Contrast-enhanced proton radiographic sensitivity limits for tumor detection

Area of Science:

• Medical Physics
• Nanotechnology
• Radiology

Background:

• Proton radiography offers anatomical imaging for proton therapy but lacks contrast to distinguish tumors.
• Functionalized nanoparticles are needed to enhance contrast in proton radiography.
• Gold nanoparticles (AuNPs) are biologically compatible, high-Z materials suitable as contrast agents.

Purpose of the Study:

• To evaluate the efficacy of gold nanoparticles (AuNPs) as a contrast agent for proton radiography.
• To determine if AuNPs can differentiate tumors from surrounding tissues in proton imaging.
• To assess the feasibility of AuNP-enhanced proton radiography for guiding proton therapy.

Main Methods:

• Simulated tumors with AuNPs using acrylic and gold phantoms.
• Correlated gold thickness to reported tumor AuNP uptake levels.
• Acquired proton radiographs using a proton magnifying lens at the LANSCE facility.
• Measured transmission changes to observe the effects of gold, modeling human tissue thickness with acrylic.

Main Results:

• A 0.005 cm gold strip was visible with a 0.2% areal density change within 1 cm of acrylic.
• A 0.0005 cm gold strip was visible behind 20 cm of acrylic.
• A 1 cm tumor with 50-nm AuNPs/cell showed a 0.63% areal density change, equivalent to 0.0005 cm gold, visible in 20 cm of tissue.

Conclusions:

• AuNP-enhanced proton radiography is a potentially feasible technology for image-guidance in proton therapy.
• This technique could reduce off-target radiation effects and spare healthy tissues.
• The findings support the development of treatment plans and clinical applications for AuNP-enhanced proton radiography.