Electricity: measuring and testing – Particle precession resonance – Determine fluid flow rate
Patent
1996-12-30
1998-07-21
O'Shea, Sandra L.
Electricity: measuring and testing
Particle precession resonance
Determine fluid flow rate
324312, 600419, G01R 3320
Patent
active
057839425
ABSTRACT:
A phase unwrapping method is provided comprising a post-processing MR operation for an array of phase-related MR data elements. The method includes the steps of defining a Region of Interest, of comparing each data element with the first and second data elements which are adjacent thereto in the array, in order to generate respectively corresponding first and second gradient values. A subset of the data elements is constructed, wherein a data element is assigned to the subset only if its corresponding first and second gradient values are less than a selected threshold value VENC/2. The data element subset is employed to generate a fitted phase function having a value at the position of each data element in the array, and the value of the fitted function thereof, for a given data element, is subtracted from the measured value thereof. A first unwrap correcting value is subtracted from the given data element if the difference is greater than a first specified level, and a second unwrap correcting value is added thereto if the difference is less than a second specified level. A measure of the number of wrapped pixels is monitored. The phase unwrap procedure can be iterated until the number of unwrapped pixels is zero, or does not decrease with further iterating.
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Bernstein et al. Proceedings of the International Society fo Magnetic Resonance in Medicine, vol. 2 (1996) "Unwrapping Quantitative Phase Contrast Images with a Polynomial Fit--Initial Experience" p. 1285.
Bernstein Matthew A.
Glover Gary H.
Eisenberg Michael
O'Shea Sandra L.
Pilarski John H.
Skarsten James O.
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