Quantitative quality control of 3D water tank using image analysis

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Control

Background:

• Accurate beam data acquisition is critical for radiation therapy commissioning and quality control (QC).
• Three-dimensional (3D) water tanks are essential tools for this process.
• Current QC methods require enhancement for precision and efficiency.

Purpose of the Study:

• To introduce and validate a novel quantitative QC method for 3D water tank systems.
• To evaluate motor drive speed stability and positional accuracy using MV images and webcam videos.
• To compare performance in continuous versus step-by-step measurement modes.

Main Methods:

• Utilized a TRUFIX mounting system for precise alignment of a steel ball with the water tank surface.
• Acquired MV images and compared them with digitally reconstructed radiographs (DRRs) to assess radiation isocenter deviations.
• Employed a webcam and custom tracking software to analyze motor drive speed and positional errors at various speed settings.

Main Results:

• The mean radiation isocenter error was found to be 0.37 ± 0.09 mm.
• Increased motor drive speed led to greater discrepancies between set and actual speeds.
• Continuous mode exhibited larger deviations compared to step-by-step mode.

Conclusions:

• The proposed method effectively quantifies radiation isocenter misalignment, tank setup deviations, and drive speed stability.
• Step-by-step mode offers superior accuracy at higher drive speeds.
• This technique enhances the quantitative QC of 3D water tank systems in radiation therapy.