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Jean-Paul Vallée

Publications and source records attributed to Jean-Paul Vallée.

17 recordsLinked to original sources
PubMed2005

Enterprise-wide PACS: beyond radiology, an architecture to manage all medical images.

RATIONALE AND OBJECTIVES: Picture archiving and communication systems (PACS) have the vocation to manage all medical images acquired within the hospital. To address the various situations encountered in the imaging specialties, the traditional architecture used for the radiology department has to evolve. MATERIALS AND METHODS: We present our preliminarily results toward an enterprise-wide PACS intended to support all kind of image production in medicine, from biomolecular images to whole-body pictures. Our solution is based on an existing radiologic PACS system from which images are distributed through an electronic patient record to all care facilities. This platform is enriched with a flexible integration framework supporting digital image communication in medicine (DICOM) and DICOM-XML formats. In addition, a generic workflow engine highly customizable is used to drive work processes. RESULTS: Echocardiology; hematology; ear, nose, and throat; and dermatology, including wounds, follow-up is the first implemented extensions outside of radiology. CONCLUSION: We also propose a global strategy for further developments based on three possible architectures for an enterprise-wide PACS.

Cardiology↗
PubMed2005

Magnetic resonance imaging with hepatospecific contrast agents in cirrhotic rat livers.

OBJECTIVE: During biliary cirrhosis in rats, organic anion-transporting peptides (Oatps) and ATP-dependent multidrug resistance-associated protein 2 (Mrp2) that are likely to transport the contrast agent Gd-BOPTA through hepatocytes are down-regulated. However, the consequences of such down-regulation on the signal intensity (SI) enhancement are unknown. Consequently, the aim of our study was to measure the hepatic SI enhancement during Gd-BOPTA perfusion as well as the Oatp and Mrp2 expression in normal and cirrhotic livers. MATERIALS AND METHODS: The hepatic SI enhancement during Gd-BOPTA perfusion was measured in livers isolated from normal rats and rats that had a bile duct ligation (BDL) 15, 30, and 60 days before the perfusion. Hepatic injury and transporter expression were measured in control and cirrhotic rats. RESULTS: BDL induced a severe hepatic injury that increased over time with a down-regulation of the transporter expression. The extracellular space (assessed by Gd-DTPA perfusion) increased with the severity of the disease. Gd-BOPTA-induced SI enhancement remained similar in BDL-15 and BDL-30 rats than in control rats but significantly decreased in severe cirrhosis (BDL-60 rats). In comparison, the Mn-DPDP-induced SI enhancement decreases proportionally to the severity of the disease. CONCLUSION: During biliary cirrhosis, Gd-BOPTA-induced SI enhancement could not be related to the hepatic expression of transporters.

ATP-Binding Cassette Transporters↗
PubMed2005

Three-dimensional reconstruction of basal cell carcinomas.

BACKGROUND: Basal cell carcinoma (BCC) is the most common type of skin cancer. One of the main problems with BCC is the risk of local recurrence of the tumor after treatment. This is mainly due to its irregular outgrowths, which cannot be detected clinically. OBJECTIVE: To better understand the tumor morphology and growth pattern of BCC, we tried to develop a method that provides a precise three-dimensional model of the tumor. METHODS: Because Mohs surgery provides the best overview of the tumor and the tumor margins (both lateral and in depth), the reconstruction was based on slides from Mohs surgery. After digitization and processing of the slides, the tumor was then surrounded by a Mohs surgeon on a computer screen. These selections (lines) were used for a three-dimensional reconstruction of the tumor using MedSurf3D software. RESULTS: This method allows three-dimensional reconstruction of any given BCC. The MedSurf3D software enables visualization of a three-dimensional model of the tissue, which is removed during the surgical procedure. CONCLUSIONS: Three-dimensional reconstruction is a fascinating tool that might improve our understanding of the behavior, growth pattern, and tumor morphology of BCCs. This technique might also be useful in other fields of cutaneous oncology, such as the calculation of the tumor volume of melanomas.

Basal Cell Carcinoma↗
PubMed2004

Comparison between tagged MRI and standard cine MRI for evaluation of left ventricular ejection fraction.

Global left ventricular function is a prognostic indicator and is used to evaluate therapeutical interventions in patients with heart failure. Regional left ventricular function can be determined with tagged MRI. Assessment of global left ventricular function using the tagging data may have additional clinical value without incurring extra scanning time, which is currently a limiting factor in cardiac imaging. Direct determination of end-diastolic volume is not possible with conventional tagged MRI. However, end-systolic volume can be directly measured because myocardium-blood contrast improves through a tagged image series. We investigated the potential of tagged MRI using frequency-domain analysis software to retrospectively track end-diastolic contour from end-systolic contour and subsequently calculate the ejection fraction. Tagged MRI was compared with the standard bright-blood cine MRI in healthy volunteers ( n=20) and patients with previous myocardial infarction ( n=8). Left ventricular ejection fraction derived from tagged MRI is linearly correlated to left ventricular ejection fraction obtained by standard cardiac cine MRI ( y=1.0 x+1.31, r>0.98, p=0.014). In addition, the inter-observer and intra-observer coefficient of variation for left ventricular ejection fraction measurements was low (CV(intra)=0.4%, CV(inter)=1.3%). With tagged MRI, only end-systolic volume needs to be manually determined, and accurate estimation of left ventricular ejection fraction is obtained because end-diastolic and end-systolic volumes are determined using identical anatomical points. Our data indicate that tagged MRI can be used to quantitatively assess both regional and global left ventricular function. Therefore, tagged MRI may be a valuable clinical tool for determining the prognosis and evaluating the effect of therapeutical intervention using a single imaging session in patients with left ventricular dysfunction.

Humans↗
PubMed2004

Hollow fiber bioreactor: new development for the study of contrast agent transport into hepatocytes by magnetic resonance imaging.

The aim of our study was to develop a magnetic resonance (MR)-compatible in vitro model containing freshly isolated rat hepatocytes to study the transport of hepatobiliary contrast agents (CA) by MR imaging (MRI). We set up a perfusion system including a perfusion circuit, a heating device, an oxygenator, and a hollow fiber bioreactor (HFB). The role of the porosity and surface of the hollow fiber (HF) as well as the perfusate flow rate applied on the diffusion of CAs and O2 was determined. Hepatocytes were isolated and injected in the extracapillary space of the HFB (4 x 10(7) cells/mL). The hepatocyte HFB was perfused with an extracellular CA, gadopentetate dimeglumine (Gd-DTPA), and gadobenate dimeglumine (Gd-BOPTA), which also enters into hepatocytes. The HFB was imaged in the MR room using a dynamic T1-weighed sequence. No adsorption of CAs was detected in the perfusion system without hepatocytes. The use of a membrane with a high porosity (0.5 microm) and surface (420 cm2), and a high flow rate perfusion (100 mL/min) resulted in a rapid filling of the HFB with CAs. The cellular viability of hepatocytes in the HFB was greater than 85% and the O2 consumption was maintained over the experimental period. The kinetics of MR signal intensity (SI) clearly showed the different behavior of Gd-BOPTA that enters into hepatocytes and Gd-DTPA that remains extracellular. Thus, these results show that our newly developed in vitro model is an interesting tool to investigate the transport kinetics of hepatobiliary CAs by measuring the MR SI over time.

Animals↗
PubMed2004

A reference data set for the evaluation of medical image retrieval systems.

Content-based image retrieval is starting to become an increasingly important factor in medical imaging research and image management systems. Several retrieval systems and methodologies exist and are used in a large variety of applications from automatic labelling of images to diagnostic aid and image classification. Still, it is very hard to compare the performance of these systems as the used databases often contain copyrighted or private images and are thus not interchangeable between research groups, also for patient privacy. Most of the currently used databases for evaluating systems are also fairly small which is partly due to the high cost in obtaining a gold standard or ground truth that is necessary for evaluation. Several large image databases, though without a gold standard, start to be available publicly, for example by the NIH (National Institutes for Health). This article describes the creation of a large medical image database that is used in a teaching file containing more than 8,700 varied medical images. The images are anonymised and can be exchanged free of charge and copyright. Ground truth (a gold standard) has been obtained for a set of 26 images being selected as query topics for content-based query by image example. To reduce the time for the generation of ground truth, pooling methods well known from the text or information retrieval field have been used. Such a database is a good starting point for comparing the current image retrieval systems and to measure the retrieval quality, especially within the context of teaching files, image case databases and the support of teaching. For a comparison of retrieval systems for diagnostic aid, specialised image databases, including the diagnosis and a case description will need to be made available, as well, including gold standards for a proper system evaluation. A first evaluation event for image retrieval is foreseen at the 2004 CLEF conference (Cross Language Evaluation Forum) to compare text-and content-based access mechanism to images.

Databases, Factual↗
PubMed2004

Casimage project: a digital teaching files authoring environment.

The goal of the Casimage project is to offer an authoring and editing environment integrated with the Picture Archiving and Communication Systems (PACS) for creating image-based electronic teaching files. This software is based on a client/server architecture allowing remote access of users to a central database. This authoring environment allows radiologists to create reference databases and collection of digital images for teaching and research directly from clinical cases being reviewed on PACS diagnostic workstations. The environment includes all tools to create teaching files, including textual description, annotations, and image manipulation. The software also allows users to generate stand-alone CD-ROMs and web-based teaching files to easily share their collections. The system includes a web server compatible with the Medical Imaging Resource Center standard (MIRC, http://mirc.rsna.org) to easily integrate collections in the RSNA web network dedicated to teaching files. This software could be installed on any PACS workstation to allow users to add new cases at any time and anywhere during clinical operations. Several images collections were created with this tool, including thoracic imaging that was subsequently made available on a CD-Rom and on our web site and through the MIRC network for public access.

CD-ROM↗
PubMed2004

Gd-BOPTA transport into rat hepatocytes: pharmacokinetic analysis of dynamic magnetic resonance images using a hollow-fiber bioreactor.

RATIONALE AND OBJECTIVES: To investigate the transport of the hepatobiliary magnetic resonance (MR) imaging contrast agent Gd-BOPTA into rat hepatocytes. MATERIALS AND METHODS: In a MR-compatible hollow-fiber bioreactor containing hepatocytes, MR signal intensity was measured over time during the perfusion of Gd-BOPTA. For comparison, the perfusion of an extracellular contrast agent (Gd-DTPA) was also studied. A compartmental pharmacokinetic model was developed to describe dynamic signal intensity-time curves. RESULTS: The dynamic signal intensity-time curves of the hepatocyte hollow-fiber bioreactor during Gd-BOPTA perfusion were adequately fitted by 2 compartmental models. Modeling permitted to discriminate between the behaviors of the extracellular contrast agent (Gd-DTPA) and the hepatobiliary contrast agent (Gd-BOPTA). It allowed the successfully quantification of the parameters involved in such differences. Gd-BOPTA uptake was saturable at high substrate concentrations. CONCLUSIONS: The transport of Gd-BOPTA into rat hepatocytes was successfully described by compartmental analysis of the signal intensity recorded over time and supported the hypothesis of a transporter-mediated uptake.

Animals↗
PubMed2003

Improvement in the quantification of myocardial perfusion using an automatic spline-based registration algorithm.

PURPOSE: To improve the quantification of myocardial perfusion by registering the time series of magnetic resonance (MR) images with injection of gadolinium. MATERIALS AND METHODS: Eight patients underwent MR scans to perform myocardial perfusion exam. Two short axis views of the left ventricle (LV) were acquired in free breathing. Two masks for performing the spatial registration of the images were evaluated. The registration was based on pixel intensity in a multi-resolution scheme. The efficiency of this correction was evaluated by calculating geometric residual displacement of the LV and by fitting the data to a compartment model fit with two parameters: K1, the blood-to-myocardium transfer coefficient, and Vd, the distribution volume of the contrast media. RESULTS: The registration stage allowed a decrease in the observed motion of the LV from more than 1.98 +/- 0.68 mm to less than 0.56 +/- 0.18 mm (mean +/- SD). Variability obtained in the perfusion analysis decreased from 46 +/- 103% to 5+/- 4% for K1 parameter and from 18 +/- 21% to 5 +/- 5% for Vd parameter. CONCLUSION: As with manual correction, this automatic motion correction leads to accurate perfusion parameters in dynamic cardiac MR imaging after contrast agent injection. This automatic stage requires placing only one mask over one frame of the perfusion study instead of manually shifting each image to fit a reference image of the perfusion study.

Algorithms↗
PubMed2003

Inflow effect in first-pass cardiac and renal MRI.

PURPOSE: To estimate the effect of the inflow effect on the arterial input function in vivo in cardiac and renal MR perfusion imaging using fast gradient echo (GRE) sequences and contrast media. MATERIALS AND METHODS: The MR exam protocol was designed to acquire images at different phases of the cardiac cycle. The arterial input was thus influenced by various blood flow velocities. RESULTS: It was found that the inflow effect was negligible in the left ventricle of the heart, while it was significantly higher in the aorta for the kidney perfusion measurement. This was principally due to the higher through-the-plane component of the blood flow velocity in the aorta than in the left ventricle. CONCLUSION: The inflow effect can be neglected in the heart cavity, but should be taken into account in renal perfusion.

Aorta↗
PubMed2003

Inflow effect correction in fast gradient-echo perfusion imaging.

The purposes of this study were to assess the extent of the inflow effect on signal intensity (SI) for fast gradient-recalled-echo (GRE) sequences used to observe first-pass perfusion, and to develop and validate a correction method for this effect. A phantom experiment with a flow apparatus was performed to determine SI as a function of Gd-DTPA concentration for various velocities. Subsequently a flow-sensitive calibration method was developed, and validated on bolus injections into an open-circuit flow apparatus and in vivo. It is shown that calibration methods based on static phantoms are not appropriate for accurate signal-to-concentration conversion in images affected by high flow. The flow-corrected calibration method presented here can be used to improve the accuracy and robustness of the arterial input function (AIF) determination for tissue perfusion quantification using MRI and contrast media.

Blood Flow Velocity↗
PubMed2003

Noninvasive measurement of absolute renal perfusion by contrast medium-enhanced magnetic resonance imaging.

OBJECTIVE: The aim of this study was to validate the quantification of absolute renal perfusion (RP) determined by dynamic magnetic resonance imaging (MRI) and contrast media using an experimental model in the rabbit and a transit-timed ultrasound flow probe around the left renal artery as comparison. MATERIAL AND METHODS: An MR-compatible ultrasonic time-of-flight flow-probe was placed around the left renal artery in 9 New Zealand white rabbits. Absolute RP in basal state, after mechanical renal artery stenosis, intravenous dopamine, angiotensin II, or colloid infusion was measured using dynamic MRI and intravenous injection of gadoteridol. The results were correlated to the renal artery flow measured inside the magnet with the transit-timed flow-probe. For the signal intensity concentration conversion, we applied different calibrations according to various velocities measured in the aorta by a phase contrast sequence to correct for inflow effect. MRI-derived RP (in mL/min) was calculated by the maximum upslope method, where RP/volume was defined as the ratio of the cortex contrast enhancement slope over the maximum of the arterial input function determined in the aorta. RESULTS: Reproducible arterial and renal transit curve with excellent contrast to noise ratio were obtained. The MRI derived perfusion was systematically underestimated by comparison to the ultrasonic transit-timed flow-probe but was linearly correlated with these measures (r = 0.80, P < 0.001). CONCLUSIONS: Using a flow-sensitive calibration, an accurate arterial input function can be measured from the blood MR signal and used in a realistic model to assess the RP. There was a good correlation between the MR-derived RP and the renal artery blood flow measured by the flow-meter. This experimental study validates absolute RP quantification by MRI and contrast media injection and justifies further clinical studies.

Animals↗
PubMed2003

Integrating content-based visual access methods into a medical case database.

In the computer vision domain, content-based access methods to all forms of multimedia data are a hot research topic. A large number of tools have been developed to find documents in multimedia repositories and to manage the (visual) information that has been created, for example by the Internet. Although no general breakthrough has been achieved with respect to searching diverse databases with automatically extracted features, the techniques have gained acceptance in a few well-defined domains such as image agencies (Corbis) and trademark research. In the medical domain, the number of digital images produced and used for teaching, diagnostics and therapy is rising in a similar way as in other domains. Still, there are only a few image retrieval systems that use automatically extracted visual features for content-based access to medical image databases. This article describes the use of an open source image retrieval system (GIFT) that has been adapted for the use with medical images using the image case database CasImage that has been developed and maintained by the University Hospital of Geneva and that is in routine use. The first results show the potential of this technique to retrieve similar cases from a case database. This is an important task for teaching and might also become important for diagnostics using case-based reasoning, for example. For the use as a diagnostic tool, it is foreseen to specialize the visual features for the domain of lung image retrieval, using high resolution computed tomography (HRCT) images.

Database Management Systems↗
PubMed2002

Use of high flip angle in T1-prepared FAST sequences for myocardial perfusion quantification.

This study reports on the first use of high flip angle and radio-frequency (RF) spoiling in T1-prepared fast acquisition in steady state (FAST) sequence for myocardial perfusion in patients. T1 dynamic range was measured in vitro with a FAST, an RF FAST and a snapshot fast low-angle shot (FLASH) sequences with a 90 degrees flip angle. Myocardial perfusion was then measured twice in 6 patients during the same MR session. The RF FAST and FLASH, but not the FAST sequence, demonstrated an extended T1 dynamic range; however, the FLASH images were degraded by artifacts not present on the RF FAST images. The myocardial perfusion indices K1 (first-order transfer constant from the blood to the myocardium for the Gd-DTPA) and Vd (distribution volume of Gd-DTPA in myocardium) did not differ significantly between the two injections. K1 was 0.48+/-0.12 ml/min g(-1) and Vd was 12.5+/-2.9%. With an extended T1 dynamic range and the sensitivity required for myocardial perfusion quantification, the RF FAST sequence with a 90 degrees flip angle outperformed the snapshot FLASH sequence in terms of image quality and the FAST sequence in terms of contrast dynamic range.

Adult↗
PubMedDate not supplied

Integration of a multimedia teaching and reference database in a PACS environment.

In one radiology department, a computerized authoring and editing environment was developed and integrated with the picture archiving and communication systems (PACS) for creation of image-based electronic teaching files to replace a collection of printed film images. This multimedia database and authoring environment allows physicians to create reference databases for teaching and research directly from clinical cases being reviewed on PACS diagnostic workstations. The database engine allows users to generate stand-alone CD-ROMs (compact disks, read-only memory) and World Wide Web-based teaching files. The system is fully compliant with the Digital Imaging and Communications in Medicine (DICOM) standard and supports a large number of standard multimedia image file formats. The focus of the development was on convenience and ease of use of a generic system adaptable to all users. The software was integrated on the PACS workstations to allow users to add new cases to the database at any time and anywhere in the department. A pilot system was implemented in clinical operation, with a central server and several client units.

CD-ROM↗
PubMedDate not supplied

Informatics in radiology (infoRAD): benefits of content-based visual data access in radiology.

The field of medicine is often cited as an area for which content-based visual retrieval holds considerable promise. To date, very few visual image retrieval systems have been used in clinical practice; the first applications of image retrieval systems in medicine are currently being developed to complement conventional text-based searches. An image retrieval system was developed and integrated into a radiology teaching file system, and the performance of the retrieval system was evaluated, with use of query topics that represent the teaching database well, against a standard of reference generated by a radiologist. The results of this evaluation indicate that content-based image retrieval has the potential to become an important technology for the field of radiology, not only in research, but in teaching and diagnostics as well. However, acceptance of this technology in the clinical domain will require identification and implementation of clinical applications that use content-based access mechanisms, necessitating close cooperation between medical practitioners and medical computer scientists. Nevertheless, content-based image retrieval has the potential to become an important technology for radiology practice.

Humans↗