kelu124 has created an ultrasound imaging project on hackaday.io that uses the BeagleBone:
Murgen: open source ultrasound imaging
This project, Murgen, has a specific target of providing a technological kit to allow scientists, academics, hackers, makers or OSHW fans to hack their way to ultrasound imaging – below 500$ – at home, with no specific equipment required.
The hardware design files and source code are hosted on GitHub: