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TLD postal dose intercomparison for megavoltage units in Poland
J Izewska1, R Gajewski, B Gwiazdowska
1Medical Physics Department, Cancer Centre, Warsaw, Poland.
Summary
This pilot study enhanced absorbed dose measurement consistency in Polish radiotherapy centers. Thermoluminescence dosimetry (TLD) identified and corrected dosimetry errors, improving accuracy for Co-60, X-ray, and electron beams.
Area of Science:
- Medical Physics
- Radiotherapy Dosimetry
- Radiation Measurement
Background:
- Inconsistent absorbed dose measurements in radiotherapy can impact treatment efficacy and patient safety.
- Standardization of dosimetry is crucial for reliable radiotherapy outcomes across regional centers.
Purpose of the Study:
- To investigate and reduce uncertainties in absorbed dose measurements.
- To improve the consistency of dose determination in Polish radiotherapy centers.
- To evaluate and minimize measurement uncertainty using thermoluminescence dosimetry (TLD).
Main Methods:
- An intercomparison of absorbed dose measurements under reference conditions for Co-60, high-energy X-rays, and electron beams.
- Utilized LiF powder (MT-N) for irradiations, read with a Harshaw TLD reader (model 2000B/2000C).
- Analyzed factors influencing accuracy and evaluated measurement uncertainty, including TLD system setup and fading.
Main Results:
- Fading of TLDs did not exceed 2% over 12 weeks.
- Relative energy correction factors were within 3% for X-rays (4-15 MV) and 4% for electrons (6-20 MeV).
- Two Co-60, three high-energy X-ray beams, and zero electron beams exceeded acceptable dose deviation levels (+/- 3.5% for photons, +/- 5% for electrons).
Conclusions:
- The pilot study successfully improved the accuracy and consistency of dosimetry in Poland.
- Identified and corrected sources of error, although two deviations remained unexplained.
- Established a foundation for enhanced quality assurance in radiotherapy dosimetry.