Atomic Magnetometer for Fetal Biomagnetism

The goal of this study is evaluation of our atomic magnetometer for adult and fetal MCG studies. The investigators will assess the signal-to-noise and bandwidth performance under human acquisition conditions. They will also gain experience with the practical issues associated with making the measurements on human subjects.

The measurement sessions will take place in the magnetically shielded room in the UW Biomagnetism Laboratory, where similar studies have been made with SQUID detectors for more than 20 years, without incident. The room contains a bed and/or chair on which the subject may comfortably lie or sit.

The subject will remove all metal and magnetic objects (e.g. watches, glasses, jewelry, coins) and change into metal-free clothing. The subject will put on laser eye protection goggles. The subject will lie or sit on the patient bed in the magnetically shielded room with his or her chest (or stomach in the case of a pregnant mother) as close as possible to the magnetometer (typically 1 cm away), and will be monitored closely through a small opening in the shielded room to ensure comfort throughout the study. Positioning of the device with respect to the patient will be done by one of the researchers. In the case of pregnant women, an ultrasound will be taken to ascertain the position of the baby and facilitate initial positioning of the magnetometer. Depending on need for possible further positioning, the researcher may or may not leave the room after device positioning. The subject will be asked to remain still during data acquisition. (Should the subject become uncomfortable or simply need to move around, he or she will have complete freedom to do so and that particular measurement will be terminated.) Visual and audio contact with the subject will be maintained at all times via an open window in the magnetically shielded room. Using the atomic magnetometer, up to five-minute MCG recordings will be made at several locations in order to map the signal. The recordings will be analyzed off-line. An MCG or fMCG may also be recorded with Dr. Wakai's commercial Magnes and Tristan SQUID magnetometers, using similar acquisition parameters and processing procedures as for the AM. The purpose of the SQUID measurement is to compare the attained waveforms. Processing procedures for the SQUID data are identical to the atomic magnetometer data.

A typical recording session will consist of about 10 minutes for magnetometer alignment and optimization, followed by several 5-minute magnetometer acquisition periods separated by rest breaks during which the subject can relax and preliminary data analysis will be conducted by the researchers. The session may be completed by a SQUID measurement, requiring an additional 15 minutes, and by a brief exit interview to see if the subject had any comfort issues that were not identified during the session. The total recording session will take up to 2 hours .