Knowledge Base

4.2 Configure the Detection Settings

Introduction to Detection Settings

The aim of the Detection Settings is to achieve an optimal intensity range for the paw prints and to filter out background noise. This is done by putting an animal of average weight on the walkway and then adjusting the Camera Gain and Green Intensity Threshold. Optionally, you can adjust the voltage (intensity) of the green and red lights in, respectively, the walkway and the illuminated ceiling. CatWalk provides quantitative feedback in order to define an optimal range between the minimum and maximum print intensity.

Make sure to turn the lights off before configuring the Detection Settings. Alternatively, you can work under red light conditions. Make sure you avoid the red ambient light from shining directly into the camera.

Make sure you completely open the camera's aperture and you focus the camera.

Detection Settings are stored in a Detection Settings profile. You can create multiple Detection Settings profiles of which one is active during acquisition. When you start up CatWalk XT for the first time, two Detection Settings profiles are present: Rats and Mice.

You can configure Detection Settings both automatically and manually. We recommend to first carry out auto detection and then manually fine-tune the settings.

Basic Procedure

1. Carry out auto detection to get optimal values for Camera Gain and Green Intensity Threshold.
2. Adjust the Camera Gain and Green Intensity Threshold to further optimize detection.
3. If necessary, adjust the Green Walkway Light and/or Red Ceiling Light to further increase the quality of the paw prints.

Auto Detection

1. First, put an animal on the walkway. Make sure the illuminated ceiling is lowered.
2. In the Profiles Explorer, double-click the Detection Settings profile you want to use: Mice or Rats. The difference between the Mice and Rats Detection Settings profile is the default intensity of the Green Walkway Light (Mice: 16.5 Volts, Rats: 16.0 Volts). For both Mice and Rats, the default value for Camera Gain is 20, for Green Intensity Threshold is 0.10 and for Red Ceiling Light is 17.7 Volts.
3. Click the Reset Prints button and then the Start Auto Detect button. The program now automatically adjusts both Camera Gain and Green Intensity Threshold in consecutive steps to achieve the optimal range. Adjustment of the Camera Gain results in a value for Maximum Green Intensity between 197 and 203 based on the prints in the Print view. Adjustment of the Green Intensity Threshold ensures that prints that do not contain pixels with an intensity above the Minimum Green Intensity are removed from the Print view. It is important in this step that the animal walks through the camera view a number of times for proper determining of the detection settings. If the animal just sits still, the detection settings might not work for a moving animal.
4. When Auto Detection is finished successfully, a message appears.
5. You can now do the following:
   • Accept the settings and proceed to Acquisition Settings.
   • Manually adjust the Camera Gain and Green Intensity Threshold to tweak the quality of the paw prints. Furthermore, you can adjust the intensity of the Green Walkway Light and/or Red Ceiling Light. This might be useful if you work with either very heavy or very light animals and the default settings in the Detection Settings profiles Rats and Mice do not result in optimal detection of the paws. Also, decreasing the intensity of the Red Ceiling Lights might result in better detection of toes for use with the Interactive Footprint Measurements.

Auto Detection Settings

Under Auto Detection Settings you can set the following:

• Maximum Range From – The Camera Gain is automatically adjusted until the Maximum Green Intensity (displayed under Results) reaches a value within this range. The default range is between 197 and 203.
• Frames Before Delta – This parameter determines how many video frames with prints should be detected before the Camera Gain is auto adjusted. A print should contain at least one pixel with an intensity above the Intensity Minimum value. The default number of frames is 5. Note: the frame rate of the CatWalk camera is 100 frames per second.
• Intensity Minimum – This is the minimum value for the intensity. Each print should contain at least one pixel with an intensity above the Intensity Minimum. The default value is 85. Prints caused by background noise (such as other light sources than the green LEDs, or dirt) that do not contain a single pixel with an intensity above 85 are automatically removed by an increase of the Green Intensity Threshold.

Manual Detection

1. First, put an animal on the walkway. Make sure the illuminated ceiling is lowered.
2. Choose Setup > Detection Settings. As soon as the Detection Settings window opens, the Print view shows the animal's cumulative prints. Under Results, the Maximum and Minimum Green Intensity of all prints shown in the Print view are displayed, based on the current settings of the Camera Gain and Green Intensity Threshold shown under Detection Settings. The Camera Gain (dB) determines the Maximum Green Intensity; the Green Intensity Threshold determines the Minimum Green Intensity.
3. Under Detection Settings, adjust the Camera Gain until the Maximum Green Intensity value for these prints is approximately 203. The absolute maximum intensity for prints is 255.