| 摘要 |
<p>A reference object (24) is disposed in an image region (20) with a subject (22) to be examined. The reference object has known parameters such as relaxation time, spin density, dimensions, and position. Magnetic resonance signals in which the spatial position of resonating nuclei is encoded in the relative phase and frequency thereof are sampled and temporarily stored in a view memory (56). A Fourier transform (60) is performed to convert the stored signals view into a representation of at least the positions and spin density of the resonating magnetic dipoles of the subject and reference object. The parameters of the reference object measured from the image representation are compared or inverse transformed back to data space for comparison with actual parameters of the reference object or thresholds. Based on the comparison, the resonance signals or the image representation are adjusted. For example, the magnetic resonance signals are rotated (78) through a phase correction to correct for offsets in the phase encoding. As other examples, the spin density may be adjusted, low magnitude data discarded, spatially offset data shifted, or the like. Alternately, the reference object may be interconnected with the subject to undergo movement therewith. The position of the reference object is then utilized to select views in which the movement of the subject is within preselected ranges or to approximately correct for the motion. The image can be shifted to a selected location or interpolated.</p> |
