Dear Doctor, Thank you very much for contacting us and for your continued use of WebCeph. Regarding the superimposition issue you reported, we would like to explain that radiographic images are fundamentally composed of pixels, and therefore require image size calibration to convert pixel-based measurements into actual distance units (millimeters). This calibration is essential for accurate measurements, analysis results, and superimposition outcomes. To perform this calibration, please click on the [Image Size Calibration] button in the digitization tab. A red virtual ruler will appear on the screen. You can drag both ends of this red ruler to align it precisely with the actual ruler embedded in the X-ray image. This allows the system to calculate the Pixels per Millimeter (PPM) ratio automatically. You may select from three available virtual ruler lengths: 10 mm, 20 mm, or 30 mm. Please choose the length that best matches the actual ruler shown in your image for the most accurate calibration. Once calibration is completed, you may click [Set Calibration as Default] to save this PPM value as your default setting. From then on, when uploading new images, the [Apply Preset Calibration] toggle will be automatically activated, and the saved PPM value will be applied. This feature is designed to save time and avoid repeated calibration, especially when the same X-ray device is used consistently in your clinic. However, if the two records used for superimposition were captured using different X-ray machines, we recommend deactivating the [Apply Preset Calibration] toggle for that record, and manually setting the correct PPM value for each image. Accurate calibration is an essential part of ensuring the reliability of superimposition results. If you need further assistance, please don’t hesitate to contact us at any time. Thank you again for your trust in WebCeph.