Parallel Imaging Reconstruction by Sense Algorithm

The problem of image reconstruction from sensitivity encoded data is formulated in a general fashion and solved for arbitrary coil configurations and k-space sampling patterns. To achieve increased acquisition speed in magnetic resonance imaging Special attention is given to the currently most practical case, namely, sampling a common Cartesian grid with reduced density. Scan time was reduced to one-half using a four-coil array in brain imaging. __________________________________________________*****_________________________________________________ I. THEORY Magnetic resonance imaging (MRI) is an imaging technique used primarily in medical settings to produce high quality images of the inside of the human body. MRI is based on the principles of nuclear magnetic resonance (NMR), a spectroscopic technique used by scientists to obtain microscopic chemical and physical information about molecules. The technique was called magnetic resonance imaging rather than nuclear magnetic resonance imaging (NMRI) because of the negative connotations associated with the word nuclear in the late 1970's. MRI started out as a tomographic imaging technique, that is it produced an image of the NMR signal in a thin slice through the human body. Today MRI has advanced beyond the tomographic Imaging technique to a volume imaging technique. The acquisition speed of magnetic resonance imaging (MRI) is an important issue. Increasing the acquisition speed shortens the total patient examination time, it reduces motion artifacts and increases the frame rate of dynamic MRI. Parallel MRI is a way to use multiple receiver coils with distinct spatial sensitivities to increase the MRI acquisition speed. The acquisition is speeded up by undersampling the k-space in the phase-encoding direction. The resulting data loss and consequent aliasing is compensated for by the use of additional information Obtained from several receiver coils. New theoretical and practical concepts have been presented for considerably enhancing the performance of magnetic resonance imaging (MRI) by means of arrays of multiple receiver coils. The receiver sensitivity generally has an encoding effect complementary to Fourier preparation by linear field gradients. This fact has been used to reconstruct the image and the technique is known as sensitivity encoding (SENSE) Thus, by using multiple receiver coils in parallel, scan time in Fourier imaging can be considerably reduced.