Proton range verification with ultrasound imaging using injectable radiation sensitive nanodroplets: a feasibility...

Area of Science:

• Medical Physics
• Nanotechnology
• Radiotherapy

Background:

• Proton therapy requires precise range verification to avoid underdosage and minimize damage to healthy tissue.
• Current safety margins in proton therapy are large due to limitations in real-time monitoring.
• Nanodroplets are injectable contrast agents that can generate ultrasound signals upon vaporization.

Purpose of the Study:

• To investigate the use of radiation-induced nanodroplet vaporization for in vivo proton range verification.
• To assess the feasibility of using ultrasound to detect vaporization events for real-time monitoring.
• To evaluate the potential of this method to reduce clinical safety margins in proton therapy.

Main Methods:

• Applied semi-empirical theory of radiation-induced vaporization to coated nanodroplets.
• Exposed nanodroplet dispersions in aqueous phantoms to proton beams of varying energies and doses.
• Utilized ultrasound imaging to detect droplet vaporization and map proton energy deposition.

Main Results:

• Radiation-induced droplet vaporization was observed proximal to the proton Bragg peak.
• A statistically significant increase in ultrasound contrast was detected at doses as low as 2 Gy.
• Vaporization profiles showed sub-millimeter reproducibility compared to expected proton ranges.
• Droplet vaporization is likely induced by high linear energy transfer (LET) recoil ions.

Conclusions:

• Superheated nanodroplets show potential as a novel tool for real-time proton range verification.
• Ultrasound imaging of radiation-induced vaporization can provide accurate range information.
• This technology may enable reduction of safety margins, improving proton therapy efficacy and safety.