On-coil multiple channel transmit system based on class-D amplification and pre-amplification with current amplitude feedback.
On-coil multiple channel transmit system based on class-D amplification and pre-amplification with current amplitude feedback.
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DOI：
10.1002/mrm.24462
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发表时间：
2013-07
影响因子：
3.3
通讯作者：
Griswold MA
中科院分区：
文献类型：
--
作者：
Gudino N;Heilman JA;Riffe MJ;Heid O;Vester M;Griswold MA
提出了一种完整的高效率发射放大器单元，设计用于在线圈发射阵列中实现。高功率容量、低功耗、可扩展性和成本最小化是对设计的一些要求。该系统由电流模式D类放大器输出级和电压模式D类放大器前置级组成。射频脉冲的幅度信息通过连接到CMCD级的具有电流幅度反馈的定制降压DC-DC转换器添加。进行了台架测量和成像实验，以分析系统的性能。B1的直接控制是可能的，其负载灵敏度降低到小于10%的变化，从空载到满载条件。当在阵列配置中使用放大器时，通过放大器去耦方法在相邻线圈之间实现了20 dB以上的隔离。通过在工作台上测量输出功率和在1.5 T扫描仪中通过翻转角量化证明了发射器的高输出电流操作。最后，通过用扫描仪的体线圈接收信号，演示了新硬件的单通道和多通道激励。
A complete high-efficiency transmit amplifier unit designed to be implemented in on-coil transmit arrays is presented. High power capability, low power dissipation, scalability and cost minimization were some of the requirements imposed to the design. The system is composed of a current mode class-D (CMCD) amplifier output stage and a voltage mode class-D (VMCD) preamplification stage. The amplitude information of the radio frequency pulse was added through a customized step-down DC-DC converter with current amplitude feedback that connects to the CMCD stage. Benchtop measurements and imaging experiments were carried out to analyze system performance. Direct control of B1 was possible and its load sensitivity was reduced to less than 10% variation from unloaded to full loaded condition. When using the amplifiers in an array configuration, isolation above 20 dB was achieved between neighboring coils by the amplifier decoupling method. High output current operation of the transmitter was proved on the benchtop through output power measurements and in a 1.5 T scanner through flip angle quantification. Finally, single and multiple channel excitations with the new hardware were demonstrated by receiving signal with the body coil of the scanner.