title: Magnetic resonance-based treatment planning for prostate intensity-modulated radiotherapy: creation of digitally reconstructed radiographs.
abstract: OBJECTIVE
  To develop a technique to create magnetic resonance (MR)-based digitally reconstructed radiographs (DRR) for initial patient setup for routine clinical applications of MR-based treatment planning for prostate intensity-modulated radiotherapy.
  
  
  METHODS
  Twenty prostate cancer patients' computed tomography (CT) and MR images were used for the study. Computed tomography and MR images were fused. The pelvic bony structures, including femoral heads, pubic rami, ischium, and ischial tuberosity, that are relevant for routine clinical patient setup were manually contoured on axial MR images. The contoured bony structures were then assigned a bulk density of 2.0 g/cm(3). The MR-based DRRs were generated. The accuracy of the MR-based DDRs was quantitatively evaluated by comparing MR-based DRRs with CT-based DRRs for these patients. For each patient, eight measuring points on both coronal and sagittal DRRs were used for quantitative evaluation.
  
  
  RESULTS
  The maximum difference in the mean values of these measurement points was 1.3 +/- 1.6 mm, and the maximum difference in absolute positions was within 3 mm for the 20 patients investigated.
  
  
  CONCLUSIONS
  Magnetic resonance-based DRRs are comparable to CT-based DRRs for prostate intensity-modulated radiotherapy and can be used for patient treatment setup when MR-based treatment planning is applied clinically.
authors.affiliation: Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA 19111, USA. lili.chen@fccc.edu
authors.forename: Lili
authors.initials: L
authors.lastname: Chen
authors.forename: Thai-Binh
authors.initials: TB
authors.lastname: Nguyen
authors.forename: Elan
authors.initials: E
authors.lastname: Jones
authors.forename: Zuoqun
authors.initials: Z
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Luo
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.forename: Robert A
authors.initials: RA
authors.lastname: Price
authors.forename: Alan
authors.initials: A
authors.lastname: Pollack
authors.forename: C-M Charlie
authors.initials: CM
authors.lastname: Ma
mesh_terms: D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy*; D011856:Radiographic Image Enhancement / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods