Figure 4.

Measured and predicted standard deviations of the sum (top row) and mean (bottom row) of an ROI as a function of the number of pixels in the ROI as it grows along the readout direction in an image with reduced effective resolution in the phase encoding direction. The solid line is the predicted standard deviation from the proposed method, the dashed line is the calculated standard deviation from 100 repeated experiments, and the dotted line is the calculated standard deviation from 100 pseudo replica reconstructions. The gray dotted line on the magnitude plots indicates the predicted standard deviation when assuming that all pixels are independent. The gray circle highlights the initial region of the curve where the actual standard deviations deviate from the gray line since even an ROI with length 1 has dependencies between the pixels. This should be compared to Fig. 5 where the pixels of an ROI with length 1 are actually independent.