title: Texture analysis for the assessment of structural changes in parotid glands induced by radiotherapy.
abstract: OBJECTIVE
  During radiotherapy (RT) for head-and-neck cancer, parotid glands undergo significant anatomic, functional and structural changes which could characterize pre-clinical signs of an increased risk of xerostomia. Texture analysis is proposed to assess structural changes of parotids induced by RT, and to investigate whether early variations of textural parameters (such as mean intensity and fractal dimension) can predict parotid shrinkage at the end of treatment.
  
  
  METHODS
  Textural parameters and volumes of 42 parotids from 21 patients treated with intensity-modulated RT for nasopharyngeal cancer were extracted from CT images. To individuate which parameters changed during RT, a Wilcoxon signed-rank test between textural indices (first and second RT week; first and last RT week) was performed. Discriminant analysis was applied to variations of these parameters in the first two weeks of RT to assess their power in predicting parotid shrinkage at the end of RT.
  
  
  RESULTS
  A significant decrease in mean intensity (1.7 HU and 3.8 HU after the second and last weeks, respectively) and fractal dimension (0.016 and 0.021) was found. Discriminant analysis, based on volume and fractal dimension, was able to predict the final parotid shrinkage (accuracy of 71.4%).
  
  
  CONCLUSIONS
  Textural features could be used in combination with volume to characterize structural modifications on parotid glands and to predict parotid shrinkage at the end of RT.
authors.affiliation: Istituto di Bioimmagini e Fisiologia Molecolare (IBFM), CNR, Segrate, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Scalco
authors.forename: Claudio
authors.initials: C
authors.lastname: Fiorino
authors.forename: Giovanni Mauro
authors.initials: GM
authors.lastname: Cattaneo
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Sanguineti
authors.forename: Giovanna
authors.initials: G
authors.lastname: Rizzo
mesh_terms: D000328:Adult; D000368:Aged; D002277:Carcinoma; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D010306:Parotid Gland / Q000473:pathology* / Q000528:radiation effects*; D011832:Radiation Injuries / Q000209:etiology* / Q000473:pathology*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D014987:Xerostomia / Q000209:etiology* / Q000473:pathology*
keywords: Adaptive radiotherapy; Fractal dimension; Parotid gland shrinkage; Texture analysis