title: Patient-specific QA and delivery verification of scanned ion beam at NIRS-HIMAC.
abstract: OBJECTIVE
  To evaluate a patient-specific QA program and system for constancy checking of a scanning delivery system developed at the National Institute of Radiological Sciences.
  
  
  METHODS
  For the patient-specific QA, all the planned beams are recalculated on a water phantom with treatment planning software (TPS). The recalculated dose distributions are compared with the measured distributions using a 2D ionization chamber array at several depths, and evaluated using gamma index analysis with criteria of 3% and 3 mm and a pass rate of 90%. For the constancy check, the authors developed the multiwire proportional chamber (MWPC), which can record the delivered 2D fluence images in a slice-by-slice manner. During irradiation for dosimetric QA with the 2D ionization chamber array and an accordion-type water phantom, the 2D fluence images are recorded using the MWPC in the delivery system. These recorded images are then compared to those taken in the treatment session to check the constancy check. This analysis also employs gamma index analysis using the same criteria as in the patient-specific QA. These patient-specific QA and constancy check evaluations were performed using the data of 122 patients.
  
  
  RESULTS
  In the patient-specific QA, the measured dose distributions agreed well with those calculated by the TPS, and the QA criteria were satisfied in all measurements. The additional check of the fluence comparison ensured the constancy of the delivered field during each treatment irradiation.
  
  
  CONCLUSIONS
  The authors established a patient-specific QA program and additional check of delivery constancy in every treatment session. Fluence comparison is a strong tool for constancy checking of the delivery system.
authors: Medical Physics Research Group, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors: Takuji
authors: T
authors: Furukawa
authors: Taku
authors: T
authors: Inaniwa
authors: Yousuke
authors: Y
authors: Hara
authors: Kota
authors: K
authors: Mizushima
authors: Toshiyuki
authors: T
authors: Shirai
authors: Koji
authors: K
authors: Noda
mesh_terms: D063193:Heavy Ion Radiotherapy / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy; D010315:Particle Accelerators; D057285:Precision Medicine / Q000295:instrumentation / Q000379:methods*; D011785:Quality Assurance, Health Care / Q000379:methods*