EPID-guided 3D dose verification of lung SBRT

Area of Science:

• Medical Physics
• Radiation Oncology
• Image Analysis

Background:

• Accurate dose verification is crucial in radiation therapy.
• Tumor motion during treatment can lead to dose inaccuracies.
• Electronic Portal Imaging Devices (EPIDs) capture images during treatment delivery.

Purpose of the Study:

• To assess the feasibility of using EPID tumor tracks to verify delivered radiation doses.
• To develop a method for calculating delivered dose based on tumor motion.
• To evaluate the accuracy of this method using phantom and patient data.

Main Methods:

• A novel method was developed to compute delivered radiation fluence using planned fluence and EPID-derived tumor motion tracks.
• A phantom study with a dynamic thorax phantom and MOSFET detectors was conducted for validation.
• The method was also applied to a lung cancer patient treated with stereotactic body radiotherapy.

Main Results:

• The delivered dose calculated using the proposed method showed good agreement with direct MOSFET measurements (0.8%-8.3% difference).
• Analysis of patient data confirmed good target volume coverage when comparing planned and delivered dose-volume histograms.
• The method successfully tracked tumor motion from EPID images for dose verification.

Conclusions:

• The delivered fluence method, utilizing EPID tumor tracks, is a feasible and accurate approach for verifying delivered radiation doses.
• This technique enables potential real-time treatment verification and adaptive correction strategies.
• Real-time dose verification can enhance treatment efficacy and ensure optimal target coverage in radiation oncology.