Sample diagnostic images
Author: MSc Marzena Zacirka, Ph.D. Marcin Just, Ph.D. Michał Tyc (DiagNova Technologies)Kymography, i.e. imaging of the function of the vocal folds using the recording of their closures and openings in a time interval, in any chosen cross-section of the vocal folds, allows for a complete, detailed analysis of the function of the vocal folds, also the diagnosis of regurgitation with the location of its occurrence.
In order to obtain really valuable kymographic images, it is necessary not only to use an appropriate camera, but also specialized software that will enable simple and effective performance of kymographic analysis, facilitating an unambiguous diagnosis, and will not be sensitive to the inevitable deviations of the recording from the ideal. Recording an image using the videostroboscopic technique also requires experience in using the equipment: maintaining a constant visibility of the vocal folds, a relatively stable image and appropriately selected moments of collecting frames in relation to the frequency of vibrations of the vocal folds, however, making a perfect recording is practically impossible.
The first basic step to start a kymographic analysis, right after videostroboscopic recording, is to select fragments that can be analyzed. This step allows not cluttering the analysis image with unnecessary fragments - it often happens that the structure in the larynx, other than the vocal folds, temporarily obscures them. Often, the recording also includes fragments completely irrelevant for the analysis, such as the time of inserting the endoscope into the patient's mouth. It is obvious that an attempt to perform a kymographic analysis on such fragments will make its image completely unreadable. During the examination it is difficult to completely avoid unnecessary fragments being recorded, so the ability to trim recordings in the program is essential. The selection of the best fragment of the recording allows for a more precise, clearer analysis of the function of the vocal folds.
The second step of the analysis, having a great impact on its quality, is cropping the recording, which perfectly eliminates image instability in the videostroboscopic recording, resulting from the unavoidable movements of the endoscope tip in relation to the patient's larynx - performing the examination in such a way that the image of the vocal folds remains in the entire video recording in the exact same place on the screen is virtually impossible.
Examples of kymographic images that show the fundamental difference in readability between the kymographic section obtained from the entire recording (including fragments unsuitable for analysis) without cropping, and the section obtained from selected fragments after cropping are shown below (Fig. 1) and clearly illustrate the key importance of the function selection of fragments and framing available in the DiagnoScope Specialist program.
Fig. 1. Comparison of the results of the kymographic analysis between images from the standard software (on the left) and images obtained from the DiagnoScope Specialist program (on the right)
A very important function is to remove brightness fluctuations, which are very characteristic of a recording made with strobe lighting. These fluctuations are visible in the time courses of the vocal folds function in the form of horizontal stripes in the image. This effect is very difficult to avoid during the recording, and at the same time makes it very difficult to analyze the function of the vocal folds and to issue a correct diagnosis. For this reason, the program includes a function that removes brightness fluctuations, which allows unifying the brightness of the image, which gives excellent results. Below (Fig. 2) there are examples of images showing the operation of the image unification function (Remove brightness variation) obtained with the use of the DiagnoScope Specialist program.
Fig. 2. Comparison of kymographic analysis images. On the right, images using the image unification function (DiagnoScope program).
In the DiagnoScope Specialist program, after completing the kymographic analysis, after selecting fragment, cropping and stabilizing the image, it is also possible to save two types of films. The first type is a cropped video. This recoding is composed of cropped frames showing the vocal folds. The advantage of cropped video over the original recording is very good visibility of the vocal folds, because when properly framed in such a video, the folds occupy the entire screen and maintain a constant position on it.
Fig. 3. On the left, time sections of the function of the vocal folds; on the right side the corresponding cropped videos (above with indicator line, below without indicator line)
The second type of movie that can be saved is a so-called joint video. This video is especially useful because it contains the function of the vocal folds in all cross-sections. On the left side there is a cropped frame with an indicator line showing the analyzed place of the folds cross-section. On the right, there is a kymographic cross-section at the place indicated on the left. The entire video consists of successive kymographic sections, the places of which are indicated on the corresponding cropped frames. Saving such a video allows user to conveniently view the function of folds in a selected place, also when viewing archival reports, and not only during the analysis. Examples of joint videos are shown below (Fig. 4).
Fig. 4. Sample joint videos containing kymographic sections in sections of the vocal folds along their entire length
The analysis of the function of the vocal folds allows for a precise diagnosis of conditions such as regurgitation or asymmetry of the vocal folds , including the precise location on the vocal folds. Due to the ease of documentation and the amount of information contained in the kymographic image, kymography can also be used for voice rehabilitation purposes to assess the effects of rehabilitation. Consequently, kymographic analysis can be particularly useful in the examination of people who work intensively with their voice in their profession, such as singers and teachers.
The following examples present kymographic sections of the function of the vocal folds obtained from the videostroboscopic recording and the corresponding images of the folds with marked places of cross-section.
Fig. 5. On the left: kymographic sections; on the right: corresponding places on the vocal folds marked on cropped frames
Kymographic analysis of the above sample recordings shows that the movement of the patient's vocal folds is strongly asymmetrical (especially the mucosal wave). The right fold opens in a longer time compared to the left fold, but closes in a shorter time. It can also be seen that the time to full opening of the left fold and the time to full opening of the right fold are equal or close to each other. From Fig. 5, which shows the function of the folds in a cross-section at the bottom of the folds (Fig. 5, upper part), it can be concluded that at this point there is regurgitation of the vocal folds, because clearly there is not a single complete occlusion over the entire time interval.
In the example images above, the presence of a patient's vocal fold regurgitation can be quickly and easily diagnosed by using kymographic analysis. The marker defining the position on the vocal folds of the currently viewed kymographic section enables precise determination of the place of the observed regurgitation.
We also invite you to read the general instruction manual for the kymography module offered by the DiagnoScope Specialist program.