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Biomedical subjects

D Revel

Publications and source records attributed to D Revel.

At least 55 records · Page 3Linked to original sources
PubMed1996

[Magnetic resonance angiography].

Magnetic resonance angiography (MRA) is a non invasive method for studying the morphology and the hemodynamic of vessels. MRA is becoming well-established for aorta examination and has replaced aortography. MRA is very competitive in screening for renovascular hypertension, intracranial aneurysm, for evaluation of the carotid bifurcation and diagnosis of venous sinus thrombosis. In the future, clinical applications will include pulmonary and coronary arteries.

Humans↗
PubMed1996

ROC assessment of compressed wrist radiographs.

The aim of this paper is to validate a compression scheme applied on a medical image database of digitized wrist radiographs. The compression scheme adapts itself to local statistical properties of the images. The diagnostic quality of the reconstructed images is evaluated using a ROC protocol involving five medical experts. The results of this evaluation enable us to validate the compression scheme on this database with a compression ratio of 40 (0.2 bits per pixel).

Humans↗
PubMed1996

Carboxymethyl-dextran-gadolinium-DTPA as a blood-pool contrast agent for magnetic resonance angiography. Experimental study in rabbits.

RATIONALE AND OBJECTIVES: The authors evaluate the efficiency of various doses of a paramagnetic macromolecular contrast agent, a gadolinium (Gd)-DTPA-dextran conjugate, as a blood-pool contrast media, in a transverse three-dimensional time-of-flight (TOF) magnetic resonance (MR) angiography sequence of the abdominal aorta in rabbits. METHODS: Imaging experiments were performed on a 1.5-T magnet, using a transverse three-dimensional TOF tilted optimized nonsaturating excitation (TONE) sequence. The macromolecular contrast media used was a carboxymethyl-dextran-Gd-DTPA (CMD-Gd-DTPA). Different concentrations of CMD-Gd-DTPA (0.005, 0.01, 0.03, 0.05 mmol Gd/kg) were evaluated. A comparative study using Gd-DOTA (0.01 and 0.1 mmol/kg) was performed. A visual analysis based on the gain in the visualized length of small arteries (renal arteries), and a quantitative analysis based on the percent contrast enhancement of the aorta plotted against distance in the slab from the top edge of the acquisition volume were obtained. RESULTS: A signal-to-noise ratio enhancement of the distal part of the aorta and an improvement in the visualized length of the renal arteries were noted for concentrations of CMD-Gd-DTPA ranging form 0.01 to 0.05 mmol Gd/kg. Venous enhancement was noted for concentrations greater than 0.01 mmol Gd/kg when using CMD-Gd-DTPA or Gd-DOTA. CONCLUSION: Carboxymethyl-dextran-Gd-DTPA reduced, in part, the saturation effect in a three-dimensional transverse TOF TONE MR angiography in rabbits. To prevent venous enhancement, observed with the higher concentrations used in this study, a decrease in the polydispersity of the polymer should be a goal in the future. Rapid extravasation of the low-molecular weight fraction of the polymer could explain the venous enhancement.

Animals↗
PubMed1996

[Functional magnetic resonance imaging (MRI) of hepatic ischemia in the rabbit. Contribution of a particulated contrast agent (AMI-25)].

A functional approach of the rabbit portal ischemia was performed on five New Zealand rabbits using magnetic-resonance (MR) imaging and an MR-specific contrast agent for the liver. The hepatic vascularization and the functionality of the phagocytosis cells were both studied with a single low dose of a unique contrast agent-superparamagnetic iron oxide particles (SPIOs). After a rapid i.v. injection of SPIOs, functional vessels and normally perfused liver parenchyma appeared with positive signal enhancement, whereas the ischemic area remained dark (cold spot). After the intravascular time period, the well-known negative enhancement induced by these particles on normal parenchyma was observed, with the difference of the ischemic liver, and could be related to the uptake of SPIOs by functional Kupffer cells.

Animals↗
PubMed1996

Thin-section CT detection of emphysema associated with bronchiectasis and correlation with pulmonary function tests.

PURPOSE: To evaluate, on thin-section CT scans, the prevalence of emphysema in patients with bronchiectasis and to correlate the results of thin-section CT scans with the results of pulmonary function tests, in order to question whether there was a particular functional test profile in this group of patients. PATIENTS AND METHODS: This is a retrospective study including 90 patients having both thin-section CT scans and pulmonary function tests for bronchiectasis. A CT scoring system was established for assessing the airway disease by the severity and extent of bronchiectasis and by the extent of emphysema. CT scans were reviewed independently by two reviewers and final interpretation was obtained by consensus. Results of thin-section CT scans were correlated with results of pulmonary function tests, including FEV1 and FEV1/FVC to assess air-way obstruction, total lung capacity and residual volume to assess air trapping, and diffusing capacity for carbon monoxide/alveolar volume (DCO/VA). RESULTS: CT evidence of emphysema, which was noted in 45% of the patients (n = 41), was mainly localized in the same bronchopulmonary segments as bronchiectasis. The presence of emphysema was in relation to the extent and to the severity of bronchiectasis. Only eight patients with CT evidence of emphysema had functional evidence of emphysema (20%). When comparing the group of patients with CT evidence of emphysema with the group of patients with no CT evidence of emphysema, the group of patients with CT evidence of emphysema had significantly higher airflow obstruction and air trapping, had significantly lesser value of diffusing capacity, but with no decreased gas transfer (DCO/VA > 80%). CONCLUSION: Our series suggests that there is a high prevalence of emphysema in patients with bronchiectasis. Emphysema that was not suggested using pulmonary function tests in most of the cases could explain in part the higher airway obstruction observed in the group of patients with CT evidence of emphysema. This study could support the suggestive notion that emphysema, which was mainly localized in bronchiectatic lobes, could be due to the inflammatory airway process.

Bronchiectasis↗
PubMed1995

Noninvasive assessment of no-reflow phenomenon in a canine model of reperfused infarction by contrast-enhanced magnetic resonance imaging.

The aim of this study was to test whether contrast-enhanced magnetic resonance (MR) imaging may assess in vivo the severity of the no-reflow phenomenon in a dog model of infarction with 2-hour coronary occlusion followed by reperfusion (6 hours). Subsecond MR imaging combined with intravenous bolus administration of superparamagnetic iron oxide particles (SPIO) was performed at the fifth hour of reperfusion. An MR index was calculated using the difference of signal-intensity enhancement between ischemic and nonischemic zones during the SPIO first pass. Dogs were separated into two groups according to the severity of ischemia: collateral blood flow in the central ischemic zone at 120 minutes of occlusion (radioactive microsphere technique) < 22.5% of the flow in the nonischemic zone (group I) or > 22.5% (group II). Mean collateral blood flow during occlusion was lower in group I (11.3% +/- 2.9%, n = 7) than in group II (66.8% +/- 19.8%, n = 6, p < 0.05). Mean infarct size was significantly larger in group I (58.6% +/- 4.9% of the area-at-risk, n = 7) than in group II (16.5% +/- 6.5%, n = 6, p < 0.05). For the entire population (n = 13), the infarct size was inversely correlated to the collateral blood flow (r = -0.64, p = 0.02, standard error of estimate = 0.24). The relative rate of enhancement in ischemic myocardium (MR index) was significantly lower in group I (38.1% +/- 10.9%) than in group II (142.8% +/- 32%; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Risk and results of bypass grafting using bilateral internal mammary and right gastroepiploic arteries.

From January 1990 to June 1994, 240 patients (mean age, 60 +/- 10 years) underwent myocardial revascularization with the exclusive use of in situ bilateral internal mammary and right gastroepiploic arteries. Left ventricular function was normal in 34% of patients, moderately impaired in 58.5%, and severely impaired in 7.5%. The mean number of distal anastomoses was 3.5 +/- 0.7 and the rate of complete myocardial revascularization was 80%. Early mortality was 0.4%, and complications occurred in 20 patients: myocardial infarction, 1.6%; intraaortic balloon pump, 0.8%; reoperation for bleeding, 0.8%; and mediastinitis, 0.4%. Early (15th postoperative day) angiographic control of grafts was performed in 51 patients; the rate of functional and patent anastomoses was 100% for internal mammary arteries and 96% for gastroepiploic arteries. Early functional results (3 +/- 1 postoperative months) were studied in 141 patients during exercise test with medical treatment: 99% were symptom-free and 14% had ischemic modification of electrocardiograms. A 2-year postoperative functional assessment without medical treatment was performed during exercise test in 66 patients: 98% were symptom-free and 26% had ischemic modification of electrocardiograms; during the same procedure, thallium myocardial scintigraphy was obtained in 50 patients and 18 patients had moderate ischemic defect on exercise. Ischemic modifications of electrocardiograms and defects seen on thallium scintigraphy were correlated significantly with incomplete revascularization (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1995

Technical aspects and late functional results of gastroepiploic bypass grafting (400 cases).

From January 1990 to February 1994, 400 patients (mean age 59 +/- 9 years) underwent myocardial revascularization using the right gastroepiploic artery (GEA) to bypass the right coronary artery trunk or branches. They represented 40% of all patients undergoing isolated coronary surgery during the same period, from 19% in 1990 to 54% in 1994. Left ventricular function was normal in 32% of patients, moderately impaired in 62% and severely impaired in 6%. The GEA was used alone in six patients, associated with one internal mammary artery (IMA) in 111 patients (two arterial grafts, 2.2 +/- 0.4 anastomoses) and with both IMAs in 283 patients (three arterial grafts, 3.4 +/- 0.6 anastomoses); no vein graft was used. The rate of complete myocardial revascularization was 79%. Early mortality was 1.7% and influenced by left ventricular ejection fraction (P < 0.05). Complications occurred in 37 patients: myocardial infarction 4%, intra-aortic balloon pump 0.5%, reoperation for bleeding 0.5%, mediastinitis 0.25%. Early (15th postoperative day) angiographic control of the GEA graft was performed in 104 patients operated from January 1990 to December 1991 and the patency rate was 92%; anomalies of GEA were three occlusions, five stenoses, three competitive flow, no string or slender sign. Early functional results (3 +/- 1 months postoperatively) were studied in 192 patients during exercise test with medical treatment: 99% were symptom-free and 14% had electrocardiographic (ECG) ischemic modification significantly correlated with incomplete revascularization (P < 0.01). The 2- and 4-year actuarial survival rate was 96.7 +/- 1.9%. The rate of late cardiac events was 2% patient/year; Angioplasty for GEA graft failure was required in four patients. A 2-year postoperative functional assessment without medical treatment was performed during exercise test in 66 patients who had received three arterial grafts: 98% were symptom-free and 26% had ECG ischemic modification significantly correlated with incomplete revascularization (P < 0.01); during the same procedure, thallium myocardial scintigraphy was obtained in 50 patients: 18 patients (36%) had asymptomatic ischemic defects on exercise significantly correlated with incomplete revascularization and ECG ischemic changes (P < 0.01). However, posterior thallium defects demonstrated limited GEA flow at the maximum level of exercise in at least 8% of patients. Myocardial revascularization using the GEA can be achieved with minimal operative risk and offers satisfactory functional results and midterm survival rate.

Adult↗
PubMed1995

Bronchiectasis detected with thin-section CT as a predictor of chronic lung allograft rejection.

PURPOSE: To evaluate bronchiectasis detected with thin-section computed tomography (CT) as a potential early finding of chronic lung allograft rejection. MATERIALS AND METHODS: Forty patients were studied at least 6 months after transplantation. Follow-up CT scans were obtained 6-48 months after transplantation and were retrospectively reviewed for evidence and anatomic extent of bronchiectasis. Irreversible dysfunction of the lung transplant, called the bronchiolitis obliterans syndrome (BOS), was staged according to pulmonary function testing. Pathologic proof of bronchiolitis obliterans was obtained. RESULTS: BOS occurred in 14 (35%) of the 40 patients. When considering bronchiectasis preceding BOS, bronchiectasis was a predictor of chronic rejection with a sensitivity of 14%, a specificity of 77%, a positive predictive value of 25%, and a negative predictive value of 63%. Bronchiectasis appeared concomitantly with BOS in eight (67%) of 12 patients. CONCLUSION: The diagnosis of chronic rejection relies on the degree of impairment of pulmonary function. When the diagnosis is only suspected on the basis of minimal impairment, CT can aid in the diagnosis of rejection by depicting early pulmonary changes.

Adolescent↗
PubMed1995

High-resolution computed tomographic findings associated with histologically diagnosed acute lung rejection in heart-lung transplant recipients.

A group of 32 lung (single lung, [n = 14] and double lung [n = 1]) or heart-lung (n = 17) transplant recipients were studied with serial high-resolution computed tomography (HRCT) scans and transbronchial biopsies from the time of surgery. These investigations were carried out routinely every 2 weeks for the first 2 months, every 2 months for a year, every 4 months in the second year, and on any clinical suspicion of acute lung rejection or infection. A total of 190 transbronchial biopsy specimens and concurrent HRCT scans were obtained. Forty (21%) of the biopsy specimens, showed histologic evidence of lung rejection, 111 (58%) were normal, and 39 (21%) were not conclusive. The more frequent HRCT pattern encountered during an acute rejection episode was the presence of patchy "ground-glass" density areas (65%). This finding was sparsely observed during minimal and mild acute rejection episodes. Using histologic diagnosis as a standard for acute rejection, ground-glass opacities on HRCT had a sensitivity of 65% in detecting lung rejection. Although ground-glass opacities were also intermittently observed during cytomegalovirus pneumonia (14%), this finding had a specificity of 85% for detecting occurrence of an acute lung complication. The detection of ground-glass opacities on lung HRCT after lung transplantation, more particularly after the first month after surgery, can aid the decision of when and where to undertake transbronchial lung biopsy.

Acute Disease↗
PubMed1995

Fast MR angiography of the aortoiliac arteries and arteries of the lower extremity: value of bolus-enhanced, whole-volume subtraction technique.

OBJECTIVE: MR angiography of the abdominal aorta and lower limb arteries has been hampered by the need to depict long segments of the arteries in short imaging times. To overcome these limitations, we combined fast acquisition of coronal sections with bolus-enhancement technique, subtraction, and whole-volume projection display. The purpose of this preliminary study was to determine the value of using this technique in patients with abdominal aortic lesions and atherosclerotic occlusive disease of the lower limbs. SUBJECTS AND METHODS: Ten healthy volunteers and 20 patients with abdominal aortic aneurysms (n = 15), vascular graft (n = 3), arteriovenous fistula (n = 1), and abdominal aortic dissection (n = 1) were examined by segmented K-space ultrafast gradient-echo sequences. Sequential 50-cm coronal sections were acquired before and after an IV bolus injection of gadolinium (0.1 mmol/kg). Subtraction images were created by subtracting precontrast from postcontrast images. In all MR images, signal intensity was measured in the aorta, the inferior vena cava, and the background tissues. The final MR angiogram was a summation image of each subtracted image and was compared with a preoperative conventional arteriogram. Data from each study were collected prospectively and analyzed in a blinded manner. The radiologist evaluated depiction of the following specific areas: the abdominal aorta, common iliac arteries on both sides, superficial femoral arteries and above-knee popliteal arteries, below-knee popliteal arteries, superior mesenteric artery, and renal arteries. The aneurysms were categorized as infrarenal or suprarenal and as involving or not involving the iliac arteries. The graft was considered patent if depicted at both its origin and its periphery. RESULTS: In the healthy volunteers, bolus-enhanced subtraction MR angiography depicted without in-plane saturation the aorta, iliac arteries, and arteries of the lower extremity in less than 2 min. Gadolinium significantly increased the aortic signal-to-noise ratio from 25 +/- 3 to 232 +/- 8 (p < .0001), whereas the signal intensity of the inferior vena cava, muscles, and fat remained relatively stable. Examinations were thought to be interpretable in all but two patients. Clear delineation of aneurysms, intimal flap and arteriovenous fistula, and graft patency (n = 3) or occlusion (n = 2) were similarly diagnosed by conventional and MR angiography. Superior mesenteric artery was depicted in all cases on postcontrast images before subtraction. The number of renal arteries (n = 29) was correctly identified in all 15 patients who had renal areas included in their aortograms on postcontrast images before subtraction. However, renal arteries throughout their full length were usually obscured by renal veins and bowel contrast enhancement on the final MR angiogram. Furthermore, bolus-enhanced subtraction MR angiography was able to depict all lower limb arteries. CONCLUSION: Although further evaluation and technical improvements are required, our preliminary results indicate that bolus-enhanced subtraction MR angiography is a promising new method for fast abdominal and peripheral vascular imaging.

Adult↗
PubMed1995

[Exploration of the thoracic aorta. Excluding the aortic valve].

MRI has become the reference technique for the diagnosis and assessment of thoracic aortic aneurysms and subacute or chronic aortic dissections, and in the postoperative surveillance of the thoracic aorta. Several MRI techniques can now be used to investigate the thoracic aorta. The technique most widely used at the present time is Spin Echo imaging, which allows a multi-plane morphological approach to the thoracic aorta. It is often completed by a dynamic gradient echo sequence (cine-MRI) and, more recently, by ultra-rapid sequences (Turbo-Flash) following the injection of contrast agent. Phase-coding has also been proposed for the various intraluminal velocities. In the emergency situation, the examination of choice is less clearly defined due to the development of new techniques (transoesophageal ultrasonography, spiral computed tomography, MRI). The diagnostic strategy depends on the patient's clinical state, the respective advantages and limitations of each technique and the human and material resources available.

Aortic Dissection↗
PubMed1995

[Exploration of the thoracic aorta, excluding the aortic valve].

MRI has become the reference technique for the diagnosis and assessment of thoracic aortic aneurysms and subacute or chronic aortic dissections, and in the postoperative surveillance of the thoracic aorta. Several MRI techniques can now be used to investigate the thoracic aorta. The technique most widely used at the present time is Spin Echo imaging, which allows a multi-plane morphological approach to the thoracic aorta. It is often completed by a dynamic gradient echo sequence (cine-MRI) and, more recently, by ultra-rapid sequences (Turbo-Flash) following the injection of contrast agent. Phase-coding has also been proposed for the various intraluminal velocities. In the emergency situation, the examination of choice is less clearly defined due to the development of new techniques (transoesophageal ultrasonography, spiral computed tomography, MRI). The diagnostic strategy depends on the patient's clinical state, the respective advantages and limitations of each technique and the human and material resources available.

Aortic Dissection↗
PubMed1994

Automated myocardial edge detection from breath-hold cine-MR images: evaluation of left ventricular volumes and mass.

This paper describes an automated edge detection method for the delineation of the endo- and epicardial borders of the left ventricle from magnetic resonance (MR) images. The feasibility of this technique was demonstrated by processing temporal series of cardiac MR images obtained in 12 healthy subjects and acquired from the apex to the base of the heart in multiple anatomic short axis planes with a breath-hold cine-MR acquisition sequence. This procedure allows the entire heart to be imaged in less than 5 min. The automatic program correctly identified the edges in most cases. In poor contrasted images, a fast and user-friendly interactive procedure was used to correct the border delineation. The proposed method for the contour tracing requires a limited degree of control by the user and thus considerably reduces the tedious and long operator time inherent in the usual manual contour tracing tool. The left ventricular volumes were directly measured from these sets of contours by using the Simpson rule, allowing the end-diastolic volumes (EDV), the end-systolic volumes (ESV), the ejection fraction (EF) and the myocardial mass to be determined. The values measured in this study with the dedicated software were similar to the literature values (EDV = 78.3 ml/m2; ESV = 21.1 ml/m2; EF = 73%). Associated with the ultrafast breath-hold cine-MR imaging, the described edge detection method provides an efficient clinical tool for the direct assessment of cardiac function.

Adult↗
PubMed1994

Coronary arteries: new design for three-dimensional arterial phantoms.

Few three-dimensional (3D) anthropomorphic phantoms are available for testing 3D reconstruction and quantitation of vessels. The authors built a new realistic model of arteries with use of stereolithography, a computer-aided design and computer-aided manufacturing technique. Each phantom is composed of the physical object and its digital "twin." The entire coronary artery tree and complex stenoses were manufactured with a precision below 0.1 mm.

Arteries↗