Modeling Respiratory Motion for Cancer Radiation Therapy Based on Patient-Specific 4DCT Data

Abstract

Abstract. Prediction of respiratory motion has the potential to substantially improve cancer radiation therapy. A nonlinear finite element (FE) model of respiratory motion during full breathing cycle has been developed based on patient specific pressure-volume relationship and 4D Computed Tomography (CT) data. For geometric modeling of lungs and ribcage we have constructed intermediate CAD surface which avoids multiple geometric smoothing procedures. For physiologically relevant respiratory motion modeling we have used pressure-volume (PV) relationship to apply pressure loading on the surface of the model. A hyperelastic soft tissue model, developed from experimental observations, has been used. Additionally, pleural sliding has been considered which results in accurate deformations in the superior-inferior (SI) direction. The finite element model has been validated using 51 landmarks from the CT data. The average differences in position is seen to be 0.07 cm (SD = 0.20 cm), 0.07 cm (0.15 cm), and 0.22 cm (0.18 cm) in the left-right, anterior-posterior, and superior-inferior directions, respectively.

Computational Modeling of Airway and Pulmonary Vascular Structure and Function: Development of a "Lung Physiome"

“…Finite element models of the lungs have been used in various applications, namely, as virtual phantoms to improve imaging protocols and image segmentation, 26 in predictive studies of tissue deformation for lung tumor tracking during radiation oncology, 27–29 for studying the effect of gravity on tissue deformation, 10,30–32 and as a tethering tissue in which model airways and vessels are embedded. 5,33 Creating an anatomically structured finite element model of the lungs and/or lobes is typically achieved in one of two ways: (i) using commercially available software to convert volumetric imaging into a triangulated mesh of the organ surface, and then filling the volume that is bounded by the surface with a (usually tetrahedral) volume mesh.…”

“…27–29,78 Lung motion confounds the localization of radiation to the lung tumor in that otherwise healthy tissue is also irradiated, causing acute and chronic changes in the tissue structure that adversely affects gas exchange function. The goal of these modeling studies is to develop a clinically applicable tool that can predict subject-specific breathing motion and regional tissue displacement during therapy in order to improve treatment planning and efficacy.…”

Toward in vivo lung's tissue incompressibility characterization for tumor motion modeling in radiation therapy

“…DeCarlo et al 17 simulated the lung ventilation with 2D FE lung model with forces applied to expand the lung model during respiration. Zhang et al, 18 Villard et al, 19 Eom et al, 20 and Werner et al 3 followed a similar approach where they used 3D FE lung model under negative pressure. They restricted lung expansion by the final volume of the lung or the chest cavity model.…”