Head and Neck Imaging - Original Article
Discrepant lesion size estimated on T1- and fat-suppressed T2-weighted MR Images: diagnostic value for differentiation between inflammatory pseudotumor and carcinoma of the nasopharynx
Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea; Department of Radiology, Hanil General Hospital, Seoul, Korea
Diagn Interv Radiol ; : -
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PURPOSE: NIPT (nasopharyngeal inflammatory pseudotumor) is hard to differentiate from infiltrating NPC (nasopharyngeal carcinoma) on conventional magnetic resonance imaging (MRI). The purpose of this study is to evaluate how the discrepant lesion size estimated on T1- and fat-suppressed T2-weighted images can help distinguish between NIPT and NPC.
METHODS: We retrospectively reviewed MRI data of histologically proved 14 NIPTs and 18 infiltrating NPCs. With the contrast-enhanced T1-weighted images as the reference images, we measured area of the lesion on precontrast T1-, fat-suppressed T2-, and contrast-enhanced T1-weighted images by placing the largest possible polygonal region-of-interest within the lesion at the same level, respectively. Based on these measurements, we calculated and compared ART1 (area ratio of T1) and ART2 (area ratio of T2) between NIPTs and NPCs. For validation, we also undertook a double blinded study by 2 reviewers and assessed the diagnostic performance and interobserver agreement.
RESULTS: For NIPTs, ART2 (median, 0.48; range, 0.18–0.97) was statistically significantly less than ART1 (median, 1.01; range, 0.80–1.99), while these values were not significantly different for NPCs. The interobserver agreement in differentiating between NIPT and NPC was good with a sensitivity of 93% and a specificity of 83%–94%.
CONCLUSION: Compared to NPCs, NIPTs become apparently smaller on fat-suppressed T2-weighted images than on T1-weighted images. This discrepancy in the lesion size estimated on T1- and fat-suppressed T2-weighted images may provide a simple and consistent way to differentiate between NIPTs and NPCs on conventional MRI.