Construction and calibration of a 50 T/m z-gradient coil for quantitative diffusion microimaging.
q-Space imaging is capable of providing quantitative geometrical information of structures at cellular resolution. However, the size of restrictions that can be probed hinges on available gradient amplitude and places very high demands on gradient performance. In this work we describe the design and construction of a small, high-amplitude (50 T/m) z-gradient coil, interfaced with a commercial 9.4 T microimaging system. We also describe a method to calibrate the coil for quantitative measurements of molecular diffusion at very high-gradient amplitudes. Calibration showed linear current response up to 50 T/m, with a gain=1.255 T/m/A. The z-gradient coil was combined with the commercial x- and y-gradients for tri-axial imaging, and its performance was demonstrated by ADC maps of free water and by q-space experiments on water sequestered around polystyrene microspheres (4.5 microm diameter), which showed the expected diffraction peak. In addition, diffusion-weighted images of a fixed mouse spinal cord illustrated the capability of this coil for quantitative imaging of tissue microstructure.
Wright
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Laboratory for Structural NMR Imaging, Department of Radiology, 1 Silverstein, University of Pennsylvania Medical Center, 3400 Spruce Street, Philadelphia, PA 19104, USA. Alexander.Wright@uphs.upenn.edu
Bataille
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Ong
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Wehrli
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Song
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Wehrli
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D000818:Animals; D002138:Calibration; D017076:Computer-Aided Design; D038524:Diffusion Magnetic Resonance Imaging / Q000295:instrumentation* / Q000592:standards*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation* / Q000592:standards*; D008280:Magnetics; D051379:Mice; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013116:Spinal Cord / Q000033:anatomy & histology* / Q000502:physiology*; D014159:Transducers; D014481:United States