Due to the limitations in data acquisition imposed by the scanner, it was not directly possible to measure the maximum frame rate of the volume rendering part. In order to do that, the system was allowed to update volume data and perform volume rendering without having to wait for a complete volume to be acquired. This means that the acquisition and reconstruction parts are made independent. In this case, the volume rendering frame rate was found to vary between 24 frames/s and 85 frames/s with an average of about 60 frames/s. The frame rate was found to depend on the view whereby the frame rate is at minimum when the probe fanning is in the front direction of the view. This is due to the fact that the required interpolation calculations depend on the view and in this particular view the interpolation required is at maximum. In all cases, the frame rates obtained are sufficient for practical 4D ultrasound and it appears that the bottleneck in this technology is on the acquisition side not the volume rendering side.