title: Corticospinal tract-sparing intensity-modulated radiotherapy treatment planning.
abstract: OBJECTIVE
  To establish intensity-modulated radiotherapy (IMRT) planning procedures that spare the corticospinal tract by integrating diffusion tensor tractography into the treatment planning software.
  
  
  BACKGROUND
  Organs at risk are generally contoured according to the outline of the organ as demonstrated by CT or MRI. But a part of the organ with specific function is difficult to protect, because such functional part of the organ cannot be delineated on CT or conventional sequence of MRI.
  
  
  METHODS
  Diagnostic and treatment planning images of glioblastoma patients who had been treated by conventional 3-dimensional conformal radiotherapy were used for re-planning of IMRT. Three-dimensional fiber maps of the corticospinal tracts were created from the diffusion tensors obtained from the patients before the surgery, and were blended with the anatomical MR images (i.e. gadolinium-enhanced T1-weighted images or T2-weighted images). DICOM-formatted blended images were transferred and fused to the planning CT images. Then, IMRT plans were attempted.
  
  
  RESULTS
  The corticospinal tracts could be contoured as organs at risk (OARs), because the blended images contained both anatomical information and fiber-tract maps. Other OARs were contoured in a way similar to that of ordinary IMRT planning. Gross tumor volumes, clinical target volumes, planning target volumes, and other OARs were contoured on the treatment planning software, and IMRT plans were made.
  
  
  CONCLUSIONS
  IMRT plans with diminished doses to the corticospinal tract were attained. This technique enabled us to spare specific neuron fibers as OARs which were formerly "invisible" and to reduce the probability of late morbidities.
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Igaki
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Sakumi
authors.affiliation: Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Akitake
authors.initials: A
authors.lastname: Mukasa
authors.affiliation: Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Saito
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kunimatsu
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Masutani
authors.affiliation: Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Shunya
authors.initials: S
authors.lastname: Hanakita
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Ino
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Haga
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Nakagawa
authors.affiliation: Department of Radiology, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Kuni
authors.initials: K
authors.lastname: Ohtomo
keywords: Corticospinal tract; Diffusion tensor tractography; Intensity-modulated radiotherapy; Malignant glioma; Organ at risk