Assessment of puncture needles and their imaging characteristics
Two MR-compatible 22-gauge puncture needleswere employed each with a length of 100 mm. A puncture needle distributed by Invivo (Schwerin, Germany; needle 1) was used in 44 interventions. It is composed of a titanium-aluminum-vanadium alloy cannulaand a non-ferromagnetic stainless steelstylet. The remaining 156 interventions were performed with a puncture needle distributed by Innovative Tomography Products (ITP, Bochum, Germany; needle 2) which is composed of a nickel-chromium-cobalt alloy cannula and a nitinol stylet. The orientation of the puncture needle relative to the B0-field of the MR-scanner and the corresponding extension of its susceptibility artifact was measured in the interventional MR-images by means of a protractor and caliper provided by the PACS System (Infinitt Version 3.0.11.4; Infinitt Healthcare, Seoul, Korea).
Statistics
The paired and unpaired t-test was used for the comparison of the susceptibility artifact of each puncture needle. The interdependency between susceptibility artifact andthepuncture needles trajectoryrelative to the B0-field of the MR-scanner was expressed with Pearson’s correlation coefficient.Statistical analyses were made with SPSS version 22 (IBM, Armonk, NY, USA). A two-tailed p-value of 0.05 was set to be the level of statistical significance.
Results
Both puncture needles performed equally well with regards to technical success (p>0.6) and puncture time (p>0.2). The interdependency between extension of the susceptibility artifactsand the puncture needles trajectory relative to the B0-field of the MR-scanner are displayed in Tab. S1. The extension of the susceptibility artifact induced by the stylet was in either case significantly larger than the extension of the artifact induced by the cannula alone (p<0.01). The non-ferromagnetic stainless steelstylet of the Invivo puncture needle yielded the broadest artifacts (p<0.01).
Discussion
Both puncture needles employed for FDSA performed equally well. We found interdependency between the extension of the susceptibility artifacts and the composition as well as the trajectory of the puncture needles relative to the B0-field of the MR-scanner in accordance with previous reports [1-3]. We suggest to use a puncture needle with a ferromagnetic stainless steel stylet if the anticipated angle to the B0-field of the MR-scanner is acute (e.g. < 10°), to yield a sufficient susceptibility artifact.
References
1. Lewin JS, Duerk JL, Jain VR, Petersilge CA, Chao CP, Haaga JR. Needle localization in MR-guided biopsy and aspiration: effects of field strength, sequence design, and magnetic field orientation. AJR Am J Roentgenol. 1996;166:1337-45.
2. Liu H, Martin AJ, Truwit CL. Interventional MRI at high-field (1.5 T): needle artifacts. J Magn Reson Imaging. 1998;8:214-9.
3. Wonneberger U, Schnackenburg B, Streitparth F, Walter T, Rump J, Teichgraber UK. Evaluation of magnetic resonance imaging-compatible needles and interactive sequences for musculoskeletal interventions using an open high-field magnetic resonance imaging scanner. Cardiovasc Intervent Radiol. 2010;33:346-51.
Table S1
Trajectory relative to B0≤20° / ≥21° / r (≤20°/≥21°) / sig.
Artifact + stylet (mm) / Artifact – stylet (mm) / Artifact + stylet (mm) / Artifact – stylet (mm)
Needle 1 (n=44) / 4.5±1.1 (2.6 – 6.0) / 1.1±0.3 (0.8 – 1.8) / 6.3±1.0 (4.0 – 8.9) / 1.6±0.7 (1.1 – 3.9) / 0.70/0.38 / p<0.01
Needle 2 (n=156) / 1.9±0.5 (1.1 – 3.5) / 1.3±0.4 (0.7 – 2.8) / 3.1±0.7 (1.3 – 4.5) / 2.0±0.6 (0.8 – 3.5) / 0.84/0.73 / p<0.01
Table S1:
The extension of the susceptibility artifact induced by the puncture needles cannula alone(– stylet) and cannula with inserted stylet (+ stylet) are provided for needle trajectories of ≤20° and ≥21° relative to the B0-field of the MR-scanner. The interdependency between extension of the artifacts and the puncture needles trajectory relative to the B0-field are expressed with the Pearson correlation coefficient (r). This correlation was more pronounced with inserted stylet. The data in the parenthesis present the range of the measurements. Needle 1: Invivo; Needle 2: ITP.