In the paper the concept of synthetic aperture used for high resolution/high frame rate ultrasonic imaging is reviewed. The synthetic aperture technique allows building extended “virtual” apertures, synthesized from smaller real aperture resulting in improved lateral resolution along full penetration depth without sacrificing the frame rate. Especially, four methods, synthetic aperture focusing (SAF), multi-element synthetic aperture focusing (M-SAF), synthetic receive aperture (SRA) and synthetic transmit aperture (STA) are addressed. The effective aperture function, describing two-way, far field radiation is a useful tool in beam pattern analysis. Some basic notations, which are used to calculate the effective aperture are introduced in Appendix.

The paper shows the usefulness of the lung mechanical model for time and frequency characteristics reconstruction proper for the mechanics of an adult human respiratory system in its various regimes of work. The complex set-up for measurements of human respiratory system mechanics is presented. Two separate scenarios were created, firstly, the mechanical model was examined using standard mechanical ventilation routine with embedded Interrupter Technique and then the Optimized Ventilator Waveform technique was tested. An analysis of experimental results is presented, as well as an outline of the issues and problems revealed during investigations.