Interfractional trend analysis of dose differences based on 2D transit portal dosimetry

Area of Science:

• Medical Physics
• Radiotherapy
• Dosimetry

Background:

• Radiotherapy dose delivery is susceptible to various influencing factors.
• Electronic portal imaging devices (EPIDs) are valuable for transit portal dosimetry verification.
• Patient-related dose differences in radiotherapy can be systematic or random.

Purpose of the Study:

• To investigate the appearance of systematic and random information in 2D transit dose distributions measured by EPID.
• To develop a methodology for examining interfractional trends to support adaptive radiotherapy.

Main Methods:

• Utilized EPID for 2D transit dose measurements throughout the treatment course.
• Employed gamma (γ) evaluation to compare predicted and measured portal doses for trend analysis.
• Extracted metrics from γ images to differentiate systematic from random dose delivery errors.

Main Results:

• Demonstrated trend analysis of interfractional dose changes using EPID transit dosimetry.
• Successfully identified causes of dose delivery differences in example cases (prostate, lung, breast cancer).
• Detected changes such as diminishing atelectasis and set-up variations influencing 2D transit dose.

Conclusions:

• Presented a method based on 2D portal transit dosimetry for recording and analyzing dose changes during radiotherapy.
• Showcased the method's ability to identify dose delivery discrepancies and inform treatment adaptation.
• Highlighted the contribution to informed decision-making for adaptive radiotherapy.