3D ultrasound measurement of large organ volume

Freehand 3D ultrasound is particularly appropriate for the measurement of o rgan volumes. For small organs, which can be fully examined with a single s weep of the ultrasound probe, the results are known to be much more accurat e than those using conventional 2D ultrasound. However, large or complex sh aped organs are difficult to quantify in this manner because multiple sweep s are required to cover the entire organ. Typically, there are significant registration errors between the various sweeps, which generate artifacts in an interpolated voxel array, making segmentation of the organ very difficu lt. This paper describes how sequential freehand 3D ultrasound, which does not employ an interpolated voxel array, can be used to measure the volume o f large organs. Partial organ cross-sections can be segmented in the origin al B-scans, and then combined, without the need for image-based registratio n, to give the organ volume. The inherent accuracy (not including position sensor and segmentation errors) is demonstrated in simulation to be within +/-2%. The in vivo precision of the complete system is demonstrated (by rep eated observations of a human liver) to be +/-5%. (C) 2001 Elsevier Science B.V. All rights reserved.