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Magnetic Resonance Microscopy (magnetic + resonance_microscopy)

Distribution by Scientific Domains

Medical Sciences	68%
Life Sciences	26%

Selected Abstracts

Magnetic resonance microscopy of the equine hoof wall: a study of resolution and potential

EQUINE VETERINARY JOURNAL, Issue 5 2006
M. D. KELLER
Summary Reasons for performing study: Obtaining magnetic resonance images of the inner hoof wall tissue at the microscopic level would enable early accurate diagnosis of laminitis and therefore more effective therapy. Objectives: To optimise magnetic resonance imaging (MRI) parameters in order to obtain the highest possible resolution of the structures beneath the equine hoof wall. Methods: Magnetic resonance microscopy (MRM) was performed in front feet from 6 cadaver horses using T2 -weighted fast spin echo (FSE-T2), and T1 -weighted gradient echo (GRE-T1) sequences. Results: In T2 weighted FSE images most of the stratum medium showed no signal, however the coronary, terminal and sole papillae were visible. The stratum lamellatum was clearly visible and primary epidermal lamellae could be differentiated from dermal lamellae. Conclusion: Most structures beneath the hoof wall were differentiated. Conventional scanners for diagnostic MRI in horses are low or high field. However this study used ultra-high field scanners currently not available for clinical use. Signal-to-noise ratio (S/N) increases as a function of field strength. An increase of spatial resolution of the image results in a decreased S/N. S/N can also be improved with better coils and the resolution of high field MRI scanners will increase as technology develops and surface array coils become more readily available. Potential relevance: Although MR images with microscopic resolution were obtained ex vivo, this study demonstrates the potential for detection of lamellar pathology as it occurs. Early recognition of the development of laminitis to instigate effective therapy at an earlier stage and may improve the outcome for laminitic horses. Clinical MR is now readily available at 3 T, while 4 T, 7 T and 9 T systems are being used for human whole body applications. [source]

Magnetic resonance microscopy at 17.6-Tesla on chicken embryos in vitro

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2001
Bianca Hogers PhD
Abstract The non-destructive nature and the rapid acquisition of a three-dimensional image makes magnetic resonance microscopy (MRM) very attractive and suitable for functional imaging investigations. We explored the use of an ultra high magnetic field for MRM to increase image quality per image acquisition time. Improved image quality was characterized by a better signal-to-noise ratio (SNR), better image contrast, and higher resolution compared to images obtained at lower magnetic field strengths. Fixed chicken embryos at several stages of development were imaged at 7.0-T (300 MHz) and at 17.6-T (750 MHz). Maximum intensity projection resulted in three-dimensional vascular images with ample detail of the embryonic vasculature. We showed that at 750 MHz frequency, an image with approximately three times better SNR can be obtained by T1 -weighting using a standard gadolinium contrast agent, compared to the same measurement at 300 MHz. The image contrast improved by around 20 percent and the contrast-to-noise ratio improved by almost a factor of 3.5. Smaller blood vessels of the vascular system were identified at the high field, which indicates a better image resolution. Thus, ultra high field is beneficial for MRM and opens new areas for functional imaging research, in particular when SNR, resolution, and contrast are limited by acquisition time. J. Magn. Reson. Imaging 2001;14:83,86. © 2001 Wiley-Liss, Inc. [source]

Magnetic Resonance Microscopy Defines Ethanol-Induced Brain Abnormalities in Prenatal Mice: Effects of Acute Insult on Gestational Day 8

ALCOHOLISM, Issue 6 2009
Scott E. Parnell
Background:, Magnetic resonance microscopy (MRM), magnetic resonance imaging (MRI) at microscopic levels, provides unprecedented opportunities to aid in defining the full spectrum of ethanol's insult to the developing brain. This is the first in a series of reports that, collectively, will provide an MRM-based atlas of developmental stage-dependent structural brain abnormalities in a Fetal Alcohol Spectrum Disorders (FASD) mouse model. The ethanol exposure time and developmental stage examined for this report is gestational day (GD) 8 in mice, when the embryos are at early neurulation stages; stages present in humans early in the fourth week postfertilization. Methods:, For this study, pregnant C57Bl/6J mice were administered an ethanol dosage of 2.8 g/kg intraperitoneally at 8 days, 0 hour and again at 8 days, 4 hours postfertilization. On GD 17, fetuses that were selected for MRM analyses were immersion fixed in a Bouin's/Prohance® solution. Control fetuses from vehicle-treated dams were stage-matched to those that were ethanol-exposed. The fetal mice were scanned ex vivo at 7.0 T and 512 × 512 × 1024 image arrays were acquired using 3-D spin warp encoding. The resulting 29 ,m (isotropic) resolution images were processed using ITK-SNAP, a 3-D segmentation/visualization tool. Linear and volume measurements were determined for selected brain, head, and body regions of each specimen. Comparisons were made between control and treated fetuses, with an emphasis on determining (dis)proportionate changes in specific brain regions. Results:, As compared with controls, the crown-rump lengths of stage-matched ethanol-exposed GD 17 fetuses were significantly reduced, as were brain and whole body volumes. Volume reductions were notable in every brain region examined, with the exception of the pituitary and septal region, and were accompanied by increased ventricular volumes. Disproportionate regional brain volume reductions were most marked on the right side and were significant for the olfactory bulb, hippocampus, and cerebellum; the latter being the most severely affected. Additionally, the septal region and the pituitary were disproportionately large. Linear measures were consistent with those of volume. Other dysmorphologic features noted in the MR scans were choanal stenosis and optic nerve coloboma. Conclusions:, This study demonstrates that exposure to ethanol occurring in mice at stages corresponding to the human fourth week postfertilization results in structural brain abnormalities that are readily identifiable at fetal stages of development. In addition to illustrating the utility of MR microscopy for analysis of an FASD mouse model, this work provides new information that confirms and extends human clinical observations. It also provides a framework for comparison of structural brain abnormalities resulting from ethanol exposure at other developmental stages and dosages. [source]

Online assessment of biofilm development, sloughing and forced detachment in tube reactor by means of magnetic resonance microscopy

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010
Michael Wagner
Abstract Magnetic resonance microscopy (MRM) was successfully applied for non-invasive online monitoring of biofilm development, sloughing, and forced detachment. Biofilm cultivation was performed in a tube reactor directly placed in the MRM scanner. Based on the differences in relaxation time of free and bound protons, the distributed water signal was allocated to the bulk and the biofilm phase. The velocity of the flowing water in the tube reactor was measured in all three directions (x, y, and z) at spatial resolutions of 78,µm. From the velocity data, maps of flow gradients (shear rates) were derived. The experiments showed that a more compact biofilm structure is sloughed off in total with nearly no biomass left on the substratum. Continued biofilm cultivation resulted in filamentous biofilm structures, which did not show any sloughing. Experiments at higher Reynolds numbers were performed in order to force biofilm detachment. Continuous measuring of proton velocity and biomass was used to characterize the different stages of biofilm development. The measurements revealed that biofilms are able to resist extremely high local shear stress being raised up to factor of 20 compared to the mean local shear stress acting on the complete biofilm surface. The maximum local shear stress of single biofilm structures exposed to flow was found to be on average seven times higher compared to the mean local shear stress of the entire biofilm surface. MRM was able to visualize and quantify the development of biofilms and interaction of biofilms with the surrounding fluid at the meso-scale. It is suggested that detachment and sloughing depends on both internal and external structural parameters. Biotechnol. Bioeng. 2010;107: 172,181. © 2010 Wiley Periodicals, Inc. [source]

Magnetic resonance microscopy versus light microscopy in human embryology teaching

CLINICAL ANATOMY, Issue 5 2004
J. Puerta-Fonollá
Abstract A study was carried out on the application of magnetic resonance microscopy (MRM) in teaching prenatal human development. Human embryos measuring 8 mm, 15 mm, 18.5 mm, and 22 mm were fixed in a 4% paraformaldehyde solution and sections obtained with magnetic resonance imaging (MRI) were compared to those prepared for light microscopy (LM), using the same embryos. The MRM and LM slices were of a similar quality. In the MRM sections, embryonic organs and systems were clearly visible, particularly the peripheral and central nervous systems, and the cardiovascular and digestive systems. The digitalization and clarity of the MRM images make them an ideal teaching aid that is suitable for students during the first years of a health-science degree, particularly medicine. As well as providing students with their first experience of MRM, these images allow students to access, at any time, all embryos used, to assess changes in the positions of different organs throughout their stages of development, and to acquire spatial vision, an absolute requirement in the study of human anatomy. We recommend that this technique be incorporated into the wealth of standard embryonic teaching methods already in use. Clin. Anat. 17:429,435, 2004. © 2004 Wiley-Liss, Inc. [source]

Optimizing the point spread function in phase-encoded magnetic resonance microscopy

CONCEPTS IN MAGNETIC RESONANCE, Issue 1 2004
A.G. Webb
Abstract Three-dimensional phase-encoded magnetic resonance microscopy is the most promising method for obtaining images with isotropic spatial resolutions on the order of a few micrometers. The attainable spatial resolution is limited by the available gradient strength (Gmax) and the molecular self-diffusion coefficient (D) of the sample. In this study, numerical simulations in the microscopic-size regime are presented in order to show that for given values of Gmax and D, there exists an optimum number of phase-encoding steps that maximize the spatial resolution in terms of minimizing the full-width at half-maximum (FWHM) of the image point spread function (PSF). Unlike the case of "macroscopic" imaging, in which diffusion plays an insignificant role in determining spatial resolution, acquiring data beyond this optimal value actually degrades the image PSF. An alternative version of phase encoding, using a variable phase-encoding time rather than a variable gradient strength, is analyzed in terms of improvements in the image PSF and/or reductions in the data acquisition time for a given spatial resolution. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 22A: 25,36, 2004. [source]

Prospects for diffusion enhancement of signal and resolution in magnetic resonance microscopy

CONCEPTS IN MAGNETIC RESONANCE, Issue 2 2003
Charles H. Pennington
Abstract The prospects for and practical requirements of the "diffusion enhancement of signal and resolution" (DESIRE) scheme proposed by Lauterbur as a method to enhance the sensitivity, spatial resolution, and contrast in magnetic resonance (MR) microscopy and localized MR spectroscopy is assessed. The method, which still has not been implemented, promises signal enhancements of 1,2 orders of magnitude in imaging or localized spectroscopy on the scale of ,10 microns and requires magnetic field gradient strengths (,10 T/m) that are not unreasonable. I emphasize the development of an understanding of the physical principles involved in this unfamiliar, "real-space" imaging method. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson Part A 19A: 71,79, 2003. [source]

A multimodal, multidimensional atlas of the C57BL/6J mouse brain

JOURNAL OF ANATOMY, Issue 2 2004
Allan MacKenzie-Graham
Abstract Strains of mice, through breeding or the disruption of normal genetic pathways, are widely used to model human diseases. Atlases are an invaluable aid in understanding the impact of such manipulations by providing a standard for comparison. We have developed a digital atlas of the adult C57BL/6J mouse brain as a comprehensive framework for storing and accessing the myriad types of information about the mouse brain. Our implementation was constructed using several different imaging techniques: magnetic resonance microscopy, blockface imaging, classical histology and immunohistochemistry. Along with raw and annotated images, it contains database management systems and a set of tools for comparing information from different techniques. The framework allows facile correlation of results from different animals, investigators or laboratories by establishing a canonical representation of the mouse brain and providing the tools for the insertion of independent data into the same space as the atlas. This tool will aid in managing the increasingly complex and voluminous amounts of information about the mammalian brain. It provides a framework that encompasses genetic information in the context of anatomical imaging and holds tremendous promise for producing new insights into the relationship between genotype and phenotype. We describe a suite of tools that enables the independent entry of other types of data, facile retrieval of information and straightforward display of images. Thus, the atlas becomes a framework for managing complex genetic and epigenetic information about the mouse brain. The atlas and associated tools may be accessed at http://www.loni.ucla.edu/MAP. [source]

Staining methods for magnetic resonance microscopy of the rat fetus

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2007
Alexandra Petiet MS
Abstract Purpose To develop a magnetic resonance histology (MRH) staining and fixation method by immersion to enhance the signal-to-noise ratio (SNR) with a paramagnetic contrast agent permitting microscopic acquisition within a 3-hour scan time. Materials and Methods Methods were optimized for embryonic day 18.5 (E18.5) rat fetuses and imaging at 9.4T with an RF refocused spin-echo pulse sequence (TR/TE = 75 msec/5.2 msec). Fixation/staining was performed by immersion in Bouin's fixative containing varied concentrations of ProHance (from 10:1 to 500:1 Bouin's:ProHance) and for varied immersion durations (up to 24 hours). Results The results showed a significant change in T1 and T2 relaxation times as a function of concentration of contrast agent and immersion duration. As the contrast agent penetrated the tissues, T1 was reduced as desired (typically by 10×), but at the same time T2 was profoundly reduced (typically by 3×) due to both protein cross-linking from the fixative and the high concentration of contrast agent. A systematic assessment of this staining protocol showed an increased SNR (by 5×) over that in unstained specimens. Conclusion This staining protocol reduced scan time for very-high-resolution images (19.5 ,m) to only 3 hours, making MRH a routine tool for evaluating fetal development. J. Magn. Reson. Imaging 2007;25:1192,1198. © 2007 Wiley-Liss, Inc. [source]

Ex vivo magnetic resonance microscopy of an osteochondral transfer,

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2003
Erik F. Petersen BS
Abstract A 49-year-old woman with right knee pain and a chondral defect on the medial femoral condyle underwent an osteochondral transfer. The patient initially had pain relief, but then sustained a twisting injury and had progressive chondromalacia and pain on the affected side. She subsequently underwent a total knee replacement, and the tissue from the osteochondral transfer (OATS) site was harvested for analysis. In vitro MR microimaging of the excised joint segment revealed undamaged, full-thickness cartilage on the OATS plug, intact cartilage on the posterior condyle, and severely thinned and damaged cartilage on the anterior condyle. Alcian blue-stained sections revealed that proteoglycans were present throughout the OATS core but were nearly absent in the native cartilage. Quantitative T1 data acquired after equilibration with Gd-DTPA indicated a distribution of matrix fixed charge in the OATS plug and anterior tissue that agreed well with histology and literature observations, while the posterior native cartilage appeared to have fixed charge similar to that of the OATS tissue. Histology revealed poor graft integration between OATS and native cartilage, with a distinct layer of fibrous tissue at the posterior interface. MRI images, by comparison, showed a hypointense feature at the posterior interface but uniform intensity across the anterior interface. Quantitative T2, magnetization transfer and T1 data acquired with and without gadolinium contrast showed dependences on depth, location, and pathology that were consistent with measurements reported in the literature for articular cartilage. J. Magn. Reson. Imaging 2003;17:603,608. Published 2003 Wiley-Liss, Inc. [source]

Magnetic resonance microscopy at 17.6-Tesla on chicken embryos in vitro

Magnetic resonance microscopy analysis of transport in a novel Tape-Cast porous ceramic

AICHE JOURNAL, Issue 10 2009
Tyler R. Brosten
Abstract Freeze-tape-cast porous ceramics allow for tailored pore structures. The impact on transport dynamics of pore structures which vary as a function of spatial depth within a ceramic is an important consideration in designing pore structures for particular applications. In this article, the application of nuclear magnetic resonance microscopy and 1H NMR techniques to characterize the transport in a novel tape-cast ceramic is presented. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Magnetic Resonance Microscopy Defines Ethanol-Induced Brain Abnormalities in Prenatal Mice: Effects of Acute Insult on Gestational Day 7

ALCOHOLISM, Issue 1 2010
Elizabeth A. Godin
Background:, This magnetic resonance microscopy (MRM)-based report is the second in a series designed to illustrate the spectrum of craniofacial and central nervous system (CNS) dysmorphia resulting from single- and multiple-day maternal ethanol treatment. The study described in this report examined the consequences of ethanol exposure on gestational day (GD) 7 in mice, a time in development when gastrulation and neural plate development begins; corresponding to the mid- to late third week postfertilization in humans. Acute GD 7 ethanol exposure in mice has previously been shown to result in CNS defects consistent with holoprosencephaly (HPE) and craniofacial anomalies typical of those in Fetal Alcohol Syndrome (FAS). MRM has facilitated further definition of the range of GD 7 ethanol-induced defects. Methods:, C57Bl/6J female mice were intraperitoneally (i.p.) administered vehicle or 2 injections of 2.9 g/kg ethanol on day 7 of pregnancy. Stage-matched control and ethanol-exposed GD 17 fetuses selected for imaging were immersion fixed in a Bouins/Prohance solution. MRM was conducted at either 7.0 Tesla (T) or 9.4 T. Resulting 29 ,m isotropic spatial resolution scans were segmented and reconstructed to provide 3D images. Linear and volumetric brain measures, as well as morphological features, were compared for control and ethanol-exposed fetuses. Following MRM, selected specimens were processed for routine histology and light microscopic examination. Results:, Gestational day 7 ethanol exposure resulted in a spectrum of median facial and forebrain deficiencies, as expected. This range of abnormalities falls within the HPE spectrum; a spectrum for which facial dysmorphology is consistent with and typically is predictive of that of the forebrain. In addition, other defects including median facial cleft, cleft palate, micrognathia, pituitary agenesis, and third ventricular dilatation were identified. MRM analyses also revealed cerebral cortical dysplasia/heterotopias resulting from this acute, early insult and facilitated a subsequent focused histological investigation of these defects. Conclusions:, Individual MRM scans and 3D reconstructions of fetal mouse brains have facilitated demonstration of a broad range of GD 7 ethanol-induced morphological abnormality. These results, including the discovery of cerebral cortical heterotopias, elucidate the teratogenic potential of ethanol insult during the third week of human prenatal development. [source]

In vivo oxygen detection using exogenous hemoglobin as a contrast agent in magnetic resonance microscopy

MAGNETIC RESONANCE IN MEDICINE, Issue 4 2003
Phillip Z. Sun
Abstract In this work we show that exogenous molecular hemoglobin (Hb) is an effective indicator of relative local oxygen tension in magnetic resonance (MR) microscopy studies in vivo. This approach is more sensitive than other MRI oximetry methods; it can be used at higher resolutions and in specimens with no blood oxygen level-dependent (BOLD) effects. Using injection studies in flies, we show that Hb can permeate through relatively dense neural tissue, and that it is not obviously disruptive to physiology. Hb-injected flies show large changes in signal intensity (40,50%) when external O2 levels are manipulated artificially from 0% to 21%. Oxygen-dependent contrast changes produced by exogenous Hb are detected in T2 -weighted imaging experiments, and can be roughly calibrated if necessary. These studies demonstrate the feasibility of a contrast agent technique that may be useful for functional MRI (fMRI) studies of metabolism at tens of microns resolution. Magn Reson Med 49:609,614, 2003. © 2003 Wiley-Liss, Inc. [source]

Design and assessment of a tissue-engineered model of human phalanges and a small joint

ORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 4 2005
WJ Landis
Structured Abstract Authors ,, Landis WJ, Jacquet R, Hillyer J, Lowder E, Yanke A, Siperko L, Asamura S, Kusuhara H, Enjo M, Chubinskaya S, Potter K, Isogai N. Objectives ,, To develop models of human phalanges and small joints by suturing different cell-polymer constructs that are then implanted in athymic (nude) mice. Design ,, Models consisted of bovine periosteum, cartilage, and/or tendon cells seeded onto biodegradable polymer scaffolds of either polyglycolic acid (PGA) or copolymers of PGA and poly-L-lactic acid (PLLA) or poly- , -caprolactone (PCL) and PLLA. Constructs were fabricated to produce a distal phalanx, middle phalanx, or distal interphalangeal joint. Setting and Sample Population ,, Studies of more than 250 harvested implants were conducted at the Northeastern Ohio Universities College of Medicine. Experimental Variable ,, Polymer scaffold, cell type, and implantation time were examined. Outcome Measure ,, Tissue-engineered specimens were characterized by histology, transmission electron microscopy, in situ hybridization, laser capture microdissection and qualitative and quantitative polymerase chain reaction analysis, magnetic resonance microscopy, and X-ray microtomography. Results ,, Over periods to 60 weeks of implantation, constructs developed through vascularity from host mice; formed new cartilage, bone, and/or tendon; expressed characteristic genes of bovine origin, including type I, II and X collagen, osteopontin, aggrecan, biglycan, and bone sialoprotein; secreted corresponding proteins; responded to applied mechanical stimuli; and maintained shapes of human phalanges with small joints. Conclusion ,, Results give insight into construct processes of tissue regeneration and development and suggest more complete tissue-engineered cartilage, bone, and tendon models. These should have significant future scientific and clinical applications in medicine, including their use in plastic surgery, orthopaedics, craniofacial reconstruction, and teratology. [source]