Birdcage (BC) coils generate a homogeneous magnetic field (∣B1∣), whose strength depends on the length of the coils, the number of legs, the resonance frequency, the excitation method, and the length‐to‐diameter ratio. BC coils with a shorter distance between the end rings produce a more intense ∣B1∣ field with a higher level of homogeneity. Here, we propose a combination of overlapping and nonoverlapping radiofrequency volumetric BC coils for small‐animal magnetic resonance imaging (MRI) working at 7 T with a frequency of 300 MHz to improve the ∣B1∣‐field homogeneity and intensity along the main magnetic field (∣B0∣) direction. The first combination consisted of two overlapping BC (o‐BC) coils, in which each coil is half the length of the imaging object. A combination of two nonoverlapping BC coils separated by a small gap (nog‐BC) was also developed. In order to improve the performance of the nog‐BC coil, we attached a decoupling capacitor. In computational calculations, the proposed o‐BC coil configuration showed an increased homogeneity in the ∣B1∣ field along the ∣B0∣ direction compared with the other coils. The experimental bench tests of the o‐BC coil configuration showed a high decoupling coefficient between the BC coils, which allowed each of them to be used individually for transmission and reception. The o‐BC coil was able to maintain a high transmission efficiency without signal interference while exhibiting an increased ∣B1∣‐field homogeneity compared with other coils. In this study, the advantages of the o‐BC coils are demonstrated using electromagnetic simulations and MRI on a homogenous phantom and an in vivo mouse body.

中文翻译：

---

鸟笼线圈多阵列法提高7 T小动物全身磁共振成像信号强度和均匀性的研究

鸟笼（BC）线圈产生均匀磁场（∣B1∣），其强度取决于线圈的长度、腿的数量、共振频率、激励方法和长径比。端环之间距离较短的 BC 线圈产生更强烈的 ∣B1∣ 场，具有更高的均匀性。在这里，我们提出了重叠和非重叠射频体积 BC 线圈的组合，用于小动物磁共振成像 (MRI)，工作频率为 7 T，频率为 300 MHz，以改善沿主磁场的 ∣B1∣ 场均匀性和强度(∣B0∣) 方向。第一种组合由两个重叠的 BC (o-BC) 线圈组成，其中每个线圈是成像对象长度的一半。还开发了由小间隙 (nog-BC) 分隔的两个非重叠 BC 线圈的组合。为了提高 nog-BC 线圈的性能，我们附加了一个去耦电容器。在计算计算中，与其他线圈相比，所提出的 o-BC 线圈配置在沿 ∣B0∣ 方向的 ∣B1∣ 场中显示出更高的均匀性。o-BC 线圈配置的实验台测试显示 BC 线圈之间的高解耦系数，这允许它们中的每一个单独用于传输和接收。与其他线圈相比，o-BC 线圈能够在没有信号干扰的情况下保持高传输效率，同时表现出更高的∣B1∣-场均匀性。在这项研究中，