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Feasibility of motion estimation and tracking in portal images during treatment of pulmonary cancers by conformal radiotherapy

Orkisz M., Frery A., Durning B., Chapet O., Magnin I.

Image Processing & Communications

2001

Vol. 7, no 3-4

63-76

Medical objective of this work is to compensate tumor's displacements due to free breathing, so as to reduce the irradiated zone and thus preserve healthy tissues. For this purpose, we are studying the feasibility of tracking the tumor's motion in portal images, i.e. in images generated by the treatment beam (high-energy X-rays). Two reference algorithms were tested on sequences of portal images of a phantom and of patients. Target tracking algorithm (block-matching), was able to correctly track the target only when the tumor was perceptible in the images. Otherwise it would require implanting of radioopaque markers in tumor's vicinity. Optical flow estimation was expected to deduce "invisible" tumor's displacements from the motion of neighboring tissues. However, the standard Horn & Schunck's algorithm gave poor results because of low contrast and absence of texture in the images. We are suggesting a modified version of this approach, based on intersections of motion constraint lines for a limited number of pixels carrying reliable and complementary motion information.

Advances of blood vessel morphology analysis in 3D magnetic resonance images

Orkisz M., Hernandez-Hoyos M., Douek P., Magnin I.

Machine Graphics and Vision

2000

Vol. 9, No. 1/2

463-471

We deal with image processing applied to 3D analysis of vascular morphology in magnetic resonance angiography (MRA) images. It is, above all, a state-of- the-art survey. Both filtering and segmentation techniques are discussed. We briefly describe out most recent contribution: an anisotropic non-linear filter which improves visualization to small blood vessels. Enhancement of small vessels is obtained by combining a directional L-filter applied according to the locally estimated orientation of image content and a 2D laplacian orthogonal to this orientation.