Method and device to process complex image data

摘要

Complex magnetic resonance (MR) image data, acquired from an examination subject that has at least two different spin species, are processed in a method and a device. At least one MR parameter that influences data acquired in an MR data acquisition is determined with spatial resolution. Complex image data are respectively acquired with each of multiple acquisition units in an MR data acquisition at multiple echo times, such that a phase difference between the first spin species and the second spin species is different at least two of the echo times. For multiple image points, a value of the at least one MR parameter is determined so that a function that depends on the at least one MR parameter and the corresponding image point in the complex image data satisfies an extreme condition.

主权项

1. A method to process complex image data, comprising:
providing, to a processor, complex image data, comprising phase and amplitude information, acquired as signals emitted from an examination subject during a plurality of echo times in a magnetic resonance (MR) data acquisition using a plurality of individual acquisition components selected from the group consisting of individual reception coils and respective portions of a multi-coil reception array, said complex image data having been acquired according to at least one MR parameter, of an MR data acquisition unit that executes said MR data acquisition, that affects said signals representing said complex image data, said examination subject comprising a first spin species and a second spin species that emit said signals, said second spin species differing from said first spin species, and a phase difference between precessing spins of said first spin species and precessing spins of said second spin species being different in at least two of said echo times; and in said processor, determining a value of said at least one MR parameter, with spatial resolution for a plurality of image points in said complex image data, that causes a function, which depends on said at least one MR parameter and a corresponding image point in said complex image data acquired during said at least two of said echo times, to satisfy an extreme condition at which said function has an extreme function value, by solving, for the multiple image points, an equation system that represents an extreme condition or multiple extreme conditions of a probability distribution depending on the at least one MR parameter, wherein the equation system represents the condition0=∑a=1N⁢∑b=1N⁢(τa-τb)⁢Exp⁡[ⅈωΔ⁢⁢B⁢⁢0⁡(τa-τb)]⁢ga⁢gb*⁢da⇀†⁢db⇀(1) wherein N is a number of the echo times and τn represents the n-th echo time, wherein a vector {right arrow over (d)}n associated with the n-th echo time τn has matrix elements that depend on image data acquired with plurality of acquisition units at the echo time τn, wherein ωΔB0 is a spatially resolved shift to be determined of a precession frequency, and wherein:
gn=r1Exp[(−1/[T2*]1)τn]+(1−r1)Exp[(−1/[T2*]2+iω2)τn]  (2) wherein r1 is the local proportion of the first spin species [T2*]2 is the T2* time of the first spin species, [T2*]2 is the T2* time of the second spin species, and ω2 is a difference between a precession frequency of the second spin species and a precession frequency of the first spin species; and making said value of said at least one MR parameter that causes said function to have said extreme function value available in electronic form at an output of said processor.