Free-breathing 3D Stack-of-Stars Gradient Echo Sequence in MR-guided Percutaneous Liver Interventions: Evaluation of Workflow and Diagnostic Quality

Purpose:To evaluate workflow efficiency and diagnostic quality of a free-breathing 3D stack-of-stars gradient echo (Radial GRE) sequence compared to a breath-hold 3D Cartesian gradient echo (Cartesian GRE) sequence for needle position control in MR-guided liver interventions. Materials and Methods:12 MR-guided liver interventions were performed on a 1.5 T Siemens Aera and analyzed retrospectively. 15 series of the Radial GRE sequence were compared to 14 series of the Cartesian GRE sequence regarding the time interval between two consecutive live-scans for needle tracking (Tracking-2-Tracking-Time). The quality of both sequences was compared by the SNR within comparable slices in liver and tumor ROIs. The CNR was calculated by subtraction of the SNR values. Subjective image quality scores of three radiologists were assessed and inter-rater reliability was tested by Fleiss' kappa. Values are given as mean & PLUSMN; SD. P-values < 0.05 were considered as significant. Results:The median Tracking-2-Tracking-Time was significantly shorter for the Radial GRE sequence, 185 +/- 42 s vs. 212 +/- 142 s (p = 0.04) and the median SNR of the liver and tumor ROIs were significantly higher in the Radial GRE sequence, 249 +/- 92 vs. 109 +/- 67 (p = 0.03) and 165 +/- 74 vs. 77 +/- 43 (p = 0.02). CNR between tumor and liver ROIs showed a tendency to be higher for the Radial GRE sequence without significance, 68 +/- 48 vs. 49 +/- 32 (p = 0.28). Mean subjective image quality was 3.33 +/- 1.08 vs. 2.62 +/- 0.95 comparing Radial and Cartesian GRE with a Fleiss' kappa of 0.39 representing fair inter-rater reliability. Conclusion:A free-breathing 3D stack-of-stars gradient echo sequence can simplify the workflow and reduce intervention time, while providing superior image quality. Under local anesthesia, it increases patient comfort and reduces potential risks for needle dislocations in MR-guided liver interventions by avoiding respiratory arrests for needle position control.