Optimize an RT configuration

Different options can be selected in CIVA to optimize an RT configuration and reduce the time of calculation or the memory size of a configuration.

First of all, a Region Of Interest (ROI) can be defined.

To define it, select “Use ROI” from the Options panel / Detector tab.

 

 

The region of interest is a small rectangular region within the film which is sub sampled to obtain a finer resolution. Select the “Up scaling” factor in the drop-down list. By selecting a refinement factor of 2, the surface of each pixel in this zone will be refined by a factor of 4, which means a significant increase in convergence rate.

Then you have to define:

• X max
• X min
• Y max
• Y min

The ROI appears on the detector in the 3D view.

 

 

Secondly, options of the Monte-Carlo calculation available from the Options panel / Computing tab can be modified to reduce the time of calculation.

Cut energy: By ticking this option and keying-in a value of energy, photons with incident energy lower than this given value will be automatically killed. This option reduces the computation time.

Cut according to order scattering: By default, CIVA can simulate up to 10 orders of scattering for a given photon. This option allows you to stop the propagation of the photon if it has reached the number of order scattering defined.

 

 

Import Monte-Carlo computation: For more information about this option, look at the tip “RELOAD AN ALREADY COMPUTED MONTE-CARLO” available below.

Thirdly, it is possible to optimize the utilization of the computer for the calculation, by modifying the Preferences (top left of the CIVA window).

A Monte-Carlo calculation is sequenced in multiple cycles, for which it is possible to define the number of photons considered. By default, a cycle is composed of 100,000 photons. By increasing this value slightly, it is possible to reduce the number of cycles that will be calculated for a given number of photons to be simulate, and thus to save time. This option is available from the X-ray tab of the Preferences.

 

 

Reduce the memory size of a CT configuration

Combining BL and Monte-Carlo calculations generates lot of images that are not always useful for the user. When the user doesn’t need to see those results, it is possible to select the “Keep only the Detector response data” option. By doing so, only images from “Response detector” or “Optical density” will be stored, and the memory size of the configuration will be significantly reduced (especially for CT configurations, for which results can exceed 100 Go of memory).