MR monitoring of tumour thermal therapy

Thermal therapy of tumour including hyperthermia and thermal ablation by he at or cold delivery requires on line monitoring. Due to its temperature sen sitivity, Magnetic Resonance Imaging (MRI) allows thermal mapping at the ti me of the treatment. The different techniques of MR temperature monitoring based on water proton resonance frequency (PRF), longitudinal relaxation ti me T1, diffusion coefficient and MR Spectroscopic Imaging (MRSI) are review ed and debated. The PRF method appears the most widely used and the most ef ficient at high magnetic field in spite of important drawbacks. The T1 meth od is the easiest method of visualisation of qualitative temperature distri bution and quantitative measurement seems possible in the tissue surroundin g the tumour up to a temperature of 45-65 degreesC. Despite its high temper ature sensitivity, application of the diffusion method in vivo is restricte d due to its high motion sensitivity. The recent MRSI technique seems very promising provided acquisition times can be reduced. Results from the liter ature indicate that MR temperature monitoring in vivo can be achieved in vi vo with a precision of about 3 degreesC in 13 s for a voxel of 16 mm(3) (1. 5 x 1.5 x 7 mm) in 1.5 T scanners. (C) 2001 Elsevier Science B.V. All right s reserved.