Use of CPMG sequences with phase cycled refocusing pulses in inside-out NMR for phase encoded imaging and to eliminate coherent ringing within one scan

摘要

A method for performing phase encoded inside-out magnetic resonance imaging. The phase of the nuclear spin is advanced by applying a magnetic field gradient between application of each of several refocusing pulse sequences so that echoes are detected during refocusing pulse sequences for different phase advances. The echoes detected for each refocusing sequence are added together and averaged. An image is then generated from the averaged echoes, such as by Fourier transform techniques. In addition, a method is provided for eliminating ringing while measuring a nuclear magnetic resonance property of a volume of earth formation surrounding a borehole. The phase of the refocusing pulses is changed so that pairs of echoes in the echo train have opposite ringing phase. Echoes in the echo train having opposite ringing phase are added to cancel ringing in the echo train. The echo train can then be analyzed for amplitude and/or decay characteristics.