title: Prostate cancer: contouring target and organs at risk by kilovoltage and megavoltage CT and MRI in patients with and without hip prostheses.
abstract: OBJECTIVE
  In radiotherapy treatment, planning target volume and organs at risk are contoured on kilovoltage CT (kVCT) images. Unlike MR images, kVCT does not provide precise information on target volume extension. Since neither kVCT nor MRI may be suitable for contouring in patients with ferrous hip prostheses, this study evaluated whether megavoltage CT (MVCT) reduced interobserver variability.
  
  
  METHODS
  Two patients without hip prostheses and one patient (Patient 3) with hip prostheses were enrolled. Six radiation oncologists contoured prostate, rectum and bladder on kVCT (Patients 1 and 3), MRI (Patient 2) and MVCT images (Patient 3). MVCT was acquired with fine, normal and coarse modalities. Interobserver variability for each organ was analysed using conformity index (CI) and coefficient of variation (CV).
  
  
  RESULTS
  In patients without hip prostheses, CIs were higher in prostate contouring with MRI than with kVCT, indicating lower interobserver variability with MRI. Very slight variations were seen in rectum and bladder contouring. In the patient with hip prostheses (Patient 3), contouring on kVCT lowered CI and increased CV in the prostate, bladder and rectum. The differences were more marked in the prostate. Only fine modality MVCT reduced interobserver variability and only for the prostate.
  
  
  CONCLUSIONS
  Even though greater noise and less soft-tissue contrast increase contouring variability with MVCT than with kVCT, lack of artefacts on MVCT could provide better image definition by this modality in hip prosthesis patients in whom MRI is precluded.
  
  
  CONCLUSIONS
  We recommend the fine modality MVCT for contouring hip prostheses patients.
authors.affiliation: 1 Department of Onco-Haematological and Gastroenterological Science, Radiation Oncology Division, Perugia General Hospital, Perugia, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Falcinelli
authors.affiliation: 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy.
authors.forename: Isabella
authors.initials: I
authors.lastname: Palumbo
authors.affiliation: 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Radicchia
authors.affiliation: 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Arcidiacono
authors.affiliation: 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Lancellotta
authors.affiliation: 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy.
authors.forename: Giampaolo
authors.initials: G
authors.lastname: Montesi
authors.affiliation: 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Matrone
authors.affiliation: 3 Department of Imaging and Laboratory Diagnosis, Medical Physics Unit, Perugia General Hospital, Perugia, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Zucchetti
authors.affiliation: 3 Department of Imaging and Laboratory Diagnosis, Medical Physics Unit, Perugia General Hospital, Perugia, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Marcantonini
authors.affiliation: 4 Internal Medicine, Endocrine and Metabolic Sciences Section, Perugia General Hospital, Perugia, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Bini
authors.affiliation: 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Aristei
mesh_terms: D016477:Artifacts; D006622:Hip Prosthesis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D015588:Observer Variation; D058958:Organs at Risk / Q000000981:diagnostic imaging* / Q000473:pathology*; D011467:Prostate / Q000000981:diagnostic imaging / Q000473:pathology; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012007:Rectum / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000473:pathology