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Publication Date: 2015-May-15
Document File: 4 page(s) / 80K

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The disclosed invention provides a technique to solve problem with patient movement during and between acquisitions of data in a magnetic resonance imaging (MRI) scanner. The technique includes a regime of continuously interleaving image based navigators, such as, 3D FatNav, during the whole exam. The image based 3D navigators, such as 3D FatNav is used by the MRI system to track motion of head of a patient. Further, 3D FatNav updates field of view (FOV) that requires scanning to ensure that it is always the intended anatomical region as planned on the localizer. This decreases number of rescans of image series and recalls of patients back to healthcare providers.

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The present invention relates generally to magnetic resonance imaging (MRI) system and more particularly to a technique to provide potential motion correction during image acquisition to increase image quality.

Generally, during magnetic resonance imaging (MRI) exam, a patient often moves during data acquisition. Patient movement results in motion artifacts, which provides bad image quality. In some instances, the image is non-diagnostic due to the artifacts. In such cases, a re-scan is required to be performed if bad image quality is noted during the MRI exam. If the bad image quality is noted after the exam, the patient is recalled. However, rescanning and recalling patients proves to be very expensive for healthcare providers.

Another problem that arises due to patient movement during MRI exam is that, patient position may be different between different image series. The different image series depict different contrasts and are acquired at different points in time. Geometrical area required to be imaged, which is referred to as field of view (FOV) of image, is however, often the same. Same FOV enables comparing anatomical areas with different contrasts. The process of choosing areas to be imaged is performed at the beginning of the MRI exam from very fast localizer images in three planes. If the patient moves during the exam, different image series is still acquired at a planned FOV in geometrical reference system of a scanner, and not relative to the patient. Consequently, if the patient has moved, the FOV imaged is not the same as planned on the localizer. As a result, issues arise while reading the images. For instance, during pre-gadolinium and a post-gadolinium image comparison for a patient, if the patient moves between two image series, the underlying anatomy does not remain the same in the two images that is compared. If the reader is not aware about movement of the patient, there is a significant risk of misinterpreting the images. Figure 1 depicts two slices of different contrast. Both the slices prescribed exactly the same but depict different anatomical regions due to movement of the patient (volunteer) between the localizer and the two different series.

Figure 1

 A conventional technique includes a two-dimensional fat navigator (FatNav) image, which is designed as a means of prospective motion correction of head-nodding motion. The proposed FatNav module includes a fat selective excitation, followed by an accelerated echo planar imaging readout played out in one central sagittal plane. Further, stepwise motion experiments with different acceleration factors, blip polarity, and matrix sizes are performed. FatNav is leaves most of the brain water magnetization unaffected and left to the host pulse sequence. Furthermore, high acceleration factors are possible with FatNav, which reduces estimation bias and the navigator...