Influence of altered position of the cephalogram on the measurements.
The most of cefalometric analysis routinely performed by computer program. Digitized data comes from either the digital X-ray apparatus or from the digital scanner. Usually positioning of the patient in X-ray apparatus during taking image has no exact rules according the sagittal inclination of the head. Even in case of presence of visual skin marks of axio-orbital plane after condilography it is difficult to position patient to make that plane parallel to horizon due to lack of special device to perform that procedure. In case of scanning digital image there is no indications to rotate image according some plane. At the same time there is a strong rule in computer based ananalizing software (for example Cadias, Gamma) how to position image during cefalometric analysis. The image automatically rotates to make axio-orbital plane parallel to horizon. That rotation is performed after full tracing of cefalogram and before cefalometric analysis! That is why cefalometric points of tangential origin may change their position according horizontal plane. The last may lead to incorrect interpretation of cefalometric data.
Methods and materials. During our investigation 10 (100) ? digital cefalograms have been evaluated. All of them were previously traced and analized by other dentists with Cadias software. Digital image with marked points has been imported to special software to edit image (Photoshop, Adobe; ACD See Pro 3, ACD Systems International Inc.) to rotate it clockwise or counterclockwise. The amount of rotation was taking 10 °, that corresponds to physiological changes in head positioning during image taking. Than rotated image was imported back to Cadias Software for the new tracing. During new tracing we could observe previously marked points as an image details. So we could repeat exactly the position of points of non-tangential origin. Those points, which have tangential origin, analyzed according horizontal and vertical planes and placed sometimes on the new places. So we excluded repeating misalignment of non-tangential points. Further computer cefalometric analyses has been provided as usual. Finally we compared trends of a jaws grows, skeletal class, brahio-doliho type and some meanings of some angles of the same image, but traced twice.
Supposed results. The way of positioning of the patient during taking the cefalogram and the parameters of taken image influence the positioning of that image in analyzing software. The lack of standardized incoming data leads to incorrect analysis. Due to that patient’s cefalometric analysis and treatment planning could be influenced.
Supposed recommendations. There are 2 propositions to standardize incoming digital data. First is by changes in dental X-ray machines: to add laser positioning device to each apparatus to correctly positioning head of the patient according axio-orbital plane. Second one is by changing software. We propose to divide image tracing on two stages – first is marking axio-orbital plane and automated rotation of the image according horizon, second stage – final tracing and analyze.