A Study about Size and Shape of Bipolar Radiofrequency Lesions

Background: Present limitations to monopolar RF include the small lesion size, difficulties in targeting, and questions about the reliability.In contrast with monopolar RF, bipolar RF create larger, more predictable, and more extensive ablative lesion.This study documents the optimal spacing of two needles, temperature, and time required to produce bipolar RF lesions.Methods: Two 20-gauge 5 mm active tip needles and 10 mm active tip needles were secured in a parallel position 6, 8, and 10 mm apart and submerged in egg white that would allow visualization of the size and shape of the lesion.RF lesions were produced at 70, 80, and 90°C.At each temperature, photographs were taken at 30, 60, 90, and 120 seconds.Results: When the 5 mm active tips with 6 mm distance were above 60 s and with 8, 10 mm distance above 120 s, continuous strip lesions were produced.10 mm active tips with 120 s were produced too.The others had discrete unipolar lesions around each cannula.The lesion size increased with a higher temperature and time.But time was the more important factor in determining lesion size.Conclusions: A continuous strip lesion was produced even though the electrode spaced 10 mm apart.And spacing the electrode 6 mm apart with 5 mm active tip and 8 mm apart with 10 mm active tip at 90°C for 90 s maximize the surface area of the lesions.(Korean J Anesthesiol 2008; 54: 197～200)