Anthropomorphic phantom for deformable lung and liver CT and MR imaging for radiotherapy

In this study, a functioning and ventilated anthropomorphic phantom was further enhanced for the purpose of CT and MR imaging of the lung and liver.A deformable lung, including respiratory tract was 3D printed.Within the lung's inner structures is a solid region shaped from a patient's lung tumour and six nitro-glycerine capsules as reference landmarks.The full internal mesh was coated, and the tumour filled, with polyorganosiloxane based gel.A moulded liver was created with an external casing of silicon filled with polyorganosiloxane gel and flexible plastic internal structures.The liver, fitted to the inferior portion of the right lung, moves along with the lung's ventilation.In the contralateral side, a cavity is designed to host a dosimeter, whose motion is correlated to the lung pressure.A 4DCT of the phantom was performed along with static and 4D T1 weighted MR images.The CT Hounsfield units (HU) for the flexible 3D printed material were -600 -100HU (lung and liver structures), for the polyorganosiloxane gel 50 -120HU (lung coating and liver filling) and for the silicon 650 -800HU (liver casing).The MR image intensity units were 0 -150, 0 -100 and 80 -110 respectively.The maximum range of motion in the 4D imaging for the superior lung was 1 -3.5mm and 3.5 -8mm in the inferior portion.The liver motion was 5.5 -8.0mm at the tip and 5.7 -10.0mm at the dome.No measurable drift in motion was observed over a two hour session and motion was reproducible over three different sessions for sin 2 (t), sin 4 (t) and a patient-like breathing curve with the interquartile range of amplitudes for all breathing cycles within 0.5mm.The addition of features within the lung and of a deformable liver will allow the phantom to be used for imaging studies such as validation of 4DMRI and pseudo CT methods.