In our use of the carbon wire loops (CWLs) for cleaning the EEG we have encountered three situations. In some subjects both the AAS and the carbon wire loops methods perform well, yielding a good quality EEG. In another subset of subjects, the carbon wire loops is preferred. These are typically cases in which there are movement artifacts, or poor quality signals in general. As shown in figure 4, in some of these cases the AAS results could be improved by manually correcting the timing of the pulses, but this is a time-consuming step. In cases where there are movement artifacts, only the carbon wire loops method is able to correct them. Finally, in about 25% of the patients, the results of the carbon wire loops correction are ambiguous, and the AAS method is also run to decide if some of the possible events are due to incomplete deletion of movement artifacts, as shown in figure 3.
We compared two different algorithms for implementing the EEG cleaning based on the carbon wire loop signals. Both had typically a good performance, so we chose the one in which the estimation of the parameters was not iterative, to avoid the chance of divergence that could theoretically result in noise being added to the signal. The chosen algorithm (van der Meer., 2016) was also the fastest.
In conclusion, we have a very favorable impression of the carbon wire loop correction. The EEG looks cleaner than when corrected with the AAS method, and in most of the subjects this correction is sufficient for our measurements at 3 T. This translates in an important reduction in reviewing time, since the AAS algorithm requires a visual verification, and possible correction, of the automatic detections of EKG peaks. This time-consuming step is no longer necessary most of the time. Another thing to note, is that there are no significant drawbacks associated with the carbon wire loops.