title: Parotid perfusion in nasopharyngeal carcinoma patients in early-to-intermediate stage after low-dose intensity-modulated radiotherapy: evaluated by fat-saturated dynamic contrast-enhanced magnetic resonance imaging.
abstract: OBJECTIVE
  To investigate parotid perfusion in early-to-intermediate stage after parotid-sparing radiation dose using fat-saturated DCE-MRI, and to verify whether the perfusion alteration was related to radiation dose and the PSV.
  
  
  METHODS
  Thirty-two parotid glands from 16 consecutive patients with pathologically proven nasopharyngeal carcinoma treated by IMRT were examined. The parotid glands received a radiation dose of 28.9±3.9Gy with a PSV of 43.1%±13.9%. Perfusion parameters were calculated using time-shifted Brix model from fat-saturated DCE-MRI data before (pre-RT) and in early-to-intermediate stage after (post-RT) IMRT. Paired t-test was used to evaluate perfusion changes, while Pearson's correlation test was used to examine perfusion dependency on radiation dose and PSV. For multiple comparisons Bonferroni correction was applied.
  
  
  RESULTS
  Successful fat saturation was achieved in 29 of 32 parotid glands. Compared with pre-RT, the post-RT parotid glands showed significantly higher A, peak enhancement, and wash-in slope, plus a lower Kel, suggesting a mixed effect of increased vascular permeability and acinar loss. Linear regression showed that peak enhancement was positively associated with radiation dose in post-RT parotid glands. Kel and slope were negatively associated with PSV, while time-to-peak was positively associated with PSV significantly.
  
  
  CONCLUSIONS
  Our results suggest that time-shifted Brix model is feasible for quantifying parotid perfusion using DCE-MRI. The perfusion alterations in early-to-intermediate stage after IMRT might be related to a mixed effect of increased vascular permeability and acinar loss with dose and PSV dependencies.
authors.affiliation: Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, Republic of China; Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, Republic of China.
authors.forename: Cheng-Chieh
authors.initials: CC
authors.lastname: Cheng
authors.forename: Su-Chin
authors.initials: SC
authors.lastname: Chiu
authors.forename: Yee-Min
authors.initials: YM
authors.lastname: Jen
authors.forename: Hing-Chiu
authors.initials: HC
authors.lastname: Chang
authors.forename: Hsiao-Wen
authors.initials: HW
authors.lastname: Chung
authors.forename: Yi-Jui
authors.initials: YJ
authors.lastname: Liu
authors.forename: Hui-Chu
authors.initials: HC
authors.lastname: Chiu
authors.forename: Cheng-Yu
authors.initials: CY
authors.lastname: Chen
authors.forename: Guo-Shu
authors.initials: GS
authors.lastname: Huang
authors.forename: Chun-Jung
authors.initials: CJ
authors.lastname: Juan
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma; D003287:Contrast Media; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D009367:Neoplasm Staging; D059351:Organ Sparing Treatments / Q000379:methods*; D010306:Parotid Gland / Q000473:pathology* / Q000528:radiation effects; D011379:Prognosis; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media
keywords: CNR; DCE; EES; IMRT; NPC; PE; PSV; ROI; RT; TTP; a.u.; arbitrary unit; contrast-to-noise ratio; dynamic contrast-enhanced; extracellular extravascular space; intensity modulated radiotherapy; nasopharyngeal carcinoma; parotid sparing volume; peak enhancement; post-RT; post-radiotherapy; pre-RT; pre-radiotherapy; radiotherapy; region of interest; time-to-peak