4D dose-position verification in radiation therapy using the RADPOS system in a deformable lung phantom

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• 4D radiotherapy requires precise monitoring of tumor motion during treatment.
• Current quality assurance methods for 4D radiotherapy may not fully capture dynamic treatment scenarios.

Purpose of the Study:

• To evaluate a novel 4D in vivo dosimetry system (RADPOS) as a quality assurance tool for 4D radiotherapy.
• To assess the accuracy of RADPOS in measuring position and dose within a deformable lung phantom.

Main Methods:

• RADPOS detectors (MOSFET dosimeter + electromagnetic positioning probe) were placed in a deformable lung phantom.
• Positional accuracy was assessed by comparing RADPOS readings to CT data.
• Dose measurements were performed during simulated free-breathing and adaptive radiotherapy delivery scenarios.

Main Results:

• RADPOS demonstrated positional accuracy better than 2.5 mm, with radial displacement agreement within 0.7 mm between CT and linac rooms.
• Dose measurements during free-breathing delivery agreed within 4-5% of treatment planning doses.
• Adaptive radiotherapy delivery showed RADPOS dose values within 1.5% of treatment plan values.

Conclusions:

• The deformable lung phantom-RADPOS system is an efficient quality assurance tool for 4D radiotherapy.
• The system's accuracy in position and dose measurement supports its use in advanced radiotherapy techniques.