title: Quantification of tissue shrinkage and dehydration caused by microwave ablation: experimental study in kidneys for the estimation of effective coagulation volume.
abstract: OBJECTIVE
  To quantify the extent of tissue shrinkage and dehydration caused by microwave (MW) ablation in kidneys for estimation of effective coagulation volume.
  
  
  METHODS
  MW ablations were carried out in ex vivo porcine kidneys. Six study groups were defined: groups 1A, 2A, and 3A for MW ablation (90 W for 5 min, 7.5 min, or 10 min), and groups 1B, 2B, and 3B for control (without MW ablation). Pre- and postinterventional volume analyses were performed. Effective coagulation volumes (original tissue included in coagulation) were determined. Postinterventional dehydration analyses were performed with calculation of mean mass fractions of water.
  
  
  RESULTS
  Mean deployed energies were 21.6 kJ ± 1.1 for group 1A, 29.9 kJ ± 1.0 for group 2A, and 42.1 kJ ± 0.5 kJ for group 3A, and were significantly different (P < .0001). Differences between pre- and postinterventional volumes were -3.8% ± 0.6 for group 1A, -5.6% ± 0.9 for group 2A, and -7.2% ± 0.4 for group 3A, and -1.1% ± 0.3 for group 1B, -1.8% ± 0.4 for group 2B, and -1.1% ± 0.4 for group 3B. Postinterventional volumes were significantly smaller than preinterventional volumes for all groups (P < .01). Underestimations of effective coagulation volume from visualized coagulation volume were 26.1% ± 3.5 for group 1A, 35.2% ± 11.2 for group 2A, and 42.1% ± 4.9 for group 3A, which were significantly different (P < .01). Mean mass fractions of water were 64.2% ± 1.4 for group 1A, 63.2% ± 1.7 for group 2A, and 62.6% ± 1.8% for group 3A, with significant differences versus corresponding control groups (P < .01).
  
  
  CONCLUSIONS
  For MW ablation in kidneys, underestimation of effective coagulation volume based on visualized coagulation volume is significantly greater with greater deployed energy. Therefore, local dehydration with tissue shrinkage is a potential contributor.
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Heidelberg, Heidelberg, Germany. christof.sommer@med.uni-heidelberg.de
authors.forename: Christof M
authors.initials: CM
authors.lastname: Sommer
authors.forename: Steffen A
authors.initials: SA
authors.lastname: Sommer
authors.forename: Theresa
authors.initials: T
authors.lastname: Mokry
authors.forename: Theresa
authors.initials: T
authors.lastname: Gockner
authors.forename: Daniel
authors.initials: D
authors.lastname: Gnutzmann
authors.forename: Nadine
authors.initials: N
authors.lastname: Bellemann
authors.forename: Anne
authors.initials: A
authors.lastname: Schmitz
authors.forename: Boris A
authors.initials: BA
authors.lastname: Radeleff
authors.forename: Hans U
authors.initials: HU
authors.lastname: Kauczor
authors.forename: Ulrike
authors.initials: U
authors.lastname: Stampfl
authors.forename: Philippe L
authors.initials: PL
authors.lastname: Pereira
mesh_terms: D000818:Animals; D003681:Dehydration / Q000209:etiology / Q000473:pathology*; D004564:Electrocoagulation / Q000009:adverse effects / Q000379:methods*; D007668:Kidney / Q000473:pathology / Q000601:surgery*; D016014:Linear Models; D008872:Microwaves / Q000009:adverse effects; D009929:Organ Size; D013552:Swine
keywords: AKS; MW; RF; appearance of kidney surface; microwave; radiofrequency