Plaque density on CT, a potential marker of ischemic stroke.

The authors sought to determine in a retrospective analysis whether carotid plaque soft TD on CT is associated with recent ischemic neurologic events. Among 141 patients (99 asymptomatic), 106 plaques with more than 50% stenosis were selected for density measurements. They found an odds ratio for neurologic events associated with a 10-point decrease in density of 1.54 (p = 0.002), showing an association between plaque density and neurologic events.

[Efficacy and safety of low-dose heparin (30 IU/kg) during coronary angioplasty]. / Efficacité et sécurité d'emploi de faibles doses d'héparine (30 UI/kg) en cours d'angioplastie coronaire.

High doses of heparin are recommended during coronary angioplasty although platelet inhibition seems to play a role in the prevention of ischaemic complications. Low dose heparin could reduce the incidence of local complications without increasing that of major coronary events. The authors report the results of a prospective register of coronary angioplasties performed by the femoral approach with a single bolus of 30 IU/Kg of heparin and immediate withdrawal of the 6 French introducer. Only patients with recent infarction or left main stem disease were excluded. All underwent clinical examination and ultrasonic scanning of the puncture site the day after the procedure. Four hundred and eighteen patients were included (mean age: 63.3 +/- 11 years; 79% men; 77% stenting). The average dose of heparin was 2253 +/- 1056 IU; the average procedure time was 25 +/- 16 minutes, and a final activated clotting time was 174 +/- 69 ms. The duration of normal compression was 7.7 +/- 3 min. Eighty-three point five per cent of patients were discharged the day after the procedure with a global cardiovascular complication rate of 2.87%. At 1 month, 1.67% of secondary cardiovascular events was recorded. Ultrasonography of the puncture site was abnormal in 7.6% of patients. Only one serious vascular complication (0.24%) requiring transfusion and surgical repair, was observed. The authors conclude that the use of low dose heparin appears effective and safe in cases without acute myocardial infarction. This protocol allows faster mobilisation and earlier hospital discharge of patients.

Accuracy of three-dimensional gadolinium-enhanced MR angiography in the assessment of extracranial carotid artery disease.

OBJECTIVE: The purpose of this study was to assess three-dimensional (3D) gadolinium-enhanced MR angiography, used alone or in association with duplex Doppler sonography, with a fast acquisition time (8 sec) for evaluating the extracranial carotid arteries. SUBJECTS AND METHODS: In this prospective study, 48 successive patients with carotid artery stenoses were examined with 3D gadolinium-enhanced MR angiography and 3D time-of-flight MR angiography. Of the 44 eligible patients, conventional angiography was available in 33 and duplex sonography in 27. We used the North American Symptomatic Carotid Endarterectomy Trial technique to quantify stenosis on all angiograms, and a 250 cm/sec threshold at duplex sonography to diagnose stenoses greater than 70%. Image quality of 3D gadolinium-enhanced MR angiography and 3D time-of-flight MR angiography was assessed, as well as sensitivity and specificity for each technique alone and in combination with duplex sonography. Conventional angiography was the gold standard. RESULTS: Three-dimensional gadolinium-enhanced MR angiography yielded good image quality in 90% of cases. When used alone, it yielded a sensitivity and a specificity of 94% and 85%, respectively, in screening stenoses greater than 70% (70-99%). When combined with duplex Doppler sonography, it provided a 100% sensitivity and specificity for detection of stenoses between 70% and 99% and would have obviated 61% of conventional angiography. In comparison, 3D time-of-flight MR angiography used alone yielded a sensitivity of 88% and a specificity of 94%. In combination with duplex Doppler sonography, its use would have obviated conventional angiography in 74% of cases. Three-dimensional gadolinium-enhanced MR angiography provided accurate results in the diagnosis of occlusions and ulcers and can visualize distant stenoses. CONCLUSION: Used alone, 3D gadolinium-enhanced MR angiography is not accurate enough to replace conventional angiography in the evaluation of extracranial carotid arteries. In association with duplex Doppler sonography, however, it is accurate and may obviate a significant number of conventional angiographic examinations.

Endovascular Doppler guide wire in renal arteries. Correlation with angiography in 20 patients.

RATIONALE AND OBJECTIVES: To evaluate the feasibility of endovascular Doppler recording in renal arteries and to compare the reliability of Doppler parameters for detection of renal artery stenosis. METHODS: The authors examined 36 renal arteries in 20 patients with a 0.018" endovascular flow wire. Peak systolic velocity and the renal artery-to-aortic peak were measured in the main renal artery. From intrarenal waveforms, acceleration, acceleration time, and the renal resistive index were obtained. Spectral analysis with consensus scoring of early systolic peak was also performed. RESULTS: Twelve significantly stenosed renal arteries and 26 normal renal arteries were examined with the Doppler guide wire, without complications. Peak systolic velocity was the only parameter significantly different in renal artery stenosis (P = 0.037). Peak systolic velocity also differed significantly between hypertensive and normotensive patients. Tardus parvus was specific for severe renal artery stenosis. CONCLUSIONS: Endovascular Doppler is a safe and accurate method for the determination of velocity measurements and may be useful during percutaneous renal artery revascularization.

[Diagnostic imaging of acute pulmonary embolism: critical analysis of the 1997 literature]. / Imagerie dans L'embolie pulmonaire alguë (EPA): analyse critique de la littérature en 1997.

With variable symptoms and a nonspecific radiographic appearance, acute pulmonary embolism (APE) is a frequent and often undiagnosed cause of mortality and morbidity; thus, availability of an accurate, noninvasive screening examination is highly desirable. Until recently, various noninvasive imaging procedures have been used to detect APE, including ventilation-perfusion scanning, MR imaging and phlebography (or sonography). The low specificity of scintigraphy explains why pulmonary angiography remains the usual "gold standard" modality for detection of APE. However, with this procedure morbidity and mortality not zero-Helical computed tomography (HCT) seems to be an accurate technique for diagnosis of pulmonary embolism except for distal thrombi. Nevertheless the exact position of HCT in the classic algorithms remains to be defined, particularly in terms or cost-benefit results.

Spatial compounding in ultrasonic imaging using an articulated scan arm.

A spatial compounding system has been designed to improve the quality of B-mode echographic images. It consists of constructing an improved image from the combination of several different images of the same cross-sectional plane. The "final" image is constructed by the registration and the superposition of the "original" images. For this, the relative position in the space of the original images has to be known. The use of a localization articulated arm, on which the ultrasonic probe is fixed, makes this possible. The main advantages of the technique are, on one hand, the elimination of the acoustic shadows following a strong reflector structure and, on the other hand, the reduction of the speckle generated in echographic images. The method of reconstruction has been validated on agar gel phantoms and provides good accuracy. In vivo experiments on human beings have also been performed. Acoustic shadows caused by bones in cross-sectional images of the thigh and the arm are eliminated. All the contours of the femur and humerus can be observed in the final images. The reduction of speckle is shown in kidney images and the signal-to-noise ratio improvement is quantified as a function of the number of images involved in the reconstruction.

Screening patients for renal artery stenosis: value of three-dimensional time-of-flight MR angiography.

OBJECTIVE: The purpose of this study was to determine the value of three-dimensional time-of-flight MR angiography in screening patients for the presence of renal artery stenoses. SUBJECTS AND METHODS: Fifty-three patients who were thought to have renovascular hypertension on clinical grounds were prospectively examined with three-dimensional time-of-flight MR angiography. IV digital subtraction angiograms and duplex sonograms were available for all patients. For 21 patients in whom IV angiograms were of high quality and showed the renal arteries to be normal, as confirmed with duplex sonograms, intraarterial digital subtraction angiograms were not obtained for MR correlation. In the other 32 patients, intraarterial angiograms of the abdominal aorta were obtained. MR angiograms were interpreted independently by two radiologists who were unaware of the findings on angiography and duplex sonography. Our preliminary clinical experience suggested that a signal loss in the renal arteries on maximum-intensity-projection MR angiograms indicated a potential stenosis and that the degree of stenosis could not be measured accurately with MR angiography. The search for stenoses was focused on the proximal and middle parts of the vessel, as far as 3 cm from the origin of the vessel. We used intraarterial angiography to measure and grade renal artery stenoses. On intraarterial angiograms, stenoses that involved more than 50% of the vessel's section were considered significant (n = 24) and stenoses that involved 50% or less of the section were considered insignificant (n = 7). These 31 stenoses were found in 26 of the 32 patients who had intraarterial digital subtraction angiography. RESULTS: All 24 significant stenoses appeared as a cutoff of signal intensity on MR angiograms. Results were false-positive in 20 cases: in eight cases, arteries were of small diameter; in seven cases, the stenoses were insignificant; in two cases, the acquisition volume was incorrectly positioned; in two cases, there was a sharp angle in the proximal part of the renal artery; and in one case, no explanation was found. MR angiography had a sensitivity of 100% for detecting stenoses in the proximal 3 cm of the renal artery; stenoses more than 3 cm from the origin of the arteries could not be detected reliably. CONCLUSION: Our results suggest that three-dimensional time-of-flight MR angiography is a simple method for detecting stenoses of the proximal portion of the main renal arteries. However, more work is needed before widespread clinical use of such a technique is feasible.

[Value and role of echo-Doppler in the screening of renovascular hypertension. A prospective study of 144 arteries with reference to angiography]. / Intérêt et place de l'écho-Doppler dans le dépistage des hypertensions réno-vasculaires. Une étude prospective portant sur 144 artères, en référence à l'angiographie.

The purpose of the study is a rigorous validation of different ultrasonic criteria of renal artery stenosis, and the presentation of the performances of duplex sonography in renal artery stenosis screening. Sixty seven patients have been investigated by ultrasonic techniques, and the results of duplex compared with intraarterial or intravenous digital subtraction angiography. Two kinds of ultrasonic investigations have been defined: complete explorations when the renal artery ostium is accessible, incomplete explorations in other cases. The main difficulty preventing the exploration from being complete is obesity: all patient with an overweight of more than 20% of their theoretical weight have an incomplete exploration of at least one of their renal arteries. Furthermore, duplex sonography was not able to demonstrate polar artery in any case. When the exploration is complete, maximum systolic frequency (F max) recorded on the renal artery course, and the systolic frequency ratio of renal and aortic recordings (RAR) are two valuable criteria of significant stenosis (> 50%): mean difference between normal and stenosed arteries for these two variables is statistically significant (p < 0.01). To obtain a good specificity, pathological threshold have been fixed at F max > 3,500 Hz and RRA > 2.5. When the exploration in incomplete, ascending time (asc. T) and resistance index (RI) of doppler recording obtained in the renal hilum are two valuable criteria for severe stenosis (> 80%), or occlusion: the mean between stenosed and non stenosed arteries is statistically different (p < 0.001 and p < 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

[Technique for measuring the atheroma volume in men]. / Techniques de mesure de la plaque athéroscléreuse chez l'homme.

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)

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.

[The concept of critical arterial stenosis: value of a model of measures obtained by an angiographic method and the Doppler technic before and after transluminal angioplasty of the iliac arteries]. / Notion de sténose artérielle critique: intérêt d'une modélisation des mesures obtenues par méthode angiographique et technique Doppler, avant et après angioplastie endoluminale des artères iliaques.

INTRODUCTION: Numerous studies in the literature have proven the fact that a critical size appears during the stenosis evolution. The work presented is a non invasive approach of this value, with correlation to the invasive results. The study was realized on a homogeneous group of 23 arteriopathic patients, selected for iliac artery angioplasty procedure. MATERIAL AND METHODS: Patients selection: twenty-three patients including 24 angioplasty procedures have been selected on a 21 month time study. Invasive data: two measurements are realized during angioplasty: trans-stenotic pressure gradient before and after angioplasty. stenosis calibration: both diameter and section have been calculated on radiological films. Non invasive data: a standard Doppler test is performed on lower limbs. Two parameters are compared with the invasive data: the ascending time of velocity curve at the common femoral level. the systolic pressure index (peripheral pressure/radial pressure). RESULTS: 1) Critical stenosis--invasive techniques (fig. 1): trans-stenotic pressure gradient versus stenotic measurements shaw an hyperbolic correlation. The critical stenotic level is found to be 60% in diameter and 80% in section. 2) Critical stenosis--non invasive techniques: stenotic measurements compared to ascending time (fig. 2) as well as pressure index at rest (fig. 3) shaw the same type of curve. The critical stenotic level is found to be the same than with invasive techniques. DISCUSSION: Some discordant results open the discussion about angioplasty as a "gold standard", specially with a geometrical analysis. Bad precision in non regular stenosis. Hemodynamic consequences of turbulent stenosis are not evaluated. Clinical interest of critical stenotic notion is underlined.(ABSTRACT TRUNCATED AT 250 WORDS)