A system obtains multiple x-ray measurements corresponding to different breathing phases of the lung by determining, based on a volumetric measurement of the patient's breathing, a breathing phase of the patient and gating an x-ray imaging apparatus to produce an x-ray projection of the patient's lung when the breathing phase matched any of a plurality of different breathing phases. The system extracts multiple displacement fields of lung tissue from the multiple x-ray measurements corresponding to different breathing. Each displacement field represents movement of the lung tissue from a first breathing phase to a second breathing phase and each breathing phase has a corresponding set of biometric parameters. The system calculates one or more biophysical parameters of a biophysical model of the lung using the multiple displacement fields of the lung tissue between different breathing phases of the lung and the corresponding sets of biometric parameters.