Requested metric: respiratory-volume-per-time #1
Description
Respiratory-volume-per-time (RVT) is a "breath-to-breath metric of respiratory variation," and can be used to generate a regressor for denoising fMRI data.
First, peak detection was used to determine the maximum and minimum for each breath. The time series of maxima and minima (max(t) and min(t)) were then interpolated to the imaging TR. A time series of the breathing period (T(t)) was determined by taking the time difference between successive maxima, assigning the resulting value to the midpoint between the successive maxima, and interpolating the resulting time series to the imaging TR. The final RVT time series was then computed as RVT(t) = (max(t) − min(t))/T(t).
A relevant metric is RPV convolved with a respiratory response function:
In addition, RVT(t) was convolved with the RRF (Birn et al., 2008), forming a separate waveform (RVT*RRF(t)).
RVT*RRF is also often lagged when used to denoise fMRI data.