Verification of IMRT dose distributions using a water beam imaging system

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image Processing

Background:

• Intensity-modulated radiotherapy (IMRT) requires precise dose verification.
• Existing methods for IMRT dose verification can be time-consuming.
• Dynamic multileaf collimators introduce complexities in dose distribution verification.

Purpose of the Study:

• To develop and validate a water beam imaging system (WBIS) for IMRT dose verification.
• To enable real-time comparison of measured and planned dose distributions.
• To address challenges posed by light scattering in scintillator-based imaging.

Main Methods:

• Developed a WBIS comprising a water container, scintillator, CCD camera, and PC.
• Calibrated the system using known radiation fields.
• Applied an iterative reconstruction algorithm to correct for image blurring caused by light scattering.
• Computed the blur function using a 10 cm x 10 cm X-ray beam and Monte Carlo simulations.

Main Results:

• The WBIS successfully captured scintillation images representing dose distributions.
• A method was developed to correct for image blurring using a multiple Gaussian fit for the blur function.
• Reconstructed dose distributions showed reasonable agreement with Monte Carlo simulations.
• The system facilitates real-time transverse plane dose verification.

Conclusions:

• The developed WBIS provides a viable method for IMRT dose verification.
• The image correction algorithm effectively mitigates blurring effects.
• This approach allows for efficient and accurate real-time dose distribution comparisons in IMRT.