Biomedical subjects

V Daanen

Publications and source records attributed to V Daanen.

4 recordsLinked to original sources

PubMed2000

MR-guided balloon angioplasty of stenosed aorta: in vivo evaluation using near-standard instruments and a passive tracking technique.

The purpose of this study was to assess the feasibility of magnetic resonance (MR)-guided balloon angioplasty of a stenosed aorta on an open low-field magnet using a passive tracking technique. Visualization of vessels and position of instruments were realized by using a fast low-angle shot (FLASH) sequence. Catheters and guidewire were prepared for susceptibility-based MR visualization. Standard balloon catheters were inflated with diluted gadolinium, and nitinol guidewires were modified by incorporation of iron oxide markers into their walls. After validation on a flow phantom, balloon angioplasty was performed on an in vivo model of arterial stenosis. Creation of abdominal aorta stenosis was realized in five piglets. MR-guided balloon angioplasty of the aorta was performed with success in all but one. In one of them, stent implantation was achieved in the descending aorta. Balloon angioplasty using a passive tracking technique is a simple concept that can be realized with near-standard instruments and any MR imaging system. This represents an advance toward MR-guided vascular interventions in the future.

Angioplasty, Balloon↗

PubMed2000

Accurate localization of needle entry point in interventional MRI.

In interventional magnetic resonance imaging (MRI), the systems designed to help the surgeon during biopsy must provide accurate knowledge of the positions of the target and also the entry point of the needle on the skin of the patient. In some cases, this needle entry point can be outside the B(0) homogeneity area, where the distortions may be larger than a few millimeters. In that case, major correction for geometric deformation must be performed. Moreover, the use of markers to highlight the needle entry point is inaccurate. The aim of this study was to establish a three-dimensional coordinate correction according to the position of the entry point of the needle. We also describe a 2-degree of freedom electromechanical device that is used to determine the needle entry point on the patient's skin with a laser spot.

Biopsy, Needle↗

PubMed1999

Automatic quality assessment protocol for MRI equipment.

The authors have developed a protocol and software for the quality assessment of MRI equipment with a commercial test object. Automatic image analysis consists of detecting surfaces and objects, defining regions of interest, acquiring reference point coordinates and establishing gray level profiles. Signal-to-noise ratio, image uniformity, geometrical distortion, slice thickness, slice profile, and spatial resolution are checked. The results are periodically analyzed to evaluate possible drifts with time. The measurements are performed weekly on three MRI scanners made by the Siemens Company (VISION 1.5T, EXPERT 1.0T, and OPEN 0.2T). The results obtained for the three scanners over approximately 3.5 years are presented, analyzed, and compared.

Image Processing, Computer-Assisted↗

PubMed1999

[Interventional MRI. Analysis of data and prospects].

In spite of its many advantages: 3D imaging, improved tissue characterization, and lack of ionizing radiation, interventional MRI remains seldom used. Several factors are involved. The purpose of this paper is to analyze the factors preventing or slowing the development of this technique based on a review of data from the literature, work presented at the second symposium on interventional MRI (Düsseldorf, 1997), and our own experimental data. The following elements will be discussed: difficulties related to image quality and open magnets, control of targeted image acquisitions, MR environment and problems related to asepsis, as well as advances of other techniques. Finally, short-term and mid-term perspectives will be presented. These are related to the goals of the technique: open or short bore closed magnets? MR unit installed in a radiology department? MR unit dedicated to interventional procedures only or mixed diagnostic-interventional unit? interventional MR unit placed in a neurosurgery operating room? interventional MR unit installed in a general surgery operating room?

Analgesia↗