title: Magnetic resonance imaging in postprostatectomy radiotherapy planning.
abstract: OBJECTIVE
  To investigate whether the use of magnetic resonance imaging (MRI) in prostate bed treatment planning could influence definition of the clinical target volume (CTV) and organs at risk.
  
  
  METHODS
  A total of 21 consecutive patients referred for prostate bed radiotherapy were included in the present retrospective study. The CTV was delineated according to the European Organization for Research and Treatment of Cancer recommendations on computed tomography (CT) and T(1)-weighted (T(1)w) and T(2)-weighted (T(2)w) MRI. The CTV magnitude, agreement, and spatial differences were evaluated on the planning CT scan after registration with the MRI scans.
  
  
  RESULTS
  The CTV was significantly reduced on the T(1)w and T(2)w MRI scans (13% and 9%, respectively) compared with the CT scans. The urinary bladder was drawn smaller on the CT scans and the rectum was smaller on the MRI scans. On T(1)w MRI, the rectum and urinary bladder were delineated larger than on T(2)w MRI. Minimal agreement was observed between the CT and T(2)w images. The main spatial differences were measured in the superior and superolateral directions in which the CTV on the MRI scans was 1.8-2.9 mm smaller. In the posterior and inferior border, no difference was seen between the CT and T(1)w MRI scans. On the T(2)w MRI scans, the CTV was larger in these directions (by 1.3 and 1.7 mm, respectively).
  
  
  CONCLUSIONS
  The use of MRI in postprostatectomy radiotherapy planning resulted in a reduction of the CTV. The main differences were found in the superior part of the prostate bed. We believe T(2)w MRI enables more precise definition of prostate bed CTV than conventional planning CT.
authors.affiliation: Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic. sefrova@post.cz
authors.forename: Jana
authors.initials: J
authors.lastname: Sefrova
authors.forename: Karel
authors.initials: K
authors.lastname: Odrazka
authors.forename: Petr
authors.initials: P
authors.lastname: Paluska
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Belobradek
authors.forename: Milos
authors.initials: M
authors.lastname: Brodak
authors.forename: Martin
authors.initials: M
authors.lastname: Dolezel
authors.forename: Petr
authors.initials: P
authors.lastname: Prosvic
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Macingova
authors.forename: Milan
authors.initials: M
authors.lastname: Vosmik
authors.forename: Petr
authors.initials: P
authors.lastname: Hoffmann
authors.forename: Miroslav
authors.initials: M
authors.lastname: Louda
authors.forename: Anna
authors.initials: A
authors.lastname: Nejedla
mesh_terms: D000368:Aged; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000097:blood / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy; D018365:Neoplasm, Residual; D009929:Organ Size; D058958:Organs at Risk / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D011184:Postoperative Period; D011467:Prostate / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000097:blood / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D018714:Radiotherapy, Adjuvant / Q000379:methods; D012007:Rectum / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D016879:Salvage Therapy / Q000379:methods; D012669:Seminal Vesicles / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden; D001743:Urinary Bladder / Q000033:anatomy & histology / Q000000981:diagnostic imaging