A digital sonomicrometer for two-point length and velocity measurements.

We have designed, fabricated, and tested an improved digital sonomicrometer for two-point ultrasound measurements in the experimental cardiology laboratory. The system design incorporates state-of-the-art analog and digital circuitry and demonstrates 1) capability for either analog or digital output; 2) a resolution of +/- 0.15 mm, readily adjustable to +/- 0.03 mm as required; 3) excellent stability; 4) low cost; and 5) ease of operation by untrained personnel. The device was calibrated in vitro and successfully evaluated by making measurements of contractile motion in the myocardium of the open-chest dog.