Department of Radiology, Stanford University, Stanford, California, USA.
Endra, Inc, Ann Arbor, Michigan, USA.
Magn Reson Med. 2017 Oct;78(4):1599-1606. doi: 10.1002/mrm.26517. Epub 2016 Oct 25.
To develop a new method capable of directly measuring specific absorption rate (SAR) deposited in tissue using the thermoacoustic signal induced by short radiofrequency (RF) pulse excitation.
A detailed model based on the thermoacoustic wave generation and propagation is presented.
We propose a new concept for direct measurement of SAR, to be used as a safety assessment/monitoring tool for MRI. The concept involves the use of short bursts of RF energy and the measurement of the resulting thermoacoustic excitation pattern by an array of ultrasound transducers, followed by image reconstruction to yield the 3D SAR distribution. We developed a simulation framework to model this thermoacoustic SAR mapping concept and verified the concept in vitro.
Simulations show good agreement between reconstructed and original SAR distributions with an error of 4.2, 7.2, and 8.4% of the mean SAR values in axial, sagittal, and coronal planes and support the feasibility of direct experimental mapping of SAR distributions in vivo. The in vitro experiments show good agreement with theory (r = 0.52).
A novel thermoacoustic method for in vivo mapping of local SAR patterns in MRI has been proposed and verified in simulation and in a phantom experiment. Magn Reson Med 78:1599-1606, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
开发一种新方法，能够使用短射频 (RF) 脉冲激发产生的热声信号直接测量组织中的比吸收率 (SAR)。
提出了一种基于热声波产生和传播的详细模型。
我们提出了一种用于直接测量 SAR 的新概念，作为 MRI 的安全评估/监测工具。该概念涉及使用短 RF 能量脉冲，并通过超声换能器阵列测量产生的热声激励模式，然后进行图像重建以获得 3D SAR 分布。我们开发了一个模拟框架来模拟这个热声 SAR 映射概念，并在体外进行了验证。
模拟结果显示，重建的 SAR 分布与原始分布之间具有良好的一致性，轴向、矢状和冠状平面的平均 SAR 值的误差分别为 4.2%、7.2%和 8.4%，支持在体内直接实验映射 SAR 分布的可行性。体外实验与理论吻合良好 (r=0.52)。
提出了一种新的用于在 MRI 中体内映射局部 SAR 模式的热声方法，并在模拟和体模实验中进行了验证。磁共振医学杂志 78:1599-1606, 2017。© 2016 国际磁共振学会。
