Potential value of non-echo-planar diffusion-weighted imaging of the nasopharynx: a primary study for differential diagnosis between recurrent nasopharyngeal carcinoma and post-chemoradiation fibrosis

Background Distinguishing recurrent nasopharyngeal carcinoma (rNPC) from post-therapeutic inflammatory changes remains a challenging clinical problem. Purpose To qualitatively and quantitatively evaluate image quality and compare the diagnostic value of non-echo-planar diffusion-weighted imaging (DWI) based on turbo spin-echo (TSE) and echo-planar imaging (EPI), to distinguish rNPC from post-chemoradiation fibrosis. Material and Methods Twenty-seven patients with newly diagnosed rNPC and 35 with biopsy-proven post-chemoradiation fibrosis were categorized into tumor and fibrosis groups, respectively. All patients underwent TSE and EP-DWI on a 3-T magnetic resonance unit. The image quality, lesion conspicuity, and distortions of the EPI and TSE images were qualitatively evaluated by two radiologists. The apparent diffusion coefficient values (ADCs), signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs) of the two sequences were also compared. Results The image quality scores indicated that TSE significantly improved image quality and reduced distortion of the nasopharyngeal lesions. Its SNR was slightly lower and CNR was significantly higher than those of EPI. The mean ADCs of the rNPC and post-chemoradiation fibrosis groups showed a significant difference in both sequences ( P < 0.001). However, the ADCs of rNPC on EP-DWI showed a wide variation and more importantly, they appreciably overlapped with those of post-chemoradiation fibrosis. The area under the curve was 0.932 in TSE, which was significantly larger than 0.835 in EPI. Conclusions The images of nasopharyngeal lesions obtained with TSE-DWI were of better quality and higher diagnostic capability than those obtained with EP-DWI for differential diagnosis between rNPC and post-treatment sequelae.