Virtual Laryngoscopy
Laryngoscopy is one of the clinically performed endoscopic evaluations that has not drawn much attention in terms of virtual imaging so far. This is rather surprising as virtual laryngoscopy (VL) is in many ways similar to bronchoscopy. It deals with an a
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Virtual Laryngoscopy A.J. AscHOFF and E.M. MERKLE
CONTENTS
3.1 3.2 3.3 3.4 3.5
Introduction 39 Pathology 39 Data Acquisition 40 Clinical Application 40 Summary 43 References 43
3.1 Introduction Laryngoscopy is one of the clinically performed endoscopic evaluations that has not drawn much attention in terms of virtual imaging so far. This is rather surprising as virtual laryngoscopy (VL) is in many ways similar to bronchoscopy. It deals with an aircontaining hollow organ that essentially forms the upper airways. Virtual bronchoscopy, on the other hand, has already been thoroughly explored by a number of researchers (BuTHIAU et al. 1996; FERRETTI et al. 1996; FLEITER et al. 1997; RODENWALDT et al. 1997; SILVERMAN et al. 1995; SUMMERS et al. 1996; VINING et al. 1996). They usually attempted to cover the entire tracheobronchial tree in one examination and optimized their imaging parameters for this purpose. Requirements for virtual laryngoscopy differ from those used for bronchoscopy. The larynx itself is smaller; accordingly the pathology tends to be smaller as well. This explains why higher spatial resolution is required. The larynx is divided into three anatomical regions. The supraglottic larynx includes the epiglottis, false vocal cords, ventricles, aryepiglottic folds, and arytenoids. The glottis includes the true vocal
A.J. ASCHOFF, MD; E.M. MERKLE MD Department of Radiology, University Hospital of Ulm, Germany
P. Rogalla et al. (eds.), Virtual Endoscopy and Related 3D Techniques © Springer-Verlag Berlin Heidelberg 2002
cords and the anterior and posterior commissures. The subglottic region begins approximately 1 em below the true vocal cords and extends to the lower border of the cricoid cartilage or the first tracheal ring. Virtual laryngoscopy is applicable for examining all three anatomical regions.
3.2
Pathology
There are numerous pathologic entities suitable for virtual laryngoscopy, including laryngeal tumors and subglottic stenoses. The detection and staging of laryngeal cancer using virtual laryngoscopy might come to be of clinical benefit. The estimated number of new cases of laryngeal cancer in the United States in 1999 is 8600 for men and 2000 for women (LANDIS et al. 1999). The estimated number of laryngeal cancer deaths during the same time period is 3300 for men and 900 for women. Similarly, the estimated number of new cases of pharyngeal cancer in the United States in 1999 is 6100 for men and 2200 for women, while the estimated number of pharyngeal cancer deaths in 1999 is 1500 for men and 600 for women. Thus, laryngeal and pharyngeal cancer together account for approximately 1.5% of all estimated new cancer cases. Histologically, the vast majority oflaryngeal cancers are of the squamous cell type. Squamous cell subtypes include keratinizing and nonkeratinizing as well as well differentiated to poorly differentiated grades. There are also a variety of nonsquamous cell laryngeal cancers (SESSIONS et al. 1997). The staging system is clinical and is based on the best possible estimate of t
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