Page 286 - Biomedical Engineering and Design Handbook Volume 2, Applications

264 DIAGNOSTIC EQUIPMENT DESIGN

Perhaps the most exciting miniaturization-related aspect of the current miniaturization trend is
the introduction of software-based beam formers. As noted in the previous paragraph, much of the
back end of a scanner has already migrated to software, usually on a conventional PC. For several
years, this migration appeared to be stalled at the receive beam former. However, the last several
years have seen the beam former yielding to DSP (digital signal processor) and even PC-based oper-
ation (Napolitano, 2003; Verasonics, 2007). Based on these developments, ultrasound scanners have
a data acquisition front end with the array, front-end signal processing (e.g., TGC amplifiers) up to
the A/D converters, and a processor-based back end. If Moore’s law can muster even mild reduction
in size for PCs, tomorrow’s ultrasound scanner is likely to be a small handheld unit.

9.7 SUMMARY

This chapter has reviewed the fundamentals of the design of ultrasound scanners with a particular
focus on the beam formation process. Different types of image data acquisition methods are
described along with a historical view of the developments. The entire process from transduction to
scan conversion has been discussed, including the relevant numerical specifications of the various
parameters. Finally, the current dominant trends that will define the future of these scanners have
been discussed. Unlike most of the other imaging modalities, it appears that ultrasound will continue
to remain highly dynamic with large shifts in applications away from the radiology and cardiology
departments in hospitals to far closer to the offices of the general practitioners and the patient.

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