A computational tool for simulation of phonosurgical procedures (Grant # R03 DC006801)

Principal Investigator: Eric Hunter

The designing and constructing stage of the model has commenced using the detailed three-dimensional laryngeal muscle data and a laryngeal cartilage database. To help with the design and flexibility of the model, the individual specimen results of laryngeal cartilage measures (44 laryngeal measures: 18 for the thyroid cartilage, 18 for the cricoid cartilage, and 8 for the arytenoid cartilage) for multiple specimens of human (male/female), canine, ovine was compiled in a single database. While previous studies have focused on average data, individual specimen data (and, thus, more detailed anatomy) are necessary to verify current biomechanical models which have been increasing in complexity and moving from generic to specific representations of functions (normal and/or abnormal) in a specific larynx. Individual subject data for four groups (sorted by cartilage) were gathered and recommendations for their use in the scientific community were made. [A paper entitled, “Individual Subject Laryngeal Dimensions of Multiple Mammalian Species for Biomechanical Models” by E.J. Hunter, and I.R. Titze was published in Annals of Otology, Rhinology and Laryngology. In addition, the electronic data has been made available for other researchers and modelers via E. J. Hunter and I.R. Titze. NCVS Memo No 09. Individual Subject Laryngeal Dimensions of Multiple Mammalian Species for Biomechanical Models: A Supplement. NCVS Online Technical Memo 09 February 2005, www.ncvs.org/ncvs/library/tech . Denver, CO.].

The range of vocal fold medialization/lateralization has been compiled from the literature to help experimental cross-validation of the proposed model and future models. It was found in a review of the literature that although there was general inter-study agreement was found in the range of vocal process motion, there was substantial variation. Best-practice guidelines and research avenues in future studies of vocal posturing were also outlined. [A paper entitled, “Review of range of arytenoid cartilage motion” by E.J. Hunter and I.R. Titze was published in ARLO].

E. J. Hunter and I. R. Titze. NCVS Memo No 09. Individual Subject Laryngeal Dimensions of Multiple Mammalian Species for Biomechanical Models: A Supplement. NCVS Online Technical Memo 09 February 2005. http://www.ncvs.org/ncvs/library/tech

E. J. Hunter and I. R. Titze. Review of range of arytenoid cartilage motion. Acoustic Research Letters Online 6 (3):112-117, 2005. [PMID: 16570110] http://scitation.aip.org/dbt/dbt.jsp?KEY=ARLOFJ&Volume=6&Issue=3

E. J. Hunter and I. R. Titze. Individual subject laryngeal dimensions of multiple mammalian species for biomechanical models. Ann.Otol.Rhinol.Laryngol. 114 (10):809-818, 2005. [PMID: 16285273]. http://www.annals.com/2005/Oct2005_abstracts.htm#809

The long-term goal of this project is to predict outcomes of laryngeal phonosurgery with physiologically based voice simulation. The proposed research will move towards this goal by developing a model of vocal fold posturing. Vocal fold posturing, a fundamental aspect of phonation control, is defined as adduction, abduction or elongation of the vocal folds. Because posturing is based on laryngeal joint mechanics and soft tissue deformation, fundamental theories of continuum mechanics are used to formulate this model. The application of continuum mechanics to laryngeal posturing requires an accurate geometric and mechanical description of various tissues in the larynx, such as the vocal ligament and intrinsic laryngeal muscles. Furthermore, because many of these tissues are fibrous and thus have distinct lines of action, a portrayal of passive and contractile stress contributions and fiber direction is needed. The specific aims of the current project are:

  1. To mathematically represent the orientation of differentiated laryngeal muscle bundles, allowing for distributed muscle forces over various cartilages.
  2. To create, with the distribution of intrinsic muscle bundles, a three-dimensional finite element model of vocal fold mechanics that can predict both the speed and the range of vocal fold medialization and lateralization.
  3. To simulate a Type I Thyroplasty phonosurgery and predict the resultant glottal configuration as well as the resultant stress distribution in the repaired vocal fold.

It is expected that the posturing model will have a significant impact on surgically based voice therapies, as well as on vocal fold modeling in general.