Percutaneous abscess drainage using near real-time MR guidance in an open 1.0-T MR scanner: proof of concept.

ABSTRACT

OBJECTIVES: The aims of our study were (1) to assess the feasibility, effectiveness, and safety of exclusively magnetic resonance (MR)-guided freehand percutaneous abscesses drainage using a 1.0-T open MR scanner and (2) to evaluate the optimal method to visualize drainage catheters in situ. MATERIAL AND METHODS: In vitro studies in a dedicated MR gelatin phantom were performed to assess visualization of 8 different sizes of drainage catheters after instillation of sole 0.9% sodium chloride (NaCl) and diluted (1.0%) or concentrated (12.0%) gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) using a T1-weighted (T1w) 2-dimensional fast field echo (FFE) and a T2-weighted single-shot (ssh) turbo spin-echo (TSE) fast dynamic sequence. The catheter artifacts were evaluated with regard to the contrast-to-noise ratio (CNR), the artifact width using the full width at half-maximum (FWHM) method, and the artifact intensity, being the product of the CNR and the FWHM. We used the general linear model procedure as the global test and the Tukey studentized range test for post hoc analysis. In vivo MR-guided freehand drainage was prospectively performed in patients with increased systemic inflammation markers and abdominal, retroperitoneal, and pelvic abscess collections. This study had been approved by the institutional review board. All patients provided written informed consent. Technical success was the primary efficacy variable. The secondary efficacy variables were visibility of the puncture needle and drainage catheter artifact, using a qualitative 5-point rating scale, intervention and procedure time, and rate of postinterventional complications. RESULTS: The FWHM, the CNR, and the artifact intensity of the drainage catheters filled with 0.9% NaCl or diluted or concentrated Gd-DTPA increased according to the drainage catheter size in an almost linear fashion in both image weighting (all P ≤ 0.006; all R(2) ≥ 0.73). The T1w FFE sequence yielded the highest FWHM, CNR, and artifact intensity of all groups, using 12.0% Gd-DTPA instillation (all P < 0.001), and the least FWHM and artifact intensity, using 1.0% Gd-DTPA instillation (all P < 0.022; all P < 0.009). The T2w ssh TSE yielded higher FWHM, using 12.0% Gd-DTPA instillation, whereas the CNR was higher for 0.9% NaCl instillation (all P < 0.001). Magnetic-resonance-guided abscess drainage was performed in 22 patients with 24 abdominal, retroperitoneal, or pelvic abscess collections. The technical success rate of in vivo MR-guided freehand drainage was 100%. Visibility of the puncture needle was excellent (≥4.4 [0.5] points). Visibility of the drainage catheters was rated with 3.9 (0.9) and 4.5 (0.8) points using T2w ssh TSE with 0.9% NaCl and 12.0% Gd-DTPA instillation as well as 4.8 (0.5) and 4.2 (0.8) points using T1w FFE with 1.0% and 12.0% Gd-DTPA instillation, respectively. The procedure and intervention time was 52.4 (16.4) minutes (range, 28-78 minutes) and 27.4 (7.2) minutes (range, 17-40 minutes). Two minor and no major complications were recorded. CONCLUSIONS: Magnetic-resonance-guided freehand percutaneous abscesses drainage using fast dynamic sequences in an open 1-T MR scanner is feasible, effective, and safe. Visualization of drainage catheters can be facilitated by instillation of 0.9% NaCl or diluted or concentrated contrast media.