Thermal phantom of the intervertebral disc for evaluating intradiscal electrothermal therapies.

STUDY DESIGN: a silicone material was evaluated as an intervertebral disc thermal phantom. Temperature mapping was performed during the intradiscal electrothermal therapy (IDET) procedure and compared with results from the cadaver studies.

OBJECTIVE: to determine whether a silicone material can be used as an intervertebral disc thermal phantom for evaluating thermal distributions of intradiscal electrothermal therapies and for reducing the need for cadaver and animal studies.

SUMMARY OF BACKGROUND DATA: studies mapping thermal profiles of intradiscal heating therapies have been performed in cadavers and animal models. These studies are expensive, require special facilities and institutional reviews, and are susceptible to intercadaver and/or interanimal variation. A search of published data yielded no proposed thermal phantoms of the intervertebral disc. METHODS.: The thermal conductivity of a silicone material was measured and compared with that of an intervertebral disc. Thermal distributions were mapped in the material during the IDET procedure and compared with the distributions seen in cadaver studies. Logarithmic regression was performed to predict temperatures at certain distances from the IDET catheter. Mapping and regression were also performed for a decompression catheter.

RESULTS: the thermal conductivity of the silicone material, 0.587 W/m · °C, was similar to that previously reported for the intervertebral disc, 0.595 W/m · °C. Thermal distributions during the IDET procedure were comparable with those seen in previous cadaver studies. Logarithmic regression analysis predicted temperatures greater than 42°C and 60°C at distances of 14.10 and 2.31 mm, respectively, for the IDET catheter. These distances were 12.98 and 3.30 mm, respectively, for the decompression catheter.

CONCLUSION: the silicone material has a thermal conductivity similar to that of intervertebral disc. Temperature distributions in the material during IDET treatment are similar to that seen in cadaver studies. The material provides an alternative to cadaver and animal studies when determining thermal distributions of intradiscal electrothermal therapies.