title: Biomechanical simulation of thorax deformation using finite element approach.
abstract: BACKGROUND
  The biomechanical simulation of the human respiratory system is expected to be a useful tool for the diagnosis and treatment of respiratory diseases. Because the deformation of the thorax significantly influences airflow in the lungs, we focused on simulating the thorax deformation by introducing contraction of the intercostal muscles and diaphragm, which are the main muscles responsible for the thorax deformation during breathing.
  
  
  METHODS
  We constructed a finite element model of the thorax, including the rib cage, intercostal muscles, and diaphragm. To reproduce the muscle contractions, we introduced the Hill-type transversely isotropic hyperelastic continuum skeletal muscle model, which allows the intercostal muscles and diaphragm to contract along the direction of the fibres with clinically measurable muscle activation and active force-length relationship. The anatomical fibre orientations of the intercostal muscles and diaphragm were introduced.
  
  
  RESULTS
  Thorax deformation consists of movements of the ribs and diaphragm. By activating muscles, we were able to reproduce the pump-handle and bucket-handle motions for the ribs and the clinically observed motion for the diaphragm. In order to confirm the effectiveness of this approach, we simulated the thorax deformation during normal quiet breathing and compared the results with four-dimensional computed tomography (4D-CT) images for verification.
  
  
  CONCLUSIONS
  Thorax deformation can be simulated by modelling the respiratory muscles according to continuum mechanics and by introducing muscle contractions. The reproduction of representative motions of the ribs and diaphragm and the comparison of the thorax deformations during normal quiet breathing with 4D-CT images demonstrated the effectiveness of the proposed approach. This work may provide a platform for establishing a computational mechanics model of the human respiratory system.
authors: Department of Biomedical Engineering, Yamaguchi University, Ube, 755-8611, Japan. zhangguangzhi1987@hotmail.com.
authors: Guangzhi
authors: G
authors: Zhang
authors: Department of Biomedical Engineering, Yamaguchi University, Ube, 755-8611, Japan. xchen@yamaguchi-u.ac.jp.
authors: Xian
authors: X
authors: Chen
authors: Department of Biomedical Engineering, Yamaguchi University, Ube, 755-8611, Japan. ohgi@yamaguchi-u.ac.jp.
authors: Junji
authors: J
authors: Ohgi
authors: Tokuyama Central Hospital, Japan Community Healthcare Organization, Shunan, 745-8522, Japan. toshiro@tokuchuhp.jp.
authors: Toshiro
authors: T
authors: Miura
authors: Tokuyama Central Hospital, Japan Community Healthcare Organization, Shunan, 745-8522, Japan. xray@tokuchuhp.jp.
authors: Akira
authors: A
authors: Nakamoto
authors: Tokuyama Central Hospital, Japan Community Healthcare Organization, Shunan, 745-8522, Japan. soliton2161@hotmail.co.jp.
authors: Chikanori
authors: C
authors: Matsumura
authors: The Department of Human and Engineered Environmental Studies, The University of Tokyo, Kashiwa, 277-0871, Japan. sugiura@k.u-tokyo.ac.jp.
authors: Seiryo
authors: S
authors: Sugiura
authors: The Department of Human and Engineered Environmental Studies, The University of Tokyo, Kashiwa, 277-0871, Japan. hisada@mech.t.u-tokyo.ac.jp.
authors: Toshiaki
authors: T
authors: Hisada
mesh_terms: D001696:Biomechanical Phenomena; D003964:Diaphragm / Q000000981:diagnostic imaging / Q000502:physiology; D020342:Finite Element Analysis; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008297:Male; D055595:Mechanical Phenomena; D008954:Models, Biological; D009068:Movement; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology; D013902:Radiography, Thoracic; D012119:Respiration; D013909:Thorax / Q000502:physiology*