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方法来确定影响两类脆弱患者在磁共振成像（MRI）检查期间的安全的关键因素/孕妇子宫内未出生的胎儿和出生后2年内扫描的婴儿。虽然安全MRI有明确的安全指南，在所有检查中都必须遵守，但这些指南对胎儿和婴儿的实施目前分别基于对未怀孕成人和中等身材儿童结果的推断。两个关键因素是受试者吸收的射频（RF）功率水平和可能导致的组织温度升高。我们将构建一个核磁共振扫描仪射频传输系统的计算机模型，并产生在怀孕的不同阶段的女性受试者和不同年龄的新生儿的解剖学精确模型。利用这些模型，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变化，以确定成像这些受试者的安全操作极限。计算将使用成熟的方法，但我们也会进行实验来验证我们的发现，以确保它是正确的。为诊断和研究目的对未出生胎儿和早产儿成像的需求越来越大。在未来，许多这些检查将在新一代的扫描仪上完成，这些扫描仪在更高的磁场强度下工作。射频吸收功率随场强的平方近似上升，因此准确确定射频吸收电平将变得越来越重要。

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.