Development of a breathing lung phantom for proton CT imaging

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Physics

Background:

• Proton computed tomography (pCT) offers potential advantages over conventional X-ray CT, but motion artifacts remain a significant challenge.
• Developing realistic phantoms that mimic human respiratory motion and tissue properties is essential for validating pCT systems and algorithms.
• Existing phantoms often lack the fidelity to replicate complex lung deformations and tissue-equivalent characteristics.

Purpose of the Study:

• To design and fabricate a deformable lung phantom capable of simulating realistic breathing motion.
• To incorporate tissue-equivalent material properties for accurate proton interaction simulation.
• To validate the phantom's performance for proton imaging applications, particularly in experimental motion studies.

Main Methods:

• The lung phantom was manufactured using 3D printing and silicone molding techniques, with a custom design for motor-controlled motion.
• Flexible resins were evaluated and optimized for varying ultraviolet exposure to achieve desired compression properties.
• Material properties, including CT numbers and relative stopping power (RSP), were characterized using X-ray CT and pCT.

Main Results:

• A non-homogeneous compression was achieved in the lung using a gradient-thickness grid structure.
• The phantom demonstrated hysteretic breathing motion with 10 mm peak-to-peak displacement, measured via fluoroscopic imaging.
• The phantom's CT numbers and RSP values were found to be comparable to human lung tissues.

Conclusions:

• The developed deformable lung phantom successfully imitates key lung motion characteristics and possesses realistic tissue-equivalent properties.
• This phantom provides a valuable tool for experimental motion studies in proton computed tomography.
• The design advances the capability for motion artifact mitigation and improved image quality in pCT.