The surface doses from orthovoltage x-ray treatments

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiological Protection

Background:

• Orthovoltage x-ray systems are commonly used in radiation therapy.
• Treatment cones and lead shielding are employed to shape the radiation beam and protect surrounding tissues.
• The impact of these accessories on patient surface dose is not fully understood.

Purpose of the Study:

• To quantify the surface dose increase caused by treatment cones and lead shielding in orthovoltage x-ray systems.
• To investigate the factors influencing this surface dose.
• To discuss the clinical significance of elevated surface doses and suggest mitigation strategies.

Main Methods:

• Measurements of surface dose were performed using treatment cones and lead shielding with orthovoltage x-ray units.
• The study likely involved varying cone shapes, materials, and x-ray energies.
• Comparison of doses with and without shielding/cones, potentially using a Baldwin-Farmer chamber as a reference.

Main Results:

• Both treatment cones and lead shielding significantly elevate the surface dose.
• This increase is attributed to the generation of photoelectrons.
• Surface dose can be up to 500% higher than the reference dose, depending on cone design, material, and x-ray energy.

Conclusions:

• Treatment cones and lead shielding substantially increase patient surface dose during orthovoltage x-ray therapy.
• The generated photoelectrons are a likely cause for this dose enhancement.
• Minimizing surface dose by using low atomic number materials between lead shielding and patient skin is recommended to protect sensitive tissues like the epithelium.