title: Feasibility study of using statistical process control to customized quality assurance in proton therapy.
abstract: OBJECTIVE
  To evaluate and improve the reliability of proton quality assurance (QA) processes and, to provide an optimal customized tolerance level using the statistical process control (SPC) methodology.
  
  
  METHODS
  The authors investigated the consistency check of dose per monitor unit (D/MU) and range in proton beams to see whether it was within the tolerance level of the daily QA process. This study analyzed the difference between the measured and calculated ranges along the central axis to improve the patient-specific QA process in proton beams by using process capability indices.
  
  
  RESULTS
  The authors established a customized tolerance level of ±2% for D/MU and ±0.5 mm for beam range in the daily proton QA process. In the authors' analysis of the process capability indices, the patient-specific range measurements were capable of a specification limit of ±2% in clinical plans.
  
  
  CONCLUSIONS
  SPC methodology is a useful tool for customizing the optimal QA tolerance levels and improving the quality of proton machine maintenance, treatment delivery, and ultimately patient safety.
authors.affiliation: Department of Radiation Oncology, Myongji Hospital, Goyang 412-270, South Korea.
authors.forename: Jeong-Eun
authors.initials: JE
authors.lastname: Rah
authors.affiliation: Proton Therapy Center, National Cancer Center, Goyang 410-769, South Korea.
authors.forename: Dongho
authors.initials: D
authors.lastname: Shin
authors.affiliation: Department of Radiation Oncology, Myongji Hospital, Goyang 412-270, South Korea.
authors.forename: Do Hoon
authors.initials: DH
authors.lastname: Oh
authors.affiliation: Proton Therapy Center, National Cancer Center, Goyang 410-769, South Korea.
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Kim
authors.affiliation: Department of Radiation Medicine and Applied Sciences, University of California, San Diego, California 92093.
authors.forename: Gwe-Ya
authors.initials: GY
authors.lastname: Kim
mesh_terms: D000465:Algorithms; D005240:Feasibility Studies; D006801:Humans; D061766:Proton Therapy / Q000295:instrumentation / Q000379:methods*; D011785:Quality Assurance, Health Care / Q000379:methods*; D011874:Radiometry / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results; D013223:Statistics as Topic