Oscillating dual-equilibrium steady state angiography using magnetic resonance imaging
First Claim
1. A method of magnetic resonance angiography comprising the steps of:
- a) placing an object to be imaged in a static magnetic field, b) applying an RF pulse and axial gradients to the object, c) detecting first signals from nuclei in the object, d) applying an RF pulse, axial gradient, and a bipolar flow-encoding pulse, e) detecting second signals from nuclei in the object, f) repeating steps b) and c) to establish a steady state of first signals, g) repeating steps d) and e) to establish a steady state of second signals, and h) subtracting the steady state of first signals from the steady state of second signals to obtain signals of non-static material.
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Abstract
A method of oscillating dual-equilibrium steady-state angiography (ODESSA), utilizes a modified steady state free precession (SSFP) pulse sequence. The SSFP sequence is modified such that flowing material reaches a steady state which oscillates between two equilibrium values, while stationary material attains a standard, non-oscillatory steady state. When alternating sequences are employed, subtraction of adjacent echoes results in large, uniform signal from all flowing spins and zero signal from stationary spins. Venous signal can be suppressed based on its reduced T2. ODESSA arterial signal is more than three times as large as that of traditional phase-contrast angiography (PCA) in the same scan time, and also compares favorably with other techniques of MR angiography. Pulse sequences are implemented in 2D, 3D, and volumetric projection modes. Angiograms of the lower leg, generated in as few as 5 s, show high arterial SNR and full suppression of other tissues.
33 Citations
26 Claims
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1. A method of magnetic resonance angiography comprising the steps of:
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a) placing an object to be imaged in a static magnetic field, b) applying an RF pulse and axial gradients to the object, c) detecting first signals from nuclei in the object, d) applying an RF pulse, axial gradient, and a bipolar flow-encoding pulse, e) detecting second signals from nuclei in the object, f) repeating steps b) and c) to establish a steady state of first signals, g) repeating steps d) and e) to establish a steady state of second signals, and h) subtracting the steady state of first signals from the steady state of second signals to obtain signals of non-static material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of magnetic resonance angiography comprising the steps of:
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a) placing an object to be imaged in a static magnetic field, b) applying a first refocused steady state precession pulse and gradient sequence to obtain first signals from nuclei in the object;
c) applying a second refocused steady state precession pulse and gradient sequence including a bipolar flow encoding pulse to obtain second signals from nuclei in the object, d) repeating step b) to establish a steady state of first signals, e) repeating step c) to establish a steady state of second signals, and f) subtracting the steady states of first signals and second signals to obtain signals of non-static material. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification