Multislice Computed Tomography Assessment of Airway Patency Changes Associated with Mandibular Advancement Appliance Therapy in Supine Patients with Obstructive Sleep Apnea

Figure 3

The minimum area (MA) on multiplanar reconstruction (MPR) images. The slice datasets were coordinated as follows: (1) The median sagittal cross-sectional image was set by using the baseline (T1) data (window level/window width [WL/WW] was set to the CT-bone value of 500/2000 HU). (2) The craniocaudal direction was set with the upper end as the palatal pharyngeal space (PPS) and the lower end as the lowermost anterior point of the fourth cervical vertebrae (C4) on the MPR image by verifying on the median sagittal, axial, and coronal cross-sectional images. (3) The WL/WW was set to the airway component value of -662/724 HU, the site where the cross-sectional area within that range was the narrowest by verifying on the axial cross-sectional image was set as the MA, and the anteroposterior diameter, width, and cross-sectional area were measured. (4) The WL/WW was again set to the CT-bone value of 500/2000 HU, and the vertical distance (d-ma) from the PPS to the MA was measured on the median sagittal cross-sectional image. (5) The median sagittal cross-sectional image was set using data with the mandibular advancement appliance (MAA), and each d-ma obtained from the baseline data was reproduced as multislice computed tomography (MSCT) data with MAA. (6) The WL/WW was set to the airway component value of -662/724 HU, and the anteroposterior diameter, width, and cross-sectional area were measured by verifying on the axial cross-sectional image.