MR Imaging‒Guided Intervention: Evaluation of MR Conditional Biopsy and Ablation Needle Tip Artifacts at 3T Using a Balanced Fast Field Echo Sequence.

Purpose: To systematically investigate artifacts produced by biopsy and ablation needles imaged at various trajectories with respect to the static magnetic field (B0).

Materials And Methods: An acrylic phantom was scanned using a rapid balanced fast field echo sequence with 3.0-T magnetic resonance imaging. A 15-gauge microwave needle, a 17-gauge cryoneedle, and an 18-gauge coaxial biopsy needle were imaged in sagittal and axial planes, in 7 different orientations to B0 (0°, 15°, 30°, 45°, 60°, 75°, and 90°). For 4 angles (15°, 30°, 60°, and 75°), images were acquired with the slice orientation aligned to the needle angulation, resulting in the frequency encoding direction being parallel to the needle's long axis for the sagittal slice and perpendicular to the needle angulation for the axial acquisition. The artifact length at the needle tip and maximum artifact width were recorded.

Results: No significant difference was noted in mean artifact length for the cryoneedle (13 mm; 95% confidence interval [CI], 7-19) and coaxial biopsy needle (8 mm; 95% CI, 5-10; P = .08). The mean artifact length was significantly smaller for the microwave ablation needle (1 mm; 95% CI, 0-2; P < .05). The mean artifact width was highest for the coaxial needle (17 mm; 95% CI, 14-19) and significantly higher than the cryoneedle (12 mm; 95% CI, 10-15; P = .024) and microwave ablation needle (8 mm; 95% CI, 6-10; P < .01). The needle tip artifact was significantly smaller when the slice orientation was aligned to the needle angulation for the coaxial and cryoablation needles (P < .01).

Conclusions: Needle tip artifact length and width increase with increasing angulation to the static field. At large angles (>15°), the needle tip position can be predicted better from images acquired when the slice orientation is aligned to the needle's angulation.