Fig 2. PICSO calibration using phantom data.

(a) Total fluctuation level and the estimated thermal noise depend on the acquired spatial resolution and the preprocessing steps. The solid line represents the identity line (i.e., PICSO = 0). The solid black rectangle represents the results processed by motion correction (M) and field-map correction (F). Results with different levels of detrending (D) orders are denoted as D1, D2, and D3. The thermal noise and total fluctuation level showed identical changes when the detrending order was set as a cubic polynomial. (b) Corresponding time series without detrending and with different detrending orders among the four acquired voxel sizes. Time series processed without detrending and processed with the first, second, and third detrending orders are represented by the black, red, blue, and green lines, respectively. The numbers that appear on the left side of the time series represent the average signal intensity. Each line space indicates an intensity increment of 10.