Figure 5.

Isotropic tissue with unipolar stimulus. (a) The ROC calculated from Eq. (11) (4E method) as a function of distance from the stimulus along the vertical line shown in inset (arrows indicate the direction and distance measured from the stimulus site in unit of nodes). Measurements are made using the DF (blue line), LS (green circles), and our method (4E, red squares). (b) Same as in (a) for points on a horizontal line as shown in inset, and (c) for points along line with equation y = 0.7x − 20 from the stimulus site as shown in inset. (d) Values of the conduction velocity (m/s) are measured using the empirical and 4E methods for points along the line shown in inset (node position is represented by node number on vertical or horizontal line in the direction of the arrow). (e) Similar to (d), conduction velocity is measured for points along a horizontal line as shown in inset, and (f) for points on a line with equation as in (c). Close to the unipolar stimulus and by the edge of the tissue, data becomes poorly correlated because activation times and wave fronts are perturbed by edge effects (tissue size is 200 × 200 nodes with a space step of 0.05 mm).