title: Hepatic Microwave Ablation Zone Size: Correlation with Total Energy, Net Energy, and Manufacturer-Provided Chart Predictions.
abstract: OBJECTIVE
  To determine whether total energy (TE) reaching the microwave (MW) applicator or net energy (NE) exiting the applicator (after correcting for reflectivity) correlates better with hepatic MW ablation zone dimensions than manufacturer-provided chart predictions.
  
  
  METHODS
  Single-applicator, nonoverlapping ablations of 93 liver tumors (0.7-5.9 cm) were performed in 52 adult patients. TE and NE were recorded for each ablation. Long axis diameter (LAD), short axis diameter (SAD), and volume (V) of each ablation zone were measured on magnetic resonance imaging or computed tomography after the procedure and retrospectively compared with TE; NE; and manufacturer-provided chart predictions of LAD, SAD, and V using correlation and regression analyses.
  
  
  RESULTS
  For treated tumors, mean (± SD) TE and NE were 49.8 kJ (± 22.7) and 36.4 kJ (± 19.4). Mean LAD, SAD, and V were 5.8 cm (± 1.3), 3.7 cm (± 0.8), and 44.1 cm(3) (± 25.4). Correlation coefficients (95% confidence interval) with LAD, SAD, and V were 0.46 (0.28, 0.61), 0.52 (0.36, 0.66), and 0.52 (0.36, 0.66) for TE; 0.42 (0.24, 0.58), 0.55 (0.39, 0.68), and 0.53 (0.36, 0.66) for NE; and 0.51 (0.34, 0.65), 0.63 (0.49, 0.74), and 0.60 (0.45, 0.73) for chart predictions. Using regression analysis and controlling for TE, SAD was 0.34 cm larger in patients with cirrhosis than in patients without cirrhosis.
  
  
  CONCLUSIONS
  Correcting for reflectivity did not substantially improve correlation of energy values with MW ablation zone size parameters and did not outperform manufacturer-provided chart predictions. Correlations were moderate and variable using all methods. The results suggest a disproportionate influence of tissue factors on MW ablation results.
authors.affiliation: Department of Radiology, Harvard Medical School, Boston, Massachusetts; Abdominal Imaging and Intervention, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115. Electronic address: pshyn@partners.org.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Shyn
authors.affiliation: Department of Radiology, Harvard Medical School, Boston, Massachusetts; Abdominal Imaging and Intervention, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115.
authors.forename: Jeffery R
authors.initials: JR
authors.lastname: Bird
authors.affiliation: Department of Radiology, Harvard Medical School, Boston, Massachusetts; Abdominal Imaging and Intervention, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115.
authors.forename: R Marie
authors.initials: RM
authors.lastname: Koch
authors.affiliation: Department of Radiology, Harvard Medical School, Boston, Massachusetts; Abdominal Imaging and Intervention, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115.
authors.forename: Servet
authors.initials: S
authors.lastname: Tatli
authors.affiliation: Department of Radiology, Harvard Medical School, Boston, Massachusetts; Abdominal Imaging and Intervention, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115.
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Levesque
authors.affiliation: Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Boston, Massachusetts.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Catalano
authors.affiliation: Department of Radiology, Harvard Medical School, Boston, Massachusetts; Abdominal Imaging and Intervention, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115.
authors.forename: Stuart G
authors.initials: SG
authors.lastname: Silverman
mesh_terms: D055011:Ablation Techniques / Q000009:adverse effects; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D016014:Linear Models; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008872:Microwaves / Q000009:adverse effects / Q000627:therapeutic use*; D008875:Middle Aged; D018579:Patient Selection; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D047368:Tumor Burden