Marco Gruwel

National Research Council Canada, Ottawa, Ontario, Canada

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Publications (69)142.17 Total impact

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    ABSTRACT: Purpose The purpose of the current study was to use diffusion tensor imaging (DTI) to conduct tractography of the optic radiations (OR) and its component bundles and to assess both the degree of hemispheric asymmetry and the inter-subject variability of Meyer's Loop (ML). We hypothesized that there are significant left versus right differences in the anterior extent of ML to the temporal pole (TP) in healthy subjects. Materials and Methods DTI data were acquired on a 3 T Siemens MRI system using a single-shot Spin Echo EPI sequence. The dorsal, central and ML bundles of the OR were tracked and visualized in forty hemispheres of twenty healthy volunteers. The uncinate fasciculus (UF) was also tracked in these subjects so that it could be used as a distinct anatomical reference. Measurements were derived for the distance between ML-TP, ML and the temporal horn (ML-TH) and ML and the uncinate fasciculus (ML-UF). Paired difference t-tests were carried out with SPSS 14.0. Results ML and the UF were successfully tracked and visualized in all 20 volunteers. Significant hemispheric asymmetries were found for all measurements with left distances shorter than the right (P < 0.005). In 50% of the subjects the left ML-UF distance was ≤1.9 mm. Conclusion The results support our hypothesis and demonstrate that left ML-TP distances are significantly shorter than right ML-TP distances. These asymmetries are also reflected in shorter left distances between ML-TH and ML-UF. Moreover, these results are of interest to left-sided temporal lobe epilepsy surgery because it is not only more likely to disturb the anterior extent of ML but also renders the often closely located posterior aspect of the left UF more vulnerable to potential surgical impact
    Epilepsy research 01/2014; · 2.48 Impact Factor
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    ABSTRACT: To: 1) Present fornix tractography in its entirety for 20 healthy individuals to assess variability. 2) Provide individual and groupwise whole tract diffusion parameter symmetry assessments prior to clinical application. 3) Compare whole tract diffusion parameter assessments with tract-based spatial statistics (TBSS).
    Journal of Magnetic Resonance Imaging 11/2013; · 2.57 Impact Factor
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    ABSTRACT: OBJECTIVES: Retrograde cerebral perfusion (RCP) has been employed to protect the brain during cardiovascular surgery, requiring temporary hypothermic circulatory arrest (HCA). However, the protocol used for RCP remains to be modified if prolonged HCA is expected. The aim of this study was to determine the efficacy of a modified protocol for this purpose. METHODS: After establishment of HCA at 15°C, 14 pigs were subjected to 90-min RCP using either the conventional protocol (i.e. alpha-stat strategy, 25-mmHg perfusion pressure and occluded inferior vena cava, Group I, n = 7) or the new protocol (i.e. pH-stat strategy, 40-mmHg perfusion pressure and unoccluded inferior vena cava, Group II, n = 7). After being rewarmed to 37°C, pigs were perfused for another 60 min. Phosphorus-31 magnetic resonance spectroscopy was used to track the changes of brain high-energy phosphates [i.e. adenosine triphosphate and phosphocreatine (PCr)] and intracellular pH (pHi). At the end, brain water content was measured. RESULTS: During RCP, high-energy phosphates decreased in both groups, whereas adenosine triphosphate decreased much faster in Group I (10.4 ± 4.3 vs 30.4 ± 4.4% of the baseline, P = 0.007, 60-min RCP). After rewarming, the recovery of high-energy phosphates and pHi was much slower in Group I (PCr: 55.7 ± 9.1 vs 78.4 ± 5.1% of the baseline, P = 0.046; adenosine triphosphate: 26.6 ± 10.6 vs 64.8 ± 4.6% of the baseline, P = 0.007; pHi: 6.5 ± 0.4 vs 7.1 ± 0.1, P = 0.021 at 30-min normothermic perfusion after rewarming). Brain tissue water content was significantly higher in Group I (81.1 ± 0.4 vs 79.5 ± 0.4%, P = 0.016). CONCLUSIONS: Application of the modified RCP protocol significantly improved cerebral energy conservation during HCA and accelerated energy recovery after rewarming.
    European journal of cardio-thoracic surgery: official journal of the European Association for Cardio-thoracic Surgery 09/2012; · 2.40 Impact Factor
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    ABSTRACT: The purpose was to investigate whether MnCl(2) can serve as an MRI contrast agent to detect chronic cryoinjury infarction in pigs in vivo and whether MnCl(2) causes significant hemodynamic disturbances. Hearts were subjected to a topical 2 min cryothermia to establish myocardial infarction (MI). Thereafter GdDTPA-enhanced MRI was performed at 0, 1, 2 and 3 weeks using a 3 T scanner. Four weeks post-cryoinjury the pigs underwent in vivo Mn-enhanced magnetic resonance imaging (MEMRI). MnCl(2) (70 μmol/kg, 14 min) was infused i.v. intermittently (n = 4) or continuously (n = 5) and T(1)-weighted images were acquired every 2 min simultaneously recording heart rate and arterial blood pressure. Either infusion scheme led to an immediate increment in MR signal intensity (SI) within the left ventricular (LV) blood pool and LV normal and cryoinjured myocardium, which reached a maximum at the end of infusion. No significant difference was observed between the normal and cryoinjured myocardium. After infusion termination, SI decreased faster within the LV blood pool and the MI, as compared with the normal myocardium in either group, resulting in significant contrast between the MI and normal tissue (intermittent: 18 ± 7 vs 49 ± 13%, p = 0.002; continuous: 19 ± 8 vs 36 ± 9%, p = 0.004). Infarction sizes were similar in Mn(2+)- and GdDTPA-enhanced images at 4 and 3 weeks post injury, respectively. Thus, in vivo MEMRI differentiated infarcted from normal myocardium in pig hearts subjected to 4-week cryoinjury. Compared with intermittent infusion, continuous infusion minimized hemodynamic fluctuations.
    Contrast Media & Molecular Imaging 11/2011; 6(6):426-36. · 2.87 Impact Factor
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    ABSTRACT: The aim of the study was the testing of sustained intrapericardial delivery of vascular growth factors (GFs) from alginate beads on cryoinjury size and perfusion. In domestic pigs (15-20 kg, n = 21), the left ventricular (LV) anterolateral wall of exposed hearts was cryoinjured using an aluminum rod (25 mm o.d.) cooled in liquid nitrogen. Alginate beads (d = 3.2 ± 0.2 mm), containing human recombinant basic fibroblast GF (bFGF, 50 µg) and vascular endothelial GF (VEGF, 50 µg) + heparin (50 µg) or heparin alone (Con, n = 5), were sutured to the cryoinjured epicardium (GF, n = 5; Con, n = 3 ) or pericardium (GF, n = 3; Con, n = 2), or no beads were implanted (n = 4). Four pigs were sham-operated. Cine and T(1) -weighted MRI was performed in vivo at ~2.5 h and 1, 2, 3 and 4 weeks after injury in a 3T imager. A double bolus of GdDTPA was injected (0.05 and 0.15 mmol/kg) and first-pass and late enhancement kinetics were monitored. After 4-week cryoinjury, following the injection of 5 x 10(6) 15-µm NIR fluorescent microspheres (FMS, 645/680 nm), hearts were sliced and examined with fluorescence imaging. Triphenyltetrazolium chloride (TTC) staining was used to determine infarct areas. Epicardial GF-containing beads were encapsulated within the hypointense 3-4-week infarct tissue. This tissue had a 75% higher LV thickening index, a lower distribution volume for GdDTPA (0.44 ± 0.12 vs 0.68 ± 0.05, p = 0.02), and 25% faster first-pass Gd kinetics relative to control infarctions. TTC staining revealed TTC-positive islands in the core of treated infarcts, which showed higher FMS fluorescence relative to surrounding infarct tissue (0.64 ± 0.14 vs. 0.31 ± 0.14; p < 0.0001) and to control infarcts (0.37 ± 0.09, p < 0.05). GF-beads attached to the pericardium were not effective. We conclude that sustained intrapericardial release of bFGF + VEGF from alginate beads attached to the epicardium facilitated vascular growth in the cryoinjured area.
    NMR in Biomedicine 09/2011; 25(1):177-88. · 3.45 Impact Factor
  • Marco L.H. Gruwel, Peter Latta, Boguslaw Tomanek
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    ABSTRACT: Magnetic resonance imaging (MRI) is known to provide a useful approach for the exploration of the chemistry and dynamics of a wide range of soft condensed materials. However, its application to solids has been limited to those materials with relatively narrow resonances. The time needed to obtain an image of a solid with a given resolution and signal-to-noise ratio (SNR) is directly proportional to the line width of the resonance. For MRI to become practical for the imaging of solids it will have to rely on the development and use of MR sequences that avoid the issues raised by line broadening of the resonance. In this paper we review the latest contributions towards MR imaging of solids from our laboratory, in particular, applications using optimized gradient waveforms. Acoustic noise reduction and SNR improvement obtained with modifications of the standard single-point imaging sequence are presented and discussed using examples.
    Canadian Journal of Chemistry 07/2011; 89(7):729-736. · 0.96 Impact Factor
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    ABSTRACT: A 2H and 14N NMR study of the solid methylammonium hexahalotellurates, (MA)2TeX6 (MA = CH3ND3+ or CD3NH3+, X = Cl, Br, and I), has been undertaken to characterize the dynamics of the methylammonium (MA) ion as a function of temperature. At room temperature, the MA ion in the hexachlorotellurate (solid II) is confined to C3 jumps about the C—N axis while a small angle libration of the C—N axis is occurring. In the room temperature phase, solid I, of (MA)2TeBr6 and (MA)2TeI6 the MA ions are performing overall reorientations on the ps time scale, averaging the 2H nuclear quadrupolar interactions to zero. Variable temperature 2H NMR spin-lattice relaxation times, T1, indicate an activation energy, EA, for "isotropic" reorientations of the CH3ND3+ ion of 5.2 ± 0.5 and 2.6 ± 0.3 kJ mol−1 for X = Br and I, respectively. Deuterium T1 values for C-deuterated MA ion in the hexaiodotellurate indicate an EA for whole-ion reorientation of 3.1 ± 0.3 kJ mol−1. At any given temperature, the correlation time, τc, derived from the T1 results was found to be the same for the two deuterium-labelled hexaiodotellurates. The similarity of both the EA and the τc values implies correlated motion of the methyl and ammonium groups. The 14N T1 results for solid I of (MA)2TeI6 indicate that C—N axis motions, with an EA = 5.6 ± 0.6 kJ mol−1, are more hindered than N—D or C—D bond dynamics. The 2H NMR spectra for (MA)2TeI6 (solid II) and (MA)2TeBr6 (solids II, III, and IV) are characterized by a Pake doublet line shape. The measured peak-to-peak splittings are less than what is predicted by C3 motion about the molecular symmetry axis. It is possible to model these line shapes by postulating that C3 rotations of the methyl and ammonium groups occur as the C—N axis librates in an effective cone about the position of the static molecular axis. For (CH3ND3)2TeBr6 and (CD3NH3)3TeBr6 the peak-to-peak splittings in the 2H NMR spectra were measured as a function of temperature in solid phases II, III, and IV and were found to be similar. Finally, the 2H NMR line shape relaxation for (MA)2TeBr6 (solid III) displays an orientation dependence indicating that rotations about the C—N axis are discrete rather than diffusive in nature. For solid phase II of (MA)2TeCl6, the line shape is observed to relax isotropically, implying that continuous C3 rotations are taking place. Keywords: 2H and 14N NMR, methylammonium hexahalotellurates, molecular motion.
    Canadian Journal of Chemistry 02/2011; 70(3):849-855. · 0.96 Impact Factor
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    ABSTRACT: MRTE; ; ;
    Canadian Journal of Botany 02/2011; · 1.40 Impact Factor
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    ABSTRACT: Here we present a novel pneumatic actuator design for brain magnetic resonance elastography (MRE). Magnetic resonance elastography is a phase contrast technique capable of tracing strain wave propagation and utilizing this information for the calculation of mechanical properties of materials and living tissues. In MRE experiments, the acoustic waves are generated in a synchronized way with respect to image acquisition, using various types of mechanical actuators. The unique feature of the design is its simplicity and flexibility, which allows reconfiguration of the actuator for different applications ranging from in vivo brain MRE to experiments with phantoms. Phantom and in vivo data are presented to demonstrate actuator performance.
    Magnetic Resonance Imaging 01/2011; 29(1):147-52. · 2.06 Impact Factor
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    ABSTRACT: To investigate progression of cryoinjury in pigs using contrast-enhanced magnetic resonance imaging (MRI) as well as optical spectroscopy and imaging. Cryoinjury was produced in 16 pigs in vivo and investigated using Gd-and Mn-enhanced MRI, optical imaging/spectroscopy and histology in acute and chronic setting up to 4 weeks after the injury. (1) Acute cryoinjury resulted in formation of a lesion with a severely reduced rate of sub-epicardial indocyanine green (intravascular optical flow tracer) passage. In vivo late Gd-enhanced MRI showed a approximately 10 mm deep hypointense area that was surrounded by a hyperintense rim while ex vivo Mn-enhanced MRI (MEMRI) detected a homogenous hypointense zone. Histological and spectroscopic examination revealed embolic erythrocytes blockages within the cryolesion with a thin necrotic rim neighboring the normal myocardium. (2) Chronic 4-week cryoinjury was characterized by uniform Gd-enhancement, whereas MEMRI revealed reduced Mn(2+)enhancement. Histological examination showed replacement of the cryoinjured myocardium by scar tissue. Acute cryoinjury resulted in formation of a no-reflow core embolized by erythrocytes and surrounded by a rim of necrotic tissue. Upon injury progression, the no-reflow zone shrunk and was completely replaced with scar tissue by 4 weeks after injury.
    Magnetic Resonance Imaging 06/2010; 28(5):753-66. · 2.06 Impact Factor
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    ABSTRACT: We have developed an ion-sensing nanoparticle that is comprised of a superparamagnetic iron oxide (SPIO) core encapsulated with a porous silica shell. The latter can be readily anchored with ligands capable of coordinating with positron-emitting metal. Evidently, this nanoparticle has a great potential for use in cell tracking with magnetic resonance (MR) imaging and positron emission tomography (PET). Herein we report the synthesis, surface functionalization and characterization of the magnetic nanoparticle-based probes and evaluate their cell-labeling efficacy, cytotoxicity and relaxivity in comparison to one of the most commonly utilized MRI contrast agents, Feridex.
    Biomaterials 04/2010; 31(10):2866-73. · 8.31 Impact Factor
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    ABSTRACT: Magnetic resonance elastography (MRE) is a phase contrast technique that provides a non-invasive means of eval-uating the viscoelastic properties of soft condensed matter. This has a profound bio-medical significance as it allows for the virtual palpation of areas of the body usually not accessible to the hands of a medical practitioner, such as the brain. Applications of MRE are not restricted to bio-medical applications, however, the viscoelastic properties of pre-packaged food products can also non-invasively be determined. Here we describe the design and use of a modular MRE acoustic actuator that can be used for experiments ranging from the human brain to pre-packaged food products. The unique feature of the used actuator design is its simplicity and flexibility, which allows easy reconfiguration.
    Measurement Science Review 01/2010; 10. · 1.23 Impact Factor
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    ABSTRACT: Viscoelastic properties of formulated food products are often associated with the textural properties of the material. Plasticity provides an important food quality factor. Unfortunately, viscoelastic properties of food stuffs are normally measured in the bulk phase, prior to packaging. Here we describe the application of a Magnetic Resonance Elastography (MRE) method using a specially designed sample holder for fast, reproducible and non-invasive measurement of spatially averaged viscoelastic constants of packaged samples. MRE experiments provide viscoelastic data as a function of position within samples and can be performed prior and post packaging, on samples including those with an optically opaque container or wrapper.
    Food Research International. 01/2010;
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    ABSTRACT: A common problem in simulations of MRI-experiments based on the numerical solution of the Bloch equations is the finite number of isochromats used in the calculations. This usually results in false or spurious signals and is a source of various differences between calculated and experimentally obtained data. In this paper, we are proposing a technique representing each sample voxel by a central and three additional isochromats, slightly shifted in orthogonal directions from center, thus providing a linear approximation of intra-voxel dephasing. This approach allows for further improvement and precision of the calculated NMR signal and virtually avoids the problem related to an finite set of isochromats. Here we provide details of the algorithm together with examples of simulations which prove the efficiency of this approach.
    Journal of Magnetic Resonance 12/2009; 203(1):44-51. · 2.30 Impact Factor
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    ABSTRACT: To determine if differences exist between control and diabetic rats in functional magnetic resonance imaging (fMRI) activity of the spinal cord and if fMRI can provide a means of early detection of diabetic neuropathy. fMRI of the spinal cord, using noxious electrical stimulation (15 V ( approximately 8 mA), 0.3 msec, 3 Hz) of the hind paw, was performed in groups of control and streptozotocin (STZ)-induced type 1 diabetic rats. Diabetic rats were lighter, hyperglycemic, and had lower blood pH than controls. fMRI activity at the lumbar enlargement of the spinal cord was identified in the dorsal horn ipsilateral to stimulus of all animals. Signal intensity changes across the lumbar spinal cord during periods of activity were not significantly different between control and diabetic rats, with a trend toward greater signal changes in controls. When specific regions of the spinal cord were analyzed, control rats exhibited significantly increased blood-oxygen level-dependent (BOLD) fMRI activity in both ipsilateral and contralateral dorsal horn compared to diabetic rats. The results of this study are consistent with reports that primary afferent input to the spinal cord is diminished by diabetes, and suggest that BOLD fMRI may be useful in early detection of diabetic neuropathy.
    Journal of Magnetic Resonance Imaging 09/2009; 30(2):271-6. · 2.57 Impact Factor
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    ABSTRACT: Woodchucks have been a preferred lab animal model of chronic hepatitis B viral infection. The model recapitulates the disease progression of HBV infection to hepatocellular carcinoma (HCC) and has documented similarities in protein glycosylation with human HCC. This study examined N-glycans in serum of animals with(out) HCC. Oligosaccharides were released enzymatically using PNGaseF from total serum or from serum partially fractionated by extraction. Two different extraction procedures - reversed-phase high-performance liquid chromatography (RP-HPLC) and solid-phase extraction (SPE) on a cation-exchange/reversed-phase STRATA-XC cartridge - were used with the purpose of confirming glycosylation profiles. Oligosaccharides were analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) after derivatization with phenylhydrazine and/or permethylation. Characteristic fragment ions produced under MS/MS conditions allowed discrimination between isomeric structures of oligosaccharides, including those sialylated with two types of acidic residues. The complementary methods allowed structural characterization of oligosaccharides from various N-glycan classes. Furthermore, to validate results, glycosylation profiles of woodchuck sera were compared to glycans obtained from mouse serum on the same conditions. In summary, we have identified 40 N-glycan structures in the serum of woodchucks and some types of oligosaccharide structures appeared to increase in HCC samples following protease digest. The study provides improved tools for the characterization of N-glycans from total serum in the progression of liver disease.
    Rapid Communications in Mass Spectrometry 09/2009; 23(18):2983-95. · 2.51 Impact Factor
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    ABSTRACT: This study assessed the potential therapeutic efficacy of adipose-derived stem cells (ASCs) on infarcted hearts. Myocardial infarction was induced in rat hearts by occlusion of the left anterior descending artery (LAD). One week after LAD occlusion, the rats were divided into three groups and subjected to transplantation of ASCs or transplantation of cell culture medium (CCM) or remained untreated. During a 1-mo recovery period, magnetic resonance imaging showed that the ASC-treated hearts had a significantly greater left ventricular (LV) ejection fraction and LV wall thickening than did the CCM-treated and untreated hearts. The capillary density in infarct border zone was significantly higher in the ASC-treated hearts than in the CCM-treated and untreated hearts. However, only 0.5% of the ASCs recovered from the ASC-treated hearts were stained positive for cardiac-specific fibril proteins. It was also found that ASCs under a normal culture condition secreted three cardiac protective growth factors: vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor-1. Results of this study suggest that ASCs were able to improve cardiac function of infarcted rat hearts. Paracrine effect may be the mechanism underlying the improved cardiac function and increased capillary density.
    AJP Heart and Circulatory Physiology 08/2009; 297(3):H1020-31. · 4.01 Impact Factor
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    ABSTRACT: Alginate-based beads labeled with contrast agent and loaded with vascular growth hormones were used for site-specific chronic delivery of hormones at the site of myocardial damage in a porcine model. Position of the beads within the pericardium could be monitored by MRI for optimal hormone delivery due to the presence of contrast agent. The beads facilitate the slow release of cytochrome c, myoglobin and methemoglobin used as protein models of growth factors. This application allows for site-specific delivery of hormones while the incorporated contrast agent in the beads provides a tool for MRI tracking in chronic studies.
    Magnetic Resonance Imaging 05/2009; 27(7):970-5. · 2.06 Impact Factor
  • Prabal K. Ghosh, Digvir S. Jayas, Marco L. H. Gruwel
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    ABSTRACT: Diffusion-weighted magnetic resonance imaging was used to determine water diffusion coefficients (D) in hull-less barley kernel components (endosperm and embryo) at 20.5±0.5°C. The D values in barley components were time-dependent and restricted in nature as indicated by the decrease in the apparent diffusion coefficient with increasing diffusion time (from 3 to 25 ms). A four-parameter Padé approximation model was used to estimate D and pore geometry (pore surface area–to-volume ratio, pore size, porosity, electrical conductivity and permeability of water) of the barley components after long diffusion time (t → ∞) using data obtained during a relatively short period of diffusion. The D of embryo and endosperm were 2.2±0.07 × 10 mm/s and 1.0±0.10 × 10 mm/s, respectively. These D values were used to simulate moisture and temperature patterns during the drying of a barley kernel using a two-dimensional simultaneous heat and moisture transfer model and compared with literature D values for validation purposes. Based on the comparison, the D values of barley components obtained from our study can be used to develop realistic models of water transport in barley during different postharvest processing operations (e.g., drying, kilning, steeping).
    Drying Technology 01/2009; 27(3):382-392. · 1.81 Impact Factor

Publication Stats

317 Citations
142.17 Total Impact Points

Institutions

  • 1997–2013
    • National Research Council Canada
      • • Institute for Biodiagnostics (IBD)
      • • Steacie Institute for Molecular Sciences (SIMS)
      • • Plant Biotechnology Institute (PBI)
      Ottawa, Ontario, Canada
  • 2007–2010
    • Slovak Academy of Sciences
      Presburg, Bratislavský, Slovakia
  • 1995–1997
    • Heinrich-Heine-Universität Düsseldorf
      • • Institut für Herz- und Kreislaufphysiologie
      • • Institut für Stoffwechselphysiologie
      Düsseldorf, North Rhine-Westphalia, Germany