Boca Radiology Group

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Volume-Rendered 3D Helical CT

Boca Raton Regional 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

Complex fractures

Equivocal fractures

Post-operative evaluation

Bone bar formation

Tarsal Coalition

Extent of disease & therapeutic planning

Intuitive presentation of complicated spatial information

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

Complex Fractures

Anterior column acetabular fracture of the hip

  • 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

CT & MR Angiography

Cerebral Aneurysms

Carotid Stenosis

Post-operative Graft Evaluation


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