1. Field
Apparatuses and methods consistent with exemplary embodiments relate to magnetic resonance imaging (MRI) apparatuses and methods thereof, and more particularly, to MRI apparatuses for obtaining magnetic resonance (MR) images by using multi-echo sequences and methods of the MRI apparatuses.
2. Description of the Related Art
Magnetic resonance imaging (MRI) apparatuses for imaging subjects by using magnetic fields may show stereoscopic images of bones, lumbar discs, joints, nerve ligaments, hearts, etc. at desired angles.
An MRI apparatus is advantageous in that the MRI apparatus is noninvasive, exhibits an excellent tissue contrast as compared to a computerized tomography (CT) apparatus, and does not have artifacts due to bone tissue. Also, because the MRI apparatus may capture various cross-sectional images in desired directions without moving an object, the MRI apparatus is widely used with other imaging apparatuses.
An MRI apparatus may obtain k-space data by using a multi-echo sequence. In detail, when a multi-echo sequence is used, a time taken to capture an image may be reduced by exciting one radio frequency (RF) pulse and then obtaining an MR signal by using a plurality of generated echoes.
When an MRI apparatus uses a multi-echo sequence, the MRI apparatus may use a method of obtaining a plurality of pieces of k-space data respectively corresponding to a plurality of echo times by applying a gradient magnetic field for phase encoding only once during one repetition time (TR).
Alternatively, the MRI apparatus may use a method of obtaining one piece of k-space data by using a plurality of echoes that are generated during one TR. This method is referred to as an echo-planar imaging (EPI) method.
A multi-echo sequence may be based on gradient echoes or spin echoes. If a multi-echo sequence is based on gradient echoes, because a sign of a readout gradient magnetic field has to be continuously reversed, an MRI apparatus may have high performance to generate a gradient magnetic field. As the performance of an MRI apparatus has recently been improved, not only a TR may be reduced when gradient echoes are used but also an image having a desired contrast ratio may be obtained.