3D ultrasound examination of large organs

Freehand 3D ultrasound is particularly appropriate for the measurement of organ volumes. For small organs, which can be fully examined with a single sweep of the ultrasound probe, the results are known to be much more accurate than those using conventional 2D ultrasound. However, large or complex shaped organs are difficult to quantify in this manner because multiple sweeps 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 difficult. This report describes how sequential freehand 3D ultrasound can be used to measure the volume of large organs without the need for an interpolated voxel array. The method is robust to registration errors and sweep orientation , as demonstrated in simulation and also using in vivo scans of a human liver, where a volume measurement precision of ±5% is achieved.