38 research outputs found
Optical Magnetometer Array for Fetal Magnetocardiography
We describe an array of spin-exchange relaxation free optical magnetometers
designed for detection of fetal magnetocardiography (fMCG) signals. The
individual magnetometers are configured with a small volume with intense
optical pumping, surrounded by a large pump-free region. Spin-polarized atoms
that diffuse out of the optical pumping region precess in the ambient magnetic
field and are detected by a probe laser. Four such magnetometers, at the
corners of a 7 cm square, are configured for gradiometry by feeding back the
output of one magnetometer to a field coil to null uniform magnetic field noise
at frequencies up to 200 Hz. Using this array, we present the first
measurements of fMCG signals using an atomic magnetometer
Ultrasensitive Atomic Magnetometers
We have developed a novel, small-volume portable single-channel atomic biomagnetometer and have used it to detect
adult MCG signals. The cryogenic-free magnetometer has sufficiently high sensitivity (20 fT/rt(Hz)) that it is fetal
MCG capable. It detects two magnetic field components simultaneously and has a bandwidth of typically 50-100 Hz.
Extensions to multiple channels will be described
Contribution of Fetal Magnetocardiography to Diagnosis, Risk Assessment, and Treatment of Fetal Arrhythmia
Background Fetal echocardiography has been the mainstay of fetal arrhythmia diagnosis; however, fetal magnetocardiography (fMCG) has recently become clinically available. We sought to determine to what extent fMCG contributed to the precision and accuracy of fetal arrhythmia diagnosis and risk assessment, and in turn, how this altered pregnancy management. Methods and Results We reviewed fMCG tracings and medical records of 215 pregnancies referred to the Biomagnetism Laboratory, UW‐Madison, over the last 10 years, because of fetal arrhythmia or risk of arrhythmia. We compared referral diagnosis and treatment with fMCG diagnosis using a rating scale and restricted our review to the 144 subjects from the tachycardia, bradycardia/AV block, and familial long QT syndrome categories. Additional fMCG findings beyond those of the referring echocardiogram, or an alternative diagnosis were seen in 117/144 (81%), and 81 (56%) were critical changes. Eight (5.5%) had resolution of arrhythmia before fMCG. At least moderate changes in management were seen in 109/144 (76%) fetuses, of which 35/144 (24%) were major. The most diverse fMCG presentation was long QT syndrome, present in all 3 referral categories. Four of 5 stillbirths were seen with long QT syndrome. Nine fetuses showed torsades de pointes ventricular tachycardia, of which only 2 were recognized before fMCG. Conclusions FMCG has a significant impact on prenatal diagnosis and management of arrhythmias or familial arrhythmia risk, which cannot be fully met by existing technology. The combination of fMCG and fetal echocardiography in fetal care centers will be needed in the future to optimize care
Linear minimum mean-square error filtering for evoked responses: Application to fetal MEG
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