Diffusion-weighted MRI in diagnosing thyroid cartilage invasion in laryngeal carcinoma.

The diagnosis of thyroid cartilage invasion in patients presenting with laryngeal carcinoma is essential for pre-therapeutic staging. Compared to CT, diffusion-weighted magnetic resonance imaging (MRI) has a similar ability to define the interface between fat and tumor, but is superior for assessing muscle and cartilage invasion. Diffusion-weighted MRI may be indicated if there are equivocal findings in the CT, including possible cartilage invasion. The aim of this study is to assess the validity of diffusion-weighted MRI in predicting inner and outer thyroid cartilage laminae invasion in patients with laryngeal carcinoma. A prospective study was carried out between August 2011 and May 2013. The study included 26 patients. Twenty-three patients underwent total laryngectomy and three patients underwent partial laryngectomy. Histopathology reports of resected specimens and pre-operative staging were blind to the consultant radiologist who reviewed the scans to comment on thyroid cartilage invasion with special emphasis on inner and outer lamina invasion by conventional MRI criteria, contrast enhancement and DWI. The sensitivity, specificity, efficiency (correct classification rate), and positive and negative predictive values of MRI for identification of inner thyroid lamina invasion were: 93, 82, 88, 88 and 90 % respectively, while those of outer thyroid lamina invasion were: 85, 85, 85, 85 and 85 %, respectively. Diffusion-weighted MRI showed high validity and precision in detecting inner and outer thyroid lamina invasion. This can have an important impact on the decision making for management of laryngeal carcinoma.