J P Vallée

University of Geneva, Genève, Geneva, Switzerland

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Publications (31)93.42 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Mesenchymal stromal cells (MSCs) are promising candidates in regenerative cell-therapies. However, optimizing their number and route of delivery remains a critical issue, which can be addressed by monitoring the MSCs’ bio-distribution in vivo using super-paramagnetic iron-oxide nanoparticles (SPIONs). In this study, amino-polyvinyl alcohol coated (A-PVA) SPIONs are introduced for cell-labeling and visualization by magnetic resonance imaging (MRI) of human MSCs. Size and surface charge of A-PVA-SPIONs differ depending on their solvent. Under MSC-labeling conditions, A-PVA-SPIONs have a hydrodynamic diameter of 42 ± 2 nm and a negative Zeta potential of 25 ± 5 mV, which enable efficient internalization by MSCs without the need to use transfection agents. Transmission X-ray microscopy localizes A-PVA-SPIONs in intracellular vesicles and as cytosolic single particles. After identifying non-interfering cell-assays and determining the delivered and cellular dose, in addition to the administered dose, A-PVA-SPIONs are found to be non-toxic to MSCs and non-destructive towards their multi-lineage differentiation potential. Surprisingly, MSC migration is increased. In MRI, A-PVA-SPION-labeled MSCs are successfully visualized in vitro and in vivo. In conclusion, A-PVA-SPIONs have no unfavorable influences on MSCs, although it becomes evident how sensitive their functional behavior is towards SPION-labeling. And A-PVA-SPIONs allow MSC-monitoring in vivo.
    Small 07/2014; 10(21):4340-4351. DOI:10.1002/smll.201400707 · 8.37 Impact Factor
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    ABSTRACT: Background Disease assessment using magnetic resonance imaging (MRI) in small animal models of rheumatoid arthritis (RA) is not a commonly used method to date. Inflammation and erosion histological scoring remain the gold standard and more recently μCT for bone erosion. Among the limitations of using histological scoring in longitudinal studies is the large number of animals needed making these studies not only time consuming but also labor intensive. Objectives The aim of this study was to validate the efficiency of MRI in assessing synovial and intra-articular oedema as well as bone erosion in affected knee joints over time in the presence and absence of anti-arthritic medication compared to other conventional methods. Methods Antigen induced Arthritis (AIA) was triggered in the right knee of 45 female Lewis rats using the following protocol; immunization twice by injecting 500 μg methylated bovine serum albumin (mBSA) emulsified in complete Freund’s adjuvant subcutaneously and 2*109 Bordetella Pertussis intraperitoneally on days -21 and -14. Mono-arthritis was induced on day 0 in the right knee: intra-articular 500μg BSA/50mL saline and left knee: 50μL saline. Animals were scanned using MRI and CT on the following days: 0, 3, 6, 10, 13, 17 and 5 animals were sacrificed at each time point. A Siemens 3T clinical scanner with 4cm loop coil was used for MRI with parameters: T2 2D-STIR for oedema, TR/TE 3700/20ms, resolution 0.156mm and 3D-GRE for bone erosion, TR/TE 14.3/5.9ms, resolution 0.31mm. Skyscan-1076 μCT was used with parameters: 65 kV anode voltage, 180mA, 0.45° rotation step, 316ms exposure time per view and final resolution of 35mm. Histology scoring of synovial infiltration and erosion were performed on H&E paraffin sections.Statistical analysis included double exponential fits of disease component score, derivative coefficients comparison (Friedman non-parametric) and time of maximum (tmax). Results On MRI, diseased joints showed rapid development of synovitis with periarticular oedema, followed by bone erosion. Fitting of scores shows consistency between animals, with good R2 also for individual animals (0.60 to 0.94). Wilcoxon analysis shows significant difference in tmax (p=0.043) for synovial and intra-articular oedema. Erosion continued to increase. A good correlation was seen between synovitis scores on MRI and histological sections, and between bone erosion scores on MRI and μCT images. Initial results indicate that MRI scores of inflammation and erosion performed on dexamethasone treated animals have the required sensitivity to detect differences due to treatment. Conclusions Noninvasive imaging techniques and specifically MRI provide a good and reliable method for long term assessment of AIA and anti-RA therapeutic trials and offer certain advantages over the conventional methods such as histological scoring. Disclosure of Interest None Declared
    Annals of the Rheumatic Diseases 01/2014; 71(Suppl 3):488-488. DOI:10.1136/annrheumdis-2012-eular.3001 · 10.38 Impact Factor
  • S. Borot · L. Crowe · P. Morel · D. Bosco · J.-P. Vallee · T. Berney
    Transplantation 11/2012; 94(10S):723. DOI:10.1097/00007890-201211271-01420 · 3.83 Impact Factor
  • International Journal of Cardiology 03/2012; 155:S97. DOI:10.1016/S0167-5273(12)70237-1 · 4.04 Impact Factor
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    Journal of Cardiovascular Magnetic Resonance 02/2012; 14 Suppl 1(Suppl 1):P60. DOI:10.1186/1532-429X-14-S1-P60 · 4.56 Impact Factor
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    Journal of Cardiovascular Magnetic Resonance 02/2012; 14 Suppl 1(Suppl 1):P80. DOI:10.1186/1532-429X-14-S1-P80 · 4.56 Impact Factor
  • S. Borot · L. Crowe · F. Ris · S. Masson · P. Morel · J.-P. Vallee · T. Berney
    Diabetes & Metabolism 03/2011; 37(1). DOI:10.1016/S1262-3636(11)70764-9 · 3.27 Impact Factor
  • 18th Scientific Meeting & Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM'10); 01/2010
  • 97th Annual Meeting of the Swiss Society of Radiology; 01/2010
  • Proceedings of 24th International Congress and Exhibition of Computer Assisted Radiology and Surgery (CARS2010); 01/2010
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    ABSTRACT: Introduction Marginal kidneys must be reanimated before their transplantation. Reanimation is conduced with hypothermic pulsatile perfusion. The tests used generally to demonstrate the viability is the vascular resistance which is not convenient for everybody. We have developed a magnetic resonance compatible perfusional technology allowing us to test the organs during the perfusion by Gd-perfusion MRI. Methods and results We have used pigs’ kidneys with no warm ischemic time to establish the basis in a normal kidney. After an eight-hour hypothermic pulsatile perfusion, kidneys are submitted to a Gd perfusion. First, we measure the anatomy of the vessels, then the distribution of Gd in the kidney. We obtain simultaneously a dynamic study of the organs where T0 represents the Gd bolus arrival in the cortex and TP the maximum saturation time of Gd. Conclusion We have observed that a normal T0 is inferior to 30 s and TP is inferior to one minute. We have compared these values with ATP resynthesis in these organs and found that they correlate. We hope for the future through that predictive use of Gd-MRI to avoid the clinical use of “too” marginal kidneys or the discard of good kidneys but not corresponding with the vascular resistance theory.
    Progrès en Urologie 05/2009; 19(5):307–312. DOI:10.1016/j.purol.2009.01.004 · 0.66 Impact Factor
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    B Delattre · J N Hyacinthe · J P Vallée · D Van De Ville
    17th Scientific Meeting & Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM'09); 01/2009
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    ABSTRACT: The aim of this study was to measure the myocardial area at risk in rat, using MRI and manganese injection during a coronary occlusion/reperfusion model at 1.5T. A sequential protocol with occlusion and MnCl2 injection immediately followed by MRI was used with the assumption that MnCl2-induced contrast persistence is enough to accurately image the area at risk 90 min after occlusion. A total of 15 adult rats underwent a single 30-min episode of coronary occlusion followed by reperfusion. MnCl2 was injected (25 micromol/kg) at the beginning of the occlusion for 11 rats (group 1) and 6 h after reperfusion for four animals (group 2). A deficit of signal enhancement was observed in all rats. Hypoenhancement area in group 1 was correlated to the area at risk delineated by methylene blue (r=0.96, P<0.0001) whereas in group 2 it was correlated to the infarct area given by triphenyltetrazolium chloride (TTC) solution (r=0.98, P=0.003). The area at risk size was significantly correlated with left ventricle ejection fraction (LVEF), end-systolic volume and anterolateral wall thickening. This work demonstrates that hypoenhanced zone obtained after manganese injection during occlusion represents the area at risk and not only the infarct zone.
    Magnetic Resonance in Medicine 06/2008; 59(6):1422-30. DOI:10.1002/mrm.21493 · 3.57 Impact Factor
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    ABSTRACT: Cardiovascular magnetic resonance has been shown to provide high data quality for myocardial perfusion assessment. However, to analyze the perfusion data, some signal processing and modeling is needed to correct for motion related artifacts and limited spatial resolution. This study describes a method based on system identification, allowing, after a first step of image registration, to integrate and correct the partial volume effect in the myocardium perfusion quantification. This method is then applied to patients with coronary artery disease or hypertrophic obstructive cardiomyopathy.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:4492-5. DOI:10.1109/IEMBS.2007.4353337
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    ABSTRACT: The overall goal was to study cardiovascular function in small animals using a clinical 1.5-T MR scanner optimizing a fast gradient-echo cine sequence to obtain high spatial and temporal resolution. Normal rat hearts (n = 9) were imaged using a 1.5-T MR scanner with a spiral fast gradient-echo (fast field echo for Philips scanners) sequence, three Cartesian fast gradient-echo (turbo field echo for Philips scanners) sequences with different in-plane resolution, and with and without flow compensation and half-Fourier acquisition. The hearts of four rats were then excised and left-ventricle mass was weighed. Inter- and intra-observer variability analysis was performed for magnetic resonance imaging (MRI) measurements. Half-Fourier acquisition with flow compensation gave the best sequence in terms of image quality, spatial as well as temporal resolution, and suppression of flow artifact. Ejection fraction was 71 +/- 4% with less than 5% inter- and intra-observer variability. A good correlation was found between MRI-calculated left-ventricular mass and wet weight. Using optimized sequences on a clinical 1.5-T MR scanner can provide accurate quantification of cardiac function in small animals and can promote cardiovascular research on small animals at 1.5-T.
    MAGMA Magnetic Resonance Materials in Physics Biology and Medicine 09/2006; 19(3):144-51. DOI:10.1007/s10334-006-0037-z · 2.87 Impact Factor
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    ABSTRACT: To compare MRI and MRA with Doppler-echocardiography (DE) in native and postoperative aortic coarctation, define the best MR protocol for its evaluation, compare MR with surgical findings in native coarctation. 136 MR studies were performed in 121 patients divided in two groups: Group I, 55 preoperative; group II, 81 postoperative. In group I, all had DE and surgery was performed in 35 cases. In group II, DE was available for comparison in 71 cases. MR study comprised: spin-echo, cine, velocity-encoded cine (VEC) sequences and 3D contrast-enhanced MRA. In group I, diagnosis of coarctation was made by DE in 33 cases and suspicion of coarctation and/or aortic arch hypoplasia in 18 cases. Aortic arch was not well demonstrated in 3 cases and DE missed one case. There was a close correlation between VEC MRI and Doppler gradient estimates across the coarctation, between MRI aortic arch diameters and surgery but a poor correlation in isthmic measurements. In group II, DE detected a normal isthmic region in 31 out of 35 cases. Postoperative anomalies (recoarctation, aortic arch hypoplasia, kinking, pseudoaneurysm) were not demonstrated with DE in 50% of cases. MRI is superior to DE for pre and post-treatment evaluation of aortic coarctation. An optimal MR protocol is proposed. Internal measurement of the narrowing does not correspond to the external aspect of the surgical narrowing.
    The International Journal of Cardiovascular Imaging 06/2006; 22(3-4):457-75. DOI:10.1007/s10554-005-9037-8 · 1.81 Impact Factor
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    ABSTRACT: PurposeTo investigate a balanced steady state free precession sequence (b-SSFP) under a large range of conditions and to compare its performance with other types of gradient echo sequences for dynamic imaging.Materials and Methods Balanced turbo field echo (b-TFE; Philips Medical Systems, Best, The Netherlands) was investigated in vitro at a range of T2/T1 along with T1-contrast enhanced turbo field echo (T1-TFE) and turbo field echo (TFE) so that a comparison could be made. Performance was quantified in terms of the initial slope of the signal-to-noise ratio (SNR) vs. 1/T1 curve (sensitivity) and the range of 1/T1 before signal saturation (contrast dynamic range [CDR]).ResultsThe b-TFE sequence was found to best perform, in terms of an optimal CDR, with a 90° flip angle (FA), saturation preparation, and short inversion time. Using these parameters, the sensitivity was also higher than that of the TFE sequence and T1-TFE sequence under their respective optimal conditions. For detection of small changes in contrast agent concentration (0.0–0.1 mM), b-TFE was also found to be the sequence of choice, with optimized parameters as follows, 90° FA, shortest TR/TE, and no magnetization preparation. The smallest matrices gave the highest signal sensitivity for all three sequences.Conclusion The CDR of b-TFE was much narrower than that of T1-TFE but could be widened under optimized conditions. The sensitivity of the b-TFE technique was the highest of the three sequences under all conditions tested. J. Magn. Reson. Imaging 2004;20:1030–1038. © 2004 Wiley-Liss, Inc.
    Journal of Magnetic Resonance Imaging 12/2004; 20(6):1030 - 1038. DOI:10.1002/jmri.20205 · 3.21 Impact Factor
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    ABSTRACT: We investigated the specificity of superparamagnetic iron oxide (SPIO)-enhanced T1-weighted spin-echo (SE) magnetic resonance (MR) images for the characterization of liver hemangiomas. When imaging liver hemangiomas, which are the most frequent benign liver tumors, a method with very high specificity is required, which will obviate other studies, follow-up, or invasive diagnostic procedures such as percutaneous biopsy. Eighty-three lesions were examined by MR imaging at 1.5 T before and after intravenous injection of SPIO particles. Lesions were categorized as follows according to the final diagnosis: 37 hemangiomas, nine focal nodular hyperplasias (FNHs), 19 hepatocellular carcinomas (HCCs), and 18 metastases. Their signal intensity values were normalized to muscle and compared. The only lesions showing a significant increase in signal intensity ratio (lesion to muscle) on postcontrast T1-weighted SE images were hemangiomas (p < 0.001). The signal intensity ratio of hemangiomas increased on average by 70%. Based on receiver operating characteristic analysis and using a cutoff level of 50% signal increase, the specificity and sensitivity of SPIO-enhanced MR imaging for the characterization of hemangiomas would be 100% and 70%, respectively. The T1 effect of SPIO particles can help differentiate hemangiomas from other focal liver lesions such as FNHs, HCCs, and metastases and may obviate biopsy. When using SPIO particles for liver imaging, it is useful to add a T1-weighted sequence to T2-weighted images, thereby providing additional information for lesion characterization.
    Abdominal Imaging 01/2004; 29(1):60-70. DOI:10.1007/s00261-003-0092-0 · 1.63 Impact Factor
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    ABSTRACT: Purpose:To improve the quantification of myocardial perfusion by registering the time series of magnetic resonance (MR) images with injection of gadolinium.Materials and Methods:Eight patients underwent MR scans to perform myocardial perfusion exam. Two short axis views of the left ventricle (LV) were acquired in free breathing. Two masks for performing the spatial registration of the images were evaluated. The registration was based on pixel intensity in a multi-resolution scheme. The efficiency of this correction was evaluated by calculating geometric residual displacement of the LV and by fitting the data to a compartment model fit with two parameters: K1, the blood-to-myocardium transfer coefficient, and Vd, the distribution volume of the contrast media.Results:The registration stage allowed a decrease in the observed motion of the LV from more than 1.98 ± 0.68 mm to less than 0.56 ± 0.18 mm (mean ± SD). Variability obtained in the perfusion analysis decreased from 46 ± 103% to 5± 4% for K1 parameter and from 18 ± 21% to 5 ± 5% for Vd parameter.Conclusion:As with manual correction, this automatic motion correction leads to accurate perfusion parameters in dynamic cardiac MR imaging after contrast agent injection. This automatic stage requires placing only one mask over one frame of the perfusion study instead of manually shifting each image to fit a reference image of the perfusion study. J. Magn. Reson. Imaging 2003;18:160–168. © 2003 Wiley-Liss, Inc.
    Journal of Magnetic Resonance Imaging 07/2003; 18(2):160 - 168. DOI:10.1002/jmri.10351 · 3.21 Impact Factor
  • A. Mehdizade · J. P. Vallee · F. Terrier · C. E. Iselin
    European Urology Supplements 02/2003; 2(1):76-76. DOI:10.1016/S1569-9056(03)80302-0 · 3.37 Impact Factor

Publication Stats

469 Citations
93.42 Total Impact Points


  • 1997–2014
    • University of Geneva
      • • Faculty of Medicine
      • • Department of Radiology and Medical Informatics
      • • Division of Radio-oncology
      Genève, Geneva, Switzerland
  • 2000–2009
    • Hôpitaux Universitaires de Genève
      • Service de radiologie
      Genève, Geneva, Switzerland
  • 2007
    • École Polytechnique Fédérale de Lausanne
      Lausanne, Vaud, Switzerland
  • 1997–1999
    • Duke University Medical Center
      • Department of Radiology
      Durham, North Carolina, United States