title: MRI thermodosimetry in laser-induced interstitial thermotherapy.
abstract: OBJECTIVE
  The aim of this study was to establish a correlation between a thermal measurement and a magnetic resonance imaging (MRI) signal during laser-induced interstitial thermotherapy (LITT) in liver.
  
  
  METHODS
  Pig liver was irradiated for 15 minutes with a diode laser at two different powers, 0.5 W (450 J) and 1.5 W (1,350 J). Tissue temperature was monitored every 20 seconds using thermocouples. Thermosensitive MRI sequences (T(1)-weighted Turbo-Flash) were acquired with the same irradiation parameters. Correlation between MRI signals (SI) and temperature measures was defined at two different distances from the fiber (5 and 10 mm).
  
  
  RESULTS
  At 0.5 W, temperatures rose progressively up to a maximum increase of 9.5 degrees C at 5 mm and 4 degrees C at 10 mm after 15 minutes. The corresponding MRI signal decreased progressively to -27.6 SI at 5 mm and -18.5 SI at 10 mm. At 1.5 W, temperatures rose dramatically at 5 mm, reaching a plateau. The temperature elevation measured at the end of the irradiation was of 30 degrees C whereas at 10 mm it was only 14.5 degrees C. The MRI signal varied accordingly, remaining inversely proportional to temperature (-76 SI at 5 mm and -35.5 SI at 10 mm).
  
  
  CONCLUSIONS
  An inversely proportional relationship was observed between MRI signal in sequential Turbo-Flash and temperature. MRI should allow to analyze heat diffusion in the liver, and thus to monitor real-time LITT treatments.
authors.affiliation: Département de Chirurgie Digestive et de Cancérologie Digestive, rue du Pr R. Debré F30900 Nîmes, France. michel.prudhomme@chu-nimes.fr
authors.forename: Michel
authors.initials: M
authors.lastname: Prudhomme
authors.forename: Martine
authors.initials: M
authors.lastname: Mattéi-Gazagnes
authors.forename: Pascale
authors.initials: P
authors.lastname: Fabbro-Peray
authors.forename: Pierre
authors.initials: P
authors.lastname: Puche
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Chabalier
authors.forename: G
authors.initials: G
authors.lastname: Delacrétaz
authors.forename: Lopez F M
authors.initials: LF
authors.lastname: François-Michel
authors.forename: Guilhem
authors.initials: G
authors.lastname: Godlewski
mesh_terms: D000818:Animals; D004058:Diffusion / Q000528:radiation effects; D004195:Disease Models, Animal; D005110:Extracellular Space / Q000502:physiology / Q000528:radiation effects*; D006979:Hyperthermia, Induced; D066298:In Vitro Techniques; D008099:Liver / Q000473:pathology* / Q000503:physiopathology / Q000528:radiation effects*; D008113:Liver Neoplasms / Q000473:pathology* / Q000503:physiopathology / Q000532:radiotherapy*; D028022:Low-Level Light Therapy; D008279:Magnetic Resonance Imaging; D011874:Radiometry; D013552:Swine