GE Global Research, Niskayuna, NY, USA.
Mayo Clinic, Department of Radiology, Rochester, MN, USA.
Magn Reson Imaging. 2022 Jan;85:168-176. doi: 10.1016/j.mri.2021.10.011. Epub 2021 Oct 16.
A recently developed compact 3 T (C3T) MRI scanner with high performance gradients [1, 2] has a dedicated radiofrequency (RF) transmit coil that exposes only the head, neck and a small portion of the upper body region during head-first scanning. Due to the unique coil geometry and patient positioning, the established SAR model used for a conventional whole-body scanner cannot be directly translated to the C3T. Here a specific absorption rate (SAR) estimation and validation framework was developed and used to implement a dedicated and accurate SAR prediction model for the C3T. Two different SAR prediction models for the C3T were defined and evaluated: one based on an anatomically derived exposed mass, and one using a fixed anatomical position located caudally to the RF coil to determine the exposed mass. After coil modeling and virtual human body simulation, the designed SAR prediction model was implemented on the C3T and verified with calorimetry and in vivo scan power monitoring. The fixed-demarcation exposed mass model was selected as appropriate exposed mass region to accurately estimate the SAR deposition in the patient on the C3T.
最近开发的一种具有高性能梯度的紧凑型 3T（C3T）MRI 扫描仪[1,2]，具有专用的射频（RF）发射线圈，在头先进扫描时仅暴露头部、颈部和上半身的一小部分区域。由于独特的线圈几何形状和患者定位，用于常规全身扫描仪的既定 SAR 模型不能直接转换为 C3T。在这里，开发并使用了一种特定吸收率（SAR）估计和验证框架，以实现 C3T 的专用和准确的 SAR 预测模型。为 C3T 定义和评估了两种不同的 SAR 预测模型：一种基于解剖学得出的暴露质量，另一种使用位于 RF 线圈下方的固定解剖位置来确定暴露质量。在对线圈进行建模和对虚拟人体进行模拟之后，在 C3T 上实现了设计的 SAR 预测模型，并通过量热法和体内扫描功率监测进行了验证。选择固定划分的暴露质量模型作为适当的暴露质量区域，以准确估计 C3T 中患者的 SAR 沉积量。
