Fig 4. Distance metric (Eq (1)) of fiducial markers for all the patients computed with the reference (top-left) and the sequential registration (top-right).

End expiration was chosen as reference of measurements, i.e. 50% phase. The top figures show the distance between the estimated and the measured fiducial markers in all phases for all patients. The estimated fiducial markers are the transformed markers from the reference phase to the corresponding 4DCT phase using the transformation found with registration. The bottom figure depicts the registration errors for the inpainted images. Only the reference registration approach is tested for the inpainted images.