I'm building a medical ultrasound scanner as an educational DSP project. I'm not expecting to produce something medical grade, but I do want to be able to detect the location of a high-density ball bearing inside a low-density balloon of ballistic gel. I'm putting together my prototype with a Saxo/FlashyD FPGA sensor acquisition device and a batch of SPM0404UD5 ultrasonic sensors, because they're cheap SMDs and I don't know why they'd be inappropriate.
I'd like to use ultrasound transducers similar to those used in medical ultrasound equipment, but unfortunately the manufacturers of those devices don't seem to publish data sheets. Also, I'm not sure who would sell such components, but it ain't digikey.
Any idea what sort of sensors they use?