| Popis: |
Publisher Summary This chapter discusses the detection of bubbles in tissues and blood. An interface between a gas and either a liquid or a solid is a very good reflector of sound because of the great difference in acoustic impedance across the boundary. Pulsed ultrasonic energy has previously been used to image internal body structures using sonar-like systems. Most Doppler systems work at an unspecified sound intensity, often just under a level that would produce periosteal pain or burns. A sound wave applied to a bubble result in the production of some second harmonic, that is, some sound of twice the original frequency is returned along with that at the basic frequency. From long-term saturation dives, it may be possible to tell if altered blood flow patterns while asleep and awake during decompression demand periodically changed schedules. |
