 As few as 2 or as many as 6 crystals can be used to perform 1-axis, 2-axis, or 3-axis length measurements of the axial planes of the heart, usually at a rate of 200 to 2000 times per second.A typical sonomicrometer system has a resolution of 12 micrometres, enabling high-resolution measurements of the axial lengths.Ventricular volume is computed directly (either in micro-liters or milli-liters) by combining the axial length measurements in standard spherical or ellipsoidal volume equations