title: Near Real-Time Assessment of Anatomic and Dosimetric Variations for Head and Neck Radiation Therapy via Graphics Processing Unit-based Dose Deformation Framework.
abstract: OBJECTIVE
  The purpose of this study was to systematically monitor anatomic variations and their dosimetric consequences during intensity modulated radiation therapy (IMRT) for head and neck (H&N) cancer by using a graphics processing unit (GPU)-based deformable image registration (DIR) framework.
  
  
  METHODS
  Eleven IMRT H&N patients undergoing IMRT with daily megavoltage computed tomography (CT) and weekly kilovoltage CT (kVCT) scans were included in this analysis. Pretreatment kVCTs were automatically registered with their corresponding planning CTs through a GPU-based DIR framework. The deformation of each contoured structure in the H&N region was computed to account for nonrigid change in the patient setup. The Jacobian determinant of the planning target volumes and the surrounding critical structures were used to quantify anatomical volume changes. The actual delivered dose was calculated accounting for the organ deformation. The dose distribution uncertainties due to registration errors were estimated using a landmark-based gamma evaluation.
  
  
  RESULTS
  Dramatic interfractional anatomic changes were observed. During the treatment course of 6 to 7 weeks, the parotid gland volumes changed up to 34.7%, and the center-of-mass displacement of the 2 parotid glands varied in the range of 0.9 to 8.8 mm. For the primary treatment volume, the cumulative minimum and mean and equivalent uniform doses assessed by the weekly kVCTs were lower than the planned doses by up to 14.9% (P=.14), 2% (P=.39), and 7.3% (P=.05), respectively. The cumulative mean doses were significantly higher than the planned dose for the left parotid (P=.03) and right parotid glands (P=.006). The computation including DIR and dose accumulation was ultrafast (∼45 seconds) with registration accuracy at the subvoxel level.
  
  
  CONCLUSIONS
  A systematic analysis of anatomic variations in the H&N region and their dosimetric consequences is critical in improving treatment efficacy. Nearly real-time assessment of anatomic and dosimetric variations is feasible using the GPU-based DIR framework. Clinical implementation of this technology may enable timely plan adaptation and improved outcome.
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California. Electronic address: xqi@mednet.ucla.edu.
authors.forename: X Sharon
authors.initials: XS
authors.lastname: Qi
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California.
authors.forename: Anand
authors.initials: A
authors.lastname: Santhanam
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California.
authors.forename: John
authors.initials: J
authors.lastname: Neylon
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California.
authors.forename: Yugang
authors.initials: Y
authors.lastname: Min
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California.
authors.forename: Tess
authors.initials: T
authors.lastname: Armstrong
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California.
authors.forename: Ke
authors.initials: K
authors.lastname: Sheng
authors.affiliation: Department of Radiation Oncology, UF Health Cancer Center - Orlando Health, Orlando, Florida.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Staton
authors.affiliation: Department of Radiation Oncology, UF Health Cancer Center - Orlando Health, Orlando, Florida.
authors.forename: Jason
authors.initials: J
authors.lastname: Pukala
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California.
authors.forename: Andrew
authors.initials: A
authors.lastname: Pham
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Low
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California.
authors.forename: Steve P
authors.initials: SP
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology, UF Health Cancer Center - Orlando Health, Orlando, Florida.
authors.forename: Michael
authors.initials: M
authors.lastname: Steinberg
authors.affiliation: Department of Radiation Oncology, UF Health Cancer Center - Orlando Health, Orlando, Florida.
authors.forename: Rafael
authors.initials: R
authors.lastname: Manon
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California.
authors.forename: Allen M
authors.initials: AM
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California.
authors.forename: Patrick
authors.initials: P
authors.lastname: Kupelian
mesh_terms: D005005:Ethmoid Sinus; D005240:Feasibility Studies; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects; D010255:Paranasal Sinus Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D010306:Parotid Gland / Q000000981:diagnostic imaging* / Q000528:radiation effects*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods; D014062:Tongue Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D014067:Tonsillar Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy