Beam rate influence on dose distribution and fluence map in IMRT dynamic technique

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Radiotherapy accelerators use variable beam rates to shorten treatment times and minimize patient motion.
• This optimization is crucial for advanced techniques like intensity-modulated radiation therapy (IMRT).

Purpose of the Study:

• To investigate the effect of different beam rates on dose distribution in IMRT plans.
• To assess the agreement between calculated and measured dose distributions across various beam rates.

Main Methods:

• IMRT plans were analyzed at two beam rates: 100 MU/min and 600 MU/min.
• Comparisons included Radiation Planning Index (RPI), monitor units (MU), and fluence map accuracy.
• Measured dose distributions were evaluated against calculated ones using the Gamma index.

Main Results:

• Lower beam rates (100 MU/min) yielded slightly improved target coverage and organ-at-risk protection.
• Plans at 100 MU/min required fewer MUs and showed greater similarity between optimal and actual fluence maps.
• Measured dose distributions more closely matched calculated ones at lower beam rates, though differences were minor.

Conclusions:

• Beam rate influences dynamic IMRT execution but results in minor differences in dose distribution.
• A slight superiority of lower beam rates was observed, without significant impact on overall treatment accuracy.