利用高介电材料提高胎儿磁共振射频安全性理论研究

探究应用高介电材料(HDM)降低胎儿磁共振成像(fetus MRI)扫描中组织射频能量比吸收率(SAR)在理论上的可行性。建立13周胎儿和成人女性盆腔混合数值模型。通过计算机仿真计算1.5 T和3 T场强下普通扫描及应用不同HDM时的部分身体比吸收率(partial body SAR)和局部比吸收率(local SAR)的分布规律,以及两种场强下普通扫描和应用两种形状HDM取得最佳胎儿local SAR最大值时的B+1场均匀性。通过应用合适的HDM,能够显著降低1.5 T和3 T fetus MRI中的SAR值。在1.5 T和3 T成像时当取得最佳胎儿local SAR最大值时,分别可使胎儿local SAR最大值比普通扫描时下降12.90%和24.75%。这项研究表明通过应用合适的HDM,可以降低在临床上进行fetus MRI时的SAR值来提高胎儿的安全性。

Theoretical study of improving the safety of radiofrequency in fetus MRI by using high dielectric material

To theoretically analyze the feasibility of reducing the specific absorption rate (SAR) of radiofrequency energy deposited inside the tissues during the fetus magnetic resonance imaging (Fetus MRI) by using high dielectric material (HDM). A 13-week fetus model was combined with an adult female pelvis model to establish the hybrid numerical model. The distribution of partial body SAR and maximum local SAR with and without HDMs at 1.5 and 3T fetus MRI were separately simulated. The B1+ uniformity was obtained with respect to various arrangements of HDMs. The optimum maximum fetus local SAR was reduced by 12.90% and 24.75% respectively, with the application of the HDMs, while the optimum maximum fetus local SAR was obtained. The study indicated that the SAR can be significantly reduced to improve the safety by using appropriate HDM at 1.5 and 3T fetus MRI.