The basic study of a bi-material range compensator for improving dose uniformity for proton therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Therapy

Background:

• Range compensators (RCs) are crucial for conformal dose distribution in heavy-charged-particle therapy.
• Standard RCs can induce dose distribution distortion and calibration errors in monitor units (MUs).
• Dose inhomogeneity from RCs affects treatment accuracy, particularly in proton therapy.

Purpose of the Study:

• To investigate the efficacy of a bi-material range compensator in reducing dose inhomogeneity.
• To compare dose distributions generated by single-material and bi-material RCs.
• To assess the impact of bi-material RCs on dose uniformity and lateral penumbra in proton therapy.

Main Methods:

• Designed and manufactured single-material and bi-material RCs with equivalent range losses.
• The bi-material RC utilized chemical wood (ABS resin) and brass.
• Measured dose distributions in water using a 160 MeV proton beam and a HIMAC biology beam port.

Main Results:

• The bi-material RC significantly reduced dose inhomogeneity compared to the single-material RC.
• Dose uniformity in the target region was substantially improved with the bi-material RC.
• The improvement in uniformity came at the cost of slightly blurred lateral penumbra.

Conclusions:

• Bi-material range compensators offer a promising solution for improving dose uniformity in heavy-charged-particle therapy.
• This method enhances the accuracy of dose delivery and MU calibration.
• A modification to the original calculation model is proposed for clinical application in patients with density inhomogeneity.