Intra- and intervariability in beam data commissioning among water phantom scanning systems.

Area of Science:

• Medical Physics
• Radiotherapy Physics
• Radiation Oncology

Background:

• Accurate beam data acquisition is critical for radiotherapy treatment planning and dose calculation.
• Commercial scanning systems are available, but comparative studies are lacking due to cost and accessibility.

Purpose of the Study:

• To evaluate the intra- and intervariability of beam profiles measured by four commercial scanning systems.
• To assess the accuracy of these systems for radiotherapy beam data collection.

Main Methods:

• Four commercial beam scanning water phantom systems from different vendors were used.
• Systems were set up per vendor recommendations and used to measure beam parameters, including percent depth dose (PDD).
• Intra- and intervariability were assessed, with one system chosen as a reference for comparison.

Main Results:

• Intervariability in PDD was very small (SD < 0.12%) deeper than 1.5 cm, with systems showing nearly identical profiles.
• Differences within the 80% radiation field were within ±0.35% (average) and ±0.80% (maximum) compared to the reference system.
• Penumbrae region agreement (DTA) was less than 1 mm for dose differences exceeding ±1%.
• Intravariability in repeated PDD measurements was small (SD < 0.5%), except in the buildup region.

Conclusions:

• All four water phantom scanning systems demonstrated adequate accuracy for beam data collection, meeting typical clinical requirements (1% dose difference or 1 mm DTA).
• The selection of a scanning system should be based on factors such as user comfort, software/hardware preference, and financial considerations rather than minor performance differences.