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Deterministic proton dose calculation from first principles.

¹Harvard University Laboratory for Particle Physics and Cosmology, 18 Hammond St., Cambridge, MA 02138, United States of America.

Physics in Medicine and Biology

|June 15, 2018

Summary

A new deterministic pencil beam algorithm accurately calculates proton beam dose in heterogeneous terrain, improving upon existing methods by incorporating realistic collimator effects and reducing the need for beam line measurements.

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Area of Science:

Medical Physics
Radiation Oncology
Computational Physics

Background:

Proton therapy requires accurate dose calculation in heterogeneous media.
Existing pencil beam algorithms often rely on water-equivalent assumptions and external measurements.
There is a need for first-principles dose calculation methods that account for material heterogeneities and beamline physics.

Purpose of the Study:

To develop a deterministic pencil beam algorithm for accurate dose computation in proton therapy.
To implement a method that handles transverse heterogeneities through dynamic splitting of pencil beams.
To validate the algorithm against experimental data and compare it with existing methods.

Main Methods:

Discretization of terrain into slabs perpendicular to the beam direction.
Transport of pencil beams (PBs) using generalized Fermi-Eyges theory with specific material properties.
Dynamic splitting of PBs to resolve transverse heterogeneities.
Accumulation of dose contributions at specified measuring planes.

Main Results:

The algorithm accurately computes dose in the high-dose region, showing good agreement with experimental data.
It effectively models collimator scatter and thickness effects, which are often ignored by conventional algorithms.
The method demonstrates good agreement with experimental data in studies of collimator scatter under varying conditions.

Conclusions:

The developed deterministic pencil beam algorithm provides accurate dose calculations for proton therapy in heterogeneous environments.
It eliminates the need for empirical beamline commissioning measurements, simplifying the process.
The algorithm is suitable for both passive beam spreading and pencil beam scanning, with potential for faster computation in PBS.