Investigation of the influence of B 0 0 drift on the performance of the PLANET method and an algorithm for drift correction

摘要

Purpose The PLANET method was designed to simultaneously reconstruct maps of T 1 and T 2 , the off‐resonance, the RF phase, and the banding free signal magnitude. The method requires a stationary B 0 field over the course of a phase‐cycled balanced SSFP acquisition. In this work we investigated the influence of B 0 drift on the performance of the PLANET method for single‐component and two‐component signal models, and we propose a strategy for drift correction. Methods The complex phase‐cycled balanced SSFP signal was modeled with and without frequency drift. The behavior of the signal influenced by drift was mathematically interpreted as a sum of drift‐dependent displacement of the data points along an ellipse and drift‐dependent rotation around the origin. The influence of drift on parameter estimates was investigated experimentally on a phantom and on the brain of healthy volunteers and was verified by numerical simulations. A drift correction algorithm was proposed and tested on a phantom and in vivo. Results Drift can be assumed to be linear over the typical duration of a PLANET acquisition. In a phantom (a single‐component signal model), drift induced errors of 4% and 8% in the estimated T 1 and T 2 values. In the brain, where multiple components are present, drift only had a minor effect. For both single‐component and two‐component signal models, drift‐induced errors were successfully corrected by applying the proposed drift correction algorithm. Conclusion We have demonstrated theoretically and experimentally the sensitivity of the PLANET method to B 0 drift and have proposed a drift correction method.