Target-tracking deliveries on an Elekta linac: a feasibility study

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Accurate radiation delivery is challenged by internal organ motion during treatment.
• Intensity-modulated radiation therapy (IMRT) requires precise beam shaping, complicated by target movement.
• Elekta MLCi systems offer advanced beam modulation capabilities.

Purpose of the Study:

• To evaluate the efficacy of target-tracking IMRT delivery using an Elekta MLCi system.
• To quantify dose blurring and organ-at-risk (OAR) dose in static vs. dynamic phantom scenarios.
• To assess the system's capability for precise radiation delivery during simulated target motion.

Main Methods:

• A solid-water phantom with a toroidal target and central OAR was used.
• Simulated 2D elliptical target motion (10s period) was programmed.
• Film dosimetry assessed dose distribution for static treatment (static/moving phantom) and target-tracking treatment (moving phantom).

Main Results:

• Target dose standard deviation was 2.8% (static/static), 7.2% (static/moving), and 2.6% (tracking/moving).
• Mean OAR dose was 38.2% (static/static), 54.0% (static/moving), and 38.2% (tracking/moving) of prescription dose.
• Target-tracking delivery significantly reduced dose blurring compared to static delivery on a moving phantom.

Conclusions:

• The Elekta linac with MLCi is capable of delivering precise target-tracking IMRT fields.
• Target-tracking significantly improves dose accuracy and OAR sparing in the presence of target motion.
• This technology holds promise for improving radiotherapy outcomes in patients with moving tumors.