RF power absorption and temperature changes in mother/fetus and neonates associated with MRI examinations.

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The aim of this 3 year project is to achieve a reliable means of determining key factors that affect safety of two categories of vulnerable patients during Magnetic Resonance Imaging (MRI) examinations /unborn fetuses in the wombs of pregnant women and babies who are scanned within the first 2 years of life. Although there are clear safety guidelines for safe MRI, which must be adhered to in all examinations, the implementation of these guideline for fetuses and babies is currently based on extrapolating from results for non-pregnant adults and medium sized children respectively. The two key factors are the level of radiofrequency (RF) power absorbed by the subject and the temperature rise in tissue that this may cause. We will construct a computer model of the RF transmit system of a MRI scanner and produce anatomically accurate models of female subjects at various stages during pregnancy and of neonates at various ages. Using these models we will apply powerful computing methods to accurately model absorbed power and temperature changes to determine safe operating limits for imaging these subjects. The calculations will use well established methods, but we will also conduct experiments to validate what we find to ensure it is correct. There is increasing demand to image the unborn fetus and premature babies for diagnostic purposes as well as for research. In future many of these examinations will be done on a new generation of scanners that operate at higher magnetic field strength. The absorbed RF power goes up approximately as the square of the field strength, so determining the absorption level accurately will be increasingly important.