Head and Neck Squamous Cell Carcinoma: Value of Diffusion- weighted MR Imaging for Nodal Staging 1 Vincent Vandecaveye, MD Frederik De Keyzer, MSc Vincent Vander Poorten, MD, PhD Piet Dirix, MD Eric Verbeken, MD, PhD Sandra Nuyts, MD, PhD Robert Hermans, MD, PhD Purpose: To evaluate diffusion-weighted (DW) magnetic resonance (MR) imaging, as compared with turbo spin-echo MR im- aging, for the detection of nodal metastases in head and neck squamous cell carcinoma (HNSCC). Materials and Methods: The study was approved by the ethics committee, and patients gave written informed consent. Before undergo- ing surgery, 33 consecutive patients underwent 1.5-T MR imaging, including DW imaging performed with a wide range of b values (0 –1000 sec/mm 2 ). The apparent diffusion coefficients (ADCs) of lymph nodes 4 mm or greater in short- axis diameter depicted on images obtained with b values of 0 and 1000 sec/mm 2 were calculated. After topographic cor- relation, the lymph nodes were evaluated microscopically with prekeratin immunostaining. The optimal ADC thresh- olds for discriminating between metastatic and benign lymph nodes were determined. The sensitivity, specificity, and ac- curacy of DW imaging were calculated separately— on per- lymph-node and per-neck-level bases—for all lymph nodes and for supracentimeter and subcentimeter lymph nodes and were compared with corresponding turbo spin-echo MR im- aging values. Results: Correlation of histopathologic and radiologic findings was possible for 301 lymph nodes. The ADC derived from the signal intensity averaged across images obtained with b values of 0 and 1000 sec/mm 2 (ADC b0-1000 ) was 1.19  10 -3 mm 2 /sec  0.22 (standard deviation) for benign lymph nodes and 0.85  10 -3 mm 2 /sec  0.27 for malignant lymph nodes (P  .0001). With an optimal ADC b0-1000 threshold of 0.94  10 -3 mm 2 /sec, 84% sensitivity, 94% specificity, and 91% accuracy for differentiation of malignant versus benign status of each lymph node and 94% sensitivity, 97% specific- ity, and 97% accuracy for differentiation at each neck level were achieved. Compared with turbo spin-echo imaging, DW imaging had higher sensitivity (76% vs 7%) but slightly lower specificity (94.0% vs 99.5%) for detection of subcenti- meter nodal metastases. Conclusion: DW imaging performed with ADC b0-1000 values had higher accuracy than turbo spin-echo MR imaging in nodal stag- ing, providing added value in the detection of subcentime- ter nodal metastases.  RSNA, 2009 1 From the Departments of Radiology (V.V., F.D.K., R.H.); Otorhinolaryngology, Head and Neck Surgery (V.V.P.); Radiation Oncology, Leuven Cancer Institute (P.D., S.N.); and Pathology (E.V.), University Hospitals Leuven, Here- straat 49, 3000 Leuven, Belgium. From the 2005 RSNA Annual Meeting. Received January 21, 2008; revision requested March 20; revision received July 30; accepted October 8; final version accepted October 26. Supported in part by the Professor Emeritus A. L. Baert research grant from Siemens Medical Solutions. Address correspondence to R.H. (e-mail: Robert.Hermans@uzleuven.be ).  RSNA, 2009 ORIGINAL RESEARCH  HEAD AND NECK IMAGING 134 radiology.rsnajnls.org ▪ Radiology: Volume 251: Number 1—April 2009 Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights.