Applications Of Three-dimensional Ultrasound To Larynx And Laryngeal Cancer

Objective: To investigate the feasibility of three-dimensional ultrasound (3-D US) applying to the larynx and to evaluate its value in the diagnosis of laryngeal cancer.Methods: 3-D US data of the larynx of eighty-five healthy volunteers were reviewed and evaluated by a three-rater committee included an ultrasonographer, a radiologist, and an otolaryngologist. The three raters evaluated the quality of image independently according to a pre-defined standard. Agreements between raters were assessed by using Kappa test. Tumors and the cervical lymph nodes in sixty-nine patients with laryngeal cancer were detected by two-dimensional ultrasound (2-D US). Transparent mode three-dimensional gray scale volume rendering and three-dimensional color Doppler imaging were applied in laryngeal cancer. The sonograms of transparent mode 3-D US were analyzed compared with the surgical findings. Correlation between vascularity index (VI) derived from three-dimensional color Doppler imaging and N-staging was evaluated. To test the accuracy of VI for predicting cervical lymph nodes involvement, receiver operating characteristic (ROC) curve was constructed and the area under the ROC curve was calculated. The best operating point was determined by Youden's index. The accuracy, sensitivity and specificity for predicting cervical lymph node metastasis by the best operating point were compared with those of 2-D US to evaluate the differences between the two methods.Results: Kappa analysis showed good interrater agreement (Kappa = 0.833 and 0.794, respectively). Rates of three-dimensional sonograms classified as I and II grade by three raters were 92.9%, 91.8% and 90.6%, respectively. There was no significant difference in accuracy for detecting infiltration into adjacent structures between 2-D and 3-D US. In three patients, 3-D US showed more spatial information missed in 2-D US. There was positive correlation between VI and N-staging (r = 0.726, P < 0.001). The area under the ROC curve was 0.903, which showed excellent accuracy for VI for predicting cervical lymph node metastasis. The analysis of the ROC curve showed that the largest value of Youden's index was 0.684, which corresponded to a VI value of 4.4565. This point was determined as the best operating point. There was no significant difference in accuracy for predicting cervical lymph node metastasis between VI and 2-D US (86% vs. 84%, P = 1.000). The specificity of VI was lower than that of 2-D US (77% vs. 94%, P = 0.031), but the sensitivity of VI was higher compared with that of 2-D US (94% vs. 73%, P = 0.022).Conclusions: Considerable quality of 3-D US sonogram and significant agreement between the raters indicate that it is feasible for 3-D US applying to the larynx. Three-dimensional gray scale volume rendering can provide more vivid information for ascertaining the spatial relationship between the body of laryngeal cancer and its adjacent structures. VI value of tumor obtained by three-dimensional color Doppler imaging may become a promising predictive factor for cervical lymph node metastasis in patients with laryngeal cancer.