doi:10.1016/j.ijrobp.2006.09.020 CLINICAL INVESTIGATION Head and Neck DETECTION OF HEAD AND NECK SQUAMOUS CELL CARCINOMA WITH DIFFUSION WEIGHTED MRI AFTER (CHEMO)RADIOTHERAPY: CORRELATION BETWEEN RADIOLOGIC AND HISTOPATHOLOGIC FINDINGS VINCENT VANDECAVEYE, M.D.,* FREDERIK DE KEYZER, M.SC.,* SANDRA NUYTS, M.D., PH.D., † KAREN DERAEDT, M.D., ‡ PIET DIRIX, M.D., † PASCAL HAMAEKERS,* VINCENT VANDER POORTEN, M.D., PH.D., § PIERRE DELAERE, M.D., PH.D., § AND ROBERT HERMANS, M.D., PH.D.* *Department of Radiology, University Hospitals Leuven, Leuven, Belgium; † Department of Radiation Oncology, University Hospitals Leuven, Leuven, Belgium; ‡ Department of Pathology, University Hospitals Leuven, Leuven, Belgium; and § Department of Otorhinolaryngology, Head and Neck Surgery, University Hospitals Leuven, Leuven, Belgium Purpose: To investigate the value of diffusion weighted magnetic resonance imaging (DW-MRI) in differentiating persistent or recurrent head and neck squamous cell carcinoma (HNSCC) from nontumoral postradiotherapeu- tic alterations. Methods and Materials: In 26 patients with suspicion of persistent or recurrent HNSCC, MRI of the head and neck was performed, including routine turbo spin-echo (TSE) sequences and an additional echo-planar DW-MRI sequence, using a large range of b-values (0 –1000 s/mm 2 ). Apparent diffusion coefficient (ADC) maps were calculated. In the suspect areas at the primary site and in the suspect lymph nodes, signal intensity was measured on the native b0 and b1000 images and ADC values were calculated for these tissues. The same was done for surrounding irradiated normal tissue. Imaging results were correlated to histopathology. Results: Signal intensity on native b0 images was significantly lower for HNSCC than for nontumoral postra- diotherapeutic tissue (p < 0.0001), resulting in a sensitivity of 66.2%, specificity of 60.8%, and accuracy of 62.4%. Signal intensity on native b1000 images was significantly higher for HNSCC than for nontumoral tissue (p < 0.0001), resulting in a sensitivity of 71.6%, specificity of 71.3%, and accuracy of 71.4%. ADC values were significantly lower for HNSCC than for nontumoral tissue (p < 0.0001), resulting in a sensitivity of 94.6%, specificity of 95.9%, and accuracy of 95.5%. When compared with computed tomography, TSE-MRI and fluorodeoxyglucose-positron emission tomography, DW-MRI yielded fewer false-positive results in persistent primary site abnormalities and in persistent adenopathies, and aided in the detection of subcentimetric nodal metastases. Conclusions: Diffusion weighted-MRI accurately differentiates persistent or recurrent HNSCC from nontumoral tissue changes after (chemo)radiotherapy. © 2007 Elsevier Inc. Diffusion weighted MRI, Tumor recurrence, (Chemo)radiotherapy, Head and neck, Cancer. INTRODUCTION At the time of diagnosis, head and neck squamous cell carcinoma (HNSCC) usually presents as locoregional dis- ease, for which both surgery and (chemo)radiotherapy (CRT) are primary treatment options (1–3). Treatment fail- ure in the head and neck after CRT is mainly related to locoregional tumor recurrence, whereas distant metastases less frequently occur as an isolated event (4). To increase the chances of a salvage procedure to be curative, posttreat- ment surveillance should aim at detecting locoregional re- current or persistent disease at an early stage (5). Conventional imaging with computed tomography (CT) has a relatively high accuracy for detecting recurrent HNSCC after radiotherapy (RT), allowing earlier identifi- cation of treatment failure than clinical examination alone (6). However, false-positive and false-negative results oc- cur, mainly as a result of RT-induced tissue distortions. This Reprint requests to: Robert Hermans, M.D., Ph.D., Department of Radiology, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium. Tel: (+32) 16-34-28-91; Fax: (+32) 16-34-37- 65; E-mail: Robert.Hermans@uzleuven.be Presented at the ESHNR 2005 in Oxford, United Kingdom, and presented at ICIS 2005, Amsterdam, The Netherlands. This work was partly supported by the research grant “Prof. em. A. L. Baert, Siemens Medical Solutions” and a research grant from the Belgian Foundation against Cancer. Conflict of interest: none. Received July 4, 2006, and in revised form Aug 29, 2006. Accepted for publication Sept 1, 2006. Int. J. Radiation Oncology Biol. Phys., Vol. 67, No. 4, pp. 960 –971, 2007 Copyright © 2007 Elsevier Inc. Printed in the USA. All rights reserved 0360-3016/07/$–see front matter 960