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

这个为期3年的项目的目的是实现一种可靠的手段，在磁共振成像(MRI)检查期间确定影响两类脆弱患者/孕妇和婴儿子宫中未出生胎儿安全的关键因素，这些患者在生命的头两年内接受扫描。尽管有明确的安全MRI安全指南，在所有检查中都必须遵守，但目前对胎儿和婴儿的这些指南的实施是基于对非怀孕成人和中等大小儿童的结果的推断。两个关键因素是受试者吸收的射频(RF)能量水平以及由此可能导致的组织温度升高。我们将建立核磁共振扫描仪射频发射系统的计算机模型，并制作怀孕不同阶段的女性受试者和不同年龄的新生儿的解剖精确模型。使用这些模型，我们将应用强大的计算方法来准确地模拟吸收功率和温度的变化，以确定成像这些对象的安全操作极限。计算将使用成熟的方法，但我们也将进行实验来验证我们的发现，以确保它是正确的。为了诊断和研究的目的，对未出生的胎儿和早产儿进行成像的需求越来越大。在未来，许多这样的检查将在新一代扫描仪上进行，这些扫描仪在更高的磁场强度下运行。吸收的射频功率与场强的平方近似成正比，因此准确确定吸收能级将变得越来越重要。

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.