Dosimetric intercomparison at the Scandinavian radiation therapy centres. I. Absorbed dose intercomparison

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Dosimetry

Background:

• Accurate absorbed dose determination is critical for effective radiation therapy.
• Dosimetric intercomparisons are essential for quality assurance in radiotherapy centers.
• Variations in dosimetry protocols can impact treatment accuracy.

Purpose of the Study:

• To conduct a dosimetric intercomparison across radiotherapy centers in Denmark, Norway, and Sweden.
• To evaluate the accuracy of absorbed dose measurements for various beam qualities used in clinical practice.
• To identify any systematic differences or deviations in dosimetry practices.

Main Methods:

• A comprehensive dosimetric intercomparison was performed at all participating centers.
• Measurements covered all beam qualities utilized in radiation therapy, excluding conventional roentgen rays.
• The ratio of measured absorbed dose to the stated dose was calculated for each center and beam quality.

Main Results:

• Mean ratios for 60Co gamma beams were 1.001 ± 0.014.
• Mean ratios for roentgen ray beams (4-45 MV) were 1.017 ± 0.023.
• Mean ratios for electron beams were 0.989 ± 0.027 (E0 < 10 MeV) and 0.996 ± 0.034 (E0 ≥ 10 MeV).
• The overall difference between the highest and lowest measured ratios was 17.8%.
• A systematic difference was identified related to the use of different protocols (NACP 1972 and 1980).

Conclusions:

• The dosimetric intercomparison demonstrated generally good agreement in absorbed dose measurements across Nordic centers.
• Observed variations highlight the importance of consistent protocol application and ongoing quality assurance.
• Differences in dosimetry protocols (NACP 1972 vs. 1980) contributed to systematic deviations.