[Keyhole-true FISP: fast T2-weighted imaging for interventional MRT at 0.2 T]

Abstract

Purpose: The aim of this study is to introduce a fast, T2 weighted true FISP keyhole sequence implemented on an open C arm low field magnetic resonance (MR) scanner for interventional procedure guidance.

Method: Following the acquisition of a reference data set using a true FISP (fast Imaging with Steady Precision) sequence, only the 32 central raw data lines (keyhole) are acquired in a fluoroscopic-like mode enabling continuous image reconstruction and update. The keyhole true-FISP sequence was tested in animal experiments and used in MR-guided interventions in 10 patients.

Results: The described true FISP keyhole sequence is characterized by an image frame rate of 2.5 images per second and a T2-like contrast. Due to system constraints with respect to the reconstruction, the actual displaying of images was delayed by up to 180 ms.

Conclusions: The use of the described keyhole sequence enabled a fluoroscopy-like guidance of interventional devices in an open, low-field system.