title: Microwave ablation at 915 MHz vs 2.45 GHz: A theoretical and experimental investigation.
abstract: OBJECTIVE
  The relationship between microwave ablation system operating frequency and ablation performance is not currently well understood. The objective of this study was to comparatively assess the differences in microwave ablation at 915 MHz and 2.45 GHz.
  
  
  METHODS
  Analytical expressions for electromagnetic radiation from point sources were used to compare power deposition at the two frequencies of interest. A 3D electromagnetic-thermal bioheat transfer solver was implemented with the finite element method to characterize power deposition and thermal ablation with asymmetrical insulated dipole antennas (single-antenna and dual-antenna synchronous arrays). Simulation results were validated against experiments in ex vivo tissue.
  
  
  RESULTS
  Theoretical, computational, and experimental results indicated greater power deposition and larger diameter ablation zones when using a single insulated microwave antenna at 2.45 GHz; experimentally, 32±4.1 mm and 36.3±1.0 mm for 5 and 10 min, respectively, at 2.45 GHz, compared to 24±1.7 mm and 29.5±0.6 mm at 915 MHz, with 30 W forward power at the antenna input port. In experiments, faster heating was observed at locations 5 mm (0.91 vs 0.49 °C/s) and 10 mm (0.28 vs 0.15 °C/s) from the antenna operating at 2.45 GHz. Larger ablation zones were observed with dual-antenna arrays at 2.45 GHz; however, the differences were less pronounced than for single antennas.
  
  
  CONCLUSIONS
  Single- and dual-antenna arrays systems operating at 2.45 GHz yield larger ablation zone due to greater power deposition in proximity to the antenna, as well as greater role of thermal conduction.
authors.affiliation: Department of Electrical and Computer Engineering, Kansas State University, Manhattan, Kansas 66506.
authors.forename: Sergio
authors.initials: S
authors.lastname: Curto
authors.affiliation: Department of Electrical and Computer Engineering, Kansas State University, Manhattan, Kansas 66506.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Taj-Eldin
authors.affiliation: Department of Electrical and Computer Engineering, Kansas State University, Manhattan, Kansas 66506.
authors.forename: Dillon
authors.initials: D
authors.lastname: Fairchild
authors.affiliation: Department of Electrical and Computer Engineering, Kansas State University, Manhattan, Kansas 66506.
authors.forename: Punit
authors.initials: P
authors.lastname: Prakash
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000379:methods*; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D006498:Hepatectomy / Q000379:methods*; D066298:In Vitro Techniques; D008099:Liver / Q000473:pathology* / Q000528:radiation effects / Q000601:surgery*; D008872:Microwaves / Q000627:therapeutic use*; D008954:Models, Biological; D011829:Radiation Dosage; D013552:Swine