title: Feasibility of image registration and intensity-modulated radiotherapy planning with hyperpolarized helium-3 magnetic resonance imaging for non-small-cell lung cancer.
abstract: OBJECTIVE
  To demonstrate the feasibility of registering hyperpolarized helium-3 magnetic resonance images ((3)He-MRI) to X-ray computed tomography (CT) for functionally weighted intensity-modulated radiotherapy (IMRT) planning.
  
  
  METHODS
  Six patients with non-small-cell lung cancer underwent (3)He ventilation MRI, which was fused with radiotherapy planning CT using rigid registration. Registration accuracy was assessed using an overlap coefficient, calculated as the proportion of the segmented (3)He-MR volume (V(MRI)) that intersects the segmented CT lung volume expressed as a percentage of V(MRI). For each patient, an IMRT plan that minimized the volume of total lung receiving a dose > or = 20 Gy (V(20)) was compared with a plan that minimized the V(20) to well-ventilated lung defined by the registered (3)He-MRI.
  
  
  RESULTS
  The (3)He-MRI and CT were registered with sufficient accuracy to enable functionally guided IMRT planning (median overlap, 89%; range, 72-97%). In comparison with the total lung IMRT plans, IMRT constrained with (3)He-MRI reduced the V(20) not only for the well-ventilated lung (median reduction, 3.1%; range, 0.4-5.1%; p = 0.028) but also for the total lung volume (median reduction, 1.6%; range, 0.2-3.7%; p = 0.028).
  
  
  CONCLUSIONS
  Statistically significant improvements to IMRT plans are possible using functional information provided by (3)He-MRI that has been registered to radiotherapy planning CT.
authors: Academic Unit of Radiology, University of Sheffield, Sheffield, United Kingdom. r.ireland@sheffield.ac.uk
authors: Rob H
authors: RH
authors: Ireland
authors: Chris M
authors: CM
authors: Bragg
authors: Mark
authors: M
authors: McJury
authors: Neil
authors: N
authors: Woodhouse
authors: Stan
authors: S
authors: Fichele
authors: Edwin J R
authors: EJ
authors: van Beek
authors: Jim M
authors: JM
authors: Wild
authors: Matthew Q
authors: MQ
authors: Hatton
mesh_terms: D000402:Airway Obstruction / Q000175:diagnosis / Q000209:etiology; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D005240:Feasibility Studies; D006371:Helium; D006801:Humans; D007554:Isotopes; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D007554:Isotopes; D006371:Helium