1. Field
One or more exemplary embodiments relate to a method of generating a magnetic resonance image, a method of acquiring phase information of a phase contrast image, a method of acquiring phase information of a susceptibility weighted image, and an apparatus for generating a magnetic resonance image, and more particularly, to a method of generating a magnetic resonance image, a method of acquiring phase information of a phase contrast image, a method of acquiring phase information of a susceptibility weighted image, and an apparatus for generating a magnetic resonance image, which use a generalized auto-calibrating partially parallel acquisition (GRAPPA) technique.
2. Description of the Related Art
Magnetic resonance imaging (MRI) apparatuses are apparatuses that photograph an object by using a magnetic field. MRI apparatuses three-dimensionally show lumbar discs, joints, and nerve ligaments, in addition to bones, at a desired angle, and thus are being widely used for obtaining an accurate diagnosis of a disease.
MRI apparatuses acquire a magnetic resonance (MR) signal, reconfigure the acquired MR signal into an image, and output the image. In detail, MRI apparatuses acquire the MR signal by using radio frequency (RF) coils, a permanent magnet, and a gradient coil. When the MR signal is acquired, an unmeasured signal is generated at a junction portion between the RF coils. When generating a final MR image, a defect and noise may occur due to the unmeasured signal. Further, while K-space data acquired by the RF coils is being restored to an MR image, noise of the K-space data may be amplified.
Therefore, in order to finally output an MR image from which the above-described defect and noise are removed, it is required to correct the acquired MR signal via image processing, such as, for example, calibration.
An example of an MRI method for processing an acquired MR signal includes a K-space-based GRAPPA technique.
The GRAPPA technique, a K-space-based imaging method, performs self-calibration to calculate spatial correlations and/or convolution kernels between a calibration signal and a measured source signal which is adjacent thereto, estimates an unmeasured signal, and uses the estimated signal.
In detail, the GRAPPA technique restores unobtained K-space lines by channel by using a measured signal that includes undersampled data and an additional auto-calibration signal (ACS) line. Furthermore, the GRAPPA technique converts K-space data (which is restored by multichannel coils) into an image, and combines images of respective channels in a magnitude domain in order to acquire a final image. By combining the images of the respective channels in the magnitude domain, a quality of an image is prevented from being degraded by a phase difference due to interference between the channels.
The GRAPPA technique processes K-space data in parallel by coils which respectively correspond to the multichannel coils. Therefore, a time taken in acquiring a final image is shortened.
However, since the final image acquired by the GRAPPA technique is obtained via the combination in the magnitude domain, the final image includes only magnitude information, and does not include phase information.
Since the final image acquired by the GRAPPA technique does not include the phase information, the final image cannot be applied to an imaging technique which uses phase information, such as, for example, a phase contrast imaging (PCI) technique and a susceptibility weighted imaging (SWI) technique.
Due to this, it is required to provide an MR image generating method and apparatus that shorten a time taken in acquiring an MR image in a similar manner as via the GRAPPA technique, and acquire phase information of a final image.