ABSTRACT
A theory, based on the Fourier-Bessel series expansion, is developed to synthesize circularly symmetric field patterns by means of concentric annular arrays. The application of this theory to the formation of variable-width uniform sector beams is studied in detail and results in a canonical design procedure. Calculated beam patterns are compared to the actual measured patterns obtained from a prototype array suitable for transcutaneous investigation of the central blood-flow system and are observed to be in good agreement. The implementation of such arrays in the compensated-first-moment flowmeter is described. Methods of beam-pattern improvement are also discussed.
Subject(s)
Rheology , Ultrasonics/instrumentation , Blood Flow Velocity , Humans , Regional Blood Flow , UltrasonographySubject(s)
Doppler Effect , Physics , Ultrasonics , Blood Flow Velocity , Models, Theoretical , Physical Phenomena , Rheology , TransducersABSTRACT
Several reports have described systemic air embolism in association with penetrating lung injuries. We produce lung lacerations in 18 dogs ventilated with air containing charcoal powder. An ultrasonic bubble detector was positioned over the carotid artery in six dogs. Evidence of arterial air embolism was found in every case of pulmonary laceration in open-chest, tension pneumothorax, and hypovolemic preparations. The quantity of air was small, producing only transient arrhythmia. No air was detected under control conditions. We conclude that systemic air embolism is a frequent accompaniment of penetrating lung injuries, that it is rarely recognized clinically because of its generally small quantity and minor, nonspecific effects, but that the potential for dangerous air embolism does exist with lung wounds and warrants precautions in management.
