Ge Medical Systems Global Technology Company, LLC

Nozomu Uetake

Susumu Kosugi

Yasushi Kato

Tsunemoto Suzuki

An eddy current induced in an RF shield by an X-axis gradient coil, a Y-axis gradient coil, and a Z-axis gradient coil respectively is homogeneously released to an earth ground simultaneously with induction. An RF shield is connected to a magnet via capacitors at four points whose angles are different from one another by 90&#xb0;. The magnet is connected to the earth ground. An eddy current induced in the RF shield can be prevented from degrading MRI image quality.

RF shield and MRI system

For the purpose of conducting optimal eddy current correction within a limited output range, a corrective value for eddy current correction for a gradient magnetic field is calculated, if the calculated value does not exceed a predetermined upper limit value, correction is conducted on the gradient magnetic field using the calculated value, and if the calculated value exceeds the predetermined upper limit value, a plurality of gradient magnetic fields affected by eddy current are simulated using a plurality of candidate corrective values not greater than the upper limit value, and correction is conducted on the gradient magnetic field using a candidate corrective value by which a relatively optimal gradient magnetic field can be obtained.

Eddy current correction method and magnetic resonance imaging apparatus

An object of the present invention is to perform multiple slice imaging accompanied by saturation irrespective of the inhomogeneity of static magnetic field strength. An error of a peak resonant frequency of spins at each slice position is measured. A maximum value is extracted from among errors of peak resonant frequencies of spins in all slices relative to a center frequency with the peak resonant frequency of spins in water between the center frequency and the peak resonant frequency of spins in fat. Spins are excited at a frequency that deviates from the center frequency towards the peak resonant frequency of spins in water by a value calculated by adding the maximum value to a theoretical change in a peak resonant frequency stemming from a chemical shift.

Spin exciting method and magnetic resonance imaging system

A method of correcting a resonance frequency variation and an MRI apparatus both capable of handling all frequency drifts including a frequency drift whose time change is slow, a frequency drift in a slice direction and a frequency drift whose time change is fast. An amount of a resonance frequency variation is measured, the frequency variation is corrected when an amount of the resonance frequency variation is smaller than a threshold value, and the amount of the resonance frequency variation is not stored. On the other hand, when the amount of the resonance frequency variation is not smaller than the threshold value, the amount of the resonance frequency variation is stored and correction operation is made based thereon later.

Method of correcting resonance frequency variation and MRI apparatus

With an intention to improve picture quality without increasing the overall number of times of data collection and to restrain artifacts resulting from differences in noise structure between parts differing in the number of times of addition, the total number V of views is equally divided into eight, and the areas of the two ends of each V/8, where the absolute value of the quantity of phase encoding is the greatest, are reduced in the number of times of addition by &frac12; of the reference number of times N, because their contributions to picture quality is small. The remaining middle 6V/8 areas are increased in the number of times of addition by &frac12; of the reference number of times N, because their contributions to picture quality are great, and further to alleviate the non-continuity of the variations of the number of times of addition, the number of times of addition in the middle 6V/8 areas is varied so as to follow either a Hamming function or a Hanning function.

MR imaging method and MRI apparatus

In order to compensate for magnetic field drift and shorten the overall scanning time, total number of pulse sequences of data acquisition for magnetic field drift compensation Md is less than the repetitive number of imaging data acquisition pulse sequences Im, and a pulse sequence of data acquisition for magnetic field drift compensation Md is inserted between imaging data acquisition pulse sequences Im.

Data acquisition method of compensation for magnetic field drift, method of compensation for magnetic field drift, and MRI apparatus

For the purpose of increasing the time available for performing a calculation on a navigator echo, the sampling frequency for a navigator echo is made higher than the sampling frequency for an imaging echo, or the number of sampling points for the navigator echo is made fewer than the number of sampling points for the imaging echo, or both measures are implemented in combination.

Magnetic resonance signal acquiring method and apparatus, recording medium and magnetic resonance imaging apparatus

For the purpose of increasing the time available for performing a calculation on a navigator echo, a method comprises: during one of two consecutive periods TR, effecting RF excitation on spins within an object and acquiring a navigator echo, and thereafter effecting RF excitation for preparation; and during the other of the two consecutive periods, effecting RF excitation on the spins within the object and acquiring an imaging echo, and thereafter effecting RF excitation for preparation.

Growing community of inventors

Tokyo, Japan

Nozomu Uetake