Abstract
Objective Magnification error is always present in radiography and calibration is necessary,
if high accuracy is required in pre-surgical planning. The goal of this study was
to verify the use of self-made markers and calibration techniques and to establish
guidelines for magnification correction.
Study Design We evaluated and compared spherical and linear markers of different sizes with focus
on practicability, accuracy and precision. Markers were placed on foam pads or attached
to flexible arms.
Results Vertical marker deviation of 1 cm from the anatomical reference point corresponded
to ∼1% of magnification error in our setting. Marker placement along the horizontal
plane showed no significant magnification in the periphery of the radiograph. All
markers showed good accuracy and the commercial spherical marker with a flexible segment
arm had the best results regarding practicability.
Conclusion Our study suggests that marker type is not solely responsible for usability and accuracy
but also the type of fixation. In the absence of a calibration marker, calculation
of the magnification factor using a measurement tape during radiography is equally
reliable. Use of a fixed averaged calculated calibration factor showed poor agreement
compared with the marker calibration, probably due to variability in size of the animals.
In conclusion, if precision matters, use of a calibration marker, which could be purchased
or self-made, is advised.
Keywords
calibration marker - magnification - radiography - orthopaedic surgery - implants
