title: Donut-shaped high-dose configuration for proton beam radiation therapy.
abstract: BACKGROUND
  The authors report on the conception and first clinical application of a donut-shaped high-dose configuration for proton therapy (PT). This approach allows one to intensify target volume dose coverage for targets encompassing a critical, dose-limiting structure--like here, the cauda equina--, whilst delivering minimal dose to other healthy structures surrounding the target, thereby reducing the integral dose.
  
  
  RESULTS
  Intensity-modulated PT methods (IMPT) for spot scanning were applied to create and deliver a donut-shaped high-dose configuration with protons, allowing treating > 75% of the target with at least 95% of the prescribed dose of 72.8 CGE, whilst restricting dose to the cauda equina to 60-65 CGE. Integral dose was lower by a factor of 3.3 as compared to intensity-modulated radiotherapy with photons (IMXT).
  
  
  CONCLUSIONS
  IMPT and spot scanning technology allow a potentially clinically useful approach which is also applicable to spare other critical structures passing through a target volume, including spinal cord, optic nerves, chiasm, brain stem, or urethra.
authors.affiliation: Division of Radiation Medicine, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland. hanspeter.rutz@psi.ch
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Rutz
authors.forename: Antony J
authors.initials: AJ
authors.lastname: Lomax
mesh_terms: D016477:Artifacts; D002420:Cauda Equina / Q000528:radiation effects; D002817:Chordoma / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D019583:Dose Fractionation, Radiation; D006801:Humans; D021621:Imaging, Three-Dimensional; D007422:Intestines / Q000528:radiation effects; D008159:Lumbar Vertebrae; D019047:Phantoms, Imaging; D017785:Photons / Q000627:therapeutic use; D019736:Prostheses and Implants; D061766:Proton Therapy; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D018714:Radiotherapy, Adjuvant; D020266:Radiotherapy, Conformal / Q000379:methods*; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D014025:Titanium; D014057:Tomography, X-Ray Computed
chemical_list: D014025:Titanium