HTS magnetometers for fetal magnetocardiography

Area of Science:

• Biophysics
• Medical Instrumentation
• Cardiology

Background:

• High temperature superconducting (HTS) SQUID sensors offer magnetic field sensitivity suitable for adult magnetocardiography (MCG).
• Fetal MCG (fMCG) presents challenges due to significantly smaller signal amplitudes compared to adult MCG.
• The performance of HTS SQUID systems for fMCG applications requires thorough evaluation.

Purpose of the Study:

• To assess the performance of a prototype HTS SQUID system for fetal magnetocardiography.
• To compare the HTS SQUID system's capabilities against a traditional low temperature superconducting (LTS) SQUID system.
• To determine the feasibility of using HTS SQUID technology for clinical fMCG measurements.

Main Methods:

• Utilized a prototype HTS SQUID system comprising three vertically-aligned HTS dc-SQUID magnetometers in a liquid nitrogen dewar.
• Configured the system to form axial gradiometers (short/long baseline) and a second-order gradiometer via electronic subtraction.
• Conducted simultaneous recordings on adult and fetal subjects using both the HTS SQUID and a LTS SQUID system.

Main Results:

• The HTS SQUID system demonstrated sufficient sensitivity to resolve fMCG signals in most near-term subjects.
• Achieved calibrated magnetometer sensitivities at 1 kHz: 109 fT/√Hz, 155 fT/√Hz, and 51 fT/√Hz.
• The HTS SQUID system exhibited a relatively low signal-to-noise ratio for fMCG and necessitated operation within a shielded room.

Conclusions:

• The prototype HTS SQUID system shows promise for fMCG but requires further optimization to improve signal-to-noise ratio.
• Current limitations include the need for a shielded environment, restricting its immediate use outside specialized facilities.
• Further development is necessary to enhance the HTS SQUID system's practicality and performance for routine fMCG applications.