Toward a content-based watermarking scheme

Image watermarking consists in embedding an unnoticeable and indelible mark inside a digital image. Watermarking technologies aims at solving copyright and integrity problems. Nevertheless classical geometrical transforms generally induce a loss of synchronization that prevent the detection of the mark. We propose in this paper a content-based watermarking scheme that uses a feature point detector to link the mark with the content of the image. In this scheme, feature point detection is followed by a triangular tessellation and the signature is embedded in each triangle of the partition. Our results show that the presented scheme is robust to local geometrical transforms and attacks such as Stirmark.Le tatouage d'images consiste à insérer une signature invisible et indélébile dans une image. Il permet de répondre à des problèmes de droit d'auteur ou d'intégrité. Les transformations géométriques peuvent cependant provoquer une perte de synchronisation et ainsi empêcher la détection de la signature. Nous proposons une méthode de tatouage fondée sur le contenu qui utilise un détecteur de points d'intérêts pour lier la signature au contenu de l'image. La détection de point d'intérêts permet de créer une partition triangulaire et la signature est ensuite insérée dans chacun des triangles. Nos résultats montrent que la méthode présentée est robuste aux déformations géométriques tels que Stirmark

Registration and visualization of transcranial magnetic stimulation on magnetic resonance images

We propose a method for the registration of MRI brain images with the physical space. Points on the patients scalp are acquired using a magnetic-field digitizer. The registration transform is the rigid transform that minimizes the mean square distance between those points and the scalp surface segmented from the MRI. The distance to the scalp surface is effciently computed using a 3d Euclidean distance transformation. We apply this method to the visualization of transcranial magnetic stimulation and show that results are precise (4mm) and reproducible (1mm)

Simultaneous Registration and Bias Correction of Brain Intra-operative MR Images

Intra-operative MR imaging is an emerging tool for image guided (neuro)surgery. Due to the small size of the magnets and the short acquisition time, the images produced by such devices are often subject to distortions. In this work, we show the particular case of images provided by an ODIN device (Odin Medical Technologies, Newton, MA 02458, USA). Such images suffer from geometric distortions and an important bias field in the luminance. In order to simultaneously correct these deformations, we propose to register a preoperative ODIN image with a diagnosis MR high resolution image while compensating the bias field

Performance-based financing as a health system reform : mapping the key dimensions for monitoring and evaluation

Peer reviewedPublisher PD