Ferrite shield to enhance the performance of optically pumped magnetometers for fetal magnetocardiography

• Ano de defesa: 2023
• Autor(a) principal: Tardelli, Gabriela Pazin
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Arritmias fetais; Blindagem magnética; Ferrita; Ferrite; Fetal arrhythmias; Fetal magnetocardiography; Magnetic shielding; Magnetocardiografia fetal; Magnetômetros de bombeamento óptico; Optically pumped magnetometers
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/59/59135/tde-22062023-080440/

Fetal magnetocardiography (fMCG) is a non-invasive technique for monitoring electrical cardiac activity during pregnancy. FMCG provides valuable information about fetal cardiac electrophysiology, improving the diagnosis and prognosis of fetal arrhythmias. Similarly, to fetal electrocardiography (fECG), which records the electric field produced by the electrical current flowing through the fetal heart, fMCG measures the magnetic field produced by the same current. Although fECG has been available for some time, its poor signal resolution has limited its use in clinical practice. In contrast, fMCG has advantages over other fetal cardiac monitoring tools, but its adoption has been limited by the high cost of Superconducting Quantum Interference Devices (SQUID). Fortunately, recent advances in atomic physics and quantum technology have led to the development of Optically Pumped Magnetometers (OPMs), which can achieve the same sensitivity at a lower cost, without the need for cryogenics, and with a smaller size. In addition, OPMs can operate within person-sized cylindrical shields, making fMCG more practical. However, one end of the shield is kept open to ensure patient comfort and prevent claustrophobia. Consequently, environmental magnetic interference can enter through the shield opening and degrade the quality of fMCG signals, especially in the longitudinal direction. This study aimed to attenuate these interferences by placing the OPM array within a small ferrite shield. Although the fetal signal was slightly attenuated, the environmental interference was reduced substantially, as well as the maternal interference. This increased the signal-to-noise ratio significantly and improved the resolution of the smaller cardiac waveform components. The ferrite shield conferred a significant advantage by enabling the measurement of the longitudinal component of the fMCG signal, which had previously been overwhelmingly affected by environmental interference, with comparable efficiency as the other components. The ferrite shield resulted in a more comprehensive characterization of the fMCG signal and, therefore, offers a practical and cost-effective alternative to enhance the OPM-fMCG system.