Presented at the 2013 AAPM Annual Meeting « Back

Factors That Affect Radiofrequency Heat Lesion Size

Eric R. Cosman, PhD, ecosmanjr@cosmanmedical.com¹, Joseph R. Dolensky, BS², Ryan Hoffman, BS¹, (1) Cosman Medical, Burlington, Massachusetts, (2) Georgia Institute of Technology, Kennesaw, Georgia

Introduction: We evaluated radiofrequency (RF) heat lesion size for all cannula tip sizes, set temperatures, and lesion times typically used in interventional pain management. Collected data informs selection of cannulae and RF generator settings for RF treatments. Methods: Over 400 lesions were created in ex vivo animal tissue using tip diameters 23, 22, 20, 18, 16 gauge; tip lengths 5, 10, 15 mm; set temperatures 60, 70, 80, 90°C; lesion times 1, 1.5, 2, 3, 5, 10 minutes. Average lesion size was assessed using computer-aided photographic temperature mapping of 5–20 lesions per configuration, and modeled using finite-element analysis. Results: Increasing cannula diameter from 22 g to 16 g increased average lateral lesion width by 65–69% (3-4 mm) at 80°C and 2 minutes. Increasing set temperature from 60°C to 90°C increased lesion width 100–150% at 2 minutes; for example, width increased from 4.2 mm to 10.4 mm for the average 16 g/10 mm tip cannula. While lesions grew most rapidly over the first minute, average lesion width was 12–21% larger at 2 minutes, and 23–34% larger at 3 minutes, compared to 1 minute. Lesion length extended distal and proximal to the tip, exceeded tip length by 1–5mm at 80°C and 2 minutes, and was larger for increased tip size, temperature, and lesion time. Conclusions: Cannula gauge, tip length, set temperature, and lesion time substantially affect radiofrequency heat lesion width and length. All four factors should be considered in performing RF treatments. References: 1) Cosman ER Jr, Gonzalez CD. Bipolar Radiofrequency Lesion Geometry: Implications for Palisade Treatment of Sacroiliac Joint Pain. Pain Practice 2011; 11(1): 3-22. 2) Cosman ER Jr, Cosman ER Sr. Electric and thermal field effects in tissue around radiofrequency electrodes. Pain Medicine 2005; 6(6): 405-424. 3) Cosman ER, Nashold BS, and Bedenbaugh P. Stereotaxic Radio Frequency Lesion Making. Applied Neurophysiology 1983; 46(1): 160-166. 4) Bogduk N, Macintosh J, Marsland A. A technical limitation to efficacy of radiofrequency neurotomy for spinal pain. Neurosurgery 1987; 20: 529–535. 5) Provenzano DA, Lassila HC, Somers D. The effect of fluid injection on lesion size during radiofrequency treatment. Reg Anesth Pain Med 2010;35(4): 338-42.

Funding: Cosman Medical, Inc. provided all funding.

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