Technical note: A novel boundary condition using contact elements for finite element based deformable image registration

Abstract

Deformable image registration is an important tool for image-guided radiotherapy. Physics-modelbased deformable image registration using finite element analysis is one of the methods currently being investigated. The calculation accuracy of finite element analysis is dependent on given boundary conditions, which are usually based on the surface matching of the organ in two images. Such a surface matching, however, is hard to obtain from medical images. In this study, we developed a new boundary condition to circumvent the traditional difficulties. Finite element contact-impact analysis was employed to simulate the interaction between the organ of interest and the surrounding body. The displacement loading is not necessarily specified. The algorithm automatically deforms the organ model into the minimum internal energy state. The analysis was performed on CT images of the lung at two different breathing phases ͑exhalation and full inhalation͒. The result gave the displacement vector map inside the lung. Validation of the result showed satisfactory agreement in most parts of the lung. This approach is simple, operator independent and may provide improved accuracy of the prediction of organ deformation. © 2004 American Association of Physicists in Medicine.

Predictive modeling of lung motion over the entire respiratory cycle using measured pressure‐volume data, 4DCT images, and finite‐element analysis

“…In an extension of this work, Didier et al 39 used the same FEM model and investigated the kinematic effects of the ribs on the motion during a breathing cycle by using a finite helical axis ͑FHA͒ method. Extending the work of Zhang et al, 37 Werner et al 34,45 recently proposed a respiratory lung motion model incorporating contact mechanics. Instead of using contact elements, an augmented Lagrangian algorithm was used for the contact formulation in the FEM software COMSOL MULTIPHYSICS ͑COMSOL AB, Sweden͒.…”

“…35 Finite-element lung models have also been used to evaluate the effect of gravity on respiratory physiology 36 and to find surface matching of organs in two images in deformable image registration techniques. [37][38][39][40] Recently, finite-element lung models for tumor tracking at the end of inhalation incorporating contact conditions have been proposed. 35,34 In FEM, the effectiveness of the model and its accuracy in predicting tumor motion depend on several important issues including the quality of the patient geometric model and the regularity and accuracy of the finite-element mesh.…”

“…Linear and nonlinear elastic material models, obtained from experiments by Radford 44 on strips of tissue excised from canine lungs, were used in the model. Zhang et al 37 proposed a lung model with pleural sliding which was driven by pressure forces applied on the surface of the lungs. This model was implicitly validated by overlaying the CT lung image at inhalation and a reconstructed image of the lung at exhalation without quantitative comparisons.…”

“…The FE model has been validated using 48 landmarks from the CT data. No tuning of FE modeling parameters including material properties, 34 contact stiffness, 37 or friction coefficients 42 was employed. In II, we present our modeling methodology, followed by a discussion of results in Sec.…”

A poroelastic model coupled to a fluid network with applications in lung modelling

“…Several parameters for lung tissue elasticity and poroelasticity have been proposed [34,5,35,10,36], although there is no consensus in the values in the literature. In this study, we have chosen parameters as shown in Table 1 …”