Simple and accurate unwrapping phase of MR data

A new method for unwrapping phase of MR data, acquired using a double gradient-echo measurement, is introduced. The method not only removes artifacts due to gradients or hardware imperfections but also simultaneously shortens the effective echo time of the measuring sequence to unwrap the phase. The acquisition is repeated twice using different echo times and the ratio of both acquired and Fourier transformed data matrices is calculated. The state of unwrapping depends on the difference of the echo times and can be very high without any distortion. Influence on the signal-to-noise of the resulting field map is the same as for the unwrapped data. This method is applicable on all MR scanners and is very suitable for magnetic field distribution measurements.