title: Improvement of registration accuracy in accelerated partial breast irradiation using the point-based rigid-body registration algorithm for patients with implanted fiducial markers.
abstract: OBJECTIVE
  To investigate image-registration errors when using fiducial markers with a manual method and the point-based rigid-body registration (PRBR) algorithm in accelerated partial breast irradiation (APBI) patients, with accompanying fiducial deviations.
  
  
  METHODS
  Twenty-two consecutive patients were enrolled in a prospective trial examining 10-fraction APBI. Titanium clips were implanted intraoperatively around the seroma in all patients. For image-registration, the positions of the clips in daily kV x-ray images were matched to those in the planning digitally reconstructed radiographs. Fiducial and gravity registration errors (FREs and GREs, respectively), representing resulting misalignments of the edge and center of the target, respectively, were compared between the manual and algorithm-based methods.
  
  
  RESULTS
  In total, 218 fractions were evaluated. Although the mean FRE/GRE values for the manual and algorithm-based methods were within 3 mm (2.3/1.7 and 1.3/0.4 mm, respectively), the percentages of fractions where FRE/GRE exceeded 3 mm using the manual and algorithm-based methods were 18.8%/7.3% and 0%/0%, respectively. Manual registration resulted in 18.6% of patients with fractions of FRE/GRE exceeding 5 mm. The patients with larger clip deviation had significantly more fractions showing large FRE/GRE using manual registration.
  
  
  CONCLUSIONS
  For image-registration using fiducial markers in APBI, the manual registration results in more fractions with considerable registration error due to loss of fiducial objectivity resulting from their deviation. The authors recommend the PRBR algorithm as a safe and effective strategy for accurate, image-guided registration and PTV margin reduction.
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Yoshimura
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Sato
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamada
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
authors.forename: Kimiko
authors.initials: K
authors.lastname: Hirata
authors.affiliation: Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto 606-8507, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Sasaki
authors.affiliation: Division of Clinical Radiology Service, Kyoto University Hospital, Kyoto 606-8507, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Fujimoto
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Ogura
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001940:Breast / Q000187:drug effects / Q000601:surgery; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000601:surgery; D003198:Computer Simulation; D005260:Female; D057918:Fiducial Markers; D006112:Gravitation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D008327:Mammography / Q000295:instrumentation / Q000379:methods*; D008875:Middle Aged; D008954:Models, Biological; D011446:Prospective Studies; D014025:Titanium; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*
chemical_list: D014025:Titanium