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Biomedical subjects

M Amiel

Publications and source records attributed to M Amiel.

At least 19 recordsLinked to original sources
PubMed1992

[Technique for measuring the atheroma volume in men].

The evaluation of the impact of therapy on the evolution of atherosclerotic lesions or restenosis after angioplasty requires the use of techniques of vascular imaging. The reference invasive method is digital angiography although it does not provide data on the arterial wall thickness. This parameter can be approached however by intravascular ultrasound imaging, a technique which has a number of important practical limitations. Of the non-invasive techniques available, Doppler ultrasonography is the only one that can be used in clinical trials. Nuclear magnetic resonance imaging is the object of much research and is without doubt the technique of the future. The choice of model of atherosclerosis influences that of the imaging technique: cineangiography for coronary arteries, digital angiography or Doppler ultra sonography for lower limb arteries and Doppler ultrasonography for the carotid arteries. Interpretation of angiography is now performed quantitatively by videodensitometry. Interpretation of other techniques should be performed by a second independent observer and "blinded" with respect to the order in which the investigations were performed and to the treatment administered. The criteria of judgment may be qualitative (progression, stabilisation, regression) or quantitative, the latter having a number of advantages over the former. Of the quantitative criteria, the percentage stenosis, though widely used, does not fully answer the question posed, and neither does the diameter of the stenosis. The volume of the arterial lumen calculated from videodensitometric data would seem to be the best, by its sensitivity and additivity, current angiographic parameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography, Digital Subtraction↗
PubMed1992

Disturbances caused by dental materials in magnetic resonance imaging.

Nuclear Magnetic Resonance (NMR) is the latest addition to medical imaging technology. This technique plays an important role in head and neck diagnosis. Radiologists may encounter patients with fixed dental prostheses that may produce image distortion on MRI scans of the face. The MRI appearances of dental prosthetic materials was studied in vitro, including precious alloys, non-precious alloys, ceramic prostheses, dental amalgam and composite materials. It was found that non-precious alloys produce large image deformations, whereas precious alloys had no effect on MRI images. An in vivo study showed the anatomical zones that were most affected on MRI scans.

Ceramics↗
PubMed1991

Dental materials and magnetic resonance imaging.

Radiologists may encounter patients with fixed dental prostheses that may produce image distortion on MRI scans of the face and jaw. In this work, we assessed the MRI appearances of dental prosthetic materials in vitro, including precious alloys, nonprecious alloys, ceramic prostheses, dental amalgam, and composite materials. For in vivo studies, these materials were placed in the patient's mouth. Nonprecious alloys produce large image deformations, whereas precious alloys had no effect on MRI images. The in vivo study showed the anatomical zones that were most affected on MRI scans. The size of these zones produced by the presence of nonprecious alloys is influenced by the volume of the prosthesis and is related to the scanning sequence used.

Adult↗
PubMed1991

Quantitation of reperfused myocardial infarction by Gd-DOTA-enhanced magnetic resonance imaging. An experimental study.

Because there is evidence that myocardial infarct size is modified by coronary artery reperfusion, an ex vivo experimental model of myocardial infarction was developed to determine the influence of the timing of gadolinium-tetraazacyclododecane tetraacetic acid (Gd-DOTA)-enhanced magnetic resonance imaging (MRI) on the accuracy of infarct size quantitation. Eighteen dogs underwent a 2-hour coronary occlusion followed by 1 (n = 6), 6 (n = 6), or 48 (n = 6) hours of reperfusion. Gd-DOTA was injected 10 minutes before the dogs were killed. T1 (SE 250/26) and T2 (SE 1500/78) weighted images were performed on excised hearts. Gd-DOTA concentration was measured in myocardium by atomic emission spectrometry, and correlated with myocardial blood flow evaluated by radioactive microspheres. All dogs presented with myocardial infarction (mean size 20.4% +/- 3.1% of the left ventricle), and a corresponding area of increased signal intensity on T1-weighted MR images. In none of the three groups did the area of high signal intensity correlate with the ischemic area. By contrast, after 6 and 48 hours of reperfusion, the high signal intensity area (17.9% +/- 2.4%) closely matched the area of nonreversible jeopardized tissue (16.4% +/- 2.5%), as determined on tetrazolium-stained heart slices. Although a noreflow phenomenon was observed in the jeopardized tissue, Gd-DOTA concentration was higher in the subendocardial central ischemic zone than in normally perfused myocardium. Gd-DOTA imaging enhancement seems to be the consequence of a delayed clearance of the agent from the injured tissue. Gd-DOTA-enhanced MRI accurately quantitates the size of reperfused myocardial infarction on the ex vivo heart for more than 6 hours after the beginning of reperfusion. It remains to be determined whether the in vitro results obtained here can be applied to assess the myocardial infarct size in vivo.

Animals↗
PubMed1991

[Obstruction of pulmonary arteries. Contribution of the scanner and MRI. Apropos of 10 cases].

We present a retrospective study of ten patients presenting non specific clinical manifestations in whom the diagnosis of pulmonary embolism was documented by CT scan and/or MRI. Results of CT scan and/or MRI were compared to DSA bi-selective pulmonary angiography findings. In a large number of cases, CT scan and MRI allowed the detection of the obstruction within the right and left pulmonary arteries (RPA and LPA). Although these techniques did not permit the diagnosis of peripheral clots, pulmonary infarcts were usually depicted by these two procedures. CT scan and/or MRI could be performed as first-line investigations in case of atypical clinical symptoms because of their high relevance for proximal pulmonary artery obstruction, although these two non-invasive procedures cannot indicate the aetiology of the obstruction etiology.

Evaluation Studies as Topic↗
PubMed1990

Reliability of phlebography in the assessment of venous thrombosis in a clinical trial.

In the frame of a multicenter controlled study comparing the efficacy of low-molecular-weight heparin to standard heparin in the prevention of postsurgical thrombosis, 94 phlebograms were centrally evaluated by two independent radiologists. Three months after the first central evaluation, a new reading was performed with the same radiologists, and discrepancies were adjudicated by a senior radiologist. The number of discrepancies between the first and the second evaluation was high: 33 interpretations (35%) had a least one difference, including 14 (14.9%) discrepancies regarding the main issue, i.e. the presence of venous thrombosis. After the adjudication by the senior radiologist, this number decreased but was still large: 22 films (23.4%) with at least one discrepant item in all and 11 related to the presence of venous thrombosis. This report shows that venous thrombosis assessed by phlebography, which is usually considered as a golden standard in clinical trials, deserves a thorough quality control procedure.

Double-Blind Method↗
PubMed1990

[Perforation of a loop of the small intestine by a Kim-Ray Greenfield endocaval filter. Report of a case].

Kim-Ray filter complications are usually benign, such as angulation or slight migration. We report and compare with the literature one case of vena cava perforation associated with a small bowel lesion. The follow-up with regular abdominal plain X-rays allows detection of filter angulation, the first step before vena cava perforation. Cavography or CT scan depicts this perforation. Complete or partial surgical removal of the filter may be necessary.

Adult↗
PubMed1990

[An attempt to quantify myocardial ischemia by selective coronary arteriography: determination of a new score. An initial study].

An original model for estimating myocardial ischaemia from coronary arteriography is proposed. Four parameters are taken into consideration: anatomical variations, the myocardial mass perfused, the degree of reduction of basal flow across the stenosis, the eventual summation of several successive stenotic lesions. This scoring system was tested by simulation on a computer and evaluated in 100 anginal patients. Analysis of our preliminary results shows statistically significant differences in the score between the following groups of patients: patients with normal and those with abnormal LV wall motion; patients with and those without previous myocardial infarction; patients with Class II stable angina and those with other forms (III, IV and unstable angina).

Adult↗
PubMed1989

Effect of iodinated contrast media on blood clotting.

Recently, blood clot formation in catheters used for the injection of nonionic contrast media (CM) during angiography has been reported as being due to activation of hemostasis in the catheter. However, CM exhibit inhibitory properties regarding coagulation and platelet functions. The effect on blood clotting of iohexol, iopamidol, ioxaglate, diatrizoate, and ioxitalamate at a ratio of 10% v/v with nonanticoagulated human whole blood was evaluated using the kinetics of fibrinopeptide A (FpA) generation. Blood aliquots were taken every 2 minutes until blood clot occurred. Two groups of contrast media were identified: (1) iohexol and iopamidol, which increased the clotting time, and (2) ioxaglate, diatrizoate, and ioxitalamate, for which all clotting times were over 30 minutes and no FpA generation occurred.

Blood Coagulation↗
PubMed1989

[Automatic quantitative analysis of vascular stenosis. Experimental study of a digital angiography system applied to cardiology].

The purpose of this study was to test the measurement reliability of the automatic stenosis quantitation program present in a digital angiography system (DG 300 General Electric CGR SA). The experimental study was performed on models mimicking circular, elliptic and irregular stenoses; it made it possible to measure the percentage of stenosis by geometric and densitometric methods. The parameters studied were the size and shape of the stenoses, the contrast medium concentration, the positioning of the stenosis in relation to the image intensifier, the number of Kvp and the angle of projection of X-ray beams in the case of elliptic and irregular stenoses. The results showed a perfect linear correlation between the thickness traversed by the X-ray beams and the value in grey level at the output of the optico-radiological chain (r between 0.987 and 0.997, p less than 0.001), using different Kvp (65 Kvp, 85 Kvp, 90 Kvp) and different X-ray doses (1 milliRoentgen and 80 microRoentgen). With all concentrations of contrast medium (320 mg I/ml to 5 mg I/ml), the values of the circular stenoses measured were very close to real values (75 p. 100) for vessels of all diameters, except those of 1.5 mm in a 22 cm field. When 16 cm and 11 cm fields were used, the results were very close to the 75 p. 100 real value (3 to 4 p. 100 of relative error), even with the 1.5 mm diameter. The values of elliptic stenoses measured by densitometry were very close to real values (1 to 4 p. 100 of relative error) with contrast medium concentrations ranging from 320 mg I/ml to 20 mg I/ml) and with three angles of projection (0 degrees, 30 degrees, 60 degrees). In contrast, the geometric method gave very different results with the three angles of projection. In the case of irregular stenosis (17 percentages of stenosis ranging from 26.2 p. 100 to 77.1 p. 100) the real values correlated very well with the estimated values (r = 0.999, p less than 0.0001). Some of the results were compared with those obtained with a digital cineradiology system (Pie Data) and were found to be equivalent.

Angiography↗
PubMed1989

[Early occlusion and dissection in coronary angioplasty. Apropos of 855 patients].

Between June 1981 and may 1987, 855 patients were treated by transluminal coronary angioplasty at the Cardiovascular Hospital, Lyon. 778 primary successes (84 p. 100) were obtained, 84 of the 855 patients (9.8 p. 100) developed occlusion and/or angiographically proven dissection within the first 24 hours. These patients fell into two groups; group A (n = 35) with occlusion and occlusive dissection, group B (n = 49) with dissection but without coronary blood flow reduction. Among the parameters examined, only three concerning the morphology of the stenosis were associated with a statistically more frequent occurrence of occlusion: eccentric stenosis (p less than 0.05), irregular stenosis (p less than 0.01) and stenosis in a curvilinear segment (p less than 0.01). In addition, among the 84 patients with occlusion and/or dissection, 14 had myocardial infarction and 2 died during the 24 hours following angioplasty. Emergency aorto-coronary bypass was performed in 12 cases, mostly after failure of redilatation. Redilatation was carried out in 26 cases and was effective in 14.

Angioplasty, Balloon↗