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  • Journal cover
    Springer
    Online: 1.1993 –
    Publisher: Springer
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
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  • Publication Date: 2013-11-02
    Description: Object Quantitative assessment of liver fat is highly relevant to preclinical liver research and should ideally be performed non-invasively. This study aimed to compare three non-invasive Magnetic Resonance (MR) and two histopathological methods against the reference standard of biochemically determined liver triglyceride content (LTC). Materials and methods A total of 50 mice [21 C57Bl/6OlaHsd mice (C57Bl/6), nine low-density lipoprotein (LDL) receptor knock-out −/− (LDL −/−) mice and 20 C57BL/6 mice] received either a high-fat, high-fat-high-cholesterol or control diet, respectively. Mice were examined 4, 8 or 12 weeks into the diet using MR [ 1 H-MR Spectroscopy, Proton Density Fat Fraction (PDFF), mDixon] and histopathological methods (visual scoring or digital image analysis (DIA) of Oil-Red-O (ORO) stained liver sections). Correlations [Pearson’s coefficient ( r )] were studied with respect to LTC. Results Microvesicular steatosis was seen in 42/50 mice. 1 H-MRS values showed normal to moderately elevated liver fat content. Visual scoring and DIA of ORO-sections correlated moderately with LTC at r  = 0.59 and r  = 0.49 ( P  < 0.001), respectively. 1 H-MRS, PDFF and mDixon correlated significantly better, at r  = 0.74, r  = 0.75 and r  = 0.82, respectively. Conclusion Non-invasively determined MR measures of normal to moderately elevated liver fat in mice had a higher correlation with LTC than invasive histopathological measures. Where available, MR is the preferred method for fat quantification.
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
    Published by Springer
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  • Publication Date: 2013-11-02
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
    Published by Springer
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  • Publication Date: 2013-10-30
    Description: Objective To study the biodistribution and lung pharmacokinetics of tracheally administered gadolinium-based contrast agents [gadoteric acid and multimodal ultra-small rigid platforms (USRPs)], to validate their pharmacokinetics against optical imaging of fluorescent USRPs, and to test their short-term toxicity. Materials and methods Ultrashort echo-time (UTE) lung proton magnetic resonance imaging (MRI) was performed at 4.7-Tesla (T) after the intratracheal instillation of different concentrations of contrast agent solutions in mice. Pharmacokinetic models were implemented on the absolute concentration calculated from the MRI signal enhancement measurements. Fluorescent USRPs were used to obtain optical images with the same protocol. Bronchoalveolar lavage inflammatory cell count and serum creatinine measurement were performed on four groups of instilled mice (sham, saline, USRPs, lipopolysaccharide). Results MR and optical imaging showed similar kinetics of the USRPs, passing from the airways to the lung tissue and to the kidneys, with negligible hepatic clearance. No significant increase of lung and renal inflammation markers were observed in USRP-instilled animals. Conclusion A T 1 -weighted radial UTE sequence was found to be valuable in quantitatively monitoring the biodistribution and pharmacokinetics of nanoparticles in the lungs of mice. The observed favorable pharmacokinetics, which was validated by fluorescence imaging, ensures the negligible toxicity of the nanoprobes, making the USRPs and the developed protocol good candidates for applications on selected lung diseases.
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
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  • Publication Date: 2013-09-19
    Description: Objective To improve carotid 3T magnetic resonance imaging (MRI) dimension measurements in patients with overt atherosclerotic carotid artery disease. Materials and methods In 31 patients with advanced atherosclerotic carotid artery disease, two high resolution (0.25 × 0.25 mm 2 ; HR) and two routinely used low resolution (0.50 × 0.50 mm 2 ; LR) carotid 3T MRI scans were performed within 1 month. After manual delineation of carotid wall contours in a dedicated image analyses program in eight slices covering the atherosclerotic plaque, image reproducibility, as well as the within-reader and between-reader variability were determined. Results We found significantly higher intraclass correlation coefficients for total wall volume, mean wall area and mean wall thickness for the HR measurements (all p  < 0.05). We found a significant lower signal-to-noise and contrast-to-noise ratio for the HR compared to the LR measurements. The carotid arterial wall dimension measurements of all parameters were significantly lower for the HR compared to the LR measurements. No significant differences were observed between the within-reader and between-reader reproducibility for HR versus LR measurements. Conclusion Increasing the in-plane resolution improves the reproducibility of 3T MRI carotid arterial wall dimension measurements. The use of HR imaging will contribute to a reduced sample size needed in intervention trials using MRI scanning of the carotid artery as surrogate marker for atherosclerosis progression.
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
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  • Publication Date: 2013-09-27
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
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  • Publication Date: 2013-09-27
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
    Published by Springer
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  • Publication Date: 2013-09-27
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
    Published by Springer
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  • Publication Date: 2013-09-27
    Description: Objectives Automatic slice alignment is important for easier operation and shorter examination times in cardiac magnetic resonance imaging (MRI) examinations. We propose a new automatic slice alignment method for six cardiac planes (short-axis, vertical long-axis, horizontal long-axis, 4-chamber, 2-chamber, and 3-chamber views). Materials and methods ECG-gated 2D steady-state free precession axial multislice images were acquired using a 1.5-T MRI scanner during a single breath-hold. The scanning time was set to <20 s in 23 volumes from 23 healthy volunteers. In this method, the positions of the mitral valve, cardiac apex, left ventricular outflow tract, tricuspid valve, anterior wall of the heart, and right ventricular corner are detected to determine the positions of six reference planes by combining knowledge-based recognition and image processing techniques. In order to evaluate the results of automatic slice alignment for the short-axis, 4-chamber, 2-chamber, and 3-chamber views, the angular and positional errors between the results obtained by our proposed method and by manual annotation were measured. Results The average angular errors for the short-axis, 4-chamber, 2-chamber, and 3-chamber views were 3.05°, 4.52°, 7.28°, and 5.79°, respectively. The average positional errors for the short-axis (base), short-axis (apex), 4-chamber, 2-chamber, and 3-chamber views were 6.61°, 3.80°, 1.55°, 1.52°, and 1.48°, respectively. Conclusion The experimental results showed that our proposed method can detect the cardiac planes quickly and accurately. Our method is therefore beneficial to both patients and operators.
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
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  • Publication Date: 2013-09-27
    Description: Object Dual-echo fast spin-echo (FSE) sequences are used in T 2 relaxometry studies of neurological disorders because of shorter clinical scanning times and protocol simplicity. However, FSE sequences have possible spatial frequency-dependent effects, and derived T 2 values may include errors that depend on the spatial frequency characteristics of the brain region of interest. Materials and methods Dual-echo FSE and multi-echo spin-echo (MESE) sequences were acquired in nine subjects. The T 2 decay curves for FSE and MESE sequences were estimated and percent error maps were generated. T 2 error values were obtained along each patient’s corticospinal tract (CST). Whole-brain white matter (WM) and gray matter (GM) T 2 error values were also obtained. The paired t test was performed to evaluate differences in T 2 values in the CST between FSE and MESE sequences. Results Histograms of error values in CST and in whole-brain WM and GM structures revealed systematic errors in FSE sequences. Significant differences ( P  < 0.001) in CST T 2 values were also observed between FSE and MESE sequences. Conclusion Our findings indicate that T 2 values derived from FSE sequences are prone to large errors, even in low spatial frequency regions such as the CST, when compared to MESE sequences. Future studies should be aware of this limitation of FSE sequences.
    Print ISSN: 0968-5243
    Electronic ISSN: 1352-8661
    Topics: Medicine , Physics
    Published by Springer
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