BACKGROUND AND PURPOSE: Differentiating recurrence from benign posttreatment changes has clinical importance in the imaging follow-up of head and neck cancer. This study aimed to investigate the utility of normalized dynamic contrast-enhanced MR imaging and ADC for their differentiation. MATERIALS AND METHODS:This study included 51 patients with a history of head and neck cancer who underwent follow-up dynamic contrast-enhanced MR imaging with DWI-ADC, of whom 25 had recurrences and 26 had benign posttreatment changes. Quantitative and semiquantitative dynamic contrast-enhanced MR imaging parameters and ADC of the ROI and reference region were analyzed. Normalized dynamic contrast-enhanced MR imaging parameters and normalized DWI-ADC parameters were calculated by dividing the ROI by the reference region.RESULTS: Normalized plasma volume, volume transfer constant between extravascular extracellular space and blood plasma per minute (K trans ), area under the curve, and wash-in were significantly higher in patients with recurrence than in those with benign posttreatment change (P ¼ .003 to ,.001). The normalized mean ADC was significantly lower in patients with recurrence than in those with benign posttreatment change (P , .001). The area under the receiver operating characteristic curve of the combination of normalized dynamic contrast-enhanced MR imaging parameters with significance (normalized plasma volume, normalized extravascular extracellular space volume per unit tissue volume, normalized K trans , normalized area under the curve, and normalized wash-in) and normalized mean ADC was 0.97 (95% CI, 0.93-1).CONCLUSIONS: Normalized dynamic contrast-enhanced MR imaging parameters, normalized mean ADC, and their combination were effective in differentiating recurrence and benign posttreatment changes in head and neck cancer.ABBREVIATIONS: AUC ¼ area under the curve; AUROCC ¼ area under the receiver operating characteristic curve; DCE ¼ dynamic contrast-enhanced; EES ¼ extravascular extracellular space; Kep ¼ rate transfer constant between EES and blood plasma per minute; K trans ¼ volume transfer constant between extravascular extracellular space and blood plasma per minute; n-¼ normalized; Ve ¼ extravascular extracellular space volume per unit tissue volume; Vp ¼ plasma volume; WI ¼ wash-in; WO ¼ washout