Cryoablation

Mechanism of Action:

1. Joule Thomson Effect –  Argon and Helium gases, and

2. Critical Point effect

  • Nitrogen is used in newer systems based on concept of Critical Point – more efficacious than Joule – Thomson based systems.
  • Critical Point of a material describes a specific pressure and temperature where the distinction between gas and liquid phases vanishes. 
  • At this juncture, certain materials like nitrogen can display significantly enhanced capabilities, often surpassing those of water, while maintaining the low viscosity characteristic of a gas. This attribute makes them effective cooling fluids suitable for circulation within confined spaces.

Ablation Zone Diameter and Thermal Synergy:

Ablation zone size corresponds to probe diameter in these systems, like 13-gauge (2.4mm), generate roughly 2.5cm ablation zones in normal liver and lung tissues, while 15-gauge (1.7mm) probes yield 1.5–2.0cm zones. Multiple probes are often used for complete tumor coverage within the lethal isotherm, enhancing efficacy through thermal synergy. Inappropriate spacing can lead to gaps between ablation zones.

Lethal Isotherm:

Lethal isotherm is the actually area damaged through cryoablation. For optimal margin optimization, needles should be positioned to generate a lethal ice zone extending beyond the outer edge of the target tissue by 5-10 mm, contingent on the tissue type. Similarly, when evaluating the effectiveness of cryoablation treatment using imaging, it’s essential to take into account that the critical lethal isotherm (-20°C to -40°C) is positioned several millimeters within the boundary of the iceball.

Benefits over Radiofrequency Ablation:

  1. Decreased Procedure-related pain
  2. Real-Time Visualization of the ablation zone and lethal isotherm
  3. Largest ablation zone achievable (use of multiple applicators – thermal synergy)

Complications:

  • Rapid release of cellular debris into the systemic circulation occurs because the ablation zone is reperfused after the ice ball melts. This probably explains the systemic complications that are seen with cryoablation (ie, cryoshock).
  1. Glassberg MB, Ghosh S, Clymer JW, Qadeer RA, Ferko NC, Sadeghirad B, Wright GW, Amaral JF. Microwave ablation compared with radiofrequency ablation for treatment of hepatocellular carcinoma and liver metastases: a systematic review and meta-analysis. Onco Targets Ther. 2019 Aug 13;12:6407-6438. doi: 10.2147/OTT.S204340. PMID: 31496742; PMCID: PMC6698169. 
  2.  Ahmed M, Brace CL, Lee Jr FT, Goldberg SN. Principles of and advances in percutaneous ablation. Radiology. 2011 Feb;258(2):351-69.
  3. Permpongkosol S , Nicol TL , Link RE , et al . Differences in ablation size in porcine kidney, liver, and lung after cryoablation using
    the same ablation protocol . AJR Am J Roentgenol 2007 ; 188 ( 4 ): 1028 – 1032 .
  4. Wang H , Littrup PJ , Duan Y , Zhang Y , Feng H , Nie Z . Thoracic masses treated with percutaneous cryotherapy: initial experience with more than 200 procedures . Radiology 2005 ; 235 ( 1 ): 289 – 298 .
Skip to content