Calibrating radiographs
Calibration tells the app the real-world size of one pixel. Every measurement and every implant template depends on this — without it, the rest of the app’s tools are locked.
Why it matters
Radiographic magnification varies between exposures. The same dog’s tibia may project as 130 mm on one X-ray and 142 mm on another. If you skip calibration and try to overlay a 65 mm implant, it’ll land at the wrong size — and you’ll plan with the wrong dimensions.
Every measurement and overlay in the app uses the calibration you set. Get this step right.
How to calibrate
The app checks every radiograph for a calibration marker as it is imported. Nothing is ever applied on its own:
- Confident match — a toast shows you the measured scale. Choose Yes, use it to accept it; there is nothing to click on the image.
- Uncertain, or no match — nothing is selected and no tool is armed. The scale stays blank until you set it yourself.
To calibrate by hand, click Calibration in the sidebar, then 25 mm. The app tries the whole image once more; if it is still unsure, click once inside the marker. Circle and the line-length button let you set a known distance yourself.
The calibration scale appears at the top of the canvas once set.
What you need in the image
A radiopaque reference of known dimension visible in the radiograph. The default is a 25 mm sphere placed in the same plane as the bone of interest — typically taped to the limb. Other reference sizes can be set in the calibration sub-panel before placing.
Common problems
- Chained or stacked markers. Two or more spheres touching can look like one large blob to most detectors. The app’s auto-calibration handles stacked spheres, but verify the picked one is the correct individual marker.
- Marker off-plane. A marker laid next to the bone but at a different distance from the X-ray plate has different magnification than the bone itself. Calibration will look right but the rest of your planning will be subtly off.
- No marker visible. You can’t calibrate without one. The app won’t let you measure or place templates until a scale is set.
Auto-detection confidence
Auto-detection produces a confidence score. It decides how hard the app looks for the marker — not whether the answer gets used. Every detection is offered to you and waits for you to accept it, and one the app is unsure of is never quietly applied.
Auto-detection is a starting point, not an authority: confirm the picked marker is the right one before you plan off it.
When to re-calibrate
- New radiograph in the same case — every image needs its own calibration.
- Suspicious measurements (a 6 kg dog’s tibia measuring 180 mm) — recalibrate before trusting the rest.