B-value calculation and correction using a linear segment gradient waveform model
First Claim
1. A method for calculating a b-value comprising:
- generating a gradient waveform comprising a plurality of timing data points and one or more waveform data points using a magnetic resonance imaging technique;
calculating two or more corner points associated with the gradient waveform;
determining an integration start point such that the start point corresponds to an excitation pulse generated by the magnetic resonance imaging technique;
determining an integration end point such that the end point corresponds to an echo time resulting from the excitation pulse;
generating an area sum by integrating one or more linear waveform segments between the start point and the end point wherein each linear waveform segment is defined by a line connecting adjacent corner points; and
calculating the b-value using the area sum.
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Abstract
A technique for calculating actual b-values in a diffusion weighted magnetic resonance imaging system and of adjusting the observed b-value until it is within a tolerance range of the prescribed b-value. A diffusion weighted image with the desired diffusion sensitivity may then be produced. Calculation of the actual b-value is accomplished by integrating the linear segments of the gradient waveform. Adjustment of observed b-value is accomplished by initially scaling the diffusion lobe amplitude and comparing a recalculated b-value to the prescribed b-value. Additional adjustment is provided by means of a numeric search iteratively performed until the recalculated b-value is within tolerance of the prescribed b-value.
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Citations
55 Claims
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1. A method for calculating a b-value comprising:
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generating a gradient waveform comprising a plurality of timing data points and one or more waveform data points using a magnetic resonance imaging technique;
calculating two or more corner points associated with the gradient waveform;
determining an integration start point such that the start point corresponds to an excitation pulse generated by the magnetic resonance imaging technique;
determining an integration end point such that the end point corresponds to an echo time resulting from the excitation pulse;
generating an area sum by integrating one or more linear waveform segments between the start point and the end point wherein each linear waveform segment is defined by a line connecting adjacent corner points; and
calculating the b-value using the area sum. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for correcting one or more b-values comprising:
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scaling an initial amplitude of a gradient diffusion lobe on a gradient axis to produce a scaled amplitude;
calculating a b-value for the axis using the scaled amplitude;
comparing the b-value with a prescribed b-value; and
adjusting the scaled amplitude if the b-value is outside a given tolerance of the prescribed b-value such that the adjustment is performed iteratively until the b-value is not outside the given tolerance of the prescribed b-value. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A magnetic resonance imaging system which calculates a b-matrix consisting of one or more b-values comprising:
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a magnetic resonance imaging scanner configured to collect one or more gradient waveforms comprising a plurality of timing data points and one or more waveform data points;
an analysis circuit configured to generate an output, to receive the gradient waveforms, and to calculate one or more b-values from the gradient waveforms such that the analysis circuit integrates one or more linear waveform segments comprising a gradient waveform to generate an area sum such that the actual b-values are calculated based upon the area sums;
a display circuit configured to receive the output and to preferably display the output via a display device; and
a control circuit configured to control the operation of the magnetic resonance imaging scanner, the analysis circuit, and the display circuit. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. A device for correcting one or more b-values comprising:
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a magnetic resonance imaging scanner configured to collect a gradient waveform comprising a plurality of timing data points and one or more waveform data points;
an analysis circuit configured to form an output and to generate a scaled amplitude from an initial amplitude of a gradient diffusion lobe and to iteratively adjust the scaled amplitude if a calculated b-value is outside a given tolerance to a prescribed b-value;
a display circuit configured to receive the output and to preferably display the output via a display device; and
a control circuit configured to control the operation of the magnetic resonance imaging scanner, the analysis circuit, and the display circuit. - View Dependent Claims (42, 43, 44, 45)
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46. A method for determining a b-matrix of one or more b-values comprising:
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calculating each b-value, the act of calculating comprising;
generating a gradient waveform comprising a plurality of timing data points and one or more waveform data points using a magnetic resonance imaging technique;
calculating two or more corner points associated with the gradient waveform;
determining an integration start point such that the start point corresponds to an excitation pulse generated by the magnetic resonance imaging technique;
determining an integration end point such that the end point corresponds to an echo time resulting from the excitation pulse;
generating an area sum by integrating one or more linear waveform segments between the start point and the end point wherein each linear waveform segment is defined by a line connecting adjacent corner points; and
calculating the b-value using the area sum. - View Dependent Claims (47, 48, 49, 50, 51, 52, 53, 54, 55)
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Specification