Biomedical subjects

J Rousseau

Publications and source records attributed to J Rousseau.

At least 37 records · Page 2Linked to original sources

PubMed1999

3D reconstruction of the cerebral arterial network from stereotactic DSA.

The authors present an automatic algorithm for 3D reconstruction of cerebral blood vessels by digital subtracted angiography. The patient is localized by a stereotactic method. The reconstruction algorithm includes two steps: first vessel extraction then 2D matching and reconstruction. Accurate vessel skeletons are generated by a combination of mathematical morphological algorithms and adaptive filters. The 3D reconstruction algorithm is based on the reconstruction of vessels center lines. For that purpose, three different projections of the vascular network are used. Reconstruction is computed segment by segment (a curved line between two nodes). For each segment point, the algorithm defines all epipolar solutions on the other views. These epipolar solutions are sorted and pooled by 2D continuity and 3D proximity criteria resulting in a 3D graph. Optimal 3D segment is defined by a recursive algorithm that looks up the better path in the 3D graph. The algorithms have been implemented on a Compatible-PC computer in C language. More than 95% of static copper phantom was reconstructed in 5 min and with 1 mm 3D accuracy. 70% of arteries (from carotid to the seventh node) of a true patient arterial network were reconstructed is less than 30 min.

Algorithms↗

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↗

PubMed1998

Design of a privileging program for diagnostic imaging: costs and implications for a large insurer in Massachusetts.

PURPOSE: To evaluate the results of a privileging program aimed to ensure that health care providers and facilities adhere to standards of care. MATERIALS AND METHODS: Technical and professional privileging applications were mailed to more than 1,800 diagnostic imaging facilities and more than 6,000 professional providers of services to members of a health care plan. Site inspections were used to determine whether facilities met standards of care. Specialty providers were assigned a range of current procedural terminology codes for which they had privileges to bill the payer. RESULTS: Of 1,004 imaging sites inspected, 197 (20%) failed with the ability to remedy the violation, 106 (10%) failed with fundamental and serious deficiencies, and 701 (70%) passed. Site inspection pass rates varied substantially by specialty. Chiropractors and podiatrists were more likely to fail than medical and surgical specialists. A strong correlation was found between refusal to participate in the inspection and failure rate. Results suggest that reduction of the number of professional claims billed led to a 2% decline in total imaging expenditures, or a more than 10:1 return on the cost of implementing technical and professional privileging programs. CONCLUSION: Health care plans can positively influence costs and quality by developing, monitoring, and enforcing their own quality standards for diagnostic imaging.

Blue Cross Blue Shield Insurance Plans↗

PubMed1997

Synthesis and tissue distribution of substituted [125I]iodophenylamine derivatives: possible brain imaging agents.

The synthesis and brain uptake in mice of the radioiodinated derivatives of N,N-dimethyl-N'-(iododimethoxyphenyl)-1,3-propanediamine, as well as the N-substituted derivatives of (iodoalkylphenyl)isopropyl, iodoalkylphenylethylamine and 3,4-(methylenedioxy)phenyl-amphetamine (MDA) are described. These compounds contain structural features of both IMP and HIPDM, the cerebral perfusion agents currently in clinical use. The radiolabeled analogs were obtained via the [125I]I exchange method, or by [125I]NaI treatment of the iodo-free precursor in the presence of an oxidant. Following intravenous injection in mice, all compounds showed important radioactivity concentrations in the lungs and kidneys. The N-substituted (iodoalkylphenyl)isopropyl and iodoalkylphenyl-ethylamine derivatives displayed a high initial brain uptake (> 10% IDg-1) followed by a rapid clearance phase, resulting in lower brain-to-blood ratios as those reported for IMP and HIPDM. In contrast, N,N-dimethyl-N'-(iododimethyphenyl)-1,3-propanediamine derivatives featuring the iodo substituent on the benzene carbon adjacent to the methyl amine group and the methoxy substituents on the 2,5- or 2,4-positions, showed low but more persistant brain uptake. Combined with fast blood clearance, this resulted in high brain-to-blood ratios at later time points. Among all compounds tested, the highest brain-to-blood ratio was observed with compound N,N-dimethyl-N'-(6-iodo-3,4-dimethyoxyphenyl)-1,3-propanediamine (27e), reaching a maximum of > 20 at 12 h post-injection.

Aniline Compounds↗

PubMed1997

Mutations that prevent associative learning in C. elegans.

The nematode Caenorhabditis elegans offers a promising system for the reductionist study of learning and memory. In this article, classical conditioning in C. elegans is demonstrated with a variety of associative learning assays. These assays allowed for the isolation and behavioral characterization of 2 mutant C. elegans lines impaired in associative learning. Both lines show no short-term or long-term associative conditioning; however, they appear relatively normal in tests of nonassociative learning and sensorimotor function. In combination with the well-described genetics and neuroanatomy of C. elegans, the isolation of mutants selectively, yet completely, blocked in associative learning provides the basis for an effective characterization of the cellular and molecular aspects of associative learning.

Animals↗

PubMed1997

Visuvalve software: an aid to the diagnosis of shunt failure.

Software designed to help the neurosurgeon in the diagnosis of shunt malfunction is presented. This software allows the possibility to record on a 3.5 diskette a patient's clinical information and four views of a CT scan performed when the patient was doing perfectly well with his shunt. This diskette, operated by MS-DOS on any IBM-compatible personal computer, can be read at any time, anywhere. The evaluation of the system demonstrated it was safe, with an excellent adhesion of the patients and of their families.

Cerebral Ventriculography↗

PubMed1997

Postoperative interstitial radiotherapy of keloids by iridium 192: a retrospective study of 46 treated scars.

BACKGROUND: Keloids are clinically vexacious scars characterized by a high recurrence rate after excision alone (50-100%). Many adjuvant techniques have been used with more or less convincing results. OBJECTIVE: The aim of this study is to show the efficiency of keloidectomy and postoperative interstitial radiotherapy by an iridium 192 wire. METHODS: During a 14-year period, 39 patients with keloids (46 keloids) were treated by this regimen. Seven patients had been previously treated by intralesional corticosteroids, surgery alone or postoperative interstitial radiotherapy, without improvement. A dose of 12 Gy (7 keloids) to 15 Gy (22 keloids) was delivered at a point 2.5 mm from the axis of the wire. For 17 keloids the dose schedule was 15 Gy at a point 5 mm to the wire. The median follow-up was 7 months. RESULTS: The overall success rate is close to 63%. A recurrence occurred in 14 cases without relation to the method used, the age or the localization of the lesions. There were no side effects observed. CONCLUSIONS: Postoperative interstitial radiotherapy represents an effective, unconstraining and safe treatment for keloids if the contraindications are respected.

Adolescent↗

PubMed1997

Assessment of image intensifier and distortion for DSA localization studies.

The authors present methods of correcting pincushion and S distortions of an image intensifier, and of measuring the geometrical parameters of the imaging device used for localization from digital subtraction angiography brain studies. Pincushion and S distortions of the image intensifier are corrected by a calibration grid. A test pattern is used to study effectiveness of the corrections. Intrinsic geometrical parameters (source-to-image distance, centre of X-ray projection) of the apparatus are measured by the use of a calibration phantom. Short-range and long-range time drift of the distortion, as well as influence of the parameters of image acquisition on the accuracy of the localization results, are considered. The results obtained successfully demonstrate the accuracy of the correction, provided that the apparatus is warm.

Angiography, Digital Subtraction↗

PubMed1997

[Determination of target volume for dosimetric planning in stereotactic radiosurgery].

Stereotactic radiosurgery needs an accurate determination of the target volumes to be irradiated and of sensitive volumes to be spared: position, external boundaries, internal volume. These parameters can be obtained by using either projection imaging (radiographs, digital angiography), or tomographic imaging (magnetic resonance imaging, computerized tomography). The authors describe the methods used in these different imaging modalities and the problems encountered in target determination. Methods of validations are described. Results obtained on phantoms and on actual target volume are given and discussed.

Humans↗

PubMed1996

Photodynamic therapy of tumours with hexadecafluoro zinc phthalocynine formulated in PEG-coated poly(lactic acid) nanoparticles.

Hexadecafluoro zinc phthalocyanine (ZnPcF16), a second-generation sensitizer for the photodynamic therapy (PDT) of cancer, was formulated in polyethylene-glycol-coated poly(lactic acid) nanoparticles (PEG-coated PLA-NP) and tested in EMT-6 tumour-bearing mice for its photodynamic activity. The tumour response was compared to that induced by the same dye formulated as a Cremophor EL (CRM) emulsion. Formulation in the biodegradable NP improved PDT response of the tumour while providing prolonged tumour sensitivity towards PDT.

Animals↗

PubMed1996

Hexadecafluorinated zinc phthalocyanine: photodynamic properties against the EMT-6 tumour in mice and pharmacokinetics using 65Zn as a radiotracer.

Hexadecafluorinated zinc phthalocyanine (ZnPcF16), an analogue of zinc phthalocyanine (ZnPc) in which all hydrogen atoms have been substituted by fluorine, was prepared as a single isomeric product via the condensation of tetrafluorophthalonitrile with zinc acetate. Fluorination renders the ZnPc soluble in most common solvents. The photodynamic properties and pharmacokinetics of the ZnPcF16 were evaluated in EMT-6 tumour-bearing Balb/c mice using 65Zn-radiolabelled analogues. Both dyes, administered i.v. at 1 mumol kg-1 as Cremophor emulsions, revealed good tumour uptake [approximately 8-9 per cent of the injected dose per g tissue (%IDg-1)] at 24 h post injection (p.i.), with the fluorinated dye reaching higher concentrations (approximately 11%IDg-1) at 48 h p.i. and subsequently higher tumour-blood ratios due to rapid blood clearance. ZnPcF16 at a dose of 5 mumol kg-1 (4.3 mg kg-1) induced complete tumour regression after phototherapy (24 h p.i., 650-700 nm band, 360 J cm-2, 200 mW cm-1). At a dose of 2 mumol kg-1 and phototherapy at 24 h p.i., the tumour volume doubling time increased to 11 days vs 6 days for the control tumours. A similar tumour growth delay was observed when phototherapy was conducted at 48 h or 72 h after dye injection implying that tumour response correlates with tumour dye concentrations rather than serum concentrations. As a result of its low solubility, the administered dose of ZnPc was limited to 1 mumol kg-1 and at this drug level significant tumour response was only observed when the dye was solubilised as the pyridinium salt. Isolation of the neoplastic cells after in vivo dye administration and in vitro exposure to red light followed by a colony formation assay showed that the ZnPcF16 exhibited a 1-2 order of magnitude higher potential for direct cell killing as compared with Photofrin and about a five times lower efficiency than ZnPc. However, all three photosensitisers induced complete occlusion of tumour vasculature immediately after PDT, suggesting that tumour regression mainly resulted from vascular stasis. The ZnPcF16 offers several advantages over ZnPc for clinical applications, including improved solubility in most solvents, resulting in facilitated drug formation, favourable pharmacokinetics as well as the potential use in fluorine magnetic resonance (F-MR) imaging.

Animals↗

PubMed1996

Measurement of tumor vascular damage in mice with 99mTc-MIBI following photodynamic therapy.

The clinical perfusion agent 99mTc-MIBI was used to monitor changes in tumor vascular perfusion (TVP) induced by Photofrin (PII)-mediated photodynamic therapy (PDT). BALB/c mice bearing an EMT-6 tumor on each hind thigh were given an intravenous injection of 1, 2 or 5 mg kg-1 PII. Twenty-four hours later, one tumor was illuminated (600-650 nm, 200 mW cm-2, 400 J cm-2) while the other served as a control. At various time intervals after PDT (0, 2 and 24 h) mice received an intravenous injection of 99mTc-hexakismethoxyisobutylisonitrile (MIBI) (0.18 MBq g-1) and were sacrificed 2 min later. The light-treated and the untreated tumors were then dissected, the radioactivity was counted and the percentage of the injected dose per gram of tumor (%ID g-1) was calculated as a measure of TVP. We observed that TVP is drug dose dependent, develops progressively with time post-PDT and is inversely related to PDT efficacy. Our data show that early tumor retention of 99mTc-MIBI is a simple method to assess TVP and vascular damage induced by PDT.

Animals↗

PubMed1996

The sacroiliac joint: anatomical study in the coronal plane and MR correlation.

The current clinical imaging technique applied to the sacroiliac joint (SIJ) is coronal Computed Tomography (CT). The aims of this study were: 1) to section the cartilage, the ligaments of the SIJ, and their relations to adjacent organs, in a coronal plane; 2) to correlate anatomical and magnetic resonance (MR) sections; 3) to extend these data in vivo. A topographic dissection of a 52 year-old female specimen was performed to identify the various components, and spatial relationships of the SIJ. Another fresh frozen 50 year-old female cadaver was chosen on CT criteria of normality, and examined with a high resolution (HR) T1-weighted spin echo sequence, in a plane parallel to the ventral limit of the first two sacral vertebrae. This cadaver was then sliced with a sliding gauge device (slice thickness: 5 mm, and device thickness: 1 mm). The SIJ of a 28 year-old nulliparous volunteer, were examined in HR MR imaging, and with a faster sequence, for comparison with the post mortem data. The slice study was correlated with conventional dissection. The continuity and thickness of the auricular cartilage, the complex fascicles of proximal ventral and dorsal sacroiliac ligaments, and distant sacrotuberous and sacrospinous ligaments, were studied. In each plane, coronal HR MR imaging studies were correlated with anatomical sections. The clinical relevance of this comparison was to extend these data in vivo. The auricular cartilage and the ligaments of the SIJ are clearly analyzed by MR imaging, which could contribute to the study of sacroiliitis.

Adult↗

PubMed1995

Treatment planning optimization by conjugate gradients and simulated annealing methods in stereotactic radiosurgery.

PURPOSE: This paper presents a new optimization method of treatment planning in linac stereotactic radiosurgery. METHODS AND MATERIALS: On a workstation integrating x-rays, computed tomography (CT), magnetic resonance imaging (MRI), and digital subtracted angiography (DSA) images, we first determine the outlines of the target volume and surrounding healthy tissues to spare. To achieve complete optimization of the treatment plans, this method decomposes the optimization process in two steps. The position of the isocenters and the diameter of the collimators are first deduced by a conjugate gradients method, from the position and size of ellipsoids or spheres modeling the target volume. The other irradiation parameters, such as the isocenter dose, the aperture, and the weight of each irradiation plane and of their irradiation sectors are finally deduced by a simulated annealing optimization algorithm. RESULTS: The system can perform multitarget/multisector treatment plans that are automatically obtained in a satisfactory time (as a rule, 20 min for a two-target irradiation), much faster than the time needed for a manual treatment planning. We present the results in two cases: the simulation of a single-target treatment and a two-target real treatment with constraints. In these two cases, we can control the dose received by target and sensitive volumes. CONCLUSION: This method achieves an excellent conformation of the estimated isodose curves with the outlines of the target volume, which allows us to avoid the surrounding healthy tissues, thanks to the different weighting factors given on each volume concerned according to the importance we grant to each of them.

Angiography, Digital Subtraction↗

PubMed1995

A frameless stereotaxic localisation system using MRI, CT and DSA.

The authors present a method of stereotaxic localisation using magnetic resonance imaging (MRI) computerized tomography (CT) and digital subtracted angiography (DSA) which does not require localisation frams fixed to the patient's skull, but uses only four cranial landmarks corresponding to the holders of the neurosurgical stereotaxic frame. The method presents no major constraints in routine examinations. The geometrical distortions of the imaging devices are corrected. Three-dimensional localisation is performed using sagittal and axial slices in MRI, axial slices in CT and only two associated frontaly and lateral views in DSA. The images data are transferred to a PC-based system. By locating the landmarks on the images, the transformation matrixes can be computed to obtain the 3D coordinates of a target in the stereotaxic space and in any imaging modality. The results obtained show the precision of the corrections and the millimetre accuracy of pin-point target localisation.

Angiography, Digital Subtraction↗

PubMed1995

RF-transmitted CsI radio-isotopic ambulatory recorder for left ventricular ejection fraction monitoring.

We have developed a CsI multidetector probe in order to produce a nuclear ambulatory recorder to study simultaneously cardiac electric activity and the left ventricular ejection fraction. To make the device lighter, the electronics were designed with surface-mounted technology, and a serial data RF transmission system was used. The data are processed on a real-time basis using a portable microcomputer. Unlike other commercially available devices, this monitor avoids the problems of volume, weight, recording time capacity and slow off-line data processing. Our device permits global and regional analysis of the ejection fraction for a moderate manufacturing cost. It is intended primarily for ambulatory use and can easily be adapted to perform a monitoring function. The first tests on patients conducted using the prototype demonstrate the technical reliability and satisfactory operation of the device.

Cesium↗

PubMed1995

PEG-coated poly(lactic acid) nanoparticles for the delivery of hexadecafluoro zinc phthalocyanine to EMT-6 mouse mammary tumours.

Hexadecafluoro zinc phthalocyanine (ZnPcF16), a second generation sensitizer for the photodynamic therapy of cancer, was incorporated in three vehicles: poly(D,L-lactic acid) (PLA) nanoparticles, polyethylene glycol (PEG)-coated nanoparticles and a Cremophor EL (CRM) oil-water emulsion. Nanoparticles were prepared by the salting-out procedure. Biodistribution of the dye was assessed by fluorescence in EMT-6 mammary tumour bearing mice after intravenous injection of 1 mumol kg-1 ZnPcF16. Plain nanoparticles were rapidly retained by the reticuloendothelial system (RES) as reflected by the low area under the blood concentration-time curve (AUC0-168, 57 micrograms h g-1). Little tumour uptake of the dye was observed with this formulation. In contrast, PEG-coated nanoparticles displayed a reduced RES uptake, leading to significantly higher blood levels over an extended period (t1/2 30 h; AUC 0-168 227 micrograms h g-1) and enhanced tumour uptake. At 48 h post injection, tumour to skin and tumour to muscle concentration ratios reached 3.5 and 10.8, respectively. Blood levels of ZnPcF16 after administration as a CRM emulsion decreased faster than with PEG-coated nanoparticles (t1/2 12 h), but since no early liver uptake was observed, the AUC0-168 and the tumour uptake were only slightly lower. However, with the CRM formulation, a late liver uptake was observed, reaching 51% of the injected dose after 7 days.

Animals↗