Three-Dimensional CT Laryngography: Clinical Application

Kim, Yong; Kim, Jong Gi; Kim, Hak Jin; Lee, Suck Hong; Wang, Soo Guen

Abstract

PURPOSE
To evaluate the clinical usefulness of 3D volume-rendering (VR) CT laryngography during quiet breathing, Valsalva, and modified Valsalva maneuvers, in those with laryngeal and pyriform sinus lesions.
MATERIALS AND METHODS
Twenty-seven patients with various laryngeal and hypopharyngeal lesions were examined by means of four-channel multidetector-row helical CT (LightSpeed QX/i; GE Medical Systems, Milwaukee, Wis., U.S.A.) during quiet breathing, Valsalva, and modified Valsalva maneuvers. The protocol included 1.25-mm slice thickness, 3.75-mm rotation, 1.25 mm interval, and a pitch ratio of 3:1. Using an Advantage Windows 3.1 workstation (GE Medical Systems), 3D VR was generated in regions of interest, including all structures with a CT attenuation of between -1022 and -125 HU. Visual assessment of the findings of 3D CT laryngography, including the images obtained during the three different breathing maneuvers, were analyzed by three radiologists, who reached a consensus. These results were then compared with the findings of axial CT. The lesions discovered, in descending order of frequency, included laryngeal cancer (n=12), pyriform sinus cancer with an intact apex (n=6), pyriform sinus cancer with apex involvement (n=6), laryngeal papilloma (n=2), and hypopharyngeal obstruction with (n=1) and without (n=2) associated vocal cord palsy. In each case, the findings were confirmed by surgical biopsy, direct laryngoscopy, or CT.
RESULTS
3D CT laryngography using the VR technique can supplement the information provided by axial images, and in the assessment of subglottic invasion and pyriform sinus apical invasion, its findings are consistent. In many of our cases, its use during quiet breathing was able to determine whether or not glottic cancer involved subglottic invasion. In laryngeal cancer cases, furthormore, modified Valasalva can be used to clarify the condition of the pyriform sinus apex. Dynamic-phase 3D CT laryngography can be used to elucidate the condition of a patient with vocal cord palsy.
CONCLUSION
3D CT laryngography is a new method for the visual diagnosis of vocal cord and laryngeal cancer. When employed after dynamic diagnosis, it is useful for the evaluation of subglottic extension, pyriform sinus apical invasion and vocal cord palsy, important indicators in the staging of cancer.