Tolerance design of patient-specific range QA using the DMAIC framework in proton therapy

Area of Science:

• Medical Physics
• Quality Assurance
• Process Improvement

Background:

• Patient-specific quality assurance (QA) is critical in radiation therapy.
• Current QA protocols may lack site-specific optimization, potentially leading to inefficiencies.
• The Define-Measure-Analyze-Improve-Control (DMAIC) methodology offers a structured approach to process enhancement.

Purpose of the Study:

• To implement the DMAIC framework for customizing patient-specific QA.
• To design site-specific range tolerances for improved quality and efficiency.
• To evaluate the impact of customized tolerances on QA time and cost.

Main Methods:

• Utilized the DMAIC framework, including process flow diagrams, cause-and-effect analysis, Pareto charts, control charts, and capability analysis.
• Analyzed 1437 patient-specific QA plans across seven treatment site groups.
• Employed the process capability index (Cpm) to guide the design of site-specific range tolerances.

Main Results:

• Prostate treatment fields demonstrated capability at the existing ±1 mm tolerance.
• Other sites showed overdesigned or insufficient tolerances based on patient-specific QA data.
• Customized tolerances were calculated, leading to a simulated 20% reduction in total QA time.
• QA failures in proton therapy can increase total costs by up to 30%.

Conclusions:

• The DMAIC framework effectively enhances QA through customized tolerances.
• Customized tolerance design balances quality with time and cost efficiency.
• Site-specific tolerance optimization is crucial for efficient patient-specific QA in proton therapy.