A new simulation method was developed that considered a tumor as a solid body and therapeutic response as deformation of the tumor using mechanical analogy. As radiation exposure to the tumor was related to the external force to the solid body, the geometrical change of the tumor could be estimated from fundamental equations in solid mechanics. A change in tumor volume was calculated using finite element (FE) method. The FE models were constructed from CT images of patients before the radiotherapy. The initial radiotherapeutic parameters of tumor radioresistance and repopulation rate were determined based on a linear-quadratic model and then revised by the comparison with actual tumor volume change. Three patients with uterine cervix carcinoma were applied in this method. Simulation results well showed tendencies of tumor volume changes with radiotherapy. In addition, this method could provide the appropriate value of radiotherapeutic parameters for individual case. In conclusion, our approach could calculate three-dimensional tumor deformation during the course of radiotherapy and will provide useful information for more effective treatment.

Keywords

Mechanical Analogy, Radiotherapy, Linear-Quadratic Model, Tumor Deformation, Finite Element Analysis

Paper information

Seishin TAKAO, Shigeru TADANO, Hiroshi TAGUCHI and Hiroki SHIRATO, “Computer Simulation of Radiotherapy for Malignant Tumor”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 4 (2009), pp.576-588 . doi:10.1299/jbse.4.576

Precise assessment of therapeutic response in radiotherapy has been an important issue in the field of radiation oncology. This study proposed a methodology to evaluate therapeutic response based on tumor geometries. Three-dimensional (3D) tumor shapes were obtained from follow-up CT scans taken once a week throughout the treatment period. Tumor geometries were represented in two-dimensional (2D) surface geometry maps. These maps indicated the distances from the tumor center to surface at each azimuthal and horizontal angle by colors, in order to represent the characteristics of tumor morphologies. This method was applied to three clinical cases of head and neck cancer. The changes of tumor geometries could be represented visually and quantitatively using surface geometry maps. These maps provided valuable information about tumors for accurate diagnosis of tumor response to radiotherapy.

Keywords

Tumor Geometry, Surface Geometry Map, Radiotherapy, Therapeutic Response

Paper information

Seishin TAKAO, Shigeru TADANO, Hiroshi TAGUCHI and Hiroki SHIRATO, “Analysis of Three-Dimensional Characteristics in Tumor Morphology”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 2 (2009), pp.221-229 . doi:10.1299/jbse.4.221