Functional magnetic resonance imaging by spatially modulating steady-state signal in steady-state free precession

摘要

A modified steady-state free-precession (SSFP) method for functional magnetic resonance imaging (fMRI) is disclosed for acquiring a complex-valued image of object. A modulating field gradient is applied to impart spatial modulation of the steady-state signal phase and magnitude across the complex-valued image of the object along the direction of the modulating field gradient. SSFP pulse sequence parameters and modulating field gradient parameters can be selected to optimize functional image contrast between, e.g., oxy- and deoxy-hemoglobin, derived from steady-state signal magnitude or phase of complex-valued images.

主权项

1. A method comprising:
(a) placing an object to be imaged in a substantially uniform non-zero magnetic field B0; (b) with the object positioned in the magnetic field B0, applying to the object a repeating sequence of (i) one or more RF pulses, (ii) one or more non-zero slice-selection field-gradient pulses, (iii) one or more phase-encoding field-gradient pulses, and (iv) one or more non-zero readout field-gradient pulses; (c) during at least a portion of each repetition cycle of the pulse sequence, applying to the object a non-zero modulating field gradient; (d) detecting and recording steady-state spin echo or gradient echo signals for multiple repetition cycles of the pulse sequence; and (e) extracting from the recorded steady-state echo signals a steady-state signal magnitude or a steady-state signal phase for each voxel of a complex-valued image of the object, wherein: (f) repetition time TR of the pulse sequence is less than the longitudinal relaxation time T1 of the object; and (g) the modulating field gradient imparts spatial modulation of the steady-state signal phase and magnitude across the complex-valued image of the object along the direction of the modulating field gradient.