Electricity: measuring and testing – Particle precession resonance – Determine fluid flow rate
Patent
1985-11-15
1987-08-25
Tokar, Michael J.
Electricity: measuring and testing
Particle precession resonance
Determine fluid flow rate
324309, G01R 3320
Patent
active
046895604
ABSTRACT:
A main magnetic field coil (10) and control (12) cause a generally uniform main magnetic field through an image region. A resonance excitation control (22) causes an R.F. coil (20) to generate excitation pulses (100). A slice gradient control (32) and a read gradient control (34) cause a gradient coil (30) to generate complementary slice selection gradient profiles (112, 114) and complementary read gradient profiles (122, 124) in such a manner that the effective first moment in time is substantially zero. By time shifting a pulse in one or both of the slice selection and read gradient sequences (FIGS. 3 and 4), resonating nuclei in the selected slice can be phase encoded. A transform algorithm (40) transforms field echo signals (102) received by the R.F. coil into image representations. A first memory (54) receives real and imaginary portions of the image representations when the read and slice selection gradients are not shifted and a second memory (56) receives the image representations when one or both of the read and slice selection gradients are time shifted. A phase difference map (70) is calculated (60) from the arctangent of phase difference values derived from the first and second images. The intensity of each pixel of the phase difference map varies with phase shift, hence velocity.
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Nayler Graham L.
Pattany Pradip M.
Picker International Inc.
Tokar Michael J.
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