title: Magnetic resonance-based visualization of thermal ablative margins around hepatic tumors by means of systemic ferucarbotran administration before radiofrequency ablation: animal study to reveal the connection between excess iron deposition and T2*-weighted hypointensity in ablative margins.
abstract: OBJECTIVE
  The objective of this study was to demonstrate experimentally that radiofrequency ablation (RFA) of ferucarbotran-accumulated healthy liver tissues causes excess iron deposition in the ablated liver tissues on postablation days and produces sustained T2*-weighted low signals indicative of ablative margins surrounding hepatic tumors.
  
  
  METHODS
  We conducted 3 experiments using 30 rats. In experiment 1, we administered either ferucarbotran (n = 6) or saline (n = 4), acquired T2*-weighted images (T2*-WIs) of the liver by using a 3-T magnetic resonance scanner, and subsequently performed RFA of healthy liver lobes. We acquired follow-up T2*-WIs up to day 7 and histologically analyzed the liver specimens. In another 4 rats, we performed sham operation, instead of RFA, in ferucarbotran-accumulated liver lobes, followed by the same image acquisition and histological analysis. In experiment 2, we administered 59Fe-labeled ferucarbotran, subsequently performed either RFA (n = 4) or sham operation (n = 4) in the liver, and acquired autoradiograms of the liver specimens on day 7. In experiment 3, we conducted RFA treatment for 8 rats bearing orthotopic hepatic tumors after ferucarbotran administration and monitored tumor growth by using serial T2*-WIs.
  
  
  RESULTS
  On days 4 and 7 of the experiment 1, T2*-WIs of 6 rats with systemic ferucarbotran administration and subsequent hepatic RFA showed low-signal regions indicative of ablated liver tissues, whereas high-signal areas were seen in 4 saline-administered rats. Neither high nor low signal areas were detected in 4 sham-operated rats. Histologically, larger amounts of iron were observed in the RFA-induced necrotic liver tissues in the ferucarbotran-administered rats than in the saline-administered-rats. The 59Fe autoradiography of the rats in experiment 2 revealed accumulation of ferucarbotran-derived iron in necrotic liver tissues. Among 6 hepatic tumors grown in 6 rats of the experiment 3, a total of 4 tumors were stable in size, but the other 2 increased markedly on day 7. Retrospectively, T2*-WIs showed the former tumor sites surrounded completely by low-signal areas on day 4.
  
  
  CONCLUSIONS
  The RFA of ferucarbotran-accumulated healthy liver tissues in the rats caused excess iron deposition in the ablated liver tissues and produced sustained T2*-weighted hypointense regions. Similar hypointense regions surrounding hepatic tumors were indicative of ablative margins.
authors.affiliation: From the *Division of Functional Imaging, Research Center for Innovative Oncology, National Cancer Center Hospital East, Kashiwa, Chiba; †Department of Radiology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki; ‡Department of Radiology, Graduate School of Medicine, University of Tokyo, Tokyo; and §Fujifilm RI Pharma Co, Ltd, Sammu, Chiba, Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Nagai
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Kensaku
authors.initials: K
authors.lastname: Mori
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Furuta
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ashino
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kurosawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kasahara
authors.forename: Manabu
authors.initials: M
authors.lastname: Minami
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Fujii
mesh_terms: D000818:Animals; D017115:Catheter Ablation; D003287:Contrast Media / Q000378:metabolism*; D003911:Dextrans / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D007089:Image Enhancement; D007501:Iron / Q000378:metabolism*; D008099:Liver / Q000473:pathology / Q000601:surgery; D008113:Liver Neoplasms / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D058185:Magnetite Nanoparticles; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D007501:Iron; C065507:ferumoxides