that specific constraints can be implemented (e.g. most of the features or spatial gradients should be in the same place in all these images) and only the contrast changes from one image to another need to be encoded. The application of this concept is particularly challenging in cardiovascular and body imaging due to the complex organ deformations, especially with the patient breathing. In this study a joint optimization framework is proposed for reconstructing multiple MR images together with a nonrigid motion model. The motion model takes into account both intra-image and inter-image motion and therefore can correct for most ghosting/blurring artifacts and misregistration between images. The framework was validated with free-breathing myocardial T2 mapping experiments from nine heart transplant patients at 1.5 T. Results showed improved image quality and excellent image alignment with the multi-image reconstruction compared to the independent reconstruction of each image. Segment-wise myocardial T2 values were in good agreement with the reference values obtained from multiple breath-holds (62.5 ± 11.1 ms against 62.2 ± 11.2 ms which was not significant with p=0.49).

International audience; To assess the pattern of right ventricular (RV) functional recovery in a cohort of patients with successful reperfusion of a first episode of acute myocardial infarction (AMI) with 2D speckle-tracking echocardiography and cardiac magnetic resonance imaging (CMR). Ninety-five revascularized AMI patients were prospectively included (56.8 ± 11.1 years, 48 inferior, 47 anterior). RV function was assessed by echocardiography and CMR within the initial 72 h and 6 months later. A RV global strain was calculated while averaging strain values from septal, lateral and inferior walls. At the acute phase, RVEFCMR was lower in inferior than in anterior AMI patients (52.5 ± 6.8 vs. 56.0 ± 4.8, p = 0.006). Similarly, RV global, inferior and lateral strains were lower in inferior MI patients (p < 0.001 for all) whereas septal strain was not significantly different across groups. At 6 months, RVEFCMR and all strain parameters improved compared to baseline. Improvements were more substantial for patients with inferior than with anterior MI. RV parameters ultimately reached similar levels in the two groups at 6 months except for inferior strain which remained lower in patients with inferior MI (-24.5 ± 6.5 vs. -27.5 ± 5.4, p = 0.03). In low risk patients after AMI, RV function ultimately recovered over the 6 months of follow up. Higher levels of both initial impairment and subsequent recovery were observed for inferior MI. Although RV function was relatively preserved in these patients, RV strain analysis revealed a persistent impairment of RV inferior strain in patients with inferior MI, which may not be identified by RVEFCMR or conventional echocardiographic parameters.

Background The place of magnetic resonance imaging (MRI) in the assessment of pulmonary hypertension (PH) remains controversial. Several studies proposed to use MRI to assess pulmonary pressure but the level of proof is low. Purpose To evaluate the diagnostic power of cardiac MRI within a non-selected population of patients suspected of PH after an echocardiography. Material and Methods Fifty-six consecutive patients, suspected of PH after an echocardiography, were assessed with right heart catheterization and cardiac MRI (including a high temporal resolution pulmonary flow curve). We extracted from the MRI data the main parameters proposed by all precedent studies available in the literature. We looked for multivariate linear relations between those parameters and the mean pulmonary arterial pressure (mPAP), and eventually assessed with a logit regression the ability of those parameters to diagnose PH in our population. Results The multivariate model retained only two parameters: the right ventricle ejection fraction and the pulmonary trunk minimum area. The prediction of mPAP (r2 = 0.5) yielded limits of agreement of 15 mmHg. However, the prediction of PH within the population was feasible and the method yielded a specificity of 80% for a sensitivity of 100%. Conclusion The performance of MRI to assess mPAP is too low to be used as a replacement for right heart catheterization but MRI could be used as second line examination after echocardiography to avoid right heart catheterization for normal patients.

Supplemental Digital Content is available in the text, To assess left ventricular ejection fraction (LVEF) accurately, cardiac magnetic resonance (CMR) can be indicated and lays on the evaluation of multiple slices of the left ventricle in short axis (CMRSAX). The objective of this study was to assess another method consisting of the evaluation of 2 long-axis slices (CMRLAX) for LVEF determination in acute myocardial infarction. One hundred patients underwent CMR 2 to 4 days after acute myocardial infarction. LVEF was computed by the area-length method on horizontal and vertical CMRLAX images. Those results were compared to reference values obtained on contiguous CMRSAX images in one hand, and to values obtained from transthoracic echocardiography (TTE) in the other hand. For CMRSAX and TTE, LVEF was computed with Simpson method. Reproducibility of LVEF measurements was additionally determined. The accuracy of volume measurements was assessed against reference aortic stroke volumes obtained by phase-contrast MR imaging. LVEF from CMRLAX had a mean value of 47 ± 8% and were on average 5% higher than reference LVEF from CMRSAX (42 ± 8%), closer to routine values from TTELAX (49 ± 8%), much better correlated with the reference LVEF from CMRSAX (R = 0.88) than that from TTE (R = 0.58), obtained with a higher reproducibility than with the 2 other techniques (% of interobserver variability: CMRLAX 5%, CMRSAX 11%, and TTE 13%), and obtained with 4-fold lower recording and calculation times than for CMRSAX. Apart from this, CMRLAX stroke volume was well correlated with phase-contrast values (R = 0.81). In patients with predominantly regional contractility abnormalities, the determination of LVEF by CMRLAX is twice more reproducible than the reference CMRSAX method, even though the LVEF is consistently overestimated compared with CMRSAX. However, the CMRLAX LVEF determination provides values closer to TTE measurements, the most available and commonly used method in clinical practice, clinical trials, and guidelines in ischemic cardiomyopathy. Moreover, LVEF determination by CMRLAX allows a 63% gain of acquisition/reading time compared with CMRSAX. Thus, despite the fact that LVEF obtained from CMRSAX remains the gold standard, CMRLAX should be considered to shorten the overall imaging acquisition and reading time as a putative replacement.