Instrumentation For Biomedical Applications

The nature of sources of bioelectric and biomagnetic fields

“…The introduction of the SQUID (superconducting quantum interference device) (14) with its ability to detect magnetic fields of picotesla strength has given rise to a greatly extended interest in the measurement of magnetic fields of biological origin. The question as to whether such measurements contribute anything basically new relative to their electrical potential counterparts continues as a controversial question since first considered with respect to fields of cardiac origin.…”

“…13 are integrated over a volume containing all sources and if the divergence theorem is applied to the left-hand side then this integral must go to zero because J' is zero at the bounding surface. Consequently I r dI fr dv=-fJ7'.V(1/r)dV (14) and Eq. 12 can also be written (15) Eq.…”

An ultra-low-noise electrical-potential probe for human-body scanning

“…This noise (referred to the input) was 30 µV Hz −1/2 at 1 Hz. For most routine heart diagnostics this is sufficient, providing, as it does, a 30:1 signal-to-noise ratio for peak heart signals [5] (around 1 mV). However, the electrical potentials generated by the body can vary widely [5,6], with the generally accepted minimum (≈10 µV) arising from foetal heart action [5].…”

“…For most routine heart diagnostics this is sufficient, providing, as it does, a 30:1 signal-to-noise ratio for peak heart signals [5] (around 1 mV). However, the electrical potentials generated by the body can vary widely [5,6], with the generally accepted minimum (≈10 µV) arising from foetal heart action [5]. Hence, there is a clear need for a non-contact sensor with a noise level close to 1 µV Hz −1/2 at 1 Hz.…”