Biomedical subjects

E Maurincomme

Publications and source records attributed to E Maurincomme.

10 recordsLinked to original sources

PubMed1998

Artifacts in intravascular ultrasound imaging during coronary artery stent implantation.

Intravascular ultrasound imaging is able to provide direct images of the stent meshwork. However, a paradoxical question remains unanswered: Why is it not possible to correct or prevent implantation defects by ultrasound-guided implantation? We postulate that these discrepancies are due to image artifacts. We performed an in vitro experiment allowing detection, physical characterization, and computerized simulations of the various aspects of these artifacts. The width of the echo of a strut is variable, dependent on its distance from the transducer. The stent strut echo orientation is variable, and depends on the position of the transducer inside the stent. The stent contour image depends on the position of the transducer. In conclusion, knowledge of these stent intravascular ultrasound image artifacts enabled us to discriminate accurately between artifacts and real stent implantation defects, and are indispensable for accurate qualitative and quantitative analyses of stents.

Arteries↗

PubMed1998

Evaluation of an automatic intraluminal edge detection technique for intravascular ultrasound images.

Intravascular ultrasound (IVUS) imaging enables detailed analysis and precise measurements of vascular cross-sections. However, to achieve a reduction in the existing level of observer variability requires the development of quantitative IVUS. We have developed a fully automatic intraluminal edge detection technique, based on adaptive active contour models and called ADDER (adaptive damping dependent on echographic regions) that allows the quantitation of the intraluminal cross-sectional area (ICSA). Using a 30-MHz mechanically rotated transducer mounted at the tip of a 3.5-F catheter, 58 normal and pathologic arterial segments (from coronary, renal, splenic, iliac, and carotid arteries) were imaged in vitro. These images were analyzed by 2 experts, E1 and E2, who manually traced the intraluminal contour twice for each image, as well as with ADDER. Intra-observer variabilities for ICSAs were found to be excellent (-1.454 +/- 3.51% for E1, 0.96 +/- 5.4% for E2). The inter-observer variability was 2.1 +/- 4.3%. The success factor for ADDER was 89%. Its intra-observer variability was null, as the method always finds a unique contour. The correlation between the automatically detected ICSA and the manual ICSA was: r = 0.99 (y = 1.03x + 0.89 mm2). Morphometric variations between manually and automatically traced contours, analyzed by the centerline method, were 100 +/- 140 mm on average. In conclusion, the ADDER automatic contour detection applied to IVUS images is robust and characterized by small systematic and random errors; therefore, quantitative IVUS is a useful tool in clinical research trials.

Blood Vessels↗

PubMed1997

X-ray angiography in stereotactic conditions: techniques and interest for interventional neuroradiology.

This paper reports work in progress on X-ray angiography acquired under stereotactic conditions. The objective is to be able to match multimodality images (typically MRI and X-ray) without a stereotactic frame but with stereotactic precision. We have identified potential problems and have studied them in detail. We conclude that, although the overall application is feasible, much work remains to be done on the estimation of the X-ray system conic projection and on automatic matching based on vascular structures.

Angiography, Digital Subtraction↗

PubMed1996

Clinical experience with stereotactic digital subtraction angiography with distortion correction software.

Recently developed software for correction of the geometric distortion in digital subtraction angiography was tested clinically. Localization and subsequent radiosurgical treatment of intracranial arteriovenous malformations was undertaken in 60 patients. During each angiographic series, a series of grid images was also acquired. All images were transferred to a workstation where the grid images were compared to a previously stored ideal image of the grid. A distortion correction was then performed on the grid images. The same pixel-by-pixel correction was applied to the respective angiographic images. The target was outlined on corrected subtracted images on the monitor. The outlined regions of interest and reference points were transferred to another workstation for dose planning, and the treatment was subsequently executed in the Gamma Knife unit. The clinical applicability of the distortion correction program was tested and possible sources of error examined. The experience gained is being used for further development of the software and for smoother data management and reduction of the processing time.

Adolescent↗

PubMed1995

Automated contour detection and acoustic quantification.

Echocardiographic left and right ventricular sequences are usually interpreted visually, but current quantitation techniques have been found to be tedious, time-consuming and associated with significant inter- and intra-observer variabilities. In an attempt to eliminate these problems, we have developed the Echocardiographic Analysis System (EAS) which uses robust automated border detection techniques both for single frames as well as for sequences. Comparison of LV cross-sectional area with the semi-automated border detection (AUTO) and those assessed from manual tracings (MAN) yielded a systematic difference (MAN-AUTO) of -6.6% (p < 0.001), and a random difference (standard deviation of paired signed differences) of 11.8%. Current developments are directed towards real-time automated border detection with an Accelerator board, integration of Acoustic Quantification (AQ) data as edge information into EAS, and intravascular echocardiographic applications.

Computers↗

PubMed1994

3D display of high resolution vertebral structure images.

In this paper we present a methodology for three-dimensional representation of vertebral structures. A set of X-ray CT images is obtained on a specific high resolution acquisition system. The images are then segmented in order to separate trabecular and cortical structures. Finally, the complex 3D surfaces are visualized using a volume rendering technique.

Humans↗

PubMed1994

[Artefacts and intravascular ultrasonography. Analysis and implications for a better reliability in the interpretation of images and measurements].

Intravascular ultrasound catheters provide cross-sectional images of vessel walls and surrounding tissues with rotating transducers, and the behavior of ultrasound in heterogeneous media both cause degradation of image quality. Qualitative and quantitative analyses of in vivo studies are operator-dependent and limited by artifacts. We investigated these limitations by an in vitro study on plexiglass phantoms and segments of fresh arteries. We observed, analyzed and interpreted the most specific reasons for image artifacts: geometric distortions, the point spread function of the imaging system and the near field effects. Various practical implications have resulted from this study. Knowledge of the most obvious pitfalls will enable the user to obtain maximum benefits from intravascular ultrasound imaging, and to appreciate its limitations.

Arterial Occlusive Diseases↗

PubMed1993

Artifacts in intravascular ultrasound imaging: analyses and implications.

The ability of an intravascular ultrasound catheter to give cross-sectional images of vessel walls and surrounding tissues, and the behavior of ultrasound in heterogeneous media, are at the origin of degradation of image quality. Qualitative and quantitative analyses of in vivo studies are then operator-dependent and are limited by artifacts. We investigated these limitations by an in vitro study on plexiglass phantoms and segments of fresh arteries. We used a 20 MHz transducer mounted on the tip of a 4.8 F catheter and an interventional ultrasound system. The ultrasound beam is reflected onto the rotating transducer at 600 rotations per minute (RPM), creating 360 degrees real-time images (10 images/second). We then observed, analyzed and interpreted the most specific reasons for image artifacts: geometric distortions, multiple echoes, the point spread function (PSF) of the imaging system, near-field effects, "petal-shaped" effect, and ultrasound speckle. Various practical implications have resulted from this study. Only a thorough knowledge of how to avoid some of the most obvious pitfalls will enable the user to obtain maximum benefits from intravascular ultrasound imaging, and to appreciate its limitations.

Arteries↗

PubMed1993

[Intravascular echographic imaging: experimental validations and limits. An in vitro study].

Intravascular ultrasound is a new method of visualizing details of vascular pathology, providing (real time) high resolution images of vascular walls. Most of the research on the technique has explored its qualitative and quantitative capabilities to improve the assessment of atherosclerotic vascular disease in vivo. Intravascular ultrasound differs from angiography and angioscopy in its ability to penetrate below the surface of the vessel lumen, demonstrating specific appearances of the distribution and composition of plaque. Image analysis is operator dependent. Although this technology is very promising limitations such as artefacts and loss of image quality in heavily calcified vessels hinder its use. There is hope that this imaging technique may ultimately improve the results of endovascular interventions.

Arteries↗

PubMedDate not supplied

3D display of high resolution vertebral structure images.

A methodology for three-dimensional (3D) representation of vertebral trabecular structures was proposed. A set of X-ray CT images was obtained using a specific high resolution acquisition system. The images were then segmented in order to separate trabecular and cortical bone structures. Finally, the complex 3D surfaces were visualized using a volume rendering technique.

Computer Graphics↗