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Biomedical subjects

Jean-François Paul

Publications and source records attributed to Jean-François Paul.

At least 19 recordsLinked to original sources
PubMed2006

Non-invasive detection of coronary artery disease in patients with left bundle branch block using 64-slice computed tomography.

OBJECTIVES: The goal of this study was to evaluate the diagnostic accuracy of 64-slice computed tomography (CT) to identify coronary artery disease (CAD) in patients with complete left bundle branch block (LBBB). BACKGROUND: Left bundle branch block increases risk of cardiac mortality, and prognosis is primarily determined by the underlying coronary disease. Non-invasive stress tests have limited performance, and conventional coronary angiography (CCA) is usually required. METHODS: Sixty-six consecutive patients with complete LBBB and sinus rhythm admitted for CCA were enrolled. Computed tomography was performed 3 +/- 3.9 days before CCA. The accuracy of 64-slice CT to detect significant stenosis (>50% lumen narrowing) was compared with quantitative coronary angiography. All segments were analyzed regardless of image quality from coronary calcification or motion artifacts. Results were analyzed by patient and by coronary segment (990) using the American Heart Association 15-segment model. RESULTS: Lower heart rates were associated with improved image quality. Computed tomography correctly identified 35 of 37 (95%) patients without significant stenosis and 28 of 29 (97%) patients with significant stenosis on CCA. Computed tomography correctly assessed 68 of 94 (72%) significant stenosis. Overall, accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of 64-slice CT for identifying CAD by patient was 95%, 97%, 95%, 93%, and 97%, respectively, and by segment was 97%, 72%, 99%, 91%, and 97%, respectively. CONCLUSIONS: In a routine clinical practice, 64-slice CT detects with excellent accuracy a significant CAD in patients with complete LBBB. A normal CT in this clinical setting is a robust tool to act as a filter and avoid invasive diagnostic procedures.

Aged↗
PubMed2006

Comparison of coronary minimal lumen area quantification by sixty-four-slice computed tomography versus intravascular ultrasound for intermediate stenosis.

The present study assessed 64-slice computed tomographic accuracy to quantify minimal lumen area (MLA) and determine lesion severity in intermediate stenosis by angiography compared with intravascular ultrasound (IVUS). Sixty-four-slice computed tomography (CT) has been shown to be effective in coronary stenotic assessment by visual estimation compared with angiography. However, angiography is not an accurate gold standard for intermediate stenotic quantification compared with IVUS. Forty patients (54 lesions) with 30% to 70% coronary stenosis by angiography in a major coronary branch were included. All patients underwent quantitative angiography, retrospective electrocardiographically gated 64-slice CT (Siemens), and IVUS (40-MHz Atlantis; Boston Scientific). MLA was manually traced by 2 blinded and independent operators on 64-slice computed tomographic cross-sectional reconstruction and compared with IVUS MLA. A lesion was considered significant if the MLA was <or=6 mm(2) for the left main coronary artery and <or=4 mm(2) for another epicardial vessel with CT and IVUS. The correlation between IVUS MLA and computed tomographic MLA was r = 0.88 (p <0.001). Interobserver variabilities (mean +/- SD) were 1.2 mm(2) for CT and 1.1 mm(2) for CT versus IVUS. Bland-Altman analysis showed a 95% confidence interval of -42% to +44% for computed tomographic measurement using IVUS as a reference. Sensitivity, specificity, accuracy, and Cohen's kappa coefficient for significant lesion classification using CT were 87%, 72%, 80%, and 0.6, respectively (p <0.0001). In conclusion, when using MLA, 64-slice CT was able to quantify coronary stenosis with good correlation compared with IVUS and determine lesion severity in patients with intermediate lesions by angiography.

Coronary Angiography↗
PubMed2006

MDCT of the coronary arteries: feasibility of low-dose CT with ECG-pulsed tube current modulation to reduce radiation dose.

OBJECTIVE: The objective of our study was to show the feasibility of coronary CT using low kilovoltage (80 kV) combined with ECG-pulsed tube current modulation in selected patients. CONCLUSION: This study showed the combined effect of lowering the kilovoltage setting (80 kV) and using an automatic modulation technique (ECG-pulsed tube current modulation) for coronary CT. Radiation dose exposure can be reduced by up to 88% for slim patients without impairing image quality.

Adolescent↗
PubMed2005

Comparison of lumens of intermediate coronary stenosis using 16-slice computed tomography versus intravascular ultrasound.

We aimed to quantify ambiguous coronary stenosis using the minimal lumen area with 16-slice computed tomography compared with intravascular ultrasound. The sensitivity, specificity, and accuracy for significant lesion classification was 68%, 86%, and 78%, respectively. The correlation between intravascular ultrasound and CT minimal lumen area was r = 0.73 (p <0.001), and the 95% confidence interval for CT measurement was -72% to +56%.

Aged↗
PubMed2005

Late defect on delayed contrast-enhanced multi-detector row CT scans in the prediction of SPECT infarct size after reperfused acute myocardial infarction: initial experience.

PURPOSE: To prospectively assess the accuracy of multi-detector row computed tomography (CT) in the prediction of infarct size after successful reperfusion of acute myocardial infarction (MI) by using single photon emission computed tomography (SPECT) images obtained 6 weeks later as the reference standard. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. A total of 34 patients (29 men and five women; mean age, 56 years +/- 13) underwent dual-phase 16-detector row CT within 3 days +/- 3 after successful reperfusion of acute MI. Iodinated contrast medium (1.5 mL per kilogram of body weight) was injected at a flow rate of 3.5 mL/sec. A first arterial phase acquisition was followed 5 minutes later by a late acquisition, without reinjection of contrast medium. A radiologist and a cardiologist used a 17-segment model in a blind analysis of images obtained during late acquisition. For each segment, presence of late defect or late enhancement was recorded. Findings were compared with SPECT studies analyzed by a nuclear medicine physician and a cardiologist 6 weeks after the acute event. CT defects were compared with SPECT defects on a segmental and per-patient basis. Mean number of segments with late defects on multi-detector row CT scans was compared with infarct size on SPECT images by using the t test. RESULTS: All patients had late enhancement in the infarcted myocardium. In 27 of 34 patients, a late defect surrounded by a subepicardial late enhancement was detected. Segments with late defect on CT scans were predictive of residual perfusion defects at 6-week follow-up, with sensitivity of 78%, specificity of 91%, and accuracy of 90%. On a per-patient basis, sensitivity was 93%, specificity was 100%, and accuracy was 94%. Mean number of segments with late defects on multi-detector row CT scans (ie, 3.1 segments) was not significantly different from infarct size on SPECT images (eg, 2.5 segments) (P = .2). CONCLUSION: Late defect on multi-detector row CT scans indicates residual perfusion SPECT defect and infarct size after successfully reperfused MI, with sensitivity of 93%, specificity of 100%, and accuracy of 94%.

Adult↗
PubMed2005

Coronary stenosis detection by 16-slice computed tomography in heart transplant patients: comparison with conventional angiography and impact on clinical management.

OBJECTIVES: We sought to find a non-invasive alternative to conventional coronary angiography (CCA) for serial detection and follow-up of coronary stenosis due to cardiac allograft vasculopathy in heart transplant patients. BACKGROUND: Cardiac allograft vasculopathy is the main factor limiting long-term success of heart transplantation. It is usually detected by CCA. Multislice computed tomography (MSCT) coronary angiography has recently proven effective for the diagnosis of coronary stenosis in non-transplant patients. METHODS: Fifty-three consecutive heart transplant patients underwent MSCT within 24 h before or after their annual routine CCA. Only angiographic segments >1.5 mm were considered for analysis; the coronary arterial tree was divided into nine segments. Three patients were excluded because of technical failure. RESULTS: Of the 450 angiographic coronary segments, 432 (96%) were evaluable by MSCT. Of the nine coronary stents in seven patients, only three, including one intrastent restenosis, were correctly evaluated by MSCT, and two intrastent restenoses were missed. Complete analysis of the coronary tree was possible for 44 (88%) of the 50 patients. For detection of coronary stenosis >50%, sensitivity was 83%, specificity 95%, positive predictive value 71%, negative predictive value 95%, and accuracy 93%. In the 22 patients with strictly normal MSCT, no stenosis was found by CCA. CONCLUSIONS: Our study suggests the following guidelines already applied in our institution: 16-slice MSCT can replace CCA in de novo heart transplant patients and patients with strictly normal MSCT at follow-up. Significant wall or lumen changes observed on annual MSCT or stents require further investigation by CCA.

Adult↗
PubMed2005

Preoperative and postoperative evaluation of airways compression in pediatric patients with 3-dimensional multislice computed tomographic scanning: effect on surgical management.

OBJECTIVES: Surgical management of airway compression of vascular origin requires an accurate analysis of anatomy and various mechanisms of compression. This study assessed the usefulness of 3-dimensional computed tomographic scanning in the preoperative and postoperative evaluation of airways compression in a pediatric population. METHODS: Thirty-seven consecutive patients (median age, 4 months) were examined with multislice 3-dimensional computed tomographic scanning: 18 patients before surgical treatment of anomalies of vascular rings, 2 patients because of respiratory symptoms after repair of esophageal atresia, and 17 patients because of persisting respiratory symptoms or prolonged mechanical ventilation after cardiac surgery for congenital heart disease. RESULTS: The procedure was successful, with high-quality diagnostic imaging obtained in all cases without any complications. The anatomy and relationship between the vascular arches and airways was analyzed in all referred patients with vascular arch anomalies confirmed on the basis of the surgical findings, and this helped the surgeon to plan the procedure and choose the best approach. After cardiac surgery, the airway and vascular structures involved and the mechanism of compression were specified in all but one case, and the 3-dimensional computed tomographic scan serves as an important tool for deciding whether to perform reoperation on patients requiring prolonged mechanical ventilation. CONCLUSION: Three-dimensional computed tomographic scanning is a safe, fast, and noninvasive method useful for accurately analyzing the mechanisms of airway compression of vascular origin and thus possible improving the surgical management of pediatric patients.

Adolescent↗
PubMed2005

[Non-invasive coronary artery imaging using multislice computed tomography].

Coronary atherosclerotic disease is the leading cause of mortality in industrialized countries. The disease can remain silent for years, being diagnosed only after acute myocardial infarction in about 50% of cases. Coronary angiography is the reference standard for coronary imaging. However, it is invasive and costly, requiring intra-arterial catheterization. In addition, coronary angiography does not visualize the arterial wall, but only the lumen. A reliable non-invasive imaging technique showing changes in both the arterial wall and the lumen would be highly useful, especially for early diagnosis. Recently, multislice computed tomography (CT) was shown to be capable of visualizing not only the coronary arteries (lumen and wall), but also the cardiac muscle, with high spatial resolution. Multislice CT provides high-quality 3D images of coronary arteries. Initial results with 4, 16 and now 64-slice CT, by comparison with conventional angiography, are very promising, and multislice CT technology is advancing rapidly. Non-invasive visualization of the coronary arteries with accurate detection of stenosis is now possible in practice using ECG-gated 16-slice CT Multislice CT can also detect non stenotic coronary plaque. Finally, visualization of cardiac muscle by multislice CT makes it possible to detect myocardial ischemia.

Coronary Angiography↗
PubMed2004

Characterization of vulnerable nonstenotic plaque with 16-slice computed tomography compared with intravascular ultrasound.

We compared 16-slice computed tomography with intravascular ultrasound in the detection of unstable component characteristics of nonstenotic plaque responsible for acute coronary syndrome. Computed tomography accurately assessed plaque eccentricity, calcification, and remodeling, and intraplaque hypodensity correlated with intravascular ultrasound echolucent area.

Adult↗
PubMed2004

Low-kilovoltage multi-detector row chest CT in adults: feasibility and effect on image quality and iodine dose.

PURPOSE: To assess the feasibility of low-kilovoltage (ie, 80-kV) chest computed tomography (CT) protocols for adults and the effect of such protocols on image quality and iodine dose. MATERIALS AND METHODS: Preliminarily, 90 patients (30 women, 60 men; mean age, 59 years) requiring contrast material-enhanced chest CT were randomly assigned to one of three protocol groups: protocol A, with use of 80 kV and 135 mAs; protocol B, with use of 80 kV and 180 mAs; or the standard protocol, with use of 120 kV and 90 mAs. Contrast material injection protocols were standardized in all groups. Image noise was calculated and plotted against patient weight. Subsequently, another 52 consecutive patients (11 women, 41 men; mean age, 57 years) were assigned to one of the protocols according to their weight: Patients weighing less than 60 kg were assigned to protocol A; patients weighing 60-75 kg, to protocol B; and patients weighing more than 75 kg, to the standard protocol. Two readers evaluated the CT images qualitatively by using a five-point scale. Statistical analyses were performed by using analysis of variance, kappa, and Fisher exact tests. RESULTS: In the preliminary study, the mean image noise values with protocols A (24 HU) and B (20 HU) were significantly higher (P <.001) than that with the standard protocol (12 HU). With protocols A and B, in the patients weighing more than 60 kg and more than 75 kg, respectively, the noise increased exponentially with patient weight. In the subsequent study, qualitative analysis revealed no significant difference between the low-kilovoltage examinations and the standard examination. Compared with use of the standard protocol, use of protocols A and B resulted in the iodine-based contrast material dose being reduced by 54% and 39%, respectively. CONCLUSION: Weight-adapted low-kilovoltage contrast-enhanced chest CT examinations can be routinely performed with 80 kV. Use of these protocols results in good diagnostic image quality and makes it possible to reduce contrast material use by more than 50%.

Adult↗
PubMed2003

Coronary plaque burden detected by multislice computed tomography after acute myocardial infarction with near-normal coronary arteries by angiography.

Nonsignificant coronary artery plaque rupture or erosion may be the origin of acute myocardial infarction (AMI). The aim of our study was to assess the ability of multislice computed tomography (MSCT) to detect coronary plaques responsible for near normal coronary angiography AMI. Eight patients with presentation of AMI and no significant coronary narrowing by angiography were enrolled. Two groups were defined: (1) true AMI and (2) myocarditis. MSCT was able to detect nonsignificant coronary soft plaques responsible for AMI and has provided information on plaque volume, eccentricity, and density. In patients with myocarditis, there was no evidence of plaque.

Adult↗
PubMed2003

Aneurysmal sizing after endovascular repair in patients with abdominal aortic aneurysm: interobserver variability of various measurement protocols and its clinical relevance.

The aim of this study was to determine the variability of various measurement protocols for measurement of abdominal aortic aneurysm (AAA) and the clinical relevance of variability. Three radiologists performed computed tomographic angiography measurements of both the aorta and the largest portion of the aneurysm on selected axial slices. Then measurements of the largest portion of the aneurysm were performed on unselected axial slices, sagittal and coronal reformatted. Finally, aortic volume was calculated. Measurements and volume calculation were performed before and after endovascular repair and assessed: Part 1: interobserver variability for maximum anteroposterior (MAP) and maximum transverse (MTR) diameters on selected slices; part 2: interobserver variability for unselected slices considering MAP and MTR; part 3: interobserver variability considering maximum diameter in any direction (MAD); part 4: interobserver variability for sagittal (SAG) and coronal (COR) free curved multiplanar reformation (MPR); and part 5: volume calculations. We then determined which technique of measurement was the most clinically relevant for detecting changes in aneurysm size or aortic volume. Parts 1 and 2: interobserver variability was 4.1 mm for both MAP and MTR; part 3: interobserver variability was 7 mm for MAD; part 4: interobserver variability was 5.5 mm (COR) and 4.9 mm (SAG); part 5: interobserver variability for volume was 5.5 ml. A combination of MAP and MTR was the most useful for detecting aortic modification. Volume calculation was needed in only a few cases. We recommend avoiding MAD and MPR measurements and suggest instead measuring both maximum anteroposterior and maximum transverse diameters. If aneurysm size remains stable after endovascular repair, aneurysm volume should be measured.

Aged↗
PubMed2003

Association of Takayasu's arteritis and Crohn's disease. Results of a study on 44 Takayasu patients and review of the literature.

Takayasu's arteritis and Crohn's colitis are exceptionally associated and characteristics of patients affected with both diseases have not been fully described. In a group of 44 consecutive Takayasu patients, 4 also had Crohn's disease. This 9% prevalence (95% confidence interval=2.5-21.7%) of Crohn's disease in the group is significantly greater than the highest reported prevalence of the disease in the general population. In these 4 patients, fulfilling 5 or more ACR criteria for Takayasu's disease, Crohn's disease was confirmed with colonoscopic examination and biopsies. Takayasu-Crohn patients were younger at diagnosis and tended to have systemic symptoms more frequently. Other clinical, radiological and biological characteristics were not different between the 2 groups. In the literature, 16 cases of this unusual association have been reported. The diagnosis of Takayasu's disease was simultaneous or posterior to Crohn's disease in 87%. Data on vascular lesions was available in 6 out of 16 patients and in the 4 patients of the present study: the distribution of vascular lesions in Takayasu-Crohn patients did not appear to be different from Takayasu patients. Our results and previous reports suggest that this association of rare diseases is not fortuitous. With respect to the indolent course of Takayasu's arteritis, early diagnosis of vascular lesions in Crohn patients is encouraged.

Adolescent↗
PubMed2002

Hydrogen activation on Mo-based sulfide catalysts, a periodic DFT study.

Hydrogen adsorption on Mo[bond]S, Co[bond]Mo[bond]S, and Ni[bond]Mo[bond]S (10 1 macro 0) surfaces has been modeled by means of periodic DFT calculations taking into account the gaseous surrounding of these catalysts in working conditions. On the stable Mo[bond]S surface, only six-fold coordinated Mo cations are present, whereas substitution by Co or Ni leads to the creation of stable coordinatively unsaturated sites. On the stable MoS(2) surface, hydrogen dissociation is always endothermic and presents a high activation barrier. On Co[bond]Mo[bond]S surfaces, the ability to dissociate H(2) depends on the nature of the metal atom and the sulfur coordination environment. As an adsorption center, Co strongly favors molecular hydrogen activation as compared to the Mo atoms. Co also increases the ability of its sulfur atom ligands to bind hydrogen. Investigation of surface acidity using ammonia as a probe molecule confirms the crucial role of sulfur basicity on hydrogen activation on these surfaces. As a result, Co[bond]Mo[bond]S surfaces present Co[bond]S sites for which the dissociation of hydrogen is exothermic and weakly activated. On Ni[bond]Mo[bond]S surfaces, Ni[bond]S pairs are not stable and do not provide for an efficient way for hydrogen activation. These theoretical results are in good agreement with recent experimental studies of H(2)[bond]D(2) exchange reactions.

Journal Article↗