Development of a 3D Printed Motion Mechanism for a 4D Respiratory Motion Phantom

Radiotherapy is recognized as an effective method of cancer treatment and management that employs ionizing radiation to produce lethal effects to localized malignant cells. In employing radiotherapy, it is important to verify that the dose administered to the patient during treatment delivery is the same as sought during the treatment planning phase. This is typically done using phantoms and dosimeters. However, most phantoms in use are static, they do not simulate respiratory motion which occur during treatment. In lieu of this, we a developing a dynamic thorax phantom which simulates the respiratory motion of a lung lesion in 4D. This paper specifically focuses on the motion mechanism for our 4D respiratory motion phantom system. To keep the cost down, we 3D printed all of mechanisms structure to house the off-shelf electro-mechanical components. Respiratory motion of a lung lesion approximated through the translational and rotational movement of a cylinder. Both these motions are actuated independently and by a linear and servo motor respectively. A simple user interface (UI) was designed to test the motion mechanism by manual control of the motors or selecting waveforms to simulate respiratory motion of the lesion. This proof of concept shows that the mechanism can be fabricated at low cost and improved upon in the future for the full 4D respiratory motion phantom system.