Mr - a method for the selective excitation

摘要

A magnetic resonance - a process for the use of rf pulses for a spatially and frequency-selective or multidimensionally spatially selective excitation of a set of nuclear spins with an output magnetization distribution in a along a z - axis oriented main magnetic field, wherein a spin magnetisation, which is connected with a predetermined target magnetization distribution is produced, and for a refocusing of the spin magnetisation, is characterized in that the radio-frequency pulse as a sequence of component pulses of independent time gradient characteristics as well as spatial and / or spectral resolution is used, comprising one or more large angle - hf - pulses with a flip angles greater than or approximately equal to 15°, which produce a coarse magnetization distribution, which can be the aim of magnetization division or a desired magnetization distribution change with an average deviation of less than or approximately equal to 15°, wherein the actual effect of the gwp to the distribution of the spin magnetisation in front of the application of the radio-frequency pulse by the integration of the bloch equations - without small angle vicinity of the bore-hole is calculated, and one or more small angle - hf - pulses with a flip angles of less than or approximately equal to 15°, a reduction of the difference between the target magnetization process by the division and the coarse magnetization distribution effect caused gwp.