Three-dimensional imaging of laryngeal cancers using high-speed helical CT scanning

To evaluate the clinical usefulness and limitations of three-dimensional (3-D) imaging of laryngeal cancers by high-speed helical (spiral) CT scanning, 3-D images were reconstructed for one dissected human larynx and 10 patients with laryngeal cancer. The larynges were scanned in 1- to 2-mm slices, and were reconstructed using a slice thickness of 0.5-1.0 mm. The macroscopic (or endoscopic) findings and the 3-D CT images of the larynx were compared. The selected threshold CT values were -600 HU (Hounsfield units) to -100 HU for the mucous membranes, and 250 HU for bone. Under these conditions, almost all of the structures remained distinct. The 3-D images of the larynx obtained by helical CT were very helpful in understanding laryngeal anatomy, especially in the subglottic area, which cannot be seen clearly by endoscopy or conventional axial CT. Clinically, this system would have advantages in the detection of subglottic cancers, or the invasion of glottic or supraglottic cancers into the subglottic area.