Tracking the Hyoid Bone in Videofluoroscopic Swallowing Studies Patrick M. Kellen a , Darci Becker b , Joseph M. Reinhardt a , and Douglas van Daele b a Dept. of Biomedical Engineering, The University of Iowa, Iowa City, IA 52242 b Dept. of Otolaryngology, The University of Iowa, Iowa City, IA 52242 ABSTRACT Difficulty swallowing, or dysphagia, has become a growing problem. Swallowing complications can lead to malnutrition, dehydration, respiratory infection, and even death. The current gold standard for analyzing and diagnosing dysphagia is the videofluoroscopic barium swallow study. In these studies, a fluoroscope is used to image the patient ingesting barium solutions of different volumes and viscosities. The hyoid bone anchors many key muscles involved in swallowing and plays a key role in the process. Abnormal hyoid bone motion during a swallow can indicate swallowing dysfunction. Currently in clinical settings, hyoid bone motion is assessed qualitatively, which can be subject to intra-rater and inter-rater bias. This paper presents a semi-automatic method for tracking the hyoid bone that makes quantitative analysis feasible. The user defines a template of the hyoid on one frame, and this template is tracked across subsequent frames. The matching phase is optimized by predicting the position of the template based on kinematics. An expert speech pathologist marked the position of the hyoid on each frame of ten studies to serve as the gold standard. Results from performing Bland-Altman analysis at a 95% confidence interval showed a bias of 0.0 ± 0.08 pixels in x and −0.08 ± 0.09 pixels in y between the manually-defined gold standard and the proposed method. The average Pearson’s correlation between the gold standard and the proposed method was 0.987 in x and 0.980 in y. This paper also presents a method for automatically establishing a patient-centric coordinate system for the interpretation of hyoid motion. This coordinate system corrects for upper body patient motion during the study and identifies superior-inferior and anterior-posterior motion components. These tools make the use of quantitative hyoid motion analysis feasible in clinical and research settings. Keywords: Segmentation, motion, swallowing, dysphagia, videofluoroscopy 1. INTRODUCTION Dysphagia, or difficulty swallowing, has become a growing problem. The elderly population is most at risk of developing dysphagia, but dysphagia also arises from a variety of medical ailments. In a study of 50-79 year olds, 35% reported some type of difficulty swallowing. 1 Stroke, multiple sclerosis, Parkinson’s disease, and gastroesophogeal reflux disease have all been shown to increase the risk of dysphagia. 2 Swallowing complications can lead to malnutrition, dehydration, respiratory infection, and even death. The most widespread effect is a general decrease in quality of life as patients lose enjoyment in eating, have anxiety about eating, and eat less. 3 The gold standard for analyzing and diagnosing dysphagia is the videofluoroscopic barium swallow study. Videofluoroscopy permits observation of the dynamic aspects of swallowing at high temporal resolution. In these studies, a fluoroscope is used to image the patient ingesting barium solutions of different volumes and viscosities. A clinician observes images of the swallow, then qualitatively assesses indicators such as the amount of bolus left in the valleculae after the swallow, transit time of the bolus, or elevation of the hyoid bone. This paper presents a method to track a user-defined template of the anterior end of the hyoid bone. The hyoid bone, a u-shaped bone, helps anchor many key muscles involved in swallowing. From the lateral view, the anterior end of the hyoid appears as a dark ellipse in the fluoroscopy images while the rest of the bone is barely distinguishable. At the beginning of the swallow, the hyoid is at rest while the bolus is in the oral cavity, (see Fig. 1(a)). Next, the inversion of the epiglottis diverts the bolus from the trachea to the esophagus, Send correspondence to JMR: joe-reinhardt@uiowa.edu; phone 1 319 335 5634; 1402 SC, Univ. of Iowa, Iowa City, IA 52242 Honorable Mention Poster Award Medical Imaging 2008: Image Processing, edited by Joseph M. Reinhardt, Josien P. W. Pluim, Proc. of SPIE Vol. 6914, 69142D, (2008) 1605-7422/08/$18 · doi: 10.1117/12.771198 Proc. of SPIE Vol. 6914 69142D-1 2008 SPIE Digital Library -- Subscriber Archive Copy