The radio frequency (RF) coil is one of the key components of the magnetic resonance imaging (MRI) system. It has a significant impact on the performance of the nuclear magnetic resonance (NMR) detection. Among numerous practical designs of RF coils for NMR imaging, the birdcage RF coil is the most popular choice from low field to ultra-high field MRI systems. In the transmission mode, it can establish a strong and homogeneous transverse magnetic field B1 for any element at its Larmor frequency. Similarly, in the reception mode, it exhibits extremely high sensitivity for the detection of even faint NMR signals from the volume of interest. Despite the sophisticated 3D structure of the birdcage coil, the developments in the design, analysis, and implementation technologies during the past decade have rendered the development of the birdcage coils quite reasonable. This article provides a detailed review of the recent progress in the birdcage RF coil technology for the MRI system.

No abstract

No abstract

No abstract

A novel double-tuned radio-frequency (RF) receiver coil for use in magnetic resonance imaging (MRI) systems has been demonstrated based on a birdcage-type circuit. The receiver coil utilises the endring current as well as the leg current of the birdcage-type circuit to detect the nuclear magnetic resonance (NMR) signals of different elements simultaneously. It was designed to detect the NMR signals of both 1 H and 31 P elements in a 4.7 T MRI system. The coil showed an excellent frequency response and provided clear magnetic resonance images of a Na 2 HPO 4 phantom when used with the 4.7 T MRI system. Introduction: Magnetic resonance imaging (MRI) is a popular choice among the existing medical imaging techniques owing to its ability to provide detailed information on the internal metabolism of a human or animal body. The radio-frequency (RF) receiver coil plays a key role in the MRI system to realise a noise-free nuclear magnetic resonance (NMR) signal detection. Especially, the double-tuned RF receiver coil enables the detection of NMR signals of 1 H and another element that also exists in a human or animal body [1,2], which leads to more sophisticated understanding of the body. Since 31 P is a relatively abundant element in human and animal bodies, there have been many attempts to realise an RF receiver coil detecting the NMR signals of both 1 H and 31 P protons simultaneously [3][4][5]. However, the previously implemented double-tuned RF receiver coils require many additional lumped elements such as resonance trap components, which increases the design complexity and makes the coil implementation process more difficult. Furthermore, the problem can be critical in the MRI system operating at 4.7 T or higher fields since the performance degradation of the MRI system due to the additional lumped elements becomes more severe as the frequency increases [6].In this Letter, we demonstrate a simple method of designing a doubletuned RF receiver coil employing a conventional birdcage-type circuit. The receiver coil can detect both NMR signals of 1 H and 31 P protons with different resonance frequencies in a 4.7 T MRI system. The key feature of this novel coil design technique is to utilise the end-ring current of the coil as well as the leg current for the detections of the NMR signals at two different frequencies instead of adding the additional lumped elements, which is inevitable in the previous works.