Study of Setting Landmarks and Frequency Control on Digital Cephalogram

Abstract

We applied Fourier transformation to investigate characteristics of the space frequency in digital cephalogram and examined the appropriate image processing conditions. Research materials were lateral cephalograms taken on the first visit of patients, who underwent orthodontic treatment. The following 8 measurement points (Sella, Na, Or, Ptm, Ans, Pns, Po, Pog) were selected from the imported images. Image processing was performed using image analysis software (NIH Image). Fourier transformation was performed in the surrounding area (512×512 dot)of each measurement point. The relationship between space frequency and power spectrum was made based on the data obtained by conversion. The X-axis showed space frequency and the Y-axis showed power spectrum (concentration difference of the image). The space frequency character at each measurement point was evaluated. In results, the space frequency was 0.05-0.97 cycle/mm at all measurement points, suggesting a large power spectrum. It was found that the power spectrum change amount was small for all measurement points at a frequency band over 1.0 cycle/mm. The present study investigated the characteristics of the frequency band for the anatomical objects of the skull in the maxillofacial area using cephalogram. The anatomical objects investigated in the present study are used in orthodontic treatment. If the space frequency of the target objects is analyzed using the same method at each department, clear images of accentuated target objects can be obtained. The method used in the present study can be widely applied not only in the dental field, but also medical field.