Electricity: measuring and testing – Particle precession resonance – Determine fluid flow rate
Patent
1985-08-16
1987-07-28
Levy, Stewart J.
Electricity: measuring and testing
Particle precession resonance
Determine fluid flow rate
324309, 128653, G01R 3320
Patent
active
046834311
ABSTRACT:
A main magnetic field coil and control cause a generally uniform main magnetic field through an image region. A resonance excitation control causes an R.F. coil to generate excitation pulses. An inversion pulse control causes the R.F. coil to generate a first 180 degree inversion pulse after the excitation pulse and a second 180 degree inversion pulse immediately preceding the excitation pulse. A slice gradient control and a read gradient control cause a gradient coil to generate complimentary slice selection gradients and complimentary read gradient profiles on either side of the first inversion pulse in such a manner that the effective first moment in time is substantially zero. By time shifting one or both of the slice selection and read gradients, resonating nuclei in the selected slice can be phase encoded. A transform algorithm transforms resonance signals received by the R.F. coil into image representations. A first memory receives real and imaginary components of the image representations when the read and slice selection gradients are not shifted and a second memory real and imaginary components of receives the image representations when one or both of the read and slice selection gradients are time shifted. From the arctangent of the real and imaginary components, first and second phase maps are calculated for storage in first and second phase memories. The intensity of each pixel of the phase maps varies with phase shift, hence velocity. By subtracting the two phase maps, correction is made for any stationary artifacts.
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Nayler Graham L.
Pattany Pradip M.
Levy Stewart J.
O'Shea Kevin D.
Picker International Inc.
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