Background: Cartilage invasion is one of the critical determinants of tumour staging for laryngeal cancer and of particular importance in assessing the suitability for partial laryngectomy and/or chemoradiation therapy
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. ultrasonography has the advantage of its non-invasive and real-time imaging features and it has been used to evaluate laryngeal tumours and it could assist tumour staging in patients with advanced laryngeal cancer.
Aim of the work: To compare between the role of US and diffusion weighted MRI in the detection of thyroid cartilage invasion in patients with laryngeal malignancy by correlating the radiological findings with the postoperative histopathological findings of the total or partial laryngectomy specimen.
Patients and Methods: A prospective study was carried out between December 2018 to September 2021. The study included 36 patients. Thirty five patients underwent total laryngectomy and one patient 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, and DWI and ultrasound.
Results: our study showed that DWMRI has sensitivity of 81.2%, specificity 50%, PPV of 86.7%, NPV of 40% and accuracy of 75% in detection of inner lamina invasion and it has sensitivity of84.6 %, specificity of 71.4%, PPV of 84.6%, NPV of 71.4% and accuracy of 80% in detection of outer thyroid lamina invasion. In our study, we found that ultrasound has sensitivity of 78.6%, specificity of 60%, PPV of 84.6%, NPV of 50% and accuracy of 73.7% in detection of inner cortex invasion. & it has sensitivity of 75%, specificity of 66.7%, PPV of 90%, NPV of 66.6% and accuracy of 78.9%in detection of outer thyroid cortex invasion.
Conclusion: Diffusion-weighted MRI and ultrasound 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.