title: Standardization of thresholding for binary conversion of vocal tract modeling in computed tomography.
abstract: Postoperative head and neck cancer patients suffer from speech disorders, which are the result of changes in their vocal tracts. Making a solid vocal tract model and measuring its transmission characteristics will provide one of the most useful tools to resolve the problem. In binary conversion of X-ray computed tomographic (CT) images for vocal tract reconstruction, nonobjective methods have been used by many researchers. We hypothesized that a standardized vocal tract model could be reconstructed by adopting the Hounsfield number of fat tissue as a criterion for thresholding of binary conversion, because its Hounsfield number is the nearest to air in the human body. The purpose of this study was to establish a new standardized method for binary conversion in reconstructing three-dimensional (3-D) vocal tract models. CT images for postoperative diagnosis were secondarily obtained from a CT scanner. Each patient's minimum settings of Hounsfield number for the buccal fat-pad regions were measured. Thresholds were set every 50 Hounsfield units (HU) from the bottom line of the buccal fat-pad region to -1024 HU, the images were converted into binary values, and were evaluated according to the three-grade system based on anatomically defined criteria. The optimal threshold between tissue and air was determined by nonlinear multiple regression analyses. Each patient's minimum settings of the buccal fat-pad regions were obtained. The optimal threshold was determined to be -165 HU from each patient's minimum settings of the Hounsfield number for the buccal fat-pad regions. To conclude, a method of 3-D standardized vocal tract modeling was established.
authors.affiliation: Department of Maxillofacial Prosthetics, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan. inohmfp@tmd.ac.jp
authors.forename: Ken
authors.initials: K
authors.lastname: Inohara
authors.forename: Yuka I
authors.initials: YI
authors.lastname: Sumita
authors.forename: Naoto
authors.initials: N
authors.lastname: Ohbayashi
authors.forename: Shuichi
authors.initials: S
authors.lastname: Ino
authors.forename: Tohru
authors.initials: T
authors.lastname: Kurabayashi
authors.forename: Tohru
authors.initials: T
authors.lastname: Ifukube
authors.forename: Hisashi
authors.initials: H
authors.lastname: Taniguchi
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging; D000368:Aged; D005260:Female; D006258:Head and Neck Neoplasms / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods / Q000592:standards*; D008297:Male; D008437:Maxilla / Q000601:surgery; D008875:Middle Aged; D008953:Models, Anatomic; D009061:Mouth Mucosa / Q000000981:diagnostic imaging; D010027:Osteotomy; D011183:Postoperative Complications / Q000000981:diagnostic imaging; D019651:Plastic Surgery Procedures; D012015:Reference Standards; D012044:Regression Analysis; D012117:Resins, Synthetic; D013064:Speech Disorders / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards*; D014827:Vocal Cords / Q000000981:diagnostic imaging*
chemical_list: D012117:Resins, Synthetic