| 摘要 |
PROBLEM TO BE SOLVED: To calculate an excitation angle of a maximum MR signal by controlling automatically elements for varying the strength of an RF pulse for imaging where the excitation angle of an atomic nucleus spin becomes spatially nonuniform. SOLUTION: The Fourier analysis separates an echo signal into signals in spatial positions in the slice direction from a time base. After that, a slice position smax where the echo signal takes a maximum value is obtained. As a flip angleα(S) in the slice position Smax exceeds 90 deg. to 180 deg. conditions, on the basis of a calculated flip angle ratio, an actual excitation angle in the center slice position Scent is obtained. A host computer outputs a power control signal Spw corresponding to a power adjustment coefficient 90 deg./α0 deg.. In a transmitter, the attenuation factor of an attenuator is changed by this power control signal Spw , thereby changing the amplitude of an RF pulse transmitted to a subject through an RF coil from the transmitter at the time of main scan to 90 deg./α0 deg. times, performing power adjustment automatically, collecting MR signals by one operation, and improving an MR image.
|
