title: Accuracy of applicator tip reconstruction in MRI-guided interstitial 192Ir-high-dose-rate brachytherapy of liver tumors.
abstract: OBJECTIVE
  To evaluate the reconstruction accuracy of brachytherapy (BT) applicators tips in vitro and in vivo in MRI-guided (192)Ir-high-dose-rate (HDR)-BT of inoperable liver tumors.
  
  
  METHODS
  Reconstruction accuracy of plastic BT applicators, visualized by nitinol inserts, was assessed in MRI phantom measurements and in MRI (192)Ir-HDR-BT treatment planning datasets of 45 patients employing CT co-registration and vector decomposition. Conspicuity, short-term dislocation, and reconstruction errors were assessed in the clinical data. The clinical effect of applicator reconstruction accuracy was determined in follow-up MRI data.
  
  
  RESULTS
  Applicator reconstruction accuracy was 1.6±0.5 mm in the phantom measurements. In the clinical MRI datasets applicator conspicuity was rated good/optimal in ⩾72% of cases. 16/129 applicators showed not time dependent deviation in between MRI/CT acquisition (p>0.1). Reconstruction accuracy was 5.5±2.8 mm, and the average image co-registration error was 3.1±0.9 mm. Vector decomposition revealed no preferred direction of reconstruction errors. In the follow-up data deviation of planned dose distribution and irradiation effect was 6.9±3.3 mm matching the mean co-registration error (6.5±2.5 mm; p>0.1).
  
  
  CONCLUSIONS
  Applicator reconstruction accuracy in vitro conforms to AAPM TG 56 standard. Nitinol-inserts are feasible for applicator visualization and yield good conspicuity in MRI treatment planning data. No preferred direction of reconstruction errors were found in vivo.
authors.affiliation: Department of Radiology, Otto von Guericke University, Medical School, Magdeburg, Germany. Electronic address: christian.wybranski@med.ovgu.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Wybranski
authors.affiliation: Department of Radiology, Otto von Guericke University, Medical School, Magdeburg, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Eberhardt
authors.affiliation: Department of Radiology, Otto von Guericke University, Medical School, Magdeburg, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Fischbach
authors.affiliation: Department of Radiology, Otto von Guericke University, Medical School, Magdeburg, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Fischbach
authors.affiliation: Department of Radiotherapy, Otto von Guericke University, Medical School, Magdeburg, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Walke
authors.affiliation: Department of Radiotherapy, Otto von Guericke University, Medical School, Magdeburg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Hass
authors.affiliation: Institute of Biometry and Medical Informatics, Otto von Guericke University, Medical School, Magdeburg, Germany.
authors.forename: Friedrich-Wilhelm
authors.initials: FW
authors.lastname: Röhl
authors.affiliation: Department of Radiology, Otto von Guericke University, Medical School, Magdeburg, Germany.
authors.forename: Ortrud
authors.initials: O
authors.lastname: Kosiek
authors.affiliation: Department of Medical Engineering, Otto von Guericke University, Magdeburg, Germany.
authors.forename: Mandy
authors.initials: M
authors.lastname: Kaiser
authors.affiliation: Department of Radiology, Otto von Guericke University, Medical School, Magdeburg, Germany.
authors.forename: Maciej
authors.initials: M
authors.lastname: Pech
authors.affiliation: Department of Radiotherapy, Essen University Hospital, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Lüdemann
authors.affiliation: Department of Radiology, Otto von Guericke University, Medical School, Magdeburg, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Ricke
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use; D008113:Liver Neoplasms / Q000532:radiotherapy*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods
chemical_list: D007496:Iridium Radioisotopes
keywords: Applicator reconstruction accuracy; Image registration; Interstitial (192)Ir-high-dose-rate brachytherapy; Liver tumors; MRI-based treatment planning; MRI-guided intervention