Mandibular Asymmetry Measurement plugin

Developer: Gerald Torgersen

Introduction

This plugin for ImageJ1 was developed for a master project in odontology2 at the Faculty of dentistry of the University of Oslo. The aim of the master project was to survey the asymmetry of the mandibles right and left side on panoramic radiographs. In the project, an index3 was used to quantify this asymmetry.

Description of plugin

This plugin simplifies the process of measuring mandibular asymmetry by letting the researcher mark two points (Co and Inc, Figure 1) and two lines (RL and ML, Figure 1) on each panoramic using the mouse. The plugin uses that input to calculate the intersection points (x, y and z, Figure 1)used to quantify the asymmetry.

Figure 1 - The points used to calculate the asymmetry index (Figure from the master thesis2)
Points:
Co = condylion (the most superior point on the condylar head)
inc = incisura mandibulae (the deepest point between processus coronoideus and processus condylaris)
x = orthogonal projection of point Co on the ramus line (RL)
y = orthogonal projection of point Inc on the ramus line (RL)
z = the intersection between RL and the mandibular line (ML) on the mandibular border 3.

The pluging generates a comma separated data file (CSV) with the name measurements.csv. In this file a line containing information about the image, date and time for measurements and the measured coordinates are saved, one line per image. The structure of the data is:

C0:     Condyle top point
Inc:    Incisure: lowest point of incisura mandibulare
RL:        Tangent line to mesial edge of ramus
ML:     Tangent line to lower edge of mandibula
C0_RL:    Projection of C0 on RL
Inc_RL:    Projection of Inc on RL
RL_ML:    Intersection point of RL and ML
each of those sites is measured for right and left side

Format of data line: Comma separated values (separator ;, x, y coordinate for each point, four coordinates for line: x,y start point and x,y end point)
filename; timestamp of measurement; unit og length; (right side) C0_r; C0_RL; Inc; Inc_RL; RL_ML; RL; ML; (left side) C0_r; C0_RL; Inc; Inc_RL; RL_ML; RL; ML; optional text comment

Download and installation of the plugin

Download and extract the file MandibularAssymetryMeasure_.zip. Put the file MandibularAssymetryMeasure_.jar in your ImageJ plugin folder. Start ImageJ and you will have the plugin in the plugin menu. The zip file also includes the source code. Feel free to use and modify it to your needs.

Quick start guide to the plugin

Open a panoramic radiograph in ImageJ and start the plugin from the plugin menu. You will see the user interface shown in Figure 2.


Figure 2 - Graphical user interface of the plugin

To minimize mouse clicks the plugin is programmed to get the input in a special order (you can change that by modifying the source code). The plugin also changes the ImageJ tool to point or line depending on the expected next input.

Measurement of one panoramic radiograph

  1. Click the right condyle top point (Figure 1)
  2. Click the right incisure bottom point (Figure 1)
  3. Draw the right ramus tangent line (Figure 1)
  4. Draw the right mandibular bottom tangent line (Figure 1)
  5. Repeat point 1 - 4 for the left side
  6. Optional: Enter a comment about this radiograph or measurement
  7. Click "Safe measurements and close" - the plugin closes and a copy of the image with the points and lines drawn is saved along with the data saved  to the file measurements.csv

Disclaimer

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

References

  1. Rasband WS. ImageJ. Bethesda: U. S. National Institutes of Health; 1997-2018.
  2. Danielsen T, Daling  AV. Mandibulær asymmetri hos kvinner fra 6 til 18 år. En longitudinell studie. [Master thesis: University of Oslo; 2018. Supervisors Lisen V. Espeland and Gerald Torgersen]
  3. Kjellberg H, Ekestubbe A, Kiliaridis S, Thilander B. Condylar height on panoramic radiographs. A methodologic study with a clinical application. Acta Odontol Scand 1994;52(1):43-50.
Av Gerald Torgersen
Publisert 30. apr. 2018 16:10 - Sist endret 2. mai 2018 15:46