[Echogenicity of blood].

The echogenicity of blood is dependent of the back scattering of the ultra-sound beam by the flowing blood-stream. This black scattering is, according to the Rayleigh theory, proportional to the fourth power of the frequency and to the size of the particles. So, for the frequencies in clinical use, the size of the particles is essential.

[Echogenicity of blood].

The echogenicity of blood is dependent of the back scattering of the ultra-sound beam by the flowing blood-stream. This back scattering is, according to the Raleigh theory, proportional to the fourth power of the frequency and to the size of the particles. So, for the frequencies in clinical use, the size of the particles is essential.

[Cerebral reserve. A method for evaluating cerebro-vascular hemodynamic risk].

Together with embolic risk, hemodynamic risk tends to play an important role in cerebrovascular pathology. Studies of cerebral reserve have resulted from the difficulty of accurately estimating the repercussions of arterial lesions. The vascular reserve of a given region is the ratio between maximum and baseline flow.

[Diagnosis of varicocele by Doppler effect].

Varicoceles, which may produce oligo-astherospermia are a curable cause of subfertility in the male. Doppler velocimetry of the anterior spermatic venous plexus or pampiniform plexus allows the diagnosis of clinical and infraclinical varicoceles to be confirmed. It can also assess and quantify the spontaneous increase in flow due to venous distension and Valsalva reflux related to valvular incompetence.