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Volume-Rendered 3D Helical CT

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Boca Raton Community Hospital is one of the first facilities in the country able to offer real-time 3D volume rendering, an exciting new technology enabling unparalleled imaging of complex data sets and anatomic information.

What is 3D Helical CT?

Displays 3D spatial relationships in a two-dimensional image Volume CT data set Sophisticated computer post-processing

Real-time 3D CT of Pilon fracture of distal tibia

Role of Helical CT in Orthopedic Imaging

CT Hardware Requirements

Requires x-ray tube capable of high heat capacity Helical (spiral) acquisition of a volume data set Narrow collimation (1 mm) Pitch of 1:1

What is Helical (Spiral) CT?

X-ray production Simultaneous table & tube movement Produces volume data set Subsecond spiral acquisition- minimizes motion artifact Anisotropic voxels (longer in the z axis than in the transverse plane)

Surface Rendered 3D image s/p 1st MPJ replacement arthroplasty utilizing a Swanson Silastic Total Hinge Joint implant

3D Surface vs Volume-Rendering

<link to source Radiographics article (Pretorius & Fishman)>

Shaded Surface Rendering	Shaded Volume Rendering
Shaded surface rendering algorithms - only uses first defined voxel as the surface of the bone Displays gross 3D relationships Fails to display lesions hidden beneath the bone surface Tend to demonstrate stair-step artifacts.	Uses entire data set Conveys more information Contributions of each data set voxel are summed May be viewed in any plane or projection and in a range of opacity from transparent to opaque

Computer Hardware Requirements

Real-time interactive display Eliminates need for editing prior to 3D rendering Rapidly obtains clinically useful images Expedites communication of results Anisotropic voxels interpolated to create cuboid isotropic voxels Isotropic data mapped into appropriate plane Rendering algorithm into 3D volume Requires considerable computer power (Silicon Graphics Workstation)

Stereo 3D Display

<link to StereoGraphics>

3D Volume CT may alter management

• Those who might otherwise have received conservative treatment but become surgical candidates
• Those in whom urgent surgery is delayed in favor of later, definitive arthrodesis or arthroplasty

Complex Fractures

Talar and calcaneal injuries easily evaluated 3D mapping for preoperative planning Complex intra-articular fractures of the distal tibia Immediate surgery vs later, definitive arthroplasty

Real-time 3D CT of Calcaneus fracture

Post-operative Imaging

CT and MR imaging limited due to artifact from implanted hardware Spiral CT with volume rendering able to compensate for streak artifact despite the presence of metal plates, pins, or prostheses.

Other Applications

Endovascular Aortic Stent Graft used for perctaneous repair of abdomial aortic aneurysm

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