**5. Conclusions**

Clinical evaluation of the mechanical tracking systems for use in 3D ultrasound guidance for focal liver ablation and prostate biopsy have been found to be easy to use. The tracker permits manual motions identical to the current conventional procedure, where restricted movements are produced by the US probe in the patient's rectum.

Reconstruction of 3D TRUS images using the hybrid approach for focal liver ablation, and rotational approach for prostate biopsy can produce accurate 3D images without significant visible discontinuity or artefacts. Volume calculations from the 3D TRUS image have shown that the 3D US systems can generate accurate volume measurements.

The patient studies have demonstrated that it is possible to minimize the effects of liver and prostate motion through a variety of mechanical and software mechanisms. However, improved solutions, which correct any patient motion automatically are still needed. It is not possible to control all patient/organ motion during the procedures, particularly if the patient moves during the prostate biopsy procedure after the firing of the prostate biopsy needle. To overcome this problem, a software module would have to be developed to inform the physician that the prostate has moved and then correct for the motion and deformation. This task must be done quickly, possibly in real-time, using an implementation of the software in a graphical processing unit (GPU).
