(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: To build realistically-shaped, elastic lung inserts with an actuation mechanism, for an anthropomorphic phantom to perform quantitative analysis of PET/CT images affected by respiratory motion.
Methods: A stationary anthropomorphic PET phantom was modified to add accurate respiratory motion. The phantom’s outer shell is cast as a single component, with an open base sealed by an acrylic plate. Removable internal compartments include the spine, ribs, lungs, and liver. The phantom is filled with radioactive water solutions to model natural tracer distributions. Realistically-shaped lungs were manufactured by rolling a silicone elastomer (Chlorosil-35, Ottobock, Germany) onto a 3D-printed mold. A water-tight base was constructed that includes a Delrin piston mechanism, mounted onto a polycarbonate base plate. The piston mechanism is driven by a programmable linear actuator (Tolomatic Inc., USA) to create a pressure differential, causing the lungs to inflate/deflate (mediated by incompressible fluid) through an air port. The respiration is controlled by a Raspberry Pi via a custom software.
Results: All components have been designed and fabricated, and assembly and testing are underway. Initial tests show the breathing mechanism to be reliable, with no leaks or risk of failure. Mechanical simulation has shown the actuator force to be about 300N. At 0.5L tidal volume (relaxed breathing for adult male), the lungs extend 3cm axially, which is anatomically realistic. The phantom will be scanned on a PET/CT scanner, and the detailed data from phantom testing and use will be presented in the meeting. The designs and control software will be published as open source.
Conclusion: A static anthropomorphic phantom was retrofitted with custom-designed, actuated lungs that have realistic shape and motion. The improved phantom can model various waveforms of the respiratory cycle, and facilitate quantitative analysis of the impact of respiratory motion on the appearance of cancer lesions in PET images.
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