SU-E-T-97: Intra and Inter Variability in Beam Data Commissioning among Water Phantom Scanning Systems

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• Accurate commissioning data is crucial for radiotherapy treatment planning.
• Various water-phantom scanning systems exist, but their data variability is not well-documented.

Purpose of the Study:

• To assess the intra- and inter-variability of commissioning data collected by modern water-phantom scanning systems.
• To evaluate the reliability and consistency of data from different vendors.

Main Methods:

• Four vendors' water-phantom scanning systems (PTW, Sun Nuclear, Standard Imaging, IBA) were used.
• Percent depth dose (PDD) and profile data were collected for photon and electron beams.
• Intra-variability was assessed through repeated measurements; inter-variability was assessed using single setups from each vendor.

Main Results:

• Intra-variability was consistently low (±0.1%) across all vendors.
• Inter-variability for PDDs was slightly higher but within acceptable ranges (e.g., 0.02±0.17% for SI vs PTW).
• Profile inter-variability was <0.1% in central regions but up to ±4.8% in penumbra; polarity effects up to 3% were observed.

Conclusions:

• Modern water-phantom scanning systems demonstrate minimal variability, achieving data accuracy within ±0.2% when used correctly.
• System selection should prioritize user comfort with software and hardware.
• This study offers a valuable comparison of data across different scanning systems.