JPH11164819A5 - - Google Patents

Claims (5)

A magnetic resonance imaging apparatus comprising: static magnetic field generating means for applying a static magnetic field to a subject; gradient magnetic field generating means for applying a gradient magnetic field to the subject; a transmission system for irradiating a radio frequency magnetic field that causes nuclear magnetic resonance in the nuclei of atoms constituting the biological tissue of the subject; a reception system for detecting echo signals emitted by the nuclear magnetic resonance as projection data; a control system for controlling the gradient magnetic field generating means, the transmission system, and the reception system in accordance with a predetermined pulse sequence; a signal processing system for performing image reconstruction calculations using the projection data detected by the reception system; and a means for displaying the obtained image,
a control system for controlling a phase encoding amount to be applied to sequentially acquired echo signals so that an apparent period of the periodic motion of the subject as seen for each of adjacent projection data in k-space differs from an actual period (Tp). 2. The magnetic resonance imaging apparatus according to claim 1, wherein the periodic motion is shifted by approximately 1/2 period for each of the projection data. 3. The magnetic resonance imaging apparatus according to claim 1,
a control system for controlling the amount of phase encoding based on a period (Tp) of the periodic movement of the subject, a repetition time (TR) in the pulse sequence, and a number (k) of data additions. 4. The magnetic resonance imaging apparatus according to claim 1,
The control system divides all projection data in the k-space into groups of projection data measured within the period (Tp), and measures each group of projection data in the phase encoding direction. In this case, if the number (n) of projection data of different phase encoding amounts measured within the period is odd, either the odd-numbered projection data or the even-numbered projection data is collected in numerical order in the first half of the period, and then the other is collected in numerical order. Measurement is repeated in the same manner until projection data of all phase encoding amounts is collected, and the different projection data measured within the period are collected. and a magnetic resonance imaging device that controls the gradient magnetic field generating means so that, when the number (n) of projection data of the phase encoding amount is even, in a first period (Tp), either the odd-numbered projection data or the even-numbered projection data is collected in numerical order in the first half of the period, and then the other is collected in numerical order, and in a next period (Tp), the other is collected in numerical order in the first half, and then the one is collected in numerical order, and similarly, the order of the projection data collected for each period is changed, and measurement is repeated until all the projection data of the phase encoding amount is collected. 5. The magnetic resonance imaging apparatus according to claim 1, wherein the control system has a function of setting an imaging region of the subject, setting an area wider in the phase encoding direction than a necessary field of view as the imaging region and imaging the area, discarding areas other than the necessary field of view after image reconstruction, and displaying only an image of the necessary field of view.