Équipe de Recherche VisAGeS

Pierrick Coupé

Contact

Email :
Address: IRISA / INRIA Rennes
Campus Universitaire de Beaulieu
35042 Rennes cedex - France
Tel: +33 2 99 84 22 31
Fax: +33 2 99 84 71 71
Assistant : +33 2 99 84 22 52 ()

Background and Position

Graduated from UTC in biomedical engineering (2003).

MS in Image Processing, Rennes I University (2004).

Since October 2004, I have been working as a PhD student on non-rigid registration of freehand 3D ultrasound with MR images.
My supervisors are Christian Barillot and Pierre Hellier (VisAGeS Team).

Research Areas

Multimodal registration of Intraoperative US and Preoperative MR images - Patent N° 07/02386

The registration of intraoperative Ultrasound (US) with preoperative Magnetic Resonance (MR) images is a challenging problem due to the difference of information contained in each image modality. To overcome this diffculty, we introduce a new probabilistic function for similarity measurements based on the mean curvature of MR isophots and US hyperchogenic structures. (pdf, html)

Left : registration given by the neuronavigation system. Right : results after correction with our registration approach. In this case, the acoustic shadow artifact was present on the US image. The signal below the lesion was totally dark. The proposed approach allowed to overcome these artifacts without specific detection of the shadows.

Denoising based on an Optimized Non Local Means filter - Software MONADE

here

For 3D MR imaging

One critical issue in the context of image restoration is the problem of noise removal while keeping the integrity of relevant image information. Denoising is a crucial step to increase image conspicuity and to improve the performances of all the processings needed for quan- titative imaging analysis. The method proposed in this paper is based on an optimized version of the Non Local (NL) Means algorithm. This approach uses the natural redundancy of information in image to remove the noise. (pdf, html)

From left to right: Original image, denoised image, and difference image centered on 128. The whole image is shown on top, and a detail is exposed on bottom.

For 3D ultrasound imaging

In ultrasound (US) imaging, preprocessing is necessary to improve the performances of quantitative image analysis techniques. A 3D version of the Non Local (NL) Means filter adapted for US images has been proposed. Originally developed for Gaussian noise removal, a Bayesian framework is used to optimize the NL means filter for the US noise model.

Results obtained with the proposed filter on a complete intraoperative brain image. The filter enhances the edges (lesion, sulci or cerebral falx) while preserving the image structures.

3D reconstruction of intraoperative freehand ultrasound - Software TULIPE

3D freehand ultrasound imaging produces a set of non parallel B-scans which are irregularly distributed in the space. Reconstruction amounts to computing a regular lattice volume and is needed to apply conventional computer vision algorithms like registration. We propose a new 3D reconstruction method taking explicitly into account the Probe Trajectory (PT). (pdf, html)

In order to underline the revelance of Probe Trajectory information in the interpolation process, we compare PT method with two other classical methods: Voxel Nearest Neighbor (VNN) and Distance Weighted (DW) interpolation.



Zoom on hepatic vessels extracted from liver reconstruction. From left to right the VNN, DW and PT methods. The images are extracted from 3D volume along the temporal axis (z) in order to under-light inherent artifacts of the VNN (i.e. discontinuities) and the DW (i.e. blur) methods.

Freehand ultrasound for Image Guided Neurosurgery and Brain shift analysis

2D ultrasound sequences of B-scans are acquired during neurosurgical procedures after the craniotomy. After a reconstruction step, the 3D ultrasound volume is used to compensate for the brainshift via a US/MR registration.

Left: 3D reconstruction of intraoperative freehand ultrasound images. Right: Corresponding preoperative MR image. The cerebral falx and the low-grade glioma appear in withe in US and in gray in MR image.