Abstract
Needle artifacts pose a major limitation for MRI-guided interventions, as they impact the visually perceived needle size and needle-to-target-distance. The objective of this agar liver phantom study was to establish an experimental basis to understand and reduce needle artifact formation during MRI-guided abdominal interventions. Using a vendor-specific prototype fluoroscopic T1-weighted gradient echo sequence with real-time multiplanar acquisition at 1.5 T, the influence of 6 parameters (flip angle, bandwidth, matrix, slice thickness, read-out direction, intervention angle relative to B0) on artifact formation of 4 different coaxial MR-compatible coaxial needles (Nitinol, 16G–22G) was investigated. As one parameter was modified, the others remained constant. For each individual parameter variation, 2 independent and blinded readers rated artifact diameters at 2 predefined positions (15 mm distance from the perceived needle tip and at 50% of the needle length). Differences between the experimental subgroups were assessed by Bonferroni-corrected non-parametric tests. Correlations between continuous variables were expressed by the Bravais–Pearson coefficient and interrater reliability was quantified using the intraclass classification coefficient. Needle artifact size increased gradually with increasing flip angles (p = 0.002) as well as increasing intervention angles (p < 0.001). Artifact diameters differed significantly between the chosen matrix sizes (p = 0.002) while modifying bandwidth, readout direction, and slice thickness showed no significant differences. Interrater reliability was high (intraclass correlation coefficient 0.776–0.910). To minimize needle artifacts in MRI-guided abdominal interventions while maintaining optimal visibility of the coaxial needle, we suggest medium-range flip angles and low intervention angles relative to B0.
Highlights
Needle artifacts pose a major limitation for Magnetic resonance imaging (MRI)-guided interventions, as they impact the visually perceived needle size and needle-to-target-distance
In addition to the central hypointense needle artifact, a hyperintense peripheral rim was observed at flip angle (FA) > 45°, which was included in the measurements
We found no significant difference in artifact diameter for each needle size (16G: 11.8–12.3 mm, 18G: 10.2–11.3 mm, 20G: 6.5–7.4 mm, 20G: 5.2–5.5 mm; p = 0.191) and no significant correlation between artifact diameter and slice thickness for any of the needles either (− 0.787 < r < 0.662; p > 0.21)
Summary
Needle artifacts pose a major limitation for MRI-guided interventions, as they impact the visually perceived needle size and needle-to-target-distance. Using a vendor-specific prototype fluoroscopic T1-weighted gradient echo sequence with real-time multiplanar acquisition at 1.5 T, the influence of 6 parameters (flip angle, bandwidth, matrix, slice thickness, read-out direction, intervention angle relative to B0) on artifact formation of 4 different coaxial MR-compatible coaxial needles (Nitinol, 16G–22G) was investigated. We here present a systematic investigation of artifact behavior of different commercially available MR-conditional Nitinol coaxial needles as a function of the intervention angle and sequence parameter variations in a vendor-specific prototype fluoroscopic T1-weighted GRE sequence with real-time multiplanar acquisition in a dedicated liver phantom at 1.5 Tesla (T). The aim of the present study was to establish an experimental basis to understand and reduce artifact formation during clinical MRI-guided abdominal interventions in patients
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