- Zero-crossings of the laplacian (Haralick's definition)
- Maxima of the gradient modulus in the gradient direction (Canny-Deriche's definition)
- others (see the huge related literature)

The edge detection is performed in 2D on each sagittal slice, and the results are collected to form a 3D volume. Edges are superimposed on the original 3D MR data volume. One may notice that the collection of 2D edges is not coherent along the third dimension.

On the other hand, 3D edges look nicer.

Original image |
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Edge detection with Deriche's recursive filter (~ exp(-alpha |x|) ) | ||
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%test-edges-pnm greg-rmn.pgm greg-rmn.a=alpha.ppm -a alpha
| ||

alpha=0.5 | alpha=1.0 | alpha=1.5 |

Edge detection with a recursive approximation of the Gaussian | ||
---|---|---|

%test-edges-pnm greg-rmn.pgm greg-rmn.s=sigma.ppm -s sigma
| ||

sigma=1.0 | sigma=2.0 | sigma=5.0 |

Hysteresis thresholding on previous results (edge detection with a recursive approximation of the Gaussian) | ||
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low threshold = 10, high threshold = 20, minimal size of connected component = 30 | ||

%test-hyster-pnm greg-rmn.s=sigma.ppm greg-rmn.s=sigma.lt=10.ht=20.ms=30.ppm -lt 10 -ht 20 -ms 30
| ||

sigma=1.0 | sigma=2.0 | sigma=5.0 |

Grégoire Malandain Last modified: Mon Feb 12 15:12:45 MET 2001