Dynamic flow quantitation with spatial orientation guided digital color Doppler imaging: In vitro validation and initial in vivo experience

Abstract

The assumptions of geometric shape and uniform velocity profile prohibit the use of conventional Doppler methods for volume flow quantification with irregularly shaped nonvascular passages in space. A flow quantification method that integrates a three-dimensional (3-D) position and orientation sensing system with digital color Doppler imaging approach has been developed. Methods: The optimized ultrasound system settings were predetermined using a static, laminar flow model. The instantaneous flow rate was measured by the integration of the area-velocity product with angle correction. Initial in vivo studies quantified gastric emptying on five healthy volunteers 10 min after ingestion of a 500-ml meat soup, postprandially. Digital Doppler images were obtained continuously covering a transpyloric flow episode, immediately following the 3-D scan of the passage. The flow direction was derived from 3-D reconstruction using the centroids of two short-axis views. Results: In vitro validation showed the Doppler flow rates were within 10% for reference flow rates ranging from 6 to 30 ml/s. The average gastric emptying lasted 0.75 s with 3.0 ml in volume. Conclusions: With appropriate instrument settings, orientation determined digital Doppler can be used for the quantification of gastric emptying with adequate accuracy. This method minimized the angular ambiguity and geometric assumptions.