For accurate diagnosis using CR cephalographic measurement points, it is very important to establish image processing conditions under which accurate measurement points can be input. We produced 2 types of CR cephalograms. Image enhancement was performed in one type and not performed in the other type. After establishing the same 20 measurement points, we indicated the error of the measurement points between the 2 types as an area of rejection ellipse, and evaluated measurement errors caused by differences in image processing conditions. From the data obtained, we produced a 95% rejection ellipse and evaluated measurement-point establishment errors from the mean value using vector quantities in 2 types. From regarding measurement points under both conditions, rejection ellipses of the measurement points of S, N, Or, U1, L1, G, Go, and Ar were comparatively small, and Ptm and Pns had narrow large rejection ellipses. The area of rejection ellipse was small at 12 of 20 measurement points on the image-processed cephalogram. It was revealed that input errors of many measurement points are low with frequency-processed cephalograms. In particular, because frequency processing can decrease the establishment errors of cephalometric measurement points, appropriate establishment of frequency processing should be performed.
Noboru Demura, Miho Hasumoto and Taichi Demura
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