Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany.
Invest Radiol. 2009 Nov;44(11):734-40. doi: 10.1097/RLI.0b013e3181b24ab7.
To develop a transmit/receive radiofrequency (RF) array for MR imaging of the human spine at 7 T. The prototype is characterized in simulations and bench measurements, and the feasibility of high-resolution spinal cord imaging at 7 T is demonstrated in in vivo images of volunteers.
The RF phased array consists of 8 overlapping surface loop coils with a dimension of 12 cm x 12 cm each. Bench measurements were obtained with a phantom made of body-simulating liquid and assessed with a network analyzer. For safety validation, numerical computations of the RF field distribution and the corresponding specific absorption rate were performed on the basis of 3 different human body models. In vivo images of 3 volunteers (2 with a documented scoliosis) were acquired using a 3D-FLASH sequence with a high spatial resolution of 0.57 mm isotropic.
The 7 T transmit/receive RF coil could be easily integrated into the patient table for examinations of the cervicothoracic or thoracolumbosacral spine. Comparable results were found for all 3 numerical calculations using different human body models. Measurements of the g-factor indicated good image quality for parallel imaging acceleration factors up to 2.7 along the head-feet direction, which could be validated in the in vivo images. The in vivo images demonstrated very fine anatomic features such as the longitudinal ligaments or the venous drainage through the vertebral bodies. A largely homogeneous excitation over an extensive field-of-view of 40 cm could be obtained.
These early results indicate that a multichannel transmit/receive phased array RF coil can be used for in vivo spine imaging at 7 T, thereby rendering high-resolution spine imaging a promising new application in 7 T clinical research.
开发一种用于 7T 人体脊柱磁共振成像的发射/接收射频（RF）阵列。该原型在模拟和台架测量中进行了特征描述，并通过志愿者体内图像证明了在 7T 下进行高分辨率脊髓成像的可行性。
RF 相控阵由 8 个重叠的表面环形线圈组成，每个线圈的尺寸为 12cm x 12cm。使用由体模液制成的体模进行台架测量，并使用网络分析仪进行评估。为了进行安全验证，根据 3 种不同的人体模型，对 RF 场分布和相应的比吸收率进行了数值计算。使用高分辨率的 0.57mm 各向同性 3D-FLASH 序列对 3 名志愿者（其中 2 名患有已知的脊柱侧凸）进行了体内成像。
7T 发射/接收 RF 线圈可轻松集成到患者检查台上，用于检查颈胸段或胸腰椎段脊柱。使用不同人体模型进行的所有 3 种数值计算都得到了相似的结果。g 因子的测量结果表明，在头脚方向上的并行成像加速因子高达 2.7 时，图像质量良好，这在体内图像中得到了验证。体内图像显示了非常精细的解剖结构特征，如纵韧带或通过椎体的静脉引流。可以在广泛的 40cm 视野内获得大致均匀的激励。
这些早期结果表明，多通道发射/接收相控阵 RF 线圈可用于 7T 体内脊柱成像，从而使高分辨率脊柱成像成为 7T 临床研究中一种很有前途的新应用。
