MRI thermodosimetry in laser-induced interstitial thermotherapy

✍ Scribed by Michel Prudhomme; Martine Mattéi-Gazagnes; Pascale Fabbro-Peray; Pierre Puche; Jean-Paul Chabalier; G. Delacrétaz; Lopez F.M. François-Michel; Guilhem Godlewski

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 119 KB
• Volume: 32
• Category: Article
• ISSN: 0196-8092
• DOI: 10.1002/lsm.10130

✦ Synopsis

Abstract

Background and Objectives

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.

Study Design/Materials and 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°C at 5 mm and 4°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°C whereas at 10 mm it was only 14.5°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. Lasers Surg. Med. 32:54–60,2003. © 2003 Wiley‐Liss, Inc.