Echo-dephased steady state free precession

Abstract

Objective: To introduce a novel positive contrast method for passive localization and visualization of paramagnetic susceptibility markers.

Materials and methods: The novel approach is based on an echo-dephased steady-state free precession (SSFP) sequence. Gradients dephase any signal by +/-pi at the centered echo-time (TE = TR/2) and induce a total dephasing of +/-2 pi per pixel within TR. This ensures that background tissues do not contribute to signal formation and thus appear dark. However, within the close vicinity of the paramagnetic marker, local gradient fields compensate for the intrinsic dephasing to form an echo. Conceptual issues of gradient compensation and its visualization characteristics are analyzed. The feasibility of the proposed technique for MR-guided intravascular interventions is demonstrated using flow phantom.

Results: Echo-dephased SSFP is able to localize and visualize paramagnetic marker with excellent suppression of the background signals. The flow phantom experiments concluded that reliable tracking of the interventional guidewire is feasible using echo-dephased SSFP.

Conclusion: With newly introduced echo-dephased SSFP approach, accurate and reliable visualization of paramagnetic interventional device is feasible.