MR-Guided Percutaneous Intradiscal Thermotherapy (MRgPIT): Evaluation of a New Technique for the Treatment of Degenerative Disc Disease in Cadaveric Lumbar Spine.

Abstract

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. We evaluated a new MR-compatible applicator system for MR-guided percutaneous intradiscal thermotherapy (MRgPIT) in an open 1.0-T MRI-system. Needleartefacts 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, 2-6W) were assessed in 50 ex vivo human intervertebral discs with subsequent histological evaluation. In vitro, we found optimal needle artefacts of 1.5-5mm for the PDw TSE sequence in all angles of the applicator system to B0. A TE of 20ms yielded the best CNR. Ex vivo, ablating with 5W 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 ± 5.7min. 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.