Ultrasonic stethoscope

Not being a doctor I don't know if this would be helpful, but if we have any doctors here I'ld like to hear your opinions.

My understanding of ultasound scanning systems is that they're big, bulky, expensive, and not very portable. This is mainly due to the logic needed to convert the image into a picture (using FFTs I believe).

How about a stethoscope whose business end has an ultrasonic transducer in it, and a signal processing chip to convert from the ultrasonic range to the audio range. Would this give any different or better information than a regular acoustic stethoscope? It could either be passive and listen for ultrasonic sounds generated in the body (if any???) or active by sending out an ultrasonic tone and listening for the echoes. It might have to subtract the outgoing tone from the received sounds to leave only the echoes, otherwise the user would hear a continuous hum. I have a gut feeling (no pun intended) that this would give a better 'picture' of a beating heart than a normal stethoscope - without the paraphenalia of a traditional ultrasound scanner. It may take some training to use competantly, but the same applies to regular stethoscopes.