title: Evaluation of radiation-induced changes to parotid glands following conventional radiotherapy in patients with nasopharygneal carcinoma.
abstract: OBJECTIVE
  Xerostomia is a common post-radiotherapy (post-RT) complication in nasopharyngeal carcinoma (NPC) patients. This study evaluated the relation of post-RT parotid gland changes with the dose received.
  
  
  METHODS
  Data from 18 NPC patients treated by radiotherapy between 1997 and 2001 were collected. Parotid gland volumes were measured and compared between their pre-RT and post-RT CT images; both sets of CT were conducted with the same scanning protocol. Doppler ultrasound was used to assess the haemodynamic condition of the glands after radiotherapy. Doppler ultrasound results were compared against 18 age-matched normal participants. A questionnaire was used to evaluate the patients' comments of xerostomia condition. Radiotherapy treatment plans of the participants were retrieved from the Eclipse treatment planning system from which the radiation doses delivered to the parotid glands were estimated. The correlations of parotid gland doses and the post-RT changes were evaluated.
  
  
  RESULTS
  The post-RT parotid glands were significantly smaller (p<0.001) than the pre-RT ones. They also demonstrated lower vascular velocity, resistive and pulsatility indices (p<0.05) than normal participants. The degree of volume shrinkage and subjective severity of xerostomia demonstrated dose dependence, but such dependence was not definite in the haemodynamic changes.
  
  
  CONCLUSIONS
  It was possible to predict the gland volume change and subjective severity of xerostomia based on the dose to the parotid glands for NPC patients. However, such prediction was not effective for the vascular changes. The damage to the gland was long lasting and had significant effects on the patients' quality of life.
authors.affiliation: Department of Health Technology and Informatics, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR. htvinwu@polyu.edu.hk
authors.forename: V W C
authors.initials: VW
authors.lastname: Wu
authors.forename: M T C
authors.initials: MT
authors.lastname: Ying
authors.forename: D L W
authors.initials: DL
authors.lastname: Kwong
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000532:radiotherapy*; D009929:Organ Size; D010306:Parotid Gland / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology / Q000528:radiation effects*; D011859:Radiography; D011879:Radiotherapy Dosage; D014655:Vascular Resistance; D014987:Xerostomia / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology*