Winter Lukas, Niendorf Thoralf
Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrück Center for Molecular Medicine, Robert-Roessle-Strasse 10, 13125, Berlin, Germany.
Experimental and Clinical Research Center (ECRC), A Joint Cooperation Between the Charité and the Max Delbrück Center for Molecular Medicine, Berlin, Germany.
MAGMA. 2016 Jun;29(3):641-56. doi: 10.1007/s10334-016-0559-y. Epub 2016 Apr 20.
This work investigates electrodynamic constraints, explores RF antenna concepts and examines the transmission fields (B 1 (+) ) and RF power deposition of dipole antenna arrays for (1)H magnetic resonance of the human brain at 1 GHz (23.5 T).
Electromagnetic field (EMF) simulations are performed in phantoms with average tissue simulants for dipole antennae using discrete frequencies [300 MHz (7.0 T) to 3 GHz (70.0 T)]. To advance to a human setup EMF simulations are conducted in anatomical human voxel models of the human head using a 20-element dipole array operating at 1 GHz.
Our results demonstrate that transmission fields suitable for (1)H MR of the human brain can be achieved at 1 GHz. An increase in transmit channel density around the human head helps to enhance B 1 (+) in the center of the brain. The calculated relative increase in specific absorption rate at 23.5 versus 7.0 T was below 1.4 (in-phase phase setting) and 2.7 (circular polarized phase setting) for the dipole antennae array.
The benefits of multi-channel dipole antennae at higher frequencies render MR at 23.5 T feasible from an electrodynamic standpoint. This very preliminary finding opens the door on further explorations that might be catalyzed into a 20-T class human MR system.
本研究探讨了电动约束，探索了射频天线概念，并研究了用于1GHz（23.5T）人脑氢磁共振的偶极天线阵列的传输场（B1(+)）和射频功率沉积。
使用离散频率[300MHz（7.0T）至3GHz（70.0T）]，在具有偶极天线平均组织模拟物的模型中进行电磁场（EMF）模拟。为了推进到人体设置，使用在1GHz下运行的20元偶极阵列，在人体头部的解剖学人体体素模型中进行EMF模拟。
我们的结果表明，在1GHz时可以实现适合人脑氢磁共振的传输场。人头周围发射通道密度的增加有助于增强脑中心的B1(+)。对于偶极天线阵列，计算得出的23.5T与7.0T时比吸收率的相对增加在同相设置下低于1.4，在圆极化设置下低于2.7。
从电动角度来看，多通道偶极天线在更高频率下的优势使得23.5T的磁共振成像可行。这一非常初步的发现为进一步探索打开了大门，这些探索可能会促成一个20T级的人体磁共振系统。
