NON-INVASIVE IMAGING OF INTERNAL BODY TEMPERATURE USING MRI FOR THERMAL THERAPIES

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Our primary aim of this research project was to establish the methodology of non-invasive internal-body temperature imaging under variety of the thermal therapies. Based on the development and assessment of the elemental technologies in 2000, we have focused on the development of the internally referenced (in other word self-referenced) temperature imaging technique using naturally contained metabolite signals. The echo planar spectroscopic imaging (EPSI) technique was modified as to have line scan capability (LSEPSI) to improve the spectrum quality under existence of the magnetic field inhomogeneity. The production technique of the birdcage coil for small animals in 3T-MRI was also refined to improve the coils transmission and reception specifications. These improvement yielded clear, internally referenced temperature distribution change maps for a 20 mM citrate phantom as well as a 10 mM NAA (N-Acetyl Aspartic acid) phantom. Our trial for a rabbit brain temperature imaging using LSEP … More SI was successful to visualize the temperature distribution change using NAA of a natural abundance (-7 mM). This internally-referenced technique does not require the pixel-by-pixel subtraction unlike the phase mapping approach. This means that the technique is more durable against the inter-scan motion or the inter-scan susceptibility change.Separate measurements for human volunteers' brains demonstrated that the water-NAA chemical shift is neither constant nor homogeneous ; It differs by locations and by individuals. The difference reaches as 0.05 ppm which corresponds to 5℃ of temperature variation. It is known that the internal brain temperature is almost homogeneous in a brain tissues, and therefore the difference is due to a factor other than temperature. Absolute brain temperature imaging still seems to be a far goal.Overall, the 2-years research in this project has established temperature change imaging using the phase mapping method (externally referenced approach) and the LSEPSI approach (internally referenced approach) of temperature imaging. The animal coil technology for a very high field (VHF, 3T) MRI has also been completed. Less