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Biomedical subjects

H Vernhet

Publications and source records attributed to H Vernhet.

At least 19 recordsLinked to original sources
PubMed2005

A numerical assessment of wall shear stress changes after endovascular stenting.

This theoretical/numerical study aims at assessing the haemodynamic changes induced by endovascular stenting. By using the classical one-dimensional linear pressure waves theory in elastic vessels, we first show that the modulus of the reflection coefficient induced by an endovascular prosthesis is most likely small since it is proportional to the stent-to-wavelength ratio. As a direct consequence, the wall motion of the elastic (stented) artery can be prescribed a priori and the coupled fluid-structure problem does not have to be solved for assessing the haemodynamic changes due to stenting. Several 2D axisymetric calculations are performed to solve the unsteady incompressible Navier-Stokes equations on moving meshes for different types of (stented) arteries. The numerical results suggest that endovascular stenting increases the systo-diastolic variations of the wall shear stress (by 35% at the middle of the stent, by almost 50% in the proximal transition region). Additional calculations show that over-dilated stents produce less haemodynamic perturbations. Indeed, the increase of the amplitude of the wall shear stress variations over the cardiac cycle is only 10% when the stent radius is equal to the radius of the elastic artery at systole (instead of being equal to the mean artery radius).

Elasticity↗
PubMed2004

[Imaging of the pulmonary arteries: when, how and when?].

For several years, catheter angiography was the standard imaging technique used for evaluating the pulmonary arteries. Technical advances with computed tomography have had a significant impact on chest imaging, especially the increasing availability of multidetector row CT units. CT pulmonary angiography (CTPA) is now the first line imaging technique to evaluate pulmonary arterial diseases, including pulmonary embolus. Pulmonary angiography is now essentially limited to the endovascular management of pulmonary arteriovenous malformations, pulmonary arteriovenous fistulas or pulmonary arterial aneurysms. Gadolinium enhanced MR angiography of the pulmonary arteries may be helpful in patients with contraindications to the use of iodinated contrast material.

Aneurysm↗
PubMed2003

[Value of thoracic CT in the management of severe hemoptysis].

PURPOSE: To assess the value of thoracic CT in the management of patients with severe hemoptysis. PATIENTS AND METHODS: Between January 1997 and January 2001, 62 patients were investigated for severe hemoptysis (>300 ml/24H). The protocol, performed before angiography and embolization, included bronchial fiberoptic examination (BFE) followed by thoracic spiral CT-angiography. Data recorded at CT and BFE were the presence and location of bleeding, the etiology of hemoptysis and the therapeutic modality. RESULTS: Nine patients with life-threatening hemoptysis directly underwent bronchial embolization. CT was available in the 53 remaining patients. No abnormality was found in 4 patients. CT assessed the presence (n=49) and the location (n=38) of the bleeding. The etiology was determined in 49 patients. BFE was feasible in 38/53 patients. BFE assessed the presence (n=38) and location (n=15) of the bleeding. The etiology was determined in 12 cases of bronchial tumour. The available findings of CT and BFE for the presence and the location of the bleeding were concordant. Comparing fiberoptic examination and thoracic CT, the percentages of localized bleedings (39% and 72%) and demonstrated etiologies (32% and 92%), were significantly different (p<0,005 and p<0.0001 respectively). CONCLUSION: Although retrospective and limited by the small number of cases, our study provides arguments to perform thoracic CT before bronchial fiberoptic examination for the management of severe hemoptysis.

Adolescent↗
PubMed2001

Reversible amiodarone-induced lung disease: HRCT findings.

The aim of this study was to describe thoracic high-resolution computed tomography (HRCT) findings of reversible amiodarone-induced lung disease (AILD). The thoracic HRCT of 20 symptomatic patients who were considered as having reversible AILD by the medical staff of our institution were retrospectively reviewed. The patient-selection criteria used were the development of new respiratory symptoms while receiving amiodarone, the exclusion of other respiratory and cardiac diseases, and the decrease of both respiratory symptoms and radiological abnormalities after cessation of amiodarone and corticotherapy. The CT data recorded were those usually sought infiltrative lung diseases. The radiological findings using chest film (n=20) and HRCT (n=4) follow-up was noted. All patients had ground-glass opacities, associated with consolidations (n=4), thin intralobular reticulations (n=5), or both (n=11), with a subpleural (n=18) or central (n=2) location. Eight patients had high-density areas and 13 had pleural thickening (n=13). Bronchial abnormalities included dilation (n=16) and wall thickening (n=19). After therapeutic management, the radiological follow-up showed complete (n=17) or incomplete (n=3) improvement. Ground-glass opacities associated with thin intralobular reticulations and/or subpleural consolidations and bronchial abnormalities are common HRCT findings in reversible AILD.

Aged↗
PubMed2001

Rhinosinusitis in severe asthma.

BACKGROUND: Chronic rhinosinusitis is a common comorbidity of asthma. However, sinonasal involvement in severe steroid-dependent asthma is still undefined. OBJECTIVE: The aim of the study was to evaluate chronic rhinosinusitis in 35 patients with severe steroid-dependent asthma by using a clinical score and coronal computed tomography (CT) scanning. METHODS: Thirty-five subjects (16 female subjects) with severe asthma requiring daily doses of oral corticosteroids were compared with 34 patients (19 female patients) with mild-to-moderate asthma. Sinonasal involvement was studied by using clinical and CT scores. Airflow obstruction, therapy requirement, and asthma triggering factors were carefully assessed. RESULTS: The proportion of patients with symptoms of rhinosinusitis was similar in both groups of asthmatic subjects (74% in patients with severe steroid-dependent asthma and 70% in patients with mild-to-moderate asthma). All subjects with steroid-dependent asthma versus 88% of subjects with mild-to-moderate asthma had abnormal CT scan results. The clinical (P <.05) and CT scan (P <.0005) severity scores were higher in the subjects with severe steroid-dependent asthma. In both groups the CT scan scores were correlated to the clinical scores (P <.0001 and P <.006), but only in the mild-to-moderate group were both scores correlated with high significance (P <.002 and P <.0005) to the absolute number of blood eosinophils. CONCLUSION: Frequency of rhinosinusitis in patients with mild-to-moderate or severe steroid-dependent asthma is similar; however, sinonasal involvement, as evaluated by clinical symptoms and CT scan imaging, is significantly greater in the patients with severe steroid-dependent asthma than in those with mild-to-moderate asthma.

Adolescent↗
PubMed2001

Changes in wall mechanics after endovascular stenting in the rabbit aorta: comparison of three stent designs.

OBJECTIVE: The aim of this study was to evaluate changes in the wall mechanics of small-diameter arteries after endovascular placement of three different stents. SUBJECTS AND METHODS: Five self-expandable stents (Wallstent), five balloon-expandable noncovered Palmaz stents, and three balloon-expandable covered stents (Jostent) were placed in the infrarenal aorta of 13 New Zealand white rabbits. Systolic blood pressure changes, blood-flow velocity, systolic diameter, and diameter changes were measured and used to calculate the diameter compliance, the distensibility coefficient, and the pulsatility index. RESULTS: Compliance (10(-3) mm kPa(-1)) was 75.3 +/- 20.1 before stenting and reached 94.7 +/- 42.2 upstream, 38.8 +/- 14.2 at the stent level (p < 0.05), and 70.8 +/- 23.2 downstream from the stent. Distensibility (10(-3) kPa(-1)) was 24.3 +/- 6.3 before stenting and reached 27.8 +/- 10.3 upstream, 10.5 +/- 4.4 at the stent level (p < 0.001), and 21.9 +/- 8.6 downstream from the stent. Compliance and distensibility were significantly lower at the stent level than upstream and downstream (p < 0.05). Aortic diameter increased significantly at the stent level from 3.11 +/- 0.40 mm before to 3.76 +/- 0.42 mm after stenting. No significant difference was found among the three stent designs for all the studied data. CONCLUSION: Regardless of the three tested stent designs, endovascular stenting produces a significant decrease in arterial wall compliance of the rabbit aorta.

Animals↗
PubMed2001

[Dysfunctioning of central venous catheters: role of the radiologist].

Malfunctioning long-term central vein catheters are related to malposition, obstruction, mechanical problems and occlusion of the catheters. The diagnosis and the management of these disorders are based upon chest film examination, catheter or venous enhancement with contrast media. Vascular interventional radiology plays a major role in low invasive management of malfunctioning central vein catheters in hemodialysed patients: transfemoral malpositioned catheter manipulations, fibrin sleeve stripping, infusion of urokinase.

Catheterization, Central Venous↗
PubMed2000

Acute changes in aortic wall mechanical properties after stent placement in rabbits.

PURPOSE: To evaluate mechanical property changes after endovascular stent placement in small-diameter arteries. MATERIALS AND METHODS: Self-expanding stents (Wallstent) were placed in the infrarenal aorta of five New Zealand White rabbits via a surgical right femoral approach. Blood pressure changes (deltaP) were monitored in the aorta. Blood flow velocity was measured with a 20-MHz, pulsed Doppler probe (n = 4) to calculate the pulsatility index. Aortic diameter (dA) and diameter changes (delta(d)) were measured with a 20-MHz probe in echo-tracking mode. Diameter compliance (Cd) and distensibility coefficient (DC) were calculated as Cd = 2(delta)d/(delta)P and DC = 2delta(d)/delta(P)/dA. RESULTS: Aortic diameter increased from 3.360 +/- 0.4033 mm to 4.020 +/- 0.3033 mm after stent placement at the stent level only. Compliance decreased from 77.644 +/- 24.306 mm kPa(-1) to 31.150 +/-8.245 x 10(-3) mm kPa(-1) at the stent level, and was then significantly lower than upstream (98.500 +/- 53.196 mm kPa(-1)) and down-stream (59.047 +/- 13.833 mm kPa(-1)). There was no significant change in pulsatility index. CONCLUSIONS: Endovascular stent placement produces a significant decrease in arterial wall compliance of the rabbit abdominal aorta.

Acute-Phase Reaction↗
PubMed2000

[Interventional radiology of the thorax].

Interventional radiology of the thorax includes a wide variety of diagnostic and/or therapeutic procedures. Transthoracic needle biopsy is a widely used technique. Generall, computed tomography is used to guide the puncture, less commonly fluoroscopy or in exceptional cases ultrasound. Targets include parenchymatous, pleural and mediastinal lesions. The biopsy specimen is used for cytology, histology, bacteriology, mycology and parasitology studies. Needle biopsy is also the first step in more complex procedures: drainage of thoracic collections, inserting harpoons, thoracic sympatholysis, palliative treatment of aspergillomas. Bronchial arteriography with embolization is an effective emergency symptomatic treatment for severe hemoptysis. Endovascular vaso-occlusion procedures can be used for rare arteriovenous pulmonary fistulas. Superior vena cava obstruction can be treated, usually in a palliative procedure, by installing an endovascular endoprosthesis.

Arteriovenous Fistula↗
PubMed1999

[Contribution of high-resolution volume computed tomography (HRVCT) for the exploration of diffuse pulmonary infiltrative disorders].

AIM: To assess high-resolution volume computed tomography (HRVCT) for the investigation of diffuse pulmonary infiltrative disorders. PATIENTS AND METHODS: Thirty patients with diffuse interstitial disease (idiopathic fibrosis n = 7, silicosis n = 4, asbestosis n = 5, sarcoidosis n = 7, histiocytosis n = 2, lymphangitis carcinomatosa n = 2, tuberculosis n = 1, bronchiolitis obliterans n = 1) were explored using high-resolution computed tomography (HRCT) and HRVCT. All diagnoses were proven by fiberscopy, bronchoalveolar lavage and respiratory function tests and/or lung biopsy. The HRVCT protocol consisted of spiral tomography using 10 mm slices. Data were processed with a Windows Advantage workstation (GE Milwaukee). Two readers compared multiprojection volume reconstruction (MPVR) using maximal intensity projection (MIP) and minimal intensity projection (MINIP) displays with millimetric HRCT slices acquired at the same volume. RESULTS: Micronodules were detected better with HRVCT than with HRCT. MIP mode enabled better distinction between nodules and vessels. MINIP mode enabled better detection of cysts in the pulmonary parenchyma than HRCT. The honeycomb aspect of pulmonary fibrosis was differentiated better than super-infected central-lobar emphysema. MINIP mode enabled detection of ground glass opacities which were not visible on HRCT. Certain anomalies were however detected only on HRCT. HRVCT was very sensitive to movement effects which altered image quality, particularly in the MINIP mode. CONCLUSION: HRVCT is a new and promising approach for investigating diffuse pulmonary infiltrative disorders.

Adult↗
PubMed1998

Endovascular management of traumatic infrarenal abdominal aortic dissection.

Dissection is a recognized finding after blunt trauma to the abdominal aorta. Immediate and long-term prognosis is poor without surgical treatment especially since most patients present severe associated injuries. On the basis of encouraging results using endovascular techniques to treat experimental dissection of the descending thoracic aorta, we treated three patients with traumatic infrarenal abdominal aortic dissection by percutaneous stent placement. There were two men 34 and 41 years of age and one 89-year-old woman. In all patients, dissection began in the infrarenal portion of the aorta and extended into the iliac arteries. All patients had multiple associated injuries. The main symptoms were acute abdominal pain (two patients) and ischemia of the lower extremities (two patients). Diagnosis was missed in one patient despite exploratory laparotomy for an associated injury. Two patients were treated in the acute phase by placement of a self-expanding endovascular prosthesis at the aortoiliac level. The third patient was treated in the chronic phase by placement of a balloon-expandable endovascular stent. All procedures were performed uneventfully by femoral route. Success of treatment was confirmed by arteriography and computed tomography (CT) scan demonstrating obliteration of the dissection. Upon late follow-up examination, all patients were in satisfactory condition, with normal Doppler ultrasound findings. These findings confirm experimental studies using endovascular treatment for dissection of the descending thoracic aorta and are promising for future clinical management.

Adult↗
PubMed1996

Interventional chest radiology.

The authors review the various interventional radiology techniques currently used in 1996 by a Medico-Radio-Surgical team. CT guided needle biopsy has an important place in the diagnostic approach to parenchymal as well as mediastinal tumours. But CT guidance allows also routine drainage of thoracic collections and sometimes thoracic sympatholysis. Superior vena cava and tracheobronchial stenting are palliative treatments as the percutaneous aspergilloma treatment. Embolization of bronchial and thoracic systemic arteries are also palliative but effective therapeutic procedures as well as vasoocclusion for arterio-venous fistulae.

Aspergillosis↗