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Biomedical subjects

R Brion

Publications and source records attributed to R Brion.

40 records · Page 3Linked to original sources
PubMed1985

[Effects of different types of continuous emission laser on human atheromatous plaques in vitro].

The laser beam is a punctual source of thermal energy which can be used to vaporize human atheroma. The physical characteristics of optimal utilisation (total energy, wave length, continuous or pulsed emission) have not been clearly defined. We carried out in vitro irradiations of human atheromatous material and healthy arterial wall with different combinations of power-emission time and three different wave lengths, using four continuous emission laser beams (Nd-Yag, two CO2 with different lenses, Argon). The beam emitted by the Nd-Yag was absorbed less than the CO2 and Argon lasers, which had comparable effects above a threshold of 2 to 14 joules. The weight of vaporized fibro-atheromatous material was 0.11 mg per joule of optical energy dissipated (CO2). No radical difference was observed in the nature of the effects of the three types of laser studied. The problems of using this technique on the beating heart remain unsolved (ballistics of the emerging ray). Other modes of emission (pulsed) and different wave lengths should be studied.

Argon↗
PubMed1985

[Pulsed emission in laser coronary angioplasty. Theoretical bases and experimental application].

The aim of this study was to evaluate the thermal diffusion of a pulsed laser beam in atheroma and to obtain in vitro vaporisation of the plaque without causing arterial wall lesions. A computerised mathematical model integrated 4 parameters: reflectivity, thermal conduction, the absorption factor and coefficient of diffusion. The thermal diffusion was shown to be dependent on the time constant and the temperature of vaporisation may be best attained with a short burst (200 ns) with a high peak power (6000 w). The experimentation was performed on fresh debris and segments of epicardial coronary arteries which were exposed to a pulsed laser beam with a frequency of 1000 Hz in bursts of 200 ns at wave lengths of 1060 and 532 nm. The results were evaluated by microscopic examination of transverse sections perpendicular to the lumen of the artery. Effective vaporisation of atheroma was observed with weak mean dissipating powers (0.4 w) about 10 times weaker than with continuous node emission; examination of the underlying arterial wall showed no thermal or mechanical damage.

Computers↗
PubMed1985

[Etiological study of 23 cases of complete block of the left branch of the bundle of His, in the absence of myocardial infarction].

An aetiological study was performed in 23 asymptomatic patients with left bundle branch block (LBBB) which included Thallium 201 myocardial scintigraphy on effort and, in 15 cases, cardiac catheterisation and coronary angiography. Thallium fixation was abnormal in all patients, but the cause of LBBB was attributed to cardiomyopathy in 9 cases, and to coronary artery disease in 2 cases. Cardiac catheterisation was normal in 4 cases. The hypofixation of Thallium 201 in LBBB can be explained either by an abnormality of left ventricular contraction due to heterotopic propagation of the depolarisation or by the unusually high incidence of the association of LBBB and left main coronary artery stenosis and/or a dominant left coronary artery. The practical implication of this study is that Thallium 201 myocardial scintigraphy is of little value in patients with LBBB.

Adult↗