Knowledge Base

Prepare Data Acquisition

Adjusting Camera Gain and Green Intensity Threshold

As a result, under Results, the Maximum and Minimum Green Intensity, and Range are changed, based on the current values for Camera Gain and Green Intensity Threshold. Each time you adjust Camera Gain, the prints in the Prints view are reset.

1. If necessary, increase the Green Intensity Threshold to remove noise, that is, prints in the Print View that are not paws. As a result, in the Print view, the noise is filtered out and under Results, the Minimum Green Intensity and Range both change.
2. Click OK when you are done.

Adjusting the Intensity of the Green Walkway Light and/or the Red Ceiling Light

Adjust the intensity of the Green Walkway Light when the Camera Gain reaches its maximum or minimum value; this can occur if, respectively, the animal's paws exert too little pressure on the glass plate or if there is too much background noise. You get an error message if this happens. For example, with a large, heavy rat, the Camera Gain can drop below the minimum value of 6. In that case, decrease the Green Walkway Light intensity from the default 16.0 to 15.5. Next, re-do auto detection.

If detection of the toes is important (for example, if you want to classify toes in the Interactive Footprint Measurements to calculate the Sciatic Functional Index), make sure to check whether manually adjusting the intensity of the Green Walkway Light (in steps of 0.25) might result in even better detection of the toes, especially for light-weighted animals. Also, reducing the intensity of the Red Ceiling Light might increase the detection of the toes. In the optimal example, the animal and its full body contour are clearly visible upon entering the walkway. If the Red Ceiling Light intensity is too low, the animal is only detected when it has already entered the walkway and the body contour is not fully visible, which results in poor performance of the automatic classification.

We recommend adjusting the intensity of the Green Walkway Light and/or the Red Ceiling Light after determining the optimal values for Camera Gain and Green Intensity Threshold. As a rule of thumb, the optimal value for Camera Gain ranges between 5 and 12 dB. If the value of Camera Gain is far outside this range (for example, 3 or 25), adjust the intensity of the Green Walkway Light and re-do auto-detection until the Camera Gain is within the optimal range (5–12 dB).

Specifying the Acquisition Settings

Choose Setup > Acquisition Settings.

When you have snapped a Background Image before acquisition (indicated by a check mark icon), you can view it by clicking the View Background Image button. When the Background Image does not cover the area of interest of the walkway, you should (re-)define the walkway.

Run Settings

You can specify the following settings:

• Auto Abort Runs When the Duration Exceeds ... Seconds – When selected, this option automatically stops acquisition when the set time is exceeded. The Auto Abort Run option is different from the Maximum Run Duration in the run criteria. When the animal exceeds the Maximum Run Duration, the run is marked non-compliant but acquisition is not aborted. CatWalk XT stops recording automatically when the run duration reaches 60 seconds. Runs longer than 60 seconds generate so much data that it can impede the computer's performance.
• Discard Auto Aborted Runs – When selected, CatWalk automatically deletes runs that exceed the time set in the Auto Abort Runs option.
• Discard User Aborted Runs – When selected, runs that are stopped by the user are deleted. When this option is not selected and you manually stop acquisition during a run, the run is saved.
• Discard Runs Not Compliant with the Run Criteria – When selected, runs that do not meet the run criteria are automatically deleted.
• Discard Incomplete Prints at the Start and End of a Run – When selected, paw prints or parts of paw prints on the border of the walkway are not included in the classification (that is, CatWalk draws no rectangle around the print). Including incomplete prints in the analysis affects parameters such as Print Area or Max Contact Area. Please note that if a paw print consists of sub-prints (for example, toes), the sub-prints that are not on the border of the walkway are not discarded. As a result, sub-prints that are not on the border are included in the classification while sub-prints on the border are not. To discard the complete print, select all labeled sub-prints and label them as Junk.

Sound Feedback

It might be useful to get auditory feedback (system beep) on the status of acquisition, especially when you are not able to view the runs on the monitor. You can select the following:

• Run Start (1 Beep) – When selected, you get one system beep when acquisition starts.
• Run Stop (2 Beeps) – When selected, you get two system beeps when acquisition stops.
• Error (3 Beeps) – When selected, you get three system beeps if an error occurs, such as a lost camera connection.

Turn Sound Feedback off when you suspect it might disturb the animals.

Source: CatWalk XT 11.0 Reference Manual - Prepare Data Acquisition, Noldus Information Technology