title: Ablation margin assessment of liver tumors with intravenous contrast-enhanced C-arm computed tomography.
abstract: OBJECTIVE
  To evaluate the feasibility of intravenous contrast-enhanced C-arm computed tomography (CT) for assessing ablative areas and margins of liver tumors.
  
  
  METHODS
  Twelve patients (5 men, 7 women; mean age, 69.5 years) who had liver tumors (8 hepatocellular carcinomas, 4 metastatic liver tumors; mean size, 16.3 mm; size range, 8-20 mm) and who underwent percutaneous radiofrequency ablations (RFAs) with a flat-detector C-arm system were retrospectively reviewed. Intravenously enhanced C-arm CT and multidetector computed tomography (MDCT) images were obtained at the end of the RFA sessions and 3-7 d after RFA to evaluate the ablative areas and margins. The ablated areas and margins were measured using axial plane images acquired by both imaging techniques, with prior contrast-enhanced MDCT images as the reference. The sensitivity, specificity, and positive and negative predictive values of C-arm CT for detecting insufficient ablative margins (< 5 mm) were calculated. Statistical differences in the ablative areas and margins evaluated with both imaging techniques were compared using a paired t-test.
  
  
  RESULTS
  All RFA procedures were technically successful. Of 48 total ablative margins, 19 (39.6%) and 20 (41.6%) margins were found to be insufficient with C-arm CT and MDCT, respectively. Moreover, there were no significant differences between these 2 imaging techniques in the detection of these insufficient ablative margins. The sensitivity, specificity, and positive and negative predictive values for detecting insufficient margins by C-arm CT were 90.0%, 96.4%, 94.7% and 93.1%, respectively. The mean estimated ablative areas calculated from C-arm CT (462.5 ± 202.1 mm(2)) and from MDCT (441.2 ± 212.5 mm(2)) were not significantly different. The mean ablative margins evaluated by C-arm CT (6.4 ± 2.2 mm) and by MDCT (6.0 ± 2.4 mm) were also not significantly different.
  
  
  CONCLUSIONS
  The efficacy of intravenous contrast-enhanced C-arm CT in assessing the ablative areas and margins after RFA of liver tumors is nearly equivalent to that of MDCT.
authors.affiliation: Jin Iwazawa, Naoko Hashimoto, Takashi Mitani, Department of Radiology, Nissay Hospital, 6-3-8 Itachibori, Nishiku, Osaka 550-0012, Japan.
authors.forename: Jin
authors.initials: J
authors.lastname: Iwazawa
authors.forename: Shoichi
authors.initials: S
authors.lastname: Ohue
authors.forename: Naoko
authors.initials: N
authors.lastname: Hashimoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Mitani