Ventricular volume measurement from a multiplanar transesophageal ultrasonic imaging system: an in vitro study

A system to assess the feasibility of using multiple transesophageal ultrasonic images to measure left-ventricular volume is discussed. The system includes a special transesophageal probe with a micromanipulator for acquiring cardiac images in multiple planes with known interplanar spatial relationship and an offline processing system to compute the volume. In vitro studies with the probe demonstrated that the distance between two targets in space can be identified within 2 mm ( sigma =0.4 mm) for points in the imaging plane and 3.4 mm ( sigma =0.5 mm) for points not lying in the imaging plane. This gives an average accuracy of +or-6.5% for distances greater than 4.5 cm. Comparison of ultrasonic measurements of the volume of water-filled balloons and excised hearts to the volume required to fill them revealed a correlation coefficient of 0.992, a regression line with a slope of 1.0 and an ordinate intercept at 0.2 mL, and a standard error of the estimate of 8 mL.