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| Dentifrice-compatible silica particulates |
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Magnetic resonance imaging of high velocity flows
| Details |
Inventors: Pattany, Pradip M.; Nayler, Graham L.;
Assignee: Picker International, Inc. (Highland Hts., OH)
Primary Examiner: Levy; Stewart J.
Assistant Examiner: O'Shea; Kevin D.
Attorney, Agent or Firm: Fay, Sharpe, Beall, Fagan, Minnich & McKee
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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DETAILED DESCRIPTION In accordance with one aspect of the present invention, a method is provided for magnetic resonance phase mapping of moving substances.
A pre-inversion of magnetization is cause before application of a magnetic resonance exciting signal during an otherwise conventional spin-echo magnetic resonance sequence.
In accordance with another aspect of the present invention, a method is provided for magnetic resonance imaging.
A resonance excitation pulse is applied.
At least one of a first read gradient and a first slice selection gradient are applied.
An inversion pulse is then applied to cause a spin-echo.
Thereafter, at least one of a second read gradient and a second slice selection gradient is applied.
The applied first and second gradients are configured and timed relative to each other such that the effective first moment in time is substantially zero.
The resultant resonance signals are reconstructed into an image.
In accordance with a further aspect of the present invention, at least one of the second read and slice selection gradients are altered, e.
g.
time shifted, and the sequence is repeated to generate a second image.
In accordance with another aspect of the present invention, first and second phase maps are calculated from the ratio of the real and imaginary components of each pixel within the first and second images.
The velocity at each pixel is calculated from the difference between the phases of the first and second phase maps.
In accordance with yet another aspect of the present invention, a magnetic resonance apparatus is provided.
Magnets provide a substantially uniform main magnetic field.
Gradient coils and controls are arranged to apply read and slice select gradients selectively across the main magnetic field.
A resonance excitation control means causes an R.
F.
coil to apply resonance excitation pulses.
An inversion pulse control means selectively causes the R.
F.
coil to apply broadband inversion pulses preceding application of the excitation pulse and subsequent to application of the excitation pulse
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