Sensitive and fast mapping based on two inversion recovery images and a reference image
Simulation of the signal intensity of the inversion recovery sequence as a function of inversion time (A) and the difference signal intensity of (B). The parameters used were , , , and for human gray matter at . In (A), the heavy dashed line before the zero crossing represents the absolute value of . The two dots represent the inversion times, and , used to calculate from the difference signal.
Pulse sequence timing diagram showing radio frequency (rf) pulses and gradients along each spatial direction . A nonselective hyperbolic inversion (180°) rf pulse is followed after the inversion time TI by a slice-selective sinc-shaped excitation (90°) pulse. is the slice selective gradient. An echoplanar image (EPI) is generated by gradients and . TE is the echo time, and TD is a variable delay time and was adjusted to yield the same repetition time for all three images. The first image according to Eq. (2) is obtained without applying a 180° pulse, while the second and third images are acquired each with a 180° pulse at delays and , respectively.
Simulation of , calculated according to Eq. (3), as a function of inversion times and , assuming a perfect inversion pulse. The simulation parameters used were and for human gray matter (A) and and for human white matter (B) at . reached a maximum at for gray matter and at for white matter with .
Images from one normal volunteer without inversion preparation (reference images, top row) and corresponding maps (bottom row) for seven slices. Representative ROIs of gray matter and white matter were drawn on the middle slice out of seven slices as indicated in the figure. Slices 3 to 6 were used to measure average values in each subject.
estimates for gray and white matter from nine volunteers.
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