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[In vitro evaluation of MR thermometry in the implementation of laser-induced thermotherapy]
T J Vogl1, M G Mack, H H Hirsch
1Strahlenklinik und Poliklinik, Virchow-Klinikum, Humboldt-Universität zu Berlin.
Purpose:
To optimize the MR sequences parameter for monitoring hyperthermic effects in the tissue during laser induced thermotherapy (LITT).
Material And Methods:
Experimental studies were performed for the evaluation of MR-thermometry using a contrast-agent-water solution and a pig-liver. A T1-weighted TurboFLASH sequence and a FLASH-2D sequence were used. The TurboFLASH sequence was used with various T1 settings (between 100 and 1250 ms). MR findings were correlated with temperature measurements using a fluoride optical temperature measuring system in a distance of 1, 2, and 5 cm from the laser applicator.
Results:
Using the contrast-agent-water solution demonstrated the temperature sensitivity of both sequences. In vitro evaluations using pig liver demonstrated a near linear increase of signal versus increasing tissue temperatures in a distance of 1 cm to the tip of the laser applicator. Optimal visualization of the temperature effects was obtained using a T1 between 100 ms and 400 ms. Using the FLASH-2D sequence a signal loss was documented at a TR of 110 ms.
Conclusion:
MR-thermometry using sequentially TurboFLASH and FLASH-2D sequences allowed a non-invasive monitoring of the laser induced temperature changes.