Statistical process control analysis for patient quality assurance of intensity modulated radiation therapy

This study applied statistical process control to set and verify the quality assurances (QA) tolerance standard for our hospital's characteristics with the criteria standards that are applied to all the treatment sites with this analysis. Gamma test factor of delivery quality assurances (DQA) was based on 3%/3 mm. Head and neck, breast, prostate cases of intensity modulated radiation therapy (IMRT) or volumetric arc radiation therapy (VMAT) were selected for the analysis of the QA treatment sites. The numbers of data used in the analysis were 73 and 68 for head and neck patients. Prostate and breast were 49 and 152 by MapCHECK and ArcCHECK respectively. C_p value of head and neck and prostate QA were above 1.0, C_pml is 1.53 and 1.71 respectively, which is close to the target value of 100%. C_pml value of breast (IMRT) was 1.67, data values are close to the target value of 95%. But value of was 0.90, which means that the data values are widely distributed. C_p and C_pml of breast VMAT QA were respectively 1.07 and 2.10. This suggests that the VMAT QA has better process capability than the IMRT QA. Consequently, we should pay more attention to planning and QA before treatment for breast Radiotherapy.