Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy
Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy
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DOI：
10.1109/tbme.2015.2506680
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发表时间：
2016-08-01
影响因子：
4.6
通讯作者：
Angelone, Leonardo M.
中科院分区：
文献类型：
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作者：
Lucano, Elena;Liberti, Micaela;Angelone, Leonardo M.
目标：本研究的目的是系统地评估五个计算模型的鸟笼线圈formmagnetic resonance imaging（MRI）的准确性和计算成本。方法：使用相同的几何模型和数值算法，但不同的驱动方法（即，线圈“失效”）。将失败的模型标记为：特异性（S2）、通用性（G32、G16）和杂交（H16、H16（fr-强迫））。使用“对称平均绝对百分比误差”（“SMAPE”），通过与频率响应以及电场幅度（平行于（E），右箭头平行于）和磁场幅度（平行于（B），右箭头平行于）方面的测量值进行比较，评估模型的准确度。结果如下：所有模型计算的平行于B的平行度在35%测量值范围内，只有S2、G32和H16能够准确模拟平行于体模内部右箭头（E）的平行度，最大SMAPE为16%。在体模外，仅S2显示SMAPE低于11%。结论：结果表明，仅基于沿线圈中心纵向线的沿着比较来评估平行于（B）的准确度可能会产生误导。通用或混合线圈-当正确建模沿着环/横档的电流时-足以准确再现体模内的场，而需要特定模型来准确建模平行于（E）的右箭头，平行于线圈和体模之间的空间。意义：鸟笼体线圈的计算建模广泛用于评价MRI期间的射频致热。需要对数值模型进行实验验证，以确定模型是否是物理线圈的准确表示。
Goal: This study aims at a systematic assessment of five computational models of a birdcage coil formagnetic resonance imaging (MRI) with respect to accuracy and computational cost. Methods: The models were implemented using the same geometrical model and numerical algorithm, but different driving methods (i.e., coil "defeaturing"). The defeatured models were labeled as: specific (S2), generic (G32, G16), and hybrid (H16, H16(fr-forced)). The accuracy of the models was evaluated using the "symmetric mean absolute percentage error" ("SMAPE"), by comparison with measurements in terms of frequency response, as well as electric (parallel to(E) over right arrow parallel to) and magnetic (parallel to(B) over right arrow parallel to) field magnitude. Results: All the models computed the parallel to B parallel to within 35% of the measurements, only the S2, G32, and H16 were able to accurately model the parallel to(E) over right arrow parallel to inside the phantom with a maximum SMAPE of 16%. Outside the phantom, only the S2 showed a SMAPE lower than 11%. Conclusions: Results showed that assessing the accuracy of parallel to(B) over right arrow parallel to based only on comparison along the central longitudinal line of the coil can be misleading. Generic or hybrid coils - when properly modeling the currents along the rings/rungs-were sufficient to accurately reproduce the fields inside a phantom while a specific model was needed to accurately model parallel to(E) over right arrow parallel to in the space between coil and phantom. Significance: Computational modeling of birdcage body coils is extensively used in the evaluation of radiofrequency-induced heating during MRI. Experimental validation of numerical models is needed to determine if a model is an accurate representation of a physical coil.