Frame-based stereotactic biopsies using an intraoperative MR-scanner are as safe and effective as conventional stereotactic procedures

Abstract

Background: Frame-based stereotactic biopsy (FBSB) is a minimally-invasive and effective procedure for the diagnosis of brain lesions and will likely gain clinical importance. Since FBSB procedures comprise a variety of imaging and sampling methods, it is necessary to compare the safety and effectiveness of individual techniques.

Objective: To assess the safety and effectiveness of FBSB using 1.5T iMRI as a one-stop procedure under general anesthesia without intraoperative histological examination.

Methods: In this single-center, retrospective analysis, 500 consecutive FBSBs using iMRI were compared to a historic control of 100 biopsies with traditional workflows (computed tomography (CT) with MRI image fusion). All procedures were performed under general anesthesia. Data on surgical procedures, pre- and postoperative neurologic patient status, complications and diagnostic yield were extracted from clinical records.

Results: Complication rates and diagnostic yield showed no significant differences between both groups. Mortality was 0.6%, 95% CI = [0.12%, 1.74%], in the iMRI and 0.0% [0.00%, 3.62%], in the control group with a morbidity of 5.4% [3.6%, 7.8%] and 6.0% [2.2%, 12.6%] and a diagnostic yield of 96.8% [94.9%, 98.2%] and 96.0% [90.1%, 98.9%]. Mean procedure duration was 124 [121, 127] minutes using iMRI and 112 [106, 118] minutes in the control group.

Conclusion: FBSB using 1.5T iMRI under general anesthesia is a safe and effective procedure and is equivalent to traditional stereotactic workflows with respect to complication rate and diagnostic yield.

Fig 1. Positioning of the patient in the iMRI-scanner and setup of coils.

The head of the patient with mounted frame and localizers is placed into the lower half of the 4-channel send/receive coil (double arrow). Due to the fact that the standard head coil (upper and lower part) does not accommodate the whole package, a flexible coil is used as upper half (black single arrow). This coil assembly was tested extensively prior to commissioning of the iMRI and yields good signal-to-noise ratios.

Fig 2. Setup of anesthesia equipment in the iMRI scanner.

The MR-capable ventilator (Dräger Fabius MRI, Drägerwerke, Lübeck, Germany) is positioned outside the 30 mT area (dark line) while the monitoring hardware has to be kept outside the 20 mT area (light yellow line).

Fig 3. Procedure duration stratified by imaging modality.

The duration of the procedures (time spent in the stereotactic frame) was significantly influenced by the imaging modality used to acquire the stereotactic dataset (One-way ANOVA, p < .000). Post-hoc testing (LSD-Bonferroni) showed significant differences between each individual imaging modality with exception of the CT/MRI pair. Procedures performed with intraoperative CT (iCT) required the least amount of time (median 110 min) followed by iMRI-based biopsies in second place (median 120 min). Imaging performed outside the OR (CT and MRI) considerably increased overall procedure time.