Two-dimensional high spatial-resolution dosimeter using europium doped potassium chloride: a feasibility study

Area of Science:

• Materials Science
• Medical Physics
• Solid State Physics

Background:

• Potassium chloride doped with europium (KCl:Eu²⁺) is a promising material for megavoltage radiation therapy dosimetry due to its radiation hardness and reusability.
• Existing dosimetry methods often lack the ideal combination of storage performance, reusability, and precise spatial resolution.

Purpose of the Study:

• To fabricate and characterize 2D KCl:Eu²⁺ storage phosphor films (SPFs) for advanced dosimetry applications.
• To investigate the fundamental mechanisms of energy storage and release in KCl:Eu²⁺.
• To evaluate the dosimetric performance, including spatial resolution, energy dependence, and dynamic range, of KCl:Eu²⁺ SPFs.

Main Methods:

• Fabrication of 2D KCl:Eu²⁺ SPFs using physical vapor deposition (PVD) and tape casting.
• X-ray diffraction (XRD) for structural and phase analysis.
• Photostimulated luminescence (PSL) and photoluminescence (PL) spectroscopy to identify storage and luminescence centers.
• Monte Carlo simulations to assess energy dependence.
• Dosimetric measurements using pellet samples to determine dynamic range and saturation limits.

Main Results:

• Highly crystalline KCl:Eu²⁺ films were successfully fabricated by PVD and tape casting, with europium incorporated into the KCl matrix.
• F(Cl⁻) centers act as electron storage sites, while Eu²⁺ ions serve as luminescence centers during photostimulation.
• Casted SPFs achieved sub-millimeter spatial resolution.
• Simulations showed minimal energy dependence for a 6 MV beam when KCl:Eu²⁺ was mixed with a low-Z polymer binder.
• Pellet samples demonstrated a wide dynamic range (0.01 cGy to 60 Gy) and high radiation hardness, saturating around 500 Gy.

Conclusions:

• KCl:Eu²⁺-based SPFs offer a viable alternative to traditional radiographic films, providing water equivalence and permanent detector identification.
• The developed SPFs exhibit desirable features for electronic dosimetry systems in radiation therapy, including excellent storage, reusability, and a broad dynamic range.
• This work validates KCl:Eu²⁺ as a robust material for high-performance dosimetry in medical applications.