[Impact of optimization algorithms on the intensity map in IMRT treatment planning.]

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Biology

Background:

• Intensity-modulated radiation therapy (IMRT) planning relies on optimization algorithms to generate optimal intensity maps.
• Understanding the impact of different optimization algorithms on these maps is essential for accurate treatment planning.

Purpose of the Study:

• To evaluate the impact of two distinct optimization algorithms, steepest descent (SD) and simulated annealing (SA), on intensity maps in IMRT planning.
• To compare the dosimetric outcomes and intensity map characteristics generated by SD and SA under various conditions.

Main Methods:

• Five treatment planning patterns were compared: SD and SA with fixed calculation time (5 min) and with terminal criteria-based optimization.
• A smoothing filter was also applied to SA with terminal criteria.
• Dosimetric parameters (D(95%) for PTV, V(70Gy) for rectum and bladder walls) and intensity map profiles were analyzed.

Main Results:

• Dosimetric differences across all patterns were negligible (e.g., D(95%) up to 0.5%, V(70Gy) up to 3.2%).
• Intensity maps generated by SA exhibited significant fluctuations and numerical artifacts compared to SD, with profile differences exceeding 7%.
• A smoothing filter effectively reduced fluctuations in SA-generated intensity maps.

Conclusions:

• Optimization algorithms significantly influence IMRT intensity map generation, even with minimal dosimetric impact.
• SA algorithms can introduce undesirable fluctuations in intensity maps, necessitating careful consideration or post-processing.
• Understanding algorithm-specific characteristics is vital for robust IMRT treatment planning and ensuring treatment efficacy.