ADAM: A breathing phantom for lung SBRT quality assurance

Radiotherapy treatment of moving lesions is a challenging task in which different strategies can be used to adequately treat the tumor while sparing the surrounding tissue. The complexity of these strategies requires accurate and appropriate quality assurance tests. For this purpose, ADAM (Anthropomorphic Dynamic breAthing Model), a new phantom which simulates realistic patient breathing, was developed aiming to test the image quality and dose delivery in lung cancer treatments.

ADAM reproduces a male torso complete with a moving anterior chest wall and internal parts. The phantom's external body is printed with a 3D printer using acrylonitrile butadiene styrene. Internal lungs, ribs, spinal cord, and lung tumor (LT) are made of materials that simulate human tissues. Driven by an Arduino programmable board, the lungs can move along linear or elliptical paths while the anterior chest wall moves up and down. Phantom features and usability, reproducibility of LT position in the phantom chest, internal and external motion repeatability and tumor-to-surface motion correlation were investigated.

Hounsfield Units of the employed materials demonstrates the phantom adequately simulates human tissues. Tests performed with the Synchrony system confirm ADAM's suitability for respiratory internal tracking. Reproducibility of the internal structure position is within 1mm as are internal and external motion repeatability. A strong positive correlation is found between the lung and chest wall positions (R²=0.999).

ADAM demonstrates to be suitable to be employed with gating and tracking devices used in the treatment of moving lesions.