In vitro assessment of needle artifacts with an interactive three-dimensional MR fluoroscopy system

To perform in vitro assessment of needle artifacts with an interactive three-dimensional (3D) near-real-time magnetic resonance (MR) fluoroscopy system for musculoskeletal interventions in a 1.5-T open-bore magnet.

One MR-compatible titanium needle, one MR-compatible Inconel (nickel-chromium superalloy) needle, and one MR-compatible carbon fiber needle were imaged with an interactive 3D MR sequence. Slice orientations, measurement parameters (fast low-angle shot, repetition time/echo time of 1,358/5 msec, flip angle of 15 degrees , bandwidth of 250 Hz/pixel; and true fast imaging with steady-state precession, repetition time/echo time of 770/2.2 msec, flip angle of 50 degrees , bandwidth of 558 Hz/pixel), phase encoding directions, and orientations to the main magnetic field (B(0)) were systematically varied. Artifact sizes, normalized artifact contrasts, and tip location errors were assessed for all variations of acquisition parameters and needles and compared with t tests.

Mean artifact sizes, normalized artifact contrast, and tip location errors were 22.9 mm, 96%, and 5.4 mm, respectively, for the Inconel needle; 6.1 mm, 70%, and 0.3 mm, respectively, for the titanium needle; and 2.8 mm, 38%, and -1.9 mm, respectively, for the carbon fiber needle. Artifact widths depended on needle materials and needle orientation to B(0), with significant differences on ttests. Artifact contrast did not depend on measurement parameters. No significant influence on artifact character was found for changes in phase encoding direction and slice orientation.

Because of its robustness in depicting needle artifacts, the interactive 3D MR fluoroscopy system appears to be suitable for MR-guided interventions. The titanium needle showed optimal artifacts with all combinations of measurement parameters. Artifacts with the other needles were too large (Inconel) or too small (carbon fiber).