Radiofrequency tissue ablation: Importance of local temperature along the electrode tip exposure in determining lesion shape and size

      This paper is only available as a PDF. To read, Please Download here.


      Rationale and Objectives

      We determined whether heat distribution along a radiofrequency (RF) electrode would be uniform when longer tip exposures are used and whether local temperature effects would influence the shape of induced tissue coagulation.


      Thermistors were embedded within 18-gauge RF electrodes at both ends and in the middle of the exposed tip. The length of tip exposure varied from 1 to 7 cm. RF was applied in vitro to pig liver for 6 min using a constant tip temperature, which was varied in 10°C increments from 60°C to 110°C. Experiments were performed in triplicate. The 3- and 5-cm probes were used at a 90°C tip temperature to create lesions in live pig liver and muscle using similar parameters. Temperature was measured throughout the procedure. Observable coagulation necrosis was measured at the end of the treatment. Regression analysis was used to evaluate the local temperature-lesion diameter relationship.


      Temperatures were not uniform along the tip exposure for any given trial. Temperature variation increased with higher tip temperatures and longer tip exposures. The diameter of local coagulation necrosis was a function of the local mean temperature. For in vitro trials, no coagulation was seen when the local temperature was less than 50°C. Temperatures above this threshold resulted in progressively greater lesion diameter, with a minimum of 1 cm of necrosis occurring at 71°C. Additional increases in lesion diameter (1.4–1.6 cm) were observed at approximately 90°C. Mathematical modeling demonstrated a best-fit curve: lesion diameter (in cm) = [1.4 + 0.03 (tip exposure)] {1 - e[−0.067(local temp - 49.5°c]} r2 = .986, SD = 0.14 cm for each curve. In living tissue, less uniformity in the shape of coagulation necrosis was seen around the electrodes. Local temperature-lesion diameter data fit the same logarithmic relation, but the threshold for coagulation necrosis was 8.5°C higher than for in vitro specimens.


      Using a single-probe technique for RF-induced tissue necrosis, the diameter of tissue coagulation may be predicted by the local temperature along the exposed electrode. The uniformity of temperature decreases with increased tip exposures. This effect may be partially corrected by creating lesions at higher tip temperatures, where necrosis diameter is increased. Because effects are more pronounced in vivo, uniform volumes of tissue necrosis are limited to tip exposures of 3 cm or less.

      Key Words

      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Academic Radiology
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Rosenthal D.I.
        • Springfield D.S.
        • Gebhart M.C.
        • Rosenberg A.E.
        • Mankin H.J.
        Percutaneous radiofrequency ablation of osteoid osteoma.
        Radiology. 1995; 197: 451-454
        • Ierace T.
        • Ballarati E.
        • Crespi L.
        • Solbiati L.
        Treatment of liver metastases with percutaneous ultrasound guided radiofrequency electrocautery.
        Radiology. 1994; 193 (abstr) ([suppl]): S179
        • Garbagnati F.
        • Spreafico C.
        • Patelli G.
        • Gervasoni G.
        • Giovannardi G.
        Percutaneous radiofrequency electrocautery of hepatic metastases.
        Euro Radiol. 1995; 5 (abstr) ([suppl]): S161
        • Anzai Y.
        • Lufkin R.
        • DeSalles A.
        • Hamilton D.R.
        • Farahani K.
        • Black K.L.
        Preliminary experience with MR-guided thermal ablation of brain tumors.
        Am J Neuroradiol. 1995; 16: 39-48
        • McGahan J.P.
        • Griffey S.M.
        • Budenz R.W.
        • Brock J.M.
        Percutaneous ultrasound-guided radiofrequency electrocautery ablation of prostate tissue in dogs.
        Acad Radiol. 1995; 2: 61-65
        • Goldberg S.N.
        • Gazelle G.S.
        • Compton C.
        • McLoud T.C.
        Radiofrequency tissue ablation in the lung: a safe, minimally invasive procedure.
        Acad Radiol. 1995; 2: 776-784
        • McGahan J.P.
        • Brock J.N.
        • Tessluk H.
        • Wei-thong G.
        • Schneider P.
        • Browning P.D.
        Hepatic ablation with use of radiofrequency electrocautery in the animal model.
        J Interven Radiol. 1992; 3: 291-297
        • Goldberg S.N.
        • Gazelle G.S.
        • Dawson S.L.
        • Rittman W.J.
        • Mueller P.R.
        • Rosenthal D.I.
        Tissue ablation with radiofrequency: effect of probe size, gauge, duration, and temperature on lesion volume.
        Acad Radiol. 1995; 2: 399-404
        • Tillotson C.O.
        • Rosenberg A.E.
        • Rosenthal D.I.
        Controlled thermal injury of bone: report of a percutaneous technique using radiofrequency electrode and generator.
        Invest Radiol. 1989; 24: 888-892
        • Rossi S.
        • Fornari F.
        • Pathies C.
        • Buscarini L.
        Thermal lesions induced by 480 KHz localized current field in guinea pig and pig liver.
        Tumori. 1990; 76: 54-57
        • Goldberg S.N.
        • Gazelle G.S.
        • Dawson S.L.
        • Mueller P.R.
        • Rittman W.J.
        • Rosenthal D.I.
        Tissue ablation with radiofrequency using multiprobe arrays.
        Acad Radiol. 1995; 2: 670-674