title: Diffusion-weighted imaging for head and neck squamous cell carcinoma: quantifying repeatability to understand early treatment-induced change.
abstract: OBJECTIVE
  The purpose of this study was to define baseline variability of apparent diffusion coefficient (ADC) on diffusion-weighted MR imaging (DWI) in patients with head and neck squamous cell carcinoma (HNSCC) and to compare it with early treatment-induced ADC change.
  
  
  METHODS
  Patients with American Joint Committee on Cancer stages III and IV HNSCC were imaged with two baseline DWI examinations 1 week apart and a third DWI examination during the 2nd week of curative-intent chemoradiation therapy. Mean ADC was measured in the primary tumor and largest lymph node for each patient on the three DWI scans. Mean baseline percentage differences (%∆ADC) were compared with intratreatment change. The repeatability coefficient for baseline %∆ADC was calculated and compared with intratreatment %∆ADC. Repeatability was also assessed with Bland-Altman plots and the intraclass correlation coefficient (ICC).
  
  
  RESULTS
  Sixteen patients underwent double baseline imaging, with 14 also undergoing intratreatment imaging. Baseline nodal disease ADC could be measured in 16 patients, but ADC in primary tumors could only be measured in five patients. The nodal mean (SD) baseline %∆ADC was 8% (± 7%), which was significantly different compared with intratreatment changes of 32% (± 31%) (p = 0.01). Baseline ICC was 0.86 for nodal disease and 0.99 for primary tumor (excellent correlation). The calculated repeatability coefficient for baseline nodal ADC was 15%. No patients had decreases in intratreatment ADC of more than 15%.
  
  
  CONCLUSIONS
  Baseline ADC variability for HNSCC is less than intratreatment ADC change for nodal disease. Assessment of response should consider intrinsic baseline variability.
authors.affiliation: 1 Division of Neuroradiology, Department of Radiology, Duke University Medical Center, Box 3808, Erwin Rd, Durham, NC 27710.
authors.forename: Jenny K
authors.initials: JK
authors.lastname: Hoang
authors.forename: Kingshuk Roy
authors.initials: KR
authors.lastname: Choudhury
authors.forename: Jim
authors.initials: J
authors.lastname: Chang
authors.forename: Oana I
authors.initials: OI
authors.lastname: Craciunescu
authors.forename: David S
authors.initials: DS
authors.lastname: Yoo
authors.forename: David M
authors.initials: DM
authors.lastname: Brizel
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000473:pathology*; D059248:Chemoradiotherapy; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011859:Radiography; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000077195:Squamous Cell Carcinoma of Head and Neck; D016896:Treatment Outcome
keywords: diffusion-weighted imaging; early treatment change; functional imaging; head and neck cancer; repeatability