Medical video recording

Kymography is an analysis of the function of the vocal folds in time interval at any selected cross-section of the fold.

Right-clicking on the selected video sequence and selecting the Strobokymography in separate examination tab option opens an additional tab 1 for kymographic analysis (Fig. 1)

Fig. 1. Kymographic analysis window; Fragment selection

The first tab Fragment Selection (Fig. 1) starts the kymography. As in the case of kymography from videostroboscopic recording, on this tab the user selects the appropriate fragment of the recording. This fragment should show the entire length of the vocal folds, if possible visible in the center of the image, without any structures that could obscure the whole or a part of the glottis.
The user marks the beginning and end of the selected fragment of the recording with sliders 2. The first slider from the top allows you to preview the video sequence. The second and third sliders allow you to define the beginning and end of the fragment to be analyzed.

In this window video recording can be corrected, deinterlaced and rotated if needed (Fig. 2). In addition, the Correction Panel button 3 allows opening the window for precise image color correction. The Color correction control panel (Fig. 3) allows to slightly correct the image or completely change the color, for example to make the blood vessels visible.

Fig. 2. Image correction

Fig. 3. Color correction control panel

After selecting the appropriate fragment of the recorded sequence, go to the next tab Stabilizing and cropping (Fig. 4a). In this tab, the user marks the place where the vocal folds occur. Use the blue line to mark the beginning and end of the vocal folds (Fig. 4b).
The user may place a marker on any selected frame where the vocal folds are best seen. The program will automatically find the indicated points on the remaining frames of the video sequence after switching to the next tab. Additionally, in case of “more difficult” recordings, the user can use the stabilization option (FIg. 5).

a)

b)

c)

Fig. 4. Kymographic analysis window - Stabilizing and cropping; a) opened tab, b) setting marker for fold position, c) folds with a marked glottis surface

Fig. 5. Stabilization options in Stabilizing and cropping tab

Stabilization options (Fig. 5) allow you to adjust the stabilization settings of the image marked in the area defined by four yellow points that move with the fold position mark.
In the case of a large blackout of the image, it is possible to edit the glottis area 12. Glottal area is set by default to reject 10% of the darkest pixels in the image. After switching on Mark the glottal area, the area under consideration is marked in blue (Fig. 4c).
Enabled Ignore glottal area for horizontal option causes that the program ignores the defined glottal area horizontally This option may be helpful when the folds vibrate with a phase difference and the glottis fissure is clearly visible (heavily blackened glottis area).
After making the correction, press the button Stabilize video 14. A preview of the kymographic image 15 will appear below to help verify the stabilization effect.

Fig. 6. Kymographic analysis window; Vocal folds length

After correctly marking the location of the vocal folds, it is possible to proceed to the next stage of the analysis – Vocal folds length (Fig. 6). In this tab, the preview of recorded voices is automatically modified based on the marking on the previous tab. Voice folds in the preview are properly cropped and stabilized. On this tab, define the Vocal folds length range (blue indicator) and the Vocal folds opening range (green indicator) using the indicators. In the event that the vocal folds are not fully visible in the image, the indicators may be positioned in a black area outside of the recorded image where the end of the creases can be expected to occur. The user-set indicators will change from gray to blue or green. In case the user does not set the marker, the program will take into account the default setting (in gray).

Fig. 7. Kymographic analysis window; Short-term kymo analysis -> Kymographic sections

Another kymographic analysis - Short-time kymo analysis (Fig. 7) begins on the Kymographic sections tab. The tab on the left side has an image showing the cropped vocal folds A with a slider to select the location of the cross-section 16. In order to select the cross-section of the folds of interest, set the slider in the appropriate place by moving it up or down with the cursor. As the slider is moved, the kymographic picture corresponding to a given cross-section appears on the right.
Likewise, the frame representing the vocal folds B corresponding to a given instant in time may be changed. For this purpose, the moment in which the frame was recorded should be determined by moving the slider on the kymographic section 17, which automatically al-lows setting the appropriate cropped frame.
Below the image of cropped folds A there are buttons: Add joint video and Add cropped video. A joint video is a combination of a frame at a given moment in time and a recording consisting of time intervals in every possible cross-section of this frame. In the saved joint video, on the left there is cropped frame (with the cross-section location selected, if the Save with indicator lines option is selected). On the right side of the video there is a recording composed of all the kymographic pictures (in the places of the cross-section shown in the cropped frame on the left). A cropped video, on the other hand, is a recording consisting of all cropped frames. The video sequences created in such a way will be saved in the main examination window in the wideo recording tab in the column containing all recorded and loaded video materials. After exiting the kymography analysis, it is possible to play the video and select frames in Frame selection window.
Below the kymographic section B, there are buttons that allow you to save images to the report. The Add joint kymographic section button allows saving an image showing a cropped frame with vocal folds along with the appropriate kymographic section 18. The Add set of sections button allows adding an image that represents the cropped frame along with the kymography of the vocal folds in seven places of the cross-sections 19(selectable places on the list next to it).

Fig. 8. Kymographic analysis window; Short-term kymo analysis -> Vocal folds edges

The next tab is Vocal folds edges (Fig. 8). On the image of the cropped vocal folds shows there are two green sliders, located halfway up the image. The sliders allow defining the area to be considered in kymographic analysis. The designated width allows correcting the degree of visible opening of the vocal folds.
Below the image of the cropped vocal folds there is a button Optimize detection parameters 20. After positioning the image of the vocal folds at the moment of their opening, pressing the button 20 will automatically adjust a set of five pairs of points to the right and left edges of the vocal folds. In the case of not all points match correctly, their position can be corrected "manually" by moving individual points to the right or left by moving using mouse. After the points have been set in the vocal fold image, the user may proceed to determining the vocal folds opening area in the kymographic image.
In the kymographic section, the program paints blue the areas where the folds are open. After pressing the button below the kymographic image Optimize detection parameters21 the program finds areas where the folds are open. In the event that not all areas fit properly, their positioning can be corrected "manually" by moving single points 22 to the right or left, reducing or increasing the brightness range, which the program takes into account when determining the area of folds in the kymographic image. It is important for the user to pay attention to which interval between the points is incorrectly determined, since the correction is performed using the point closest to this section. By moving the slider to the left and right, it is possible to reduce the brightness range (decrease the selected area) and increase the brightness range (increase the selected area).
For the correct determination of parameters and phonovibrograms, the number of complete cycles (full opening and closing) of the folds function occurring on the analyzed recording should also be indicated (Number of full cycles).

Fig. 10. Kymographic analysis window – Short-term kymo analysis -> Verifying ranges

In the Verifying ranges tab (Fig. 10) there is a kymographic image and an image of the vocal folds. The simplified graph 23 allows for precise verification of the marked ranges of vocal folds lengths and vocal folds opening. Additionally, in the tab there are graphs showing the edges of the vocal folds. The graph 24 shows the edges of the folds with symmetry correction (the Calculate symmetry correction button). In the graph 25, the edges of the vocal folds are shown according to the settings made on the Vocal folds edges tab. In this tab, the user can also correct the number of complete cycles (Declared number of cycles).
Additionally, the user can select Phase difference view and open a new chart 26.

Fig. 11. Kymographic analysis window; Short-term kymo analysis -> Parametric analysis

Fig. 12. Kymographic analysis window; Short-term kymo analysis -> Parametric analysis

After making the appropriate corrections, you can go to the next tab - Parametric analysis (Fig. 11). This tab displays graphs and short-term parameters determined on the basis of the settings. Charts can be added to the list of saved images for the report by double-clicking on the chart. Description of short-term parameters (Fig. 12) is presented in the tables below. The amplitude analyzer examines the movements of the vocal folds in a direction per-pendicular to their axis. Specifies the range of edge position changes of right and left vocal fold. The analyzer is associated with a chart 27 with three data series (description in table 6.1) and global parameters presented in table 6.2. The unit of the X axis is the percentage of the fold length (%FL).

The fold closure analyzer examines the movements of the vocal folds perpendicular to their axis. The percentage of the time that the folds cycle when the folds are fully closed (edges touching) is determined. The analyzer is associated with one graph 28 with two data series (description in table 6.3) and global parameters presented in table 6.4. The unit of the X axis is the opening factor.

The symmetry analyzer examines the movements of the vocal folds in a direction perpen-dicular to their axis. The level of asymmetry is determined. The analyzer is associated with one graph 29 with two data series (description in table 6.5) and global parameters pre-sented in table 6.6. The unit of the X axis is percentages.

The phase difference analyzer examines the movements of the vocal folds in a direction perpendicular to their axis. The phase difference between the movement of the two folds is determined. The analyzer is associated with one graph 30 with one data series (description in Table 6.7) and global parameters presented in Table 6.8 The unit of the X axis is degrees. The phase difference is determined by describing both edges of the folds with periodic functions similar to sinusoids and determining the phase difference between these functions.

Fig. 13. Kymographic analysis window; Short-term kymo analysis -> Phonovibrogram

The next tab is Phonovibrogram (Fig. 13). The phonovibrogram is a map presenting information about the movement of the vocal folds during the entire slow motion sequence. This graph provides information on the movement of the entire vocal folds over the entire time interval (not just one cross-section). When creating a phonovibrogram, information about the movement of the contours of the oscillating vocal folds is collected from the video sequence and then transformed into a monochrome phonovibrogram image.