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Journal Cover Magnetic Resonance Materials in Physics, Biology and Medicine
  [SJR: 0.787]   [H-I: 46]   [3 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0968-5243 - ISSN (Online) 1352-8661
   Published by Springer-Verlag Homepage  [2350 journals]
  • Radial MRI with variable echo times: reducing the orientation dependency
           of susceptibility artifacts of an MR-safe guidewire
    • Authors: Katharina E. Schleicher; Michael Bock; Klaus Düring; Stefan Kroboth; Axel J. Krafft
      Pages: 235 - 242
      Abstract: Objectives Guidewires are indispensable tools for intravascular MR-guided interventions. Recently, an MR-safe guidewire made from a glass-fiber/epoxy compound material with embedded iron particles was developed. The size of the induced susceptibility artifact, and thus the guidewire’s visibility, depends on its orientation against B 0. We present a radial acquisition scheme with variable echo times that aims to reduce the artifact’s orientation dependency. Materials and methods The radial acquisition scheme uses sine-squared modulated echo times depending on the physical direction of the spoke to balance the susceptibility artifact of the guidewire. The acquisition scheme was studied in simulations based on dipole fields and in phantom experiments for different orientations of the guidewire against B 0. The simulated and measured artifact widths were quantitatively compared. Results Compared to acquisitions with non-variable echo times, the proposed acquisition scheme shows a reduced angular variability. For the two main orientations (i.e., parallel and perpendicular to B 0), the ratio of the artifact widths was reduced from about 2.2 (perpendicular vs. parallel) to about 1.2 with the variable echo time approach. Conclusion The reduction of the orientation dependency of the guidewire’s artifact via sine-squared varying echo times could be verified in simulations and measurements. The more balanced artifact allows for a better overall visibility of the guidewire.
      PubDate: 2018-04-01
      DOI: 10.1007/s10334-017-0645-9
      Issue No: Vol. 31, No. 2 (2018)
       
  • Automated reference-free detection of motion artifacts in magnetic
           resonance images
    • Authors: Thomas Küstner; Annika Liebgott; Lukas Mauch; Petros Martirosian; Fabian Bamberg; Konstantin Nikolaou; Bin Yang; Fritz Schick; Sergios Gatidis
      Pages: 243 - 256
      Abstract: Objectives Our objectives were to provide an automated method for spatially resolved detection and quantification of motion artifacts in MR images of the head and abdomen as well as a quality control of the trained architecture. Materials and methods T1-weighted MR images of the head and the upper abdomen were acquired in 16 healthy volunteers under rest and under motion. Images were divided into overlapping patches of different sizes achieving spatial separation. Using these patches as input data, a convolutional neural network (CNN) was trained to derive probability maps for the presence of motion artifacts. A deep visualization offers a human-interpretable quality control of the trained CNN. Results were visually assessed on probability maps and as classification accuracy on a per-patch, per-slice and per-volunteer basis. Results On visual assessment, a clear difference of probability maps was observed between data sets with and without motion. The overall accuracy of motion detection on a per-patch/per-volunteer basis reached 97%/100% in the head and 75%/100% in the abdomen, respectively. Conclusion Automated detection of motion artifacts in MRI is feasible with good accuracy in the head and abdomen. The proposed method provides quantification and localization of artifacts as well as a visualization of the learned content. It may be extended to other anatomic areas and used for quality assurance of MR images.
      PubDate: 2018-04-01
      DOI: 10.1007/s10334-017-0650-z
      Issue No: Vol. 31, No. 2 (2018)
       
  • Improving fMRI in signal drop-out regions at 7 T by using tailored
           radio-frequency pulses: application to the ventral occipito-temporal
           cortex
    • Authors: Catarina Rua; Stephen J. Wastling; Mauro Costagli; Mark R. Symms; Laura Biagi; Mirco Cosottini; Alberto Del Guerra; Michela Tosetti; Gareth J. Barker
      Pages: 257 - 267
      Abstract: Objective Signal drop-off occurs in echo-planar imaging in inferior brain areas due to field gradients from susceptibility differences between air and tissue. Tailored-RF pulses based on a hyperbolic secant (HS) have been shown to partially recover signal at 3 T, but have not been tested at higher fields. Materials and methods The aim of this study was to compare the performance of an optimized tailored-RF gradient-echo echo-planar imaging (TRF GRE-EPI) sequence with standard GRE-EPI at 7 T, in a passive viewing of faces or objects fMRI paradigm in healthy subjects. Results Increased temporal-SNR (tSNR) was observed in the middle and inferior temporal lobes and orbitofrontal cortex of all subjects scanned, but elsewhere tSNR decreased relative to the standard acquisition. In the TRF GRE-EPI, increased functional signal was observed in the fusiform, lateral occipital cortex, and occipital pole, regions known to be part of the visual pathway involved in face-object perception. Conclusion This work highlights the potential of TRF approaches at 7 T. Paired with a reversed-gradient distortion correction to compensate for in-plane susceptibility gradients, it provides an improved acquisition strategy for future neurocognitive studies at ultra-high field imaging in areas suffering from static magnetic field inhomogeneities.
      PubDate: 2018-04-01
      DOI: 10.1007/s10334-017-0652-x
      Issue No: Vol. 31, No. 2 (2018)
       
  • Rapid measurement of intravoxel incoherent motion (IVIM) derived perfusion
           fraction for clinical magnetic resonance imaging
    • Authors: Emma M. Meeus; Jan Novak; Hamid Dehghani; Andrew C. Peet
      Pages: 269 - 283
      Abstract: Objective This study aimed to investigate the reliability of intravoxel incoherent motion (IVIM) model derived parameters D and f and their dependence on b value distributions with a rapid three b value acquisition protocol. Materials and methods Diffusion models for brain, kidney, and liver were assessed for bias, error, and reproducibility for the estimated IVIM parameters using b values 0 and 1000, and a b value between 200 and 900, at signal-to-noise ratios (SNR) 40, 55, and 80. Relative errors were used to estimate optimal b value distributions for each tissue scenario. Sixteen volunteers underwent brain DW-MRI, for which bias and coefficient of variation were determined in the grey matter. Results Bias had a large influence in the estimation of D and f for the low-perfused brain model, particularly at lower b values, with the same trends being confirmed by in vivo imaging. Significant differences were demonstrated in vivo for estimation of D (P = 0.029) and f (P < 0.001) with [300,1000] and [500,1000] distributions. The effect of bias was considerably lower for the high-perfused models. The optimal b value distributions were estimated to be brain500,1000, kidney300,1000, and liver200,1000. Conclusion IVIM parameters can be estimated using a rapid DW-MRI protocol, where the optimal b value distribution depends on tissue characteristics and compromise between bias and variability.
      PubDate: 2018-04-01
      DOI: 10.1007/s10334-017-0656-6
      Issue No: Vol. 31, No. 2 (2018)
       
  • 2D and 3D texture analysis to differentiate brain metastases on MR images:
           proceed with caution
    • Authors: Monika Béresová; Andrés Larroza; Estanislao Arana; József Varga; László Balkay; David Moratal
      Pages: 285 - 294
      Abstract: Objective To find structural differences between brain metastases of lung and breast cancer, computing their heterogeneity parameters by means of both 2D and 3D texture analysis (TA). Materials and methods Patients with 58 brain metastases from breast (26) and lung cancer (32) were examined by MR imaging. Brain lesions were manually delineated by 2D ROIs on the slices of contrast-enhanced T1-weighted (CET1) images, and local binary patterns (LBP) maps were created from each region. Histogram-based (minimum, maximum, mean, standard deviation, and variance), and co-occurrence matrix-based (contrast, correlation, energy, entropy, and homogeneity) 2D, weighted average of the 2D slices, and true 3D TA were obtained on the CET1 images and LBP maps. Results For LBP maps and 2D TA contrast, correlation, energy, and homogeneity were identified as statistically different heterogeneity parameters (SDHPs) between lung and breast metastasis. The weighted 3D TA identified entropy as an additional SDHP. Only two texture indexes (TI) were significantly different with true 3D TA: entropy and energy. All these TIs discriminated between the two tumor types significantly by ROC analysis. For the CET1 images there was no SDHP at all by 3D TA. Conclusion Our results indicate that the used textural analysis methods may help with discriminating between brain metastases of different primary tumors.
      PubDate: 2018-04-01
      DOI: 10.1007/s10334-017-0653-9
      Issue No: Vol. 31, No. 2 (2018)
       
  • Highly accelerated intracranial 4D flow MRI: evaluation of healthy
           volunteers and patients with intracranial aneurysms
    • Authors: Jing Liu; Louise Koskas; Farshid Faraji; Evan Kao; Yan Wang; Henrik Haraldsson; Sarah Kefayati; Chengcheng Zhu; Sinyeob Ahn; Gerhard Laub; David Saloner
      Pages: 295 - 307
      Abstract: Objectives To evaluate an accelerated 4D flow MRI method that provides high temporal resolution in a clinically feasible acquisition time for intracranial velocity imaging. Materials and methods Accelerated 4D flow MRI was developed by using a pseudo-random variable-density Cartesian undersampling strategy (CIRCUS) with the combination of k-t, parallel imaging and compressed sensing image reconstruction techniques (k-t SPARSE-SENSE). Four-dimensional flow data were acquired on five healthy volunteers and eight patients with intracranial aneurysms using CIRCUS (acceleration factor of R = 4, termed CIRCUS4) and GRAPPA (R = 2, termed GRAPPA2) as the reference method. Images with three times higher temporal resolution (R = 12, CIRCUS12) were also reconstructed from the same acquisition as CIRCUS4. Qualitative and quantitative image assessment was performed on the images acquired with different methods, and complex flow patterns in the aneurysms were identified and compared. Results Four-dimensional flow MRI with CIRCUS was achieved in 5 min and allowed further improved temporal resolution of <30 ms. Volunteer studies showed similar qualitative and quantitative evaluation obtained with the proposed approach compared to the reference (overall image scores: GRAPPA2 3.2 ± 0.6; CIRCUS4 3.1 ± 0.7; CIRCUS12 3.3 ± 0.4; difference of the peak velocities: −3.83 ± 7.72 cm/s between CIRCUS4 and GRAPPA2, −1.72 ± 8.41 cm/s between CIRCUS12 and GRAPPA2). In patients with intracranial aneurysms, the higher temporal resolution improved capturing of the flow features in intracranial aneurysms (pathline visualization scores: GRAPPA2 2.2 ± 0.2; CIRCUS4 2.5 ± 0.5; CIRCUS12 2.7 ± 0.6). Conclusion The proposed rapid 4D flow MRI with a high temporal resolution is a promising tool for evaluating intracranial aneurysms in a clinically feasible acquisition time.
      PubDate: 2018-04-01
      DOI: 10.1007/s10334-017-0646-8
      Issue No: Vol. 31, No. 2 (2018)
       
  • A novel framework for evaluating the image accuracy of dynamic MRI and the
           application on accelerated breast DCE MRI
    • Authors: Yuan Le; Marcel Dominik Nickel; Stephan Kannengiesser; Berthold Kiefer; Bruce Spottiswoode; Brian Dale; Victor Soon; Chen Lin
      Pages: 309 - 320
      Abstract: Objective To develop a novel framework for evaluating the accuracy of quantitative analysis on dynamic contrast-enhanced (DCE) MRI with a specific combination of imaging technique, scanning parameters, and scanner and software performance and to test this framework with breast DCE MRI with Time-resolved angiography WIth Stochastic Trajectories (TWIST). Materials and methods Realistic breast tumor phantoms were 3D printed as cavities and filled with solutions of MR contrast agent. Full k-space raw data of individual tumor phantoms and a uniform background phantom were acquired. DCE raw data were simulated by sorting the raw data according to TWIST view order and scaling the raw data according to the enhancement based on pharmaco-kinetic (PK) models. The measured spatial and temporal characteristics from the images reconstructed using the scanner software were compared with the original PK model (ground truth). Results Images could be reconstructed using the manufacturer’s platform with the modified ‘raw data.’ Compared with the ‘ground truth,’ the RMS error in all images was <10% in most cases. With increasing view-sharing acceleration, the error of the initial uptake slope decreased while the error of peak enhancement increased. Deviations of PK parameters varied with the type of enhancement. Conclusion A new framework has been developed and tested to more realistically evaluate the quantitative measurement errors caused by a combination of the imaging technique, parameters and scanner and software performance in DCE-MRI.
      PubDate: 2018-04-01
      DOI: 10.1007/s10334-017-0648-6
      Issue No: Vol. 31, No. 2 (2018)
       
  • Spectroscopic sampling of the left side of long-TE spin echoes: a free
           lunch'
    • Authors: Robert V. Mulkern; Mukund Balasubramanian
      Pages: 321 - 340
      Abstract: Objective Use of spectroscopically-acquired spin echoes typically involves Fourier transformation of the right side of the echo while largely neglecting the left side. For sufficiently long echo times, the left side may have enough spectral resolution to offer some utility. Since the acquisition of this side is “free”, we deemed it worthy of attention and investigated the spectral properties and information content of this data. Materials and methods Theoretical expressions for left- and right-side spectra were derived assuming Lorentzian frequency distributions. For left-side spectra, three regimes were identified based upon the relative magnitudes of reversible and irreversible transverse relaxation rates, R 2′ and R 2, respectively. Point-resolved spectroscopy (PRESS) data from muscle, fat deposit and bone marrow were acquired at 1.5 T to test aspects of the theoretical expressions. Results For muscle water or methylene marrow resonances, left-side signals were substantially or moderately larger than right-side signals but were similar in magnitude for muscle choline and creatine resonances. Left- versus right-side spectral-peak amplitude ratios depend sensitively on the relative values of R 2 and R 2′ , which can be estimated given this ratio and a right-side linewidth measurement. Conclusion Left-side spectra can be used to augment signal-to-noise and to estimate spectral R 2 and R 2′ values under some circumstances.
      PubDate: 2018-04-01
      DOI: 10.1007/s10334-017-0647-7
      Issue No: Vol. 31, No. 2 (2018)
       
  • Increased hepatic fatty acid polyunsaturation precedes ectopic lipid
           deposition in the liver in adaptation to high-fat diets in mice
    • Authors: Ana Francisca Soares; João M. N. Duarte; Rolf Gruetter
      Pages: 341 - 354
      Abstract: Objective We monitored hepatic lipid content (HLC) and fatty acid (FA) composition in the context of enhanced lipid handling induced by a metabolic high-fat diet (HFD) challenge and fasting. Materials and methods Mice received a control diet (10% of kilocalories from fat, N = 14) or an HFD (45% or 60% of kilocalories from fat, N = 10 and N = 16, respectively) for 26 weeks. A subset of five mice receiving an HFD (60% of kilocalories from fat) were switched to the control diet for the final 7 weeks. At nine time points, magnetic resonance spectroscopy was performed in vivo at 14.1 T, interleaved with glucose tolerance tests. Results Glucose intolerance promptly developed with the HFD, followed by a progressive increase of fasting insulin level, simultaneously with that of HLC. These metabolic defects were normalized by dietary reversal. HFD feeding immediately increased polyunsaturation of hepatic FA, before lipid accumulation. Fasting-induced changes in hepatic lipids (increased HLC and FA polyunsaturation, decreased FA monounsaturation) in control-diet-fed mice were not completely reproduced in HFD-fed mice, not even after dietary reversal. Conclusion A similar adaptation of hepatic lipids to both fasting and an HFD suggests common mechanisms of lipid trafficking from adipose tissue to the liver. Altered hepatic lipid handling with fasting indicates imperfect metabolic recovery from HFD exposure.
      PubDate: 2018-04-01
      DOI: 10.1007/s10334-017-0654-8
      Issue No: Vol. 31, No. 2 (2018)
       
  • Design of a sustainable prepolarizing magnetic resonance imaging system
           for infant hydrocephalus
    • Authors: Johnes Obungoloch; Joshua R. Harper; Steven Consevage; Igor M. Savukov; Thomas Neuberger; Srinivas Tadigadapa; Steven J. Schiff
      Abstract: Objectives The need for affordable and appropriate medical technologies for developing countries continues to rise as challenges such as inadequate energy supply, limited technical expertise, and poor infrastructure persist. Low-field magnetic resonance imaging (LF MRI) is a technology that can be tailored to meet specific imaging needs within such countries. Its low power requirements and the possibility of operating in minimally shielded or unshielded environments make it especially attractive. Although the technology has been widely demonstrated over several decades, it is yet to be shown that it can be diagnostic and improve patient outcomes in clinical applications. We here demonstrate the robustness of prepolarizing MRI (PMRI) technology for assembly and deployment in developing countries for the specific application to infant hydrocephalus. Hydrocephalus treatment planning and management requires only modest spatial resolution, such that the brain can be distinguished from fluid—tissue contrast detail within the brain parenchyma is not essential. Materials and Methods We constructed an internally shielded PMRI system based on the Lee-Whiting coil system with a 22-cm diameter of spherical volume. Results In an unshielded room, projection phantom images were acquired at 113 kHz with in-plane resolution of 3 mm × 3 mm, by introducing gradient fields of sufficient magnitude to dominate the 5000 ppm inhomogeneity of the readout field. Discussion The low cost, straightforward assembly, deployment potential, and maintenance requirements demonstrate the suitability of our PMRI system for developing countries. Further improvement in image spatial resolution and contrast of LF MRI will broaden its potential clinical utility beyond hydrocephalus.
      PubDate: 2018-04-11
      DOI: 10.1007/s10334-018-0683-y
       
  • A novel MR-compatible sensor to assess active medical device safety:
           stimulation monitoring, rectified radio frequency pulses, and
           gradient-induced voltage measurements
    • Authors: Thérèse Barbier; Sarra Aissani; Nicolas Weber; Cédric Pasquier; Jacques Felblinger
      Abstract: Purpose 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. Materials and methods 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. Results 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. Conclusion 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.
      PubDate: 2018-03-30
      DOI: 10.1007/s10334-018-0682-z
       
  • Optimization of diffusion-weighted single-refocused spin-echo EPI by
           reducing eddy-current artifacts and shortening the echo time
    • Authors: Manoj Shrestha; Pavel Hok; Ulrike Nöth; Bianca Lienerth; Ralf Deichmann
      Abstract: Objective The purpose of this work was to optimize the acquisition of diffusion-weighted (DW) single-refocused spin-echo (srSE) data without intrinsic eddy-current compensation (ECC) for an improved performance of ECC postprocessing. The rationale is that srSE sequences without ECC may yield shorter echo times (TE) and thus higher signal-to-noise ratios (SNR) than srSE or twice-refocused spin-echo (trSE) schemes with intrinsic ECC. Materials and methods The proposed method employs dummy scans with DW gradients to drive eddy currents into a steady state before data acquisition. Parameters of the ECC postprocessing algorithm were also optimized. Simulations were performed to obtain minimum TE values for the proposed sequence and sequences with intrinsic ECC. Experimentally, the proposed method was compared with standard DW-trSE imaging, both in vitro and in vivo. Results Simulations showed substantially shorter TE for the proposed method than for methods with intrinsic ECC when using shortened echo readouts. Data of the proposed method showed a marked increase in SNR. A dummy scan duration of at least 1.5 s improved performance of the ECC postprocessing algorithm. Conclusion Changes proposed for the DW-srSE sequence and for the parameter setting of the postprocessing ECC algorithm considerably reduced eddy-current artifacts and provided a higher SNR.
      PubDate: 2018-03-30
      DOI: 10.1007/s10334-018-0684-x
       
  • Evaluation of retained products of conception using pulsed continuous
           arterial spin-labeling MRI: clinical feasibility and initial results
    • Authors: Nobuyuki Kosaka; Yasuhiro Fujiwara; Tetsuji Kurokawa; Tsuyoshi Matsuda; Masayuki Kanamoto; Naoyuki Takei; Kenji Takata; Jin Takahashi; Yoshio Yoshida; Hirohiko Kimura
      Abstract: Objectives We evaluated the vascularity of retained products of conception (RPOC) using arterial spin-labeling magnetic resonance imaging (ASL-MRI) to clarify the clinical feasibility of this approach. Materials and methods A pulsed-continuous ASL sequence with echo-planar imaging (EPI) acquisitions was used. Ten consecutive patients with RPOC were enrolled. All ASL images were evaluated visually and semiquantitatively and compared with the findings of Doppler ultrasound (US) and dynamic contrast-enhanced MRI (DCE-MRI). Results The technical success rate was 93.7% (15/16 scans). One failed case was excluded from the analysis. Six patients showed quite high signals over RPOC, while three patients showed no abnormal signals. Doppler US alone failed to detect the hypervascular area in two cases, and ASL-MRI alone failed in three. A significant linear correlation was found between semiquantitative values of ASL-MRI and DCE-MRI. All six patients showing high signals on ASL-MRI underwent follow-up MRI after therapy. High signals in five patients decreased visually and semiquantitatively, while one patient showed signal increases. Conclusion Evaluation of RPOC using ASL-MRI was clinically feasible and response to therapy could be evaluated. However, the clinical advantages over conventional imaging remain unclear and need to be evaluated.
      PubDate: 2018-03-16
      DOI: 10.1007/s10334-018-0681-0
       
  • Toward faster inference of micron-scale axon diameters using Monte Carlo
           simulations
    • Authors: Morgan Mercredi; Melanie Martin
      Abstract: Object Recent advances have allowed oscillating gradient (OG) diffusion MRI to infer the sizes of micron-scale axon diameters. Here the effects on the precision of the inferred diameters are studied when reducing the number of images collected to reduce imaging time for clinical feasibility. Materials and methods Monte Carlo simulations of cosine OG sequences (50–1000 Hz) using a two-compartment model on a parallel cylinder (diameters 1–5 μm) geometry were conducted. Temporal diffusion spectroscopy was used to infer axon diameters. Three different gradient sets were simulated with different combinations of gradient strengths. Results Five frequencies were adequate for d = 3–5 μm with single-sized cylinders and for effective mean axon diameters greater than 2 μm for cylinders with a distributions of diameters. There was some improvement in precision for d = 1–2 μm with 10 frequencies. It is better to repeat measurements at higher gradient strengths than to use a range of gradient strengths. The improvement tended to be greatest when using fewer frequencies and was especially noticeable at very high gradient strengths. Conclusion Images can be collected with fewer gradient strengths and frequencies without sacrificing the precision of the measurements. This could be useful in reducing imaging time so that OG techniques can be used in clinical settings.
      PubDate: 2018-03-07
      DOI: 10.1007/s10334-018-0680-1
       
  • Vessel radius mapping in an extended model of transverse relaxation
    • Authors: Lukas Reinhold Buschle; Christian H. Ziener; Ke Zhang; Volker J. F. Sturm; Thomas Kampf; Artur Hahn; Gergely Solecki; Frank Winkler; Martin Bendszus; Sabine Heiland; Heinz-Peter Schlemmer; Felix T. Kurz
      Abstract: Objectives Spin dephasing of the local magnetization in blood vessel networks can be described in the static dephasing regime (where diffusion effects may be ignored) by the established model of Yablonskiy and Haacke. However, for small capillary radii, diffusion phenomena for spin-bearing particles are not negligible. Material and methods In this work, we include diffusion effects for a set of randomly distributed capillaries and provide analytical expressions for the transverse relaxation times T2* and T2 in the strong collision approximation and the Gaussian approximation that relate MR signal properties with microstructural parameters such as the mean local capillary radius. Results Theoretical results are numerically validated with random walk simulations and are used to calculate capillary radius distribution maps for glioblastoma mouse brains at 9.4 T. For representative tumor regions, the capillary maps reveal a relative increase of mean radius for tumor tissue towards healthy brain tissue of \(128 \pm 23 \%\) (p < 0.001). Conclusion The presented method may be used to quantify angiogenesis or the effects of antiangiogenic therapy in tumors whose growth is associated with significant microvascular changes.
      PubDate: 2018-02-24
      DOI: 10.1007/s10334-018-0677-9
       
  • Gestational and lactational exposure to dichlorinated bisphenol A induces
           early alterations of hepatic lipid composition in mice
    • Authors: Dounia El Hamrani; Amandine Chepied; William Même; Marc Mesnil; Norah Defamie; Sandra Même
      Abstract: Objective Using non-invasive magnetic resonance (MR) techniques and a histological approach, we assessed the outcomes of perinatal exposure at a low dose of 3,3′-DCBPA (2-chloro-4-[1-(3-chloro-4-hydroxyphenyl)-1-methylethyl]phenol) and/or 3,5-DCBPA (2,6-dichloro-4-[1-(4-hydroxyphenyl)-1-methylethyl]phenol) on mice livers. Materials and methods Fertilized female Swiss mice were injected intraperitoneally during gestation and lactation with either vehicle control, 20 μg/kg/day of BPA, 3,5-DCBPA, 3,3′-DCBPA or a mixture (mix-DCBPA). Complementary methods were used to evaluate, in male and female pups, (1) liver structure by texture analysis of images obtained through MR imaging (MRI) and histology, (2) hepatic lipid composition through in vivo 1H MR spectroscopy (1H MRS). Results Principal component analysis of texture parameters showed no structural modification of the liver with BPA and DCBPA treatments. Accordingly, no hepatic microvesicular steatosis was observed through hematoxylin–eosin staining. Compared to control, MRS revealed no difference in lipid composition for BPA, 3,5-DCBPA or 3,3′-DCBPA groups. However, MRS detected a significant increase in the mix-DCBPA groups for the saturated component of fatty acids (FA), total unsaturated FA bond index and polyunsaturated FA bond index. Conclusion Prior to any structural changes, polyunsaturated fatty acids significantly increased in young male and female mice exposed perinatally at a low dose to a mixture of dichlorinated BPA.
      PubDate: 2018-02-20
      DOI: 10.1007/s10334-018-0679-7
       
  • The impact of fibre orientation on T 1 -relaxation and apparent tissue
           water content in white matter
    • Authors: Felix Schyboll; Uwe Jaekel; Bernd Weber; Heiko Neeb
      Abstract: Objective Recent MRI studies have shown that the orientation of nerve fibres relative to the main magnetic field affects the R2*(= 1/T2*) relaxation rate in white matter (WM) structures. The underlying physical causes have been discussed in several studies but are still not completely understood. However, understanding these effects in detail is of great importance since this might serve as a basis for the development of new diagnostic tools and/or improve quantitative susceptibility mapping techniques. Therefore, in addition to the known angular dependence of R2*, the current study investigates the relationship between fibre orientation and the longitudinal relaxation rate, R1 (= 1/T1), as well as the apparent water content. Materials and methods For a group of 16 healthy subjects, a series of gradient echo, echo-planar and diffusion weighted images were acquired at 3T from which the decay rates, the apparent water content and the diffusion direction were reconstructed. The diffusion weighted data were used to determine the angle between the principle fibre direction and the main magnetic field to examine the angular dependence of R1 and apparent water content. Results The obtained results demonstrate that both parameters depend on the fibre orientation and exhibit a positive correlation with the angle between fibre direction and main magnetic field. Conclusion These observations could be helpful to improve and/or constrain existing biophysical models of brain microstructure by imposing additional constraints resulting from the observed angular dependence R1 and apparent water content in white matter.
      PubDate: 2018-02-20
      DOI: 10.1007/s10334-018-0678-8
       
  • Advances in cardiovascular MR imaging
    • Authors: Tim Leiner; Gustav Strijkers
      PubDate: 2018-02-06
      DOI: 10.1007/s10334-018-0676-x
       
  • Segmentation and texture analysis of structural biomarkers using
           
    • Authors: Manohar Latha; Ganesan Kavitha
      Abstract: Objective Schizophrenia (SZ) is a psychiatric disorder that especially affects individuals during their adolescence. There is a need to study the subanatomical regions of SZ brain on magnetic resonance images (MRI) based on morphometry. In this work, an attempt was made to analyze alterations in structure and texture patterns in images of the SZ brain using the level-set method and Laws texture features. Materials and methods T1-weighted MRI of the brain from Center of Biomedical Research Excellence (COBRE) database were considered for analysis. Segmentation was carried out using the level-set method. Geometrical and Laws texture features were extracted from the segmented brain stem, corpus callosum, cerebellum, and ventricle regions to analyze pattern changes in SZ. Results The level-set method segmented multiple brain regions, with higher similarity and correlation values compared with an optimized method. The geometric features obtained from regions of the corpus callosum and ventricle showed significant variation (p < 0.00001) between normal and SZ brain. Laws texture feature identified a heterogeneous appearance in the brain stem, corpus callosum and ventricular regions, and features from the brain stem were correlated with Positive and Negative Syndrome Scale (PANSS) score (p < 0.005). Conclusion A framework of geometric and Laws texture features obtained from brain subregions can be used as a supplement for diagnosis of psychiatric disorders.
      PubDate: 2018-02-03
      DOI: 10.1007/s10334-018-0674-z
       
  • Introductory editorial
    • Authors: David Norris
      PubDate: 2018-01-08
      DOI: 10.1007/s10334-017-0672-6
       
 
 
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