NMR blood vessel imaging method and apparatus
First Claim
1. A high speed method of forming computed images of blood vessels based on measurements of characteristics of a body comprising the steps of:
- subjecting a predetermined body area containing blood vesesls of interest to, successively, a plurality of applications of a short repetition time (TR) NMR pulse sequence during the period of high blood velocity and then to a corresponding plurality of said applications during the period of low blood velocity for a plurality of successive heart beat cycles wherein each application during said period of high blood velocity corresponds to a different phase encoding and said sequence of phase encodings is substantially repeated during said period of low blood velocity and collecting data from which an image of the blood vessels can be formed;
weighting the collected imaging data from each application of the NMR pulse sequence according to whether the data was acquired during the period of high blood velocity or a period of low blood velocity of the corresponding heart beat cycle;
accumulating weighted imaging data from a plurality of NMR pulse sequences corresponding to high blood velocit;
y periods and from a plurality of NMR pulse sequences corresponding to low blood velocity periods;
subtracting said weighted imaging data corresponding to each specific phase encoding acquired during the high blood velocity periods from said weighted imaging data for the same phase encoding corresponding to low blood velocity periods in order to compute blood vessel imaging data; and
forming an image of the blood vessels of interest from said blood vessel imaging data.
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Abstract
High speed selective imaging of blood vessels is accomplished by subjecting an area of interest to a plurality of short repetition time NMR pulse sequences during each high velocity period and low velocity period of a heart beat cycle for several or more heart beats. The imaging data from each NMR pulse sequence is collected and weighted according to whether it corresponds to a high velocity period or a low blood velocity period. The weighted imaging data corresponding to high blood velocity periods is then subtracted from weighted imaging data corresponding to low blood velocity periods and the resulting data used to form an image which depicts only the blood vessels of interest. Also, an imaging data processing apparatus is disclosed which operates in real time so as to permit an operator to optimize diagnostic performance.
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Citations
20 Claims
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1. A high speed method of forming computed images of blood vessels based on measurements of characteristics of a body comprising the steps of:
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subjecting a predetermined body area containing blood vesesls of interest to, successively, a plurality of applications of a short repetition time (TR) NMR pulse sequence during the period of high blood velocity and then to a corresponding plurality of said applications during the period of low blood velocity for a plurality of successive heart beat cycles wherein each application during said period of high blood velocity corresponds to a different phase encoding and said sequence of phase encodings is substantially repeated during said period of low blood velocity and collecting data from which an image of the blood vessels can be formed; weighting the collected imaging data from each application of the NMR pulse sequence according to whether the data was acquired during the period of high blood velocity or a period of low blood velocity of the corresponding heart beat cycle; accumulating weighted imaging data from a plurality of NMR pulse sequences corresponding to high blood velocit;
y periods and from a plurality of NMR pulse sequences corresponding to low blood velocity periods;subtracting said weighted imaging data corresponding to each specific phase encoding acquired during the high blood velocity periods from said weighted imaging data for the same phase encoding corresponding to low blood velocity periods in order to compute blood vessel imaging data; and forming an image of the blood vessels of interest from said blood vessel imaging data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A high speed method of forming computed images of blood vessels based on measurements of NMR characteristics of a body comprising the steps of:
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subjecting a predetermined body area containing blood vessels of interest to a plurality of applications of 2 variants of a short repetition time (TR) NMR pulse sequence, said variants devised such that images of static structure will appear substantially identical and images of moving structures will not, said plurality of applications being applied, successively, during the high blood velocity period of a heart beat cycle and then during the low blood velocity period of a heart beat cycle for each of a plurality of successive heart beat cycles, and collecting signal data from which images can be formed; applying each of said 2 variants of each of said plurality of applications of an NMR pulse sequence at each of a plurality of separate phase encodings; subtracting at each separate phase encoding said signal data measured from application of one of two said variants of said NMR pulse sequence from signal data measured from application of the other variant of said NMR pulse sequence in order to compute blood vessel imaging data; and forming an image of the blood vessels of interest from said blood vessel imaging data. - View Dependent Claims (11, 12, 13, 14)
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15. An NMR imaging system for constructing and displaying real time images of selected blood vessels of interest which are derived from NMR measurements comprising:
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means for monitoring the cardiac period; means for performing NMR measurements on blood vessels using, successively, a plurality of applications of a short repetition time (TR) NMR pulse sequence during the high blood velocity period of a heart beat cycle and then a plurality of said applications during the low blood velocity period for a plurality of succesive heart beat cycles, wherein each application during said period of high blood velocity corresponds to a different phase encoding and said sequence of phase encodings is substantially repeated during said period of low blood velocity, said pulse sequences each having a TR time of about 10-100 milliseconds; means for calculating and storing NMR measurement data and blood pressure data after each pulse sequence to generate imaging data, said means for calculating and storing serving to manipulate parameters including imaging data, encoded phase, and cardiac period; means for computing an average of previous successive imaging data contribution and adding each new imaging data contribution thereto to provide updated imaging data; and means for successively constructing and displaying blood vessel images based on said updated imaging data, said images being displayed on a real time basis. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification