IMRT national audit in Portugal

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• The International Atomic Energy Agency (IAEA) developed an end-to-end audit for Intensity-Modulated Radiation Therapy (IMRT) verification.
• This audit assesses the physical aspects of IMRT dose delivery for Head and Neck (H&N) cancer treatments.

Purpose of the Study:

• To present the national results of the IAEA's IMRT audit conducted in Portugal in 2018.
• To evaluate the physical accuracy of IMRT dose delivery for H&N cancer patients in Portugal.

Main Methods:

• Twenty-four institutions performing IMRT in Portugal voluntarily participated.
• A Shoulder, Head and Neck End-to-End phantom (SHANE) was used to simulate H&N IMRT treatments.
• Ionization chambers and EBT3 films measured doses at reference points, compared against calculated doses using FilmQA Pro software.

Main Results:

• Ionization chamber measurements showed percent differences within ±5% for planning target volumes (PTVs) and ±7% for the spinal cord.
• Film analysis yielded an average gamma passing rate of 96.9% ± 2.9% (3%/3 mm criterion), exceeding the 90% acceptance limit.

Conclusions:

• The audit confirmed compliance between planned and delivered IMRT doses for H&N cancers in Portugal.
• Recommendations for quality improvement were made based on identified factors contributing to dose delivery uncertainties in some institutions.