Effect of Orthognathic Surgery on the Upper Airway System

摘要

Sleep apnea is a disease which has not been getting an adequate amount of attention in the research community for a long time. However, the strain on the cardiovascular system and other serious problems, such as daytime sleepiness and even neurocognitive dysfunction, that it causes may be severe in advanced cases of the illness, as such it can significantly affect the heart especially and lead to cardiac arrest. Thus, it has been receiving a lot of attention recently. Tampere University Hospital has a goal of creating a comprehensive upper airway airflow model for surgery outcome prediction. That requires knowledge of available models and analysis of static magnetic resonance images, among other things. This document deals with these two main issues.This thesis has two major parts, one of them being a literature review of sleep apnea and models used in airflow modelling in the upper airways. Modelling of airflow generally includes acquisition of a static upper airway system model (in the case of upper airway modelling) and then adding a dynamic component to it. The second part of this thesis deals with acquisition of the static model, which involves segmentation of MRI image sets from 3 patients (pre- and post-operative sequences). It also answers the question, whether the effect of orhtognathic surgery on the upper airway system can be seen from volumetric analysis of the segmented images and the segmented images themselves.The main methods of adding a dynamic component to the static model turned out to be computational fluid mechanics and finite element modelling, including their sub-methods, such as direct numerical simulation of large eddy simulation. As with the second part of the thesis, the volumetric segmentation data is rather inconclusive and should not be related solely for evaluation of the effect of orthognathic surgery on the upper airway system. It can be said, nonetheless, that the volume of the upper airway itself is rather easily obtainable and reliable. The images themselves, however, provide very visual information about that, and shifting of certain muscles and muscle groups and other structures can be seen.