  X-ray imaging is a fundamental tool of routine clinical diagnosis.
Fluoroscopic imaging can further acquire X-ray images at video frame rates,
thus enabling non-invasive in-vivo motion studies of joints, gastrointestinal
tract, etc. For both the qualitative and quantitative analysis of static and
dynamic X-ray images, the data should be free of systematic biases. Besides
precise fabrication of hardware, software-based calibration solutions are
commonly used for modelling the distortions. In this primary research study, a
robust photogrammetric bundle adjustment was used to model the projective
geometry of two fluoroscopic X-ray imaging systems. However, instead of relying
on an expert photogrammetrist's knowledge and judgement to decide on a
parametric model for describing the systematic errors, a self-tuning
data-driven approach is used to model the complex non-linear distortion profile
of the sensors. Quality control from the experiment showed that 0.06 mm to 0.09
mm 3D reconstruction accuracy was achievable post-calibration using merely 15
X-ray images. As part of the bundle adjustment, the location of the virtual
fluoroscopic system relative to the target field can also be spatially resected
with an RMSE between 3.10 mm and 3.31 mm.
