CT Technology Including 3D - Learning Modules

Learning Modules ❯ CT Technology Including 3D

Cinematic Rendering of CT Data: Current State of the Art

Elliot K. Fishman M.D.
Johns Hopkins Hospital

3D Imaging in Radiology: A 40 Year Evolution

Computer hardware
Computer software (algorithms)
User interface and design
CT scan data resolution
Increased clinical experience to drive demand for image post-processing

Computer Hardware

DEC PDP-11
Pixar
Sun Microsystems
Silicon Graphics (SGI)
Dell
NVIDIA
Migration from dedicated hardware to special purpose boards and GPU’s

Computer Software (Algorithms)

Shaded Surface Technique (SSD)
Maximum Intensity Projection (MIP)
Volume Rendering Technique (VRT)
Cinematic Rendering (CR)

CT Scan Datasets

Slice thickness
Interslice interval
Spatial resolution
Speed of acquisition
Dual energy CT
Perfusion CT

Increased clinical experience drive demand

Increased diagnostic accuracy
Improved communication between the radiologist and the referring clinician
Increased use of laprascopic surgery and robotic surgery
ACR and “Value over Volume” initiative

LucasFilms 1985

“ Volumetric rendering differs from surface rendering in that all the information from the CT scans is preserved, not just surface boundaries. Object thickness and internal contours can be seen in the 3D projection.”
Volumetric Rendering Technique: Applications for Three-dimensional Imaging of the Hip
Fishman EK, Drebin RA, Ney DR et al.
Radiology 1987 Jun;163(3):737-738

Volume Rendering Technique-Facts

The technique is implemented using a probabilistic classification involving a trapezoidal approximation
Each tissue type (bone, muscle,fat) is assigned a nominal value range that represents that tissue type
Each voxel is assigned a color and transparency by taking a weighted sum of the percentage of each tissue present in the voxel
Trapezoids can be adjusted in real time

Volume Rendering Technique-Facts

The final image is produced by casting simulated rays of light through the volume containing the classified and colored voxels
This image is then projected onto the computer screen

Nice Tendons

Cinematic Rendering

Principles
Implementation
Clinical applications
Future directions
Potential applications beyond visualization

The range of visualizations in any case must change to visualize structures ranging from bone, to vasculature to muscle. Here is a case with IVDA and groin infection

Cinematic Rendering

“In addition to the fact that photo-realistic volume renderings tend to be aesthetically more pleasing, it has been shown that realistic lighting contributes to 3D understanding and can improve depth-related task performance . With this work and the implementation that we have made available, we hope to contribute to the uptake of realistic illumination in interactive direct volume rendering applications.”
Exposure Render: An Interactive Photo-Realistic Volume Rendering Framework
Thomas Kroes et al.
PLOS ONE 7(7): e38586. doi: 10.1371/journal.pone.0038586

“Cinematic rendering produces volume rendered images with photorealistic image quality. It uses a global illumination model, which takes direct and indirect illumination into account when constructing an image, to achieve rendering quality. The result of the integration is a numerical rendering algorithm known as path tracing: thousands of light rays are traced to compute the resulting image.”
MDCT angiography with 3D rendering: A novel cinematic rendering algorithm for enhanced anatomic detail
Johnson PT, Schneider R, Lugo-Fagundo C, Johnson M, Fishman EK
AJR Am J Roentgenol. 2017 Aug;209(2):309-312.

“The light model off of which cinematic rendering and classic volume rendering are based when reconstructing the images accounts for the difference between the two technologies. The primary reason why classic volume rendering results in images that are relatively less photorealistic is the use of the local lighting model – only local properties, such as the local gradient, influence the resulting image. Inversely, cinematic rendering assumes the global illumination model, which accounts for the impact that all light rays have on image reproduction.”
MDCT angiography with 3D rendering: A novel cinematic rendering algorithm for enhanced anatomic detail
Johnson PT, Schneider R, Lugo-Fagundo C, Johnson M, Fishman EK
AJR 2017 Aug;209(2):309-312

Image Creation: How we do it

Creating the trapezoids to optimize image visualization
Creating presets to speed up the process
Interactive rendering of the presets to optimize for the individual case

Trapezoid Creation

Current Preset Values

Common Questions

There are no special protocols for the datasets where you do cinematic rendering
The image processing is done by the Radiologist
The average time for study is under 5 minutes

Proven Clinical Applications

GI Applications