Michel Jourlin

A new minimum variance region growing algorithm for image segmentation

Abstract Region growing is a very useful technique for image segmentation. Its efficiency mainly depends on its aggregation criterion. In the present paper, a new algorithm is proposed with a homogeneity criterion based on an adequate tuning between spatial neighbourhood and histogram neighbourhood. It differs from other techniques by reconsidering the pixel (or voxel) assignments on each step by a process which minimizes variance through special dilations. Thus, the region created by an initial seed can be non-connected and possibly does not contain this seed. Examples are given in dental surgery for 2D X-Ray images (and their associated 3D block) and for 3D images acquired by the Morphometre, the new 3D scanner constructed by GEMSE (General Electric Medical Systems).

Image dynamic range enhancement and stabilization in the context of the logarithmic image processing model

Abstract Images of a scene observed under a variable illumination or with a variable optical aperture are not identical. Does a privileged representant exist? In which physical setting? In which mathematical context? With which meaning and criterion? How to obtain it? The authors answer to such questions in the physical setting of logarithmic imaging processes. For such a purpose, they use the logarithmic image processing (LIP) model, known to be a compatible mathematical framework. After short recalls on this model, the paper presents two image transforms: one performs an optimal enhancement and stabilization of the overall dynamic range, and the other does of the mean dynamic range. The results obtained on X-ray images, as well as for some natural scenes, are shown. Also the implementation of the transforms is addressed.

LIP‐model‐based three‐dimensional reconstruction and visualization of HIV‐infected entire cells

This paper presents a global solution from acquisition to visualization for the three‐dimensional reconstruction of cell sections. Original techniques are proposed for the correct handling of the geometrical section distortions, and a new interpretation based on the logarithmic image processing (LIP) model is applied in order to create normalized grey‐level sections where these are missing. Finally, a new method for generating a mesh of triangles to describe the envelope of the reconstructed cell is proposed, as well as a visualization mixing image synthesis and grey‐level information. The product allows the user to explore the reconstructed cellular block in any desired direction, by showing user‐defined grey‐level sections inside the block mixed to a synthetic view of the cell envelope.

Criteria for the assessment of intrinsic performances of digital radiographic intraoral sensors

RATIONALE AND OBJECTIVES In sensor-based dental digital radiographic imaging systems, it should be possible to assess the intrinsic performance of the sensor by means of objective criteria, independent of the related electronic hardware and image-treatment software. METHODS Six criteria are presented and discussed for the objective assessment and quantification of the intrinsic performance of intraoral sensors for dental digital radiography, independent of the characteristics of the subsequent image-treatment software. The criteria are signal-to-noise ratio, blooming, sensitivity, spatial uniformity, modulation transfer function, and geometric deformations. These criteria have been used to evaluate the Visualix sensor. RESULTS For each criterion, a series of numerical data are presented as graphs. CONCLUSION A method is proposed for objective assessment of radiographic sensors that makes it possible to compare sensors with each other and with conventional radiographs. The criteria proposed also increase understanding of digital diagnostic images and improve their clinical use.

Polymer molding simulation : a mathematical imaging approach based on propagation of discrete distances

Abstract A new approach to polymer molding simulation is presented, based on a mathematical imaging algorithm (F. Darsonville, P. Michoud, G. Courbebaisse, M. Jourlin, R. Favier, J.C. Charpentier, Entropy Revue 206 (1998) 61–64). A model is elaborated using discrete propagation of distances as a tool to simulate dynamic injection. The present objective involves the examination of this approach based on mathematical metrics. This paper concerns recent progress in the formulation of this problem.