Development of a deformable lung phantom for the evaluation of deformable registration

A deformable lung phantom was developed to simulate patient breathing motion and to evaluate a deformable image registration algorithm. The phantom consisted of an acryl cylinder filled with water and a latex balloon located in the inner space of the cylinder. A silicon membrane was attached to the inferior end of the phantom. The silicon membrane was designed to simulate a real lung diaphragm and to reduce motor workload. This specific design was able to reduce the use of metal, which may prevent infrared sensing of the real position management (RPM) gating system for four-dimensional (4D) CT image acquisition. Verification of intensity based three-dimensional (3D) demons deformable registration was based on the peak exhale and peak inhale breathing phases. The registration differences ranged from 0.60 mm to 1.11 mm and accuracy was determined according to inner target deformation. The phantom was able to simulate features and deformation of a real human lung and has the potential for wide application for 4D radiation treatment planning.