Comparison of dose distributions in IMRT planning using the gamma function.

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Intensity-modulated radiotherapy (IMRT) requires precise verification of planned dose distributions against measured data.
• Existing methods for dose comparison, like point-to-point dose difference or distance to agreement, have limitations.

Purpose of the Study:

• To develop and evaluate a software tool, Dose Distribution Evaluator (DDE), for verifying IMRT dose distributions.
• To implement a comprehensive verification method based on the gamma index, incorporating both dose difference and distance to agreement.

Main Methods:

• The study implemented a software tool (DDE) based on Low's gamma index method.
• DDE evaluates the agreement between measured and calculated dose distribution matrices.
• Verification was performed using film and MapCheck for measurements against CadPlan calculations in simple geometry and clinical cases (head-neck, prostate).

Main Results:

• The DDE software demonstrated very good agreement between measured and calculated dose distributions.
• Film dosimetry, due to its higher resolution, provided more accurate results than MapCheck.
• Comparable accuracy to film can be achieved with MapCheck using appropriate measurement techniques.

Conclusions:

• The DDE software is an effective tool for real-time verification of IMRT treatment plans.
• The gamma index method, as implemented in DDE, provides valuable information for treatment plan decision-making.
• Accurate dose verification is crucial for ensuring the efficacy and safety of IMRT.