Proton penetration and control in nonhomogeneous phantoms

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• Accurate dose delivery is essential in proton beam therapy.
• Modifications to the patient's surface, such as air cavities, can distort proton beam-stopping profiles.
• Customized bolus materials are required to compensate for surface irregularities and optimize dose distribution.

Purpose of the Study:

• To investigate the impact of air volumes on proton beam-stopping profiles.
• To evaluate the effectiveness of custom-shaped lucite bolus in achieving desired beam-stopping profiles.
• To establish methods for verifying bolus effectiveness in clinical settings.

Main Methods:

• Proton beam-stopping profiles were measured photographically in phantom setups.
• Phantom materials included lucite, styrofoam, and tissue-equivalent materials.
• Custom lucite bolus was designed and implemented to correct for distortions.

Main Results:

• Air volumes were identified as the primary cause of significant distortions in proton beam profiles.
• Custom-cut lucite bolus successfully modified beam-stopping profiles as intended.
• The study demonstrated the feasibility of using tailored bolus to control beam penetration.

Conclusions:

• Customized lucite bolus can effectively correct for air-induced distortions in proton therapy.
• Precise control of beam penetration within 5 mm is achievable with appropriate bolus design.
• In situ verification of bolus effect is critical for ensuring accurate dose delivery in proton therapy.