Validation of histogram-based virtual source models for different IGRT kV-imaging systems.

Area of Science:

• Medical Physics
• Radiotherapy
• Radiation Dosimetry

Background:

• Image-guided radiotherapy (IGRT) enhances tumor control but may increase late side effects due to additional imaging doses.
• Accurate quantification of these imaging doses is crucial for integration into therapeutic workflows.
• Current software limitations hinder patient-specific dose computation across diverse imaging systems.

Purpose of the Study:

• To develop a common methodology for modeling four different kV-imaging systems used in radiotherapy.
• To utilize a novel virtual source model (VSM) based on Monte Carlo calculations for dose estimation.
• To enable precise, patient-specific 3D dose mapping for various kV-imaging procedures.

Main Methods:

• Constructed simplified virtual source models (VSMs) summarizing phase-space files from initial Monte Carlo simulations.
• Employed VSMs as photon generators for secondary Monte Carlo simulations to compute dose distributions.
• Validated VSMs against standard Monte Carlo simulations and experimental measurements in homogeneous phantoms.

Main Results:

• VSMs achieved dose calculation agreement within 1% compared to phase-space files within the imaging field-of-view.
• A reduction in calculation time by at least a factor of 2.8 was observed using VSMs.
• VSM-based calculations showed significantly lower statistical uncertainties for equivalent simulation times.

Conclusions:

• Validated VSMs are ready for preclinical studies in heterogeneous or anthropomorphic phantoms.
• The developed cross-system modeling methodology facilitates accurate patient-specific dose mapping in IGRT.
• This approach supports improved integration of imaging doses into radiotherapy planning.