Comparison of MR Imaging and Dual-Energy CT for the Evaluation of Cartilage Invasion by Laryngeal and Hypopharyngeal Squamous Cell Carcinoma

Abstract

Background and purpose: Dual-energy CT can distinguish iodine-enhanced tumors from nonossified cartilage and has been investigated for evaluating cartilage invasion in patients with laryngeal and hypopharyngeal squamous cell carcinomas. In this study, we compared the diagnostic accuracy of MR imaging and of a combination of weighted-average and iodine overlay dual-energy CT images in detecting cartilage invasion by laryngeal and hypopharyngeal squamous cell carcinomas, in particular thyroid cartilage invasion.

Materials and methods: Fifty-five consecutive patients who underwent 3T MR imaging and 128-slice dual-energy CT for preoperative initial staging of laryngeal or hypopharyngeal squamous cell carcinomas were included. Two blinded observers evaluated laryngeal cartilage invasion on MR imaging and dual-energy CT using a combination of weighted-average and iodine-overlay images. Pathologic findings of surgically resected specimens were used as the reference standard for evaluating sensitivity, specificity, and the areas under the receiver operating characteristic curve of both modalities for cartilage invasion by each type of cartilage and for all cartilages together. Sensitivity and specificity were compared using the McNemar test and generalized linear mixed models.

Results: Dual-energy CT showed higher specificity than MR imaging for diagnosing all cartilage together (84% for MR imaging versus 98% for dual-energy CT, P < .004) and for thyroid cartilage (64% versus 100%, P < .001), with a similar average area under the curve (0.94 versus 0.95, P = .70). The sensitivity did not differ significantly for all cartilages together (97% versus 81%, P = .16) and for thyroid cartilage (100% versus 89%, P = .50), though there was a trend toward increased sensitivity with MR imaging.

Conclusions: Dual-energy CT showed higher specificity and acceptable sensitivity in diagnosing laryngeal cartilage invasion compared with MR imaging.

Fig 1.

False-positive findings for thyroid cartilage invasion on MR imaging in a 59-year-old man with hypopharyngeal cancer. A, T2-weighted MR image obtained at the glottis level shows a tumor (T) arising from the right piriform sinus with intermediate signal intensity. The adjacent posterior right thyroid lamina also shows an area of intermediate signal intensity (arrow). B, T1-weighted image shows that the tumor (T) has low signal intensity, whereas adjacent thyroid cartilage has similar signal intensity (arrow). C, Contrast-enhanced fat-suppressed T1-weighted MR image shows similar contrast enhancement of the tumor (T) and adjacent thyroid cartilage (arrow). A weighted-average image does not show erosion or lysis at the same level (D, soft-tissue window; E, bone window). F, Iodine overlay image shows enhancement of tumor (T) more clearly and is not used for the diagnosis of cartilage according to the findings of the WA image. G, A micrograph of the corresponding axial slice of the surgical specimen at the same level shows that the squamous cell carcinoma cells do not permeate into the right thyroid cartilage lamina (hematoxylin-eosin stain; original magnification, ×5). H, Magnified photograph (square in G) of the posterior part of the right thyroid cartilage lamina with enhancement on MR imaging shows moderate infiltration of lymphocytes into the medullary space, accompanied by fibrosis and aggregation of macrophages, without tumor (H&E stain; original magnification, ×200).

Fig 2.

Graph shows 2 crossing ROC curves and corresponding AUCs in the prediction of thyroid cartilage invasion. There was no evidence of differences in the average areas under the ROC curve between MR imaging and dual-energy CT (0.938 versus 0.952, respectively; P = .70).