title: Evaluating organ delineation, dose calculation and daily localization in an open-MRI simulation workflow for prostate cancer patients.
abstract: BACKGROUND
  This study describes initial testing and evaluation of a vertical-field open Magnetic Resonance Imaging (MRI) scanner for the purpose of simulation in radiation therapy for prostate cancer. We have evaluated the clinical workflow of using open MRI as a sole modality for simulation and planning. Relevant results related to MRI alignment (vs. CT) reference dataset with Cone-Beam CT (CBCT) for daily localization are presented.
  
  
  METHODS
  Ten patients participated in an IRB approved study utilizing MRI along with CT simulation with the intent of evaluating the MRI-simulation process. Differences in prostate gland volume, seminal vesicles, and penile bulb were assessed with MRI and compared to CT. To evaluate dose calculation accuracy, bulk-density-assignments were mapped onto respective MRI datasets and treated IMRT plans were re-calculated. For image localization purposes, 400 CBCTs were re-evaluated with MRI as the reference dataset and daily shifts compared against CBCT-to-CT registration. Planning margins based on MRI/CBCT shifts were computed using the van Herk formalism.
  
  
  RESULTS
  Significant organ contour differences were noted between MRI and CT. Prostate volumes were on average 39.7% (p = 0.002) larger on CT than MRI. No significant difference was found in seminal vesicle volumes (p = 0.454). Penile bulb volumes were 61.1% higher on CT, without statistical significance (p = 0.074). MRI-based dose calculations with assigned bulk densities produced agreement within 1% with heterogeneity corrected CT calculations. The differences in shift positions for the cohort between CBCT-to-CT registration and CBCT-to-MRI registration are -0.15 ± 0.25 cm (anterior-posterior), 0.05 ± 0.19 cm (superior-inferior), and -0.01 ± 0.14 cm (left-right).
  
  
  CONCLUSIONS
  This study confirms the potential of using an open-field MRI scanner as primary imaging modality for prostate cancer treatment planning simulation, dose calculations and daily image localization.
authors.affiliation: Department of Radiation Oncology, Henry Ford Health System, 2799 W. Grand Blvd, Detroit, MI, 48202, USA. adoemer1@hfhs.org.
authors.forename: Anthony
authors.initials: A
authors.lastname: Doemer
authors.affiliation: Department of Radiation Oncology, Henry Ford Health System, 2799 W. Grand Blvd, Detroit, MI, 48202, USA. ichetty1@hfhs.org.
authors.forename: Indrin J
authors.initials: IJ
authors.lastname: Chetty
authors.affiliation: Department of Radiation Oncology, Henry Ford Health System, 2799 W. Grand Blvd, Detroit, MI, 48202, USA. churst2@hfhs.org.
authors.forename: Carri
authors.initials: C
authors.lastname: Glide-Hurst
authors.affiliation: Department of Radiation Oncology, 21st Century Oncology, 28585 Orchard Lake Rd, Suite 110, Farmington Hills, MI, 48334, USA. teamour.nurushev@rtsx.com.
authors.forename: Teamour
authors.initials: T
authors.lastname: Nurushev
authors.affiliation: Department of Radiology, Henry Ford Health System, 2799 W. Grand Blvd, Detroit, MI, 48202, USA. daveh@rad.hfh.edu.
authors.forename: David
authors.initials: D
authors.lastname: Hearshen
authors.affiliation: Department of Radiology, Henry Ford Health System, 2799 W. Grand Blvd, Detroit, MI, 48202, USA. milan@rad.hfh.edu.
authors.forename: Milan
authors.initials: M
authors.lastname: Pantelic
authors.affiliation: Philips Healthcare, 603 Alpha Park, Cleveland, OH, 44143, USA. melanie.kotys@philips.com.
authors.forename: Melanie
authors.initials: M
authors.lastname: Traughber
authors.affiliation: Department of Radiation Oncology, Henry Ford Health System, 2799 W. Grand Blvd, Detroit, MI, 48202, USA. jkim8@hfhs.org.
authors.forename: Joshua
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Henry Ford Health System, 2799 W. Grand Blvd, Detroit, MI, 48202, USA. klevin2@hfhs.org.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Levin
authors.affiliation: Department of Radiation Oncology, Henry Ford Health System, 2799 W. Grand Blvd, Detroit, MI, 48202, USA. melshai1@hfhs.org.
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Elshaikh
authors.affiliation: Department of Radiation Oncology, Henry Ford Health System, 2799 W. Grand Blvd, Detroit, MI, 48202, USA. ewalker1@hfhs.org.
authors.forename: Eleanor
authors.initials: E
authors.lastname: Walker
authors.affiliation: Department of Radiation Oncology, Henry Ford Health System, 2799 W. Grand Blvd, Detroit, MI, 48202, USA. bmovsas1@hfhs.org.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Movsas
mesh_terms: D000465:Algorithms; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012669:Seminal Vesicles / Q000473:pathology* / Q000528:radiation effects; D014057:Tomography, X-Ray Computed / Q000379:methods; D057188:Workflow