title: Local anatomic changes in parotid and submandibular glands during radiotherapy for oropharynx cancer and correlation with dose, studied in detail with nonrigid registration.
abstract: OBJECTIVE
  To quantify the anatomic changes caused by external beam radiotherapy in head-and-neck cancer patients in full three dimensions and to relate the local anatomic changes to the planned mean dose.
  
  
  METHODS
  A nonrigid registration method was adapted for RT image registration. The method was applied in 10 head-and-neck cancer patients, who each underwent a planning and a repeat computed tomography scan. Contoured structures (parotid, submandibular glands, and tumor) were registered in a nonrigid manner. The accuracy of the transformation was determined. The transformation results were used to summarize the anatomic changes on a local scale for the irradiated and spared glands. The volume reduction of the glands was related to the planned mean dose.
  
  
  RESULTS
  Transformation was accurate with a mean error of 0.6 +/- 0.5 mm. The volume of all glands and the primary tumor decreased. The lateral regions of the irradiated parotid glands moved inward (average, 3 mm), and the medial regions tended to remain in the same position. The irradiated submandibular glands shrank and moved upward. The spared glands showed only a small deformation ( approximately 1 mm in most regions). Overall, the primary tumors shrank. The volume loss of the parotid glands correlated significantly with the planned mean dose (p <0.001).
  
  
  CONCLUSIONS
  General shrinkage and deformation of irradiated glands was seen. The spared glands showed few changes. These changes were assessed by a nonrigid registration method, which effectively described the local changes occurring in the head-and-neck region after external beam radiotherapy.
authors.affiliation: Department of Radiation Oncology, Daniel den Hoed Cancer Center, Erasmus Medical Center, Rotterdam, The Netherlands. e.vasquezosorio@erasmumc.nl
authors.forename: Eliana M
authors.initials: EM
authors.lastname: Vásquez Osorio
authors.forename: Mischa S
authors.initials: MS
authors.lastname: Hoogeman
authors.forename: Abrahim
authors.initials: A
authors.lastname: Al-Mamgani
authors.forename: David N
authors.initials: DN
authors.lastname: Teguh
authors.forename: Peter C
authors.initials: PC
authors.lastname: Levendag
authors.forename: Ben J M
authors.initials: BJ
authors.lastname: Heijmen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size / Q000528:radiation effects; D009959:Oropharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D010306:Parotid Gland / Q000000981:diagnostic imaging / Q000473:pathology / Q000528:radiation effects*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D013363:Submandibular Gland / Q000000981:diagnostic imaging / Q000473:pathology / Q000528:radiation effects*; D014057:Tomography, X-Ray Computed