Chest wall irradiation with MLC-shaped photon and electron fields.

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Technology

Background:

• Chest wall irradiation is crucial for treating specific cancers.
• Accurate dose delivery in the match-line region is critical for treatment efficacy and minimizing side effects.
• Current techniques may have limitations in dose homogeneity and reproducibility.

Purpose of the Study:

• To develop and evaluate an improved chest wall irradiation technique using the multileaf collimator (MLC) of the MM50 Racetrack Microtron.
• To optimize beam shaping for both photon and electron beams.
• To assess dose delivery in the match-line region compared to the routine technique.

Main Methods:

• Utilized diode and film phantom measurements to determine optimal photon beam segments and positions.
• Investigated dose homogeneity in the match-line region using phantom and in vivo dosimetry during patient treatment.
• Compared an improved technique (3 photon segments) with a routine technique (2 photon segments).

Main Results:

• The improved technique achieved dose values of 88-109% in the match-line region, compared to 80-115% for the routine technique.
• During patient treatment, average doses were 95-115% with the improved technique versus 78-127% with the routine technique.
• Interfraction dose variation decreased from 11.0% to 4.6% (1 SD), and treatment time was reduced from 10 to 4.5 minutes.

Conclusions:

• The developed technique using the MM50's MLC for shaping photon and electron beams improves chest wall irradiation.
• This method is less labor-intensive, faster, and provides more homogeneous and reproducible dose delivery.
• The findings suggest a superior approach for chest wall radiotherapy planning and delivery.