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Biomedical subjects

O Basset

Publications and source records attributed to O Basset.

6 recordsLinked to original sources
PubMed1998

Stereoscopic visualization of three-dimensional ultrasonic data applied to breast tumours.

OBJECTIVE: This paper presents a technique for stereoscopic visualization applied to three-dimensional (3D) ultrasonic breast data. METHODS: A motorized acquisition system has been designed to translate regularly a linear-phased array transducer, in order to provide a series of parallel echographic slices of the breast. During acquisition, the breast is compressed between a plane support and a plexiglass plate to avoid breast motion. A window in this plate provides access for ultrasonic exploration. From the series of cross-sectional scans, a 3D volume is formed by interpolation between the successive ultrasonic images. A stereoscopic computer-graphic method has been developed to visualize these 3D ultrasonic data. Two conical transparent projections of the volume are computed from two slightly different viewpoints. These two projections make up the stereoscopic pair. This pair is displayed on a stereoscopic monitor for the visualization of the 3D data with the depth dimension. RESULTS: The acquisition system and the method for computing the stereo-echograms were validated using an agar gel phantom. In vivo breast experiments were also performed. CONCLUSION: Visualization of stereo-echographic projections improves the perception of depth and shape of breast tumours.

Breast Diseases↗
PubMed1998

Multiresolution texture based adaptive clustering algorithm for breast lesion segmentation.

OBJECTIVE: A specific algorithm is presented for the automatic extraction of breast tumors in ultrasonic imaging. METHOD: The algorithm involves two-dimensional adaptive K-means clustering of the gray scale and textural feature images. The segmentation problem is formulated as a maximum a posteriori (MAP) estimation problem. The MAP estimation is achieved using Besag's iterated conditional modes algorithm for the minimization of an energy function. This function has three components: the first constrains the region to be close to the data; the second imposes spatial continuity; and the third takes into consideration the texture of the various regions. A multiresolution implementation of the algorithm is performed using a waveless basis. RESULTS: Experiments were carried out on synthetic images and on in vivo breast ultrasound images. Various parameters involved in the algorithm are discussed to evaluate the robustness and accuracy of the segmentation method. CONCLUSION: Including textural features in the segmentation of ultrasonic data improves the robustness of the algorithm and makes the segmentation result less parameter dependent.

Adenocarcinoma↗
PubMed1996

Spatial compounding in ultrasonic imaging using an articulated scan arm.

A spatial compounding system has been designed to improve the quality of B-mode echographic images. It consists of constructing an improved image from the combination of several different images of the same cross-sectional plane. The "final" image is constructed by the registration and the superposition of the "original" images. For this, the relative position in the space of the original images has to be known. The use of a localization articulated arm, on which the ultrasonic probe is fixed, makes this possible. The main advantages of the technique are, on one hand, the elimination of the acoustic shadows following a strong reflector structure and, on the other hand, the reduction of the speckle generated in echographic images. The method of reconstruction has been validated on agar gel phantoms and provides good accuracy. In vivo experiments on human beings have also been performed. Acoustic shadows caused by bones in cross-sectional images of the thigh and the arm are eliminated. All the contours of the femur and humerus can be observed in the final images. The reduction of speckle is shown in kidney images and the signal-to-noise ratio improvement is quantified as a function of the number of images involved in the reconstruction.

Agar↗
PubMed1993

Texture analysis of ultrasonic images of the prostate by means of co-occurrence matrices.

As speckle on ultrasonic B-scan may reveal information relative to tissue structure, the present work attempts to discriminate the various prostatic tissues (normal tissue, benign prostatic hypertrophy and cancer) by means of texture analysis. We select regions of interest by their homogeneous appearance. A pre-processing stage is required to obtain stationary samples. The method used measures the second-order statistics, namely co-occurrence matrices. Fairly good tissue signatures have been obtained with parameters derived from these matrices. Of 37 images processed, 78 percent of the samples were classified with success, which is a high score considering that the images cannot be discriminated visually. However, while such results are obtained when wide regions of interest are investigated (64 x 64 pixels), they are not as good with smaller sample sizes, i.e., when the pathological area is very small.

Humans↗
PubMed1991

Volume measurement by ultrasonic transverse or sagittal cross-sectional scanning.

A technique is described that provides an accurate estimation of the volume of an organ from its ultrasonic cross-sectional images. The technique is applied to two types of ultrasonic investigation, one providing transverse and the other sagittal images. The organ outline has to be traced on each scan. The computer first calculates the area and then the volume from the vector areas and the centroids of a series of sections. The technique has been tested with phantoms of various shapes and volumes made with agar gel. These experiments show that the error in the volume estimation is less than 10% and the variability of measurements is less than 2%.

Acoustics↗