A High-Performance Quiet Head Gradient Coil for High-field MRI

描述（由申请人提供）：与当前使用全身梯度线圈的实践相比，先进的头部梯度线圈保证了两倍以上的梯度强度（用于更高的分辨率）和至少三倍的转换速率（用于更快的成像序列），神经刺激减少了一个数量级，声学噪声大大降低。十多年来，高性能头部梯度线圈的潜在有用性已得到广泛认可，世界各地的许多团队都投入了数百万美元试图开发令人满意的解决方案，但效果有限。过去一年中报告的头部MR RF线圈的S/N大幅增加进一步加强了高性能专用头部梯度线圈的合理性。初步模拟表明，我们先前的新月形线圈方法中的许多改进的最佳组合将允许实现具有显著降低的声学噪声、更高的梯度强度和显著降低的制造成本的实用的、鲁棒的头部梯度线圈。更高的梯度性能是特别需要在更高的领域，以改善脑功能成像（fMRI）。临床应用的主要依据可能是在弥散加权MRI技术中获得的S/N改善。下一代超快速超极化13 C技术也将受益。此外，专用头部MR扫描仪将比全身扫描仪更便宜，同时为所有年龄的患者的头部和四肢应用以及婴儿的全身成像提供大大改进的性能。这种系统可以在更多情况下取代X射线CT。根据初步模拟，预期性能如下：900 A时梯度为200 mT/m; 1400 V时转换速率为520 T/m/s;均匀成像直径为25 cm，均方根非均匀性为10%;残余涡流效应低于0.4%; 3 T场中典型EPI脑序列的噪声低于100 dB;和机械坚固性，适用于在至少高达8 T的磁场下无电流降额的操作。RT校正器将通过Z4提供主要校正，包括动态Z 0和Z2。第一阶段将完成详细的模拟和所有参数的平衡优化。将建造一个原型线圈，并完成初步测试。在第二阶段期间，将在另一个机构进行更广泛的测试，然后根据吸取的经验教训进行修订，并制作和测试生产前版本。

DESCRIPTION (provided by applicant): Compared to current practice with whole-body-gradient coils, an advanced head gradient coil promises over twice the gradient strength (for higher resolution) and at least three times higher slew rates (for faster imaging sequences), with an order of magnitude reduction in nerve stimulation and greatly reduced acoustic noise. The potential usefulness of a high-performance head gradient coil has been widely recognized for more than a decade, and many groups around the world have each put millions of dollars into attempting to developing a satisfactory solution, but to limited avail. The enormous increases in S/N in head MR RF coils reported over the past year serve to further strengthen the justification for a high-performance dedicated head gradient coil. Preliminary simulations indicate that an optimal combination of a number of improvements in our pre- vious crescent-coil approach will permit the realization of a practical, robust, head gradient coil with dramatically reduced acoustic noise, higher gradient strength, and substantially reduced manufacturing cost. The higher gradient performance is especially needed at higher fields for improved brain functional imaging (fMRI). The primary justification in clinical applications may be the improved S/N that will be obtained in Diffusion Weighted MRI techniques. Next-generation ultra-fast hyperpolarized 13C techniques will also benefit. Moreover, a dedicated head MR scanner would be less expensive than a whole body scanner while providing greatly improved performance for head and extremity applications in patients of all ages, and for whole-body imaging of infants. Such a system could supplant x-ray CT in more cases. Based on preliminary simulations, the following performance is expected: 200 mT/m gradient at 900 A; slew rate of 520 T/m/s at 1400 V; 25 cm Region of Uniformity imaging diameter with 10% rms non-uniformity; residual eddy current effects under 0.4%; acoustic noise below 100 dB for a typical EPI brain sequence in a 3 T field; and mechanical robustness suitable for operation with no current de-rating at fields at least up to 8 T. The RT shims will provide major corrections through Z4, including dynamic Z0 and Z2. The Phase I will complete detailed simulations and balanced optimization of all parameters. A prototype coil will be constructed, and preliminary tests will be completed. More extensive testing will be carried out during Phase II at another institution, followed by revisions based on lessons learned and construction and testing of the pre-production version.