Figure 6.

(A) A representative subject with noticeable ringing artifact is illustrated. (B) Each axial slice of the ring-mask was collapsed into a (C) noise-vector. The noise-vector is equal to the median non-zero voxel for each column of voxels of the ring-mask, as in Equation (8). (D) The noise-vector difference is equal the absolute value of the difference between shifted versions of the noise-vector, where $C=\frac{|A-B|}{20}$, as in Equation (10). The feature ASF2 was computed as the max of the sum of the noise-vector difference as in Equation (11). This procedure is illustrated for a representative axial slice, z = 57.