Helical tomotherapy radiation leakage and shielding considerations

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Intensity-modulated radiation therapy (IMRT) requires longer beam-on times, increasing leakage radiation concerns.
• Tomotherapy, a form of IMRT, further intensifies these issues due to its slice-by-slice delivery method, necessitating enhanced shielding.

Purpose of the Study:

• To investigate the interplay between high modulation and enhanced shielding in tomotherapy systems.
• To quantify room leakage radiation levels during continuous gantry rotations.
• To assess primary radiation exposure and forward-directed patient leakage dose.

Main Methods:

• Measurements of room leakage radiation at 4 meters from the isocenter.
• Analysis of primary radiation exposure levels.
• Calculation of patient leakage dose for a typical treatment scenario.

Main Results:

• Room leakage radiation was measured to be less than 3 x 10(-4) relative to calibration output.
• Patient leakage dose to the periphery region was calculated to be only 1% for a 12-min treatment.
• A method for estimating worst-case patient leakage dose was developed.

Conclusions:

• Enhanced shielding in tomotherapy effectively mitigates room leakage radiation.
• Patient exposure to leakage radiation is minimal, with potential for further reduction through optimized treatment planning.
• The study provides a method for assessing patient leakage dose in tomotherapy treatments.