Automatic dose verification system for breast radiotherapy: Method validation, contour propagation and DVH parameters...

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Image-guided radiotherapy (IGRT) enables monitoring of anatomical changes during external beam radiotherapy (EBRT).
• Assessing the dosimetric impact of these anatomical changes is challenging due to the lack of contours and dose recalculations on cone-beam CT (CBCT) scans.
• Current IGRT strategies often do not provide dose-volume histograms (DVH) for real-time analysis.

Purpose of the Study:

• To investigate the feasibility of using automatically calculated DVH parameters on CBCT scans.
• To evaluate an independent dose calculation engine combined with propagated contours for DVH analysis.
• To assess the reliability of automated DVH recalculation in IGRT for breast cancer patients.

Main Methods:

• A prospective study involved 31 breast cancer patients with 70 CBCT scans.
• Manual and automatically propagated contours were generated for each CBCT.
• An automatic dose recalculation was performed, and DVH parameters (target dose, target volume coverage, mean heart dose) were compared against the treatment planning system (TPS).

Main Results:

• Differences in DVH parameters between the TPS and the automated system with propagated contours were minimal.
• Mean target dose differences ranged from -1.3% to 0.7%.
• Mean heart dose (MHD) differences were -0.3 to 0.2 Gy, and target volume coverage differences were -3.9% to 2.9%.

Conclusions:

• An independent, fully automated dose verification system with contour propagation is feasible and reliable for recalculating CBCT-based DVHs during breast EBRT.
• This automated approach can help assess the dosimetric impact of anatomical changes.
• Volume coverage parameters, specifically V95%, were found to be sensitive to contouring variations.