The reasons ultrasound machines are expensive are not technical, it's mostly low volume and high overhead to comply with all rules and regulations.
You can make a useful ultrasound machine with just one transducer (e.g., to measure blood flow through the heart using Doppler, or using mechanical scanning).
You don't need fast CPU for processing, just downconvert to audio range and then 80286 is fast enough.
Source: wrote embedded software for one of those machines back in the day. 16 kB for everything, from keypad debouncing to GUI.
You can make a useful ultrasound machine with just one transducer (e.g., to measure blood flow through the heart using Doppler, or using mechanical scanning).
You don't need fast CPU for processing, just downconvert to audio range and then 80286 is fast enough.
Source: wrote embedded software for one of those machines back in the day. 16 kB for everything, from keypad debouncing to GUI.