Quality control study of cervical cancer interstitial brachytherapy treatment plans using statistical process control.

Abstract

Objective: This study explored using statistical process control for quality control of cervical cancer interstitial brachytherapy treatment plans.

Materials and methods: For retrospective analysis, interstitial brachytherapy treatment plans were divided into first (n = 300) and second phases (n = 200). The first phase was chronologically divided 2:1 into training and validation sets. The Dn2cm³ (D2cm³ divided by the high-risk clinical target volume D90) of the organs at risk (the bladder, rectum, and sigmoid colon) were analyzed to draw individual control charts. Process capability analysis charts were drawn, and the statistical process capability was evaluated using the process capability index C_pk. The centerline of the organ at risk dose in the first-phase plan's training set was used as the optimization parameter for the second-phase dataset plan.

Results: The Dn2cm³ centerlines for the bladder, rectum, and sigmoid colon were 0.6980, 0.5440, and 0.4910 in the training set and 0.6845, 0.4528, and 0.4144 in the second phase, respectively. The first-phase δ values were 0.0099, 0.0530, and 0.0268, respectively. The process capability analysis for the first and second phases showed that all indicators had a C_pk >1.

Conclusion: For all organs at risk, the Dn2cm³ centerlines were lower in the second phase than in the first phase, indicating that quality control of cervical cancer interstitial brachytherapy treatment plans continuously improved through statistical process control. This method is simple and practical and warrants promotion for application in radiotherapy treatment plan quality control.