title: Influence of the correlation modeling period on the prediction accuracy of infrared marker-based dynamic tumor tracking using a gimbaled X-ray head.
abstract: OBJECTIVE
  To assess the utility of 10 s and 20 s modeling periods, rather than the 40 s currently used, in the clinical construction of practical correlation models (CMs) in dynamic tumor tracking irradiation using the Vero4DRT.
  
  
  METHODS
  The CMs with five independent parameters (CM parameters) were analyzed retrospectively for 10 consecutive lung cancer patients. CM remodeling was performed two or three times per treatment session. Three different CMs trained over modeling periods of 10, 20, and 40 s were built from a single, original CM log file. The predicted target positions were calculated from the CM parameters and the vertical displacement of infrared markers on the abdomen (PIR) during the modeling. We assessed how the CM parameters obtained over modeling periods of T s (T = 10, 20, and 40 s) were robust to changes in respiratory patterns after several minutes. The mimic-predicted target positions after several minutes were computed based on the previous CM parameters and PIR during the next modeling. The 95th percentiles of the differences between mimic-predicted and detected target positions over 40 s (E95robust,T: T = 10, 20, and 40 s) were then calculated.
  
  
  RESULTS
  Strong correlations greater than 0.92 were observed between the E95robust,20 and E95robust,40 values. Meanwhile, irregular respiratory patterns with inconsistent amplitudes of motion created differences between the E95robust,10 and E95robust,40 values of ≥10 mm.
  
  
  CONCLUSIONS
  The accuracies of CMs derived using 20 s were almost identical to those obtained over 40 s, and superior to those obtained over 10 s.
authors: Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Japan. Electronic address: m_nkmr@kuhp.kyoto-u.ac.jp.
authors: Mitsuhiro
authors: M
authors: Nakamura
authors: Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors: Mami
authors: M
authors: Akimoto
authors: Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors: Nobutaka
authors: N
authors: Mukumoto
authors: Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors: Masahiro
authors: M
authors: Yamada
authors: Division of Radiation Oncology, Institute of Biomedical Research and Innovation, Japan.
authors: Hiroaki
authors: H
authors: Tanabe
authors: Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors: Nami
authors: N
authors: Ueki
authors: Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors: Yukinori
authors: Y
authors: Matsuo
authors: Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors: Takashi
authors: T
authors: Mizowaki
authors: Department of Radiation Oncology, Kobe City Medical Center General Hospital, Japan.
authors: Masaki
authors: M
authors: Kokubo
authors: Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Japan.
authors: Masahiro
authors: M
authors: Hiraoka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D057918:Fiducial Markers; D006801:Humans; D007259:Infrared Rays; D008175:Lung Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011881:Radiotherapy, Computer-Assisted / Q000592:standards*; D012119:Respiration; D013997:Time Factors; D014965:X-Rays
keywords: IR tracking; Modeling period; Prediction accuracy; Vero4DRT