title: Real patient data based cross verification of kilovoltage and megavoltage CT calibration for proton therapy.
abstract: OBJECTIVE
  We propose a methodology to evaluate the stoichiometric calibration method on MVCT against the corresponding kVCT calibration using patient data.
  
  
  METHODS
  Stoichiometric calibrations were conducted for a MVCT and a kVCT scanner, respectively. We retrospectively analyzed kVCT and MVCT images of 21 patients by picking small tissue volumes in kVCT images and performing image registration to locate the tissue volumes in corresponding MVCT images. We computed the difference between the mean proton stopping power derived through kVCT and MVCT calibration, taking into account the uncertainties in calibration, imaging, and image registration.
  
  
  RESULTS
  kVCT and MVCT calibration curves were in good agreement for soft tissues such as muscle and brain, but showed statistically significant difference (p < 0.05) in stopping power of adipose (2.4 ± 1.7%) and bony structures such as spongiosa, and cranium (-3.2 ± 1.4 and -3.1 ± 2.1%, respectively).
  
  
  CONCLUSIONS
  The MVCT calibration might not agree with the corresponding kVCT calibration for some tissues.
authors.affiliation: Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA.
authors.forename: Shie
authors.initials: S
authors.lastname: Nishioka
authors.affiliation: Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA.
authors.forename: Joo Han
authors.initials: JH
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Zou
authors.affiliation: Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA.
authors.forename: Miao
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA.
authors.forename: Ning J
authors.initials: NJ
authors.lastname: Yue
authors.affiliation: Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA. Electronic address: chent4@cinj.rutgers.edu.
authors.forename: Ting
authors.initials: T
authors.lastname: Chen
mesh_terms: D002138:Calibration; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D061766:Proton Therapy / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D035501:Uncertainty
keywords: CT calibration; Image registration; Megavoltage CT; Proton therapy