ABSTRACT
PURPOSE: Evaluation of MR feasibility and real-time control of an innovative thermoablative applicator for intradiscal thermotherapy and histological analysis of laser annuloplasty in human ex vivo intervertebral discs. MATERIALS AND METHODS: We evaluated a new MR-compatible applicator system for MR-guided percutaneous intradiscal thermotherapy (MRgPIT) in an open 1.0-T MRI-system. Needle artefacts and contrast-to-noise ratios (CNR) of six interactive sequences (PD-, T1-, T2w TSE, T1-, T2w GRE, bSSFP) with varying echo-times (TE) and needle orientations to the main magnetic field (B0) were analysed. Additionally, five laser protocols (Nd: YAG Laser, 2-6 W) were assessed in 50 ex vivo human intervertebral discs with subsequent histological evaluation. RESULTS: In vitro, we found optimal needle artefacts of 1.5-5 mm for the PDw TSE sequence in all angles of the applicator system to B0. A TE of 20 ms yielded the best CNR. Ex vivo, ablating with 5 W induced histological denaturation of collagen at the dorsal annulus, correlating with a rise in temperature to at least 60 °C. The MRgPIT procedure was feasible with an average intervention time of 17.1 ± 5.7 min. CONCLUSION: Real-time MR-guided positioning of the MRgPIT-applicator in cadaveric intervertebral disc is feasible and precise using fast TSE sequence designs. Laser-induced denaturation of collagen in the dorsal annulus fibrosus proved to be accurate.
