Interactive stereotactic interventions in superconducting open 0.5 tesla MRI.

Purpose: Evaluation of an interactive, stereotactic biopsy device integrated in an open superconductive 0.5 tesla MR-scanner with a vertical gap. Material and methods: In addition to ''in-vitro'' experiments performed on a plexiglas phantom with holes of varying diameters (5-20 mm) biopsies on eleven patients (7 women, 4 men; average age 55 years) were performed in the interventional MR-system. Lesions in the abdomen (n=6), muscle (n=1), thyroid (n=3) and breast (n=1) were targeted with 18-20 G aspiration biopsy needles of 5-15 cm length, The intervention was interactively guided by a fast T-1-weighted 2-D gradient echo sequence. Results: All of the 15 and 20 mm holes of the phantom, but only 83% of the 10 and 5 mm holes were hit. No complications occurred during the MR-guided patient procedures. All lesions (mean size 3.5 cm, distance from the skin 2 cm to 10 cm) were biopsied successfully. The fast image acquisition in combination with the stereotactic technique enables interactive control of the needle. Conclusions: Stereotactic, interactively controlled biopsies in the interventional MR are technical feasible. However, the range of meaningful indications for MR-guided biopsies is limited.