Research Article Odd-Leg Birdcages for Geometric Decoupling in Multinuclear Imaging and Spectroscopy Joseph Busher , 1 Edith Touchet-Valle, 2 Chenhao Sun, 2 Steven M. Wright, 1,2 and Mary P. McDougall 1,2 1 Department of Biomedical Engineering, Texas A&M University, College Station, TX 77840, USA 2 Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX 77840, USA Correspondence should be addressed to Mary P. McDougall; mpmcdougall@tamu.edu Received 18 August 2022; Revised 1 February 2023; Accepted 11 February 2023; Published 10 April 2023 Academic Editor: Lars G. Hanson Copyright©2023JosephBusheretal.TisisanopenaccessarticledistributedundertheCreativeCommonsAttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te utility of interleaved odd•number leg birdcage coils is demonstrated for decoupling in double• and triple•tuned multinuclear applications. Te birdcage was designed to geometrically decouple from a planar double•tuned ( 1 H• 23 Na) array and from a 31 P saddle coil insert to create a triple•tuned confguration. Comparisons between an actively detuned coil and a purely geometrically decoupled architecture were used to demonstrate the capabilities of the design. In particular cases, the simplicity and adaptability of the interleaved nine•leg design for multinuclear nuclear magnetic resonance (NMR) ofer a straightforward alternative to the often complex and lossy designs currently available for multinuclear birdcages and volume coils. 1.Introduction Te development of multinuclear nuclear magnetic reso• nance (NMR) techniques yields many unique challenges for engineers in the clinical adoption of these methods. Sen• sitivity to X•nuclei such as 23 Na, 31 P, and 13 C has the po• tential to elucidate underlying physiological processes for the study and treatment of numerous disease states [1–5]. Tese nuclei, however, have much lower natural abundance and sensitivity than hydrogen and thus require specialized hardware for detection, such as array coils to increase sensitivity and signal•to•noise ratio (SNR) [6, 7]. Addi• tionally, achieving reliable shimming in X•nuclei studies is a challenge and immediately presents the need for double• tuning with 1 H [8]. Given the low sensitivity when detecting naturally abundant second nuclei, the short lifetime, ex• pense, and nonuniform distribution in hyperpolarized ap• plications, shimming requires the use of a 1 H coil without moving the X•nucleus coil between scans. Tis system of multinuclear transmit and receive hardware requires a complex chain of specialized coils, multiband amplifers, receivers, and often switching drivers, either for switch• tuned coils or active detuning. Te process of designing these multiband systems benefts from low•complexity coil de• signs to test individual components for the optimization of the resultant system, initially motivating the volume coil design presented here [9]. One of the most common transmit coil designs is the birdcage due to its highly homogeneous feld over a large volume [10, 11]. Traditionally, birdcages are constructed of two end rings and integer multiples of four evenly spaced legs connecting these end rings to create the symmetry and respective highly homogeneous felds characteristic of birdcage coils [12]. To create multituned birdcages, one of the most common methods is to add traps on the rungs [13–15]. Tis design involves an iterative tuning process for multiple traps while maintaining the circular symmetry of the birdcage. Te result is therefore highly efective, but can be complex and results in a reported loss of quality factor (Q) [16]. A four•ring design also has been proposed in which an inner birdcage is constructed between two outer birdcages using common legs but diferent end rings [17–19]. Tis confguration creates a homogeneous double resonant structure, but with a diference in flling factors potentially Hindawi Concepts in Magnetic Resonance Part B, Magnetic Resonance Engineering Volume 2023, Article ID 7137889, 10 pages https://doi.org/10.1155/2023/7137889