Functional magnetic resonance imaging using steady state free precession
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsKarla L. Miller, John M. Pauly
Life of this patent
Estimating the term…
Abstract
A method for functional magnetic resonance imaging (fMRI) uses steady-state free precession (SSFP) to image changes in blood oxygenation between two time periods. A center frequency of the SSFP sequence is placed between the different resonant frequencies for oxyhemoglobin and deoxyhemoglobin whereby the signals have a phase difference of 180° and tend to cancel. By repeating the SSFP imaging sequence at different times, the difference in the measured signals provides a measure of change in oxyhemoglobin. RF flip angle of the SSFP sequence is chosen to maximize signal level in the frequency range from that of water in the presence of oxyhemoglobin and that of water in the presence of deoxyhemoglobin.
Claims14
A method for functional magnetic resonance imaging (fMRI) comprising the steps of:
- a) applying a steady-state free precession (SSFP) imaging sequence to a body having oxyhemoglobin and deoxyhemoglobin therein, with the oxyhemoglobin and the deoxyhemoglobin having different resonance frequencies, a center frequency of the SSFP sequence being between the resonance frequencies, and
- b) measuring MRI signals from the body whereby signals from water in the presence of deoxyhemoglobin subtract from signals from water in the presence of oxyhemoglobin thereby providing a measure of difference in oxyhemoglobin and deoxyhemoglobin.
A method of measuring change in blood oxygenation in a body using magnetic resonance imaging comprising the steps of:
- a) placing the body in a magnetic field,
- b) applying axial magnetic fields to the body,
- c) applying a plurality of RF excitation pulses to the body at a repetition time, TR, to flip nuclei spins,
- d) rewinding all gradients over the repetition time, TR,
- e) measuring refocused MRI signals at time TE whereby the phases of the measured signals for oxyhemoglobin and deoxyhemoglobin differ by approximately 180°,
- f) repeating steps a) through e) at a second time period differing from a first time period for steps a)–e), and
- g) using the measured refocused MRI signals from step e) and repeated step e) to measure change in blood oxygenation from the first time period to the second time period.
Dependencies are inferred from the claim text.