Magnetic Resonance Imaging of Diffusion in the Presence of Background Gradients and Imaging of Background Gradients |
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| Affiliation: | 1. Martinos Center for Biomedical Imaging, Harvard Medical School, Boston, MA, USA;2. Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany;3. École Polytechnique, University of Montreal, Montréal, Canada;1. Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany;2. Siemens Healthcare, Zurich, Switzerland;3. Swiss Center for Musculoskeletal Imaging (SCMI), Balgrist Campus, Zurich, Switzerland;4. Department of Neuroradiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany;5. Department of Neurology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany;6. Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany;1. Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada;2. MR Clinical Science, Philips Healthcare Canada, Markham, ON L6C 2S3, Canada;3. Department of Clinical Sciences, Lund University, 22184, Lund, Sweden;4. Random Walk Imaging AB, 22224, Lund, Sweden;5. Department of Radiology, Boston Children’s Hospital, Boston, MA 02115, United States;1. UCL Great Ormond Street Institute of Child Health, University College London, London, UK;2. UCL Centre for Medical Image Computing, University College London, London, UK;3. UCL School of Pharmacy, University College London, London, UK;4. Department of Radiology, Brigham and Women’s Hospital, Boston, Massachusetts, US;5. Harvard Medical School, Boston, Massachusetts, US;6. Clinical Sciences Lund, Lund University, Lund, Sweden;7. Bioxydyn Limited, Manchester, UK;8. UCL Queen Square Institute of Neurology, University College London, London, UK;9. National Physical Laboratory, Teddington, UK |
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| Abstract: | ![]()
The measurement of the self-diffusion coefficient D by an NMR technique that uses an applied gradient GA can be corrupted by systems that have a background magnetic field gradient G0 and also by imaging gradients G1, when used in an imaging mode. In a nonimaging mode, the corrupting cross term GA · G0can be eliminated in the diffusion measurement by use of an alternating-pulse-field-gradient (APFG) sequence that allows an accurate and uncorrupted measurement of D. A Carr-Purcell echo train enables the measurement of the expectation value, 〈DG20〉; assuming D and G0 to be uncorrelated will allow 〈G20〉 to be determined. An image of D or of 〈DG20〉 may be obtained without the corrupting GA · G0 and GA · GI terms by appending a standard imaging sequence to an APFG sequence or a Carr-Purcell sequence, respectively; assuming D and G0 to be uncorrelated will allow (〈G20〉 to be determined within each pixel. Measurements of D and 〈G20〉 and their images are made in apple flesh in which minute air bubbles are shown to produce the large 〈G20〉. Their values in an 81 g Golden Delicious apple at a measuring frequency of 100 MHz were D = 1.42 × 10−5 cm2/s and [formula] = 8.9 G/cm. |
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