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VISBONE - 3D Bone Visualization System This is a joint project on surgical planning between the HKU
CSIS Department Computer Graphics Group and the Department of Orthopaedic Surgery at Queen Mary Hospital.
A new method of orthopaedic surgery called bone cement injection, was developed which can adhere and reinforce the broken bones. Bone cement is something
like glue which can be injected into the broken bones and pervades into the gaps in the bone. By now, surgeons can only use their experienceto examine the
result of injection by studying the 2D slices obtained by computer tomography (CT). Successive scans are made through the bone which resembles the axial slices
of anatomy. Each pixel in the CT images are assigned a value relating to the density of the tissue at that pixel location. When looking at these CT slides,
surgeons use their expertise, and at the same time incorporate also their imagination to stack the 2D images into a 3D volume. Since the density is the only
information obtained by CT, the parts of bone cement are easily mixed up with bone cortices, which are the hardest parts in the bone and their density is very
similar to the density of bone cement.
By comparing the same bone before injecting the bone cement and after injecting bone cement, the part filled with bone cement can be shown clearly
without the disturbance of bone cortices. The challenge is that the two positions of scanning before and after injection are normally not the same. The
alignment between these two volume datasets of scanning must be done before comparing. And the limitation of discrete data space increases the difficulty.
A special approach was developed to find feature points in both volume datasets first and another method was used to match two sets of feature points,
which can reach the best balance between speed and accuracy.
This project aims at assisting surgeons to have a better 3D visualization of the bone cement injected into the bone. Surgeons will no longer rely on
their imagination for a 3D volume but can actually examine a 3D bone interactively on a computer graphics system. The part of bone cement is visible to
the surgeons who can then determine the result of injection. This will be more helpful to train the students of Orthopaedic Surgery and Traumatology to
distinguish the part of bone cement and other tissues.
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