Method and computer for aiding determination of obstructive sleep apnea
A computer for aiding determination of Obstructive Sleep Apnea (OSA) includes a storage device storing with a medical image and a central processing unit (CPU). The CPU executes a method for aiding determination of OSA. The method for aiding determination of OSA includes the following steps. The medical image is obtained. An upper airway model is established. A narrowest cross-section and a nasopharyngeal boundary cross-section are defined in the airway model. A cross-sectional area of the narrowest cross-section and a cross-sectional area of the nasopharyngeal boundary cross-section are calculated. A stenosis rate is calculated according to the cross-sectional area of the narrowest cross-section and the cross-sectional area of the nasopharyngeal boundary cross-section. The stenosis rate is provided. In addition, in the method for aiding determination of OSA, a respiratory flow field simulation may be further performed to obtain and provide a flow field pressure distribution of the upper airway model.
1. A method for aiding determination of Obstructive Sleep Apnea (OSA), comprising:
obtaining a medical image;
establishing an upper airway model according to the medical image;
defining a narrowest cross-section having a smallest cross-sectional area orthogonal to a skull axis in the upper airway model and defining a nasopharyngeal boundary cross-section orthogonal to the skull axis in the upper airway model;
calculating a cross-sectional area of the narrowest cross-section and a cross-sectional area of the nasopharyngeal boundary cross-section;
calculating a stenosis rate according to the cross-sectional area of the narrowest cross-section and the cross-sectional area of the nasopharyngeal boundary cross-section;
generating an internal mesh data of the upper airway model;
setting a boundary condition comprising an inlet region, an outlet region, and a respiratory gas amount;
performing a respiratory flow field simulation according to the upper airway model, the internal mesh data, and the boundary condition, so as to obtain a flow field pressure distribution of the upper airway model;
calculating an upper airway pressure difference according to the flow field pressure distribution; and
establishing a first relation curve between the stenosis rate and the upper airway pressure difference, for aiding determination.
2. The method for aiding determination of OSA according to claim 1 , wherein the medical image is obtained according to a computed tomography scan (CT scan) of a part of the upper airway.
3. The method for aiding determination of OSA according to claim 1 , wherein the medical image is a file of Digital Imaging and Communications in Medicine (DICOM).
4. The method for aiding determination of OSA according to claim 1 , wherein the upper airway model is a three dimensional (3D) model.
5. The method for aiding determination of OSA according to claim 4 , wherein the step of establishing the upper airway model according to the medical image comprises:
processing the medical image in a thresholding segmentation means to obtain an upper airway image segmentation region; and
establishing the upper airway model corresponding to the upper airway image segmentation region with a Marching Cubes algorithm.
6. The method for aiding determination of OSA according to claim 1 , wherein the stenosis rate is
1.0
-
(
the
cross
-
sectional
area
of
the
narrowest
cross
-
section
the
cross
-
sectional
area
of
the
nasopharyngeal
boundary
cross
-
section
)
.
7. The method for aiding determination of OSA according to claim 1 , further comprising:
determining whether the stenosis rate is larger than a stenosis threshold.
8. The method for aiding determination of OSA according to claim 1 , further comprising:
determining whether the upper airway pressure difference is larger than a pressure difference threshold.
9. The method for aiding determination of OSA according to claim 1 , wherein the upper airway pressure difference is obtained according to respiratory flow resistance information generated by the flow field simulation.
10. The method for aiding determination of OSA according to claim 1 , wherein the upper airway pressure difference is obtained according to a mean pressure on surfaces of the inlet region and the outlet region.
11. The method for aiding determination of OSA according to claim 1 , further comprising:
establishing a second relation curve between the stenosis rate and apnea hypopnea indexes, for aiding determination.
12. A computer for aiding determination of Obstructive Sleep Apnea (OSA), comprising:
a storage device, for storing a medical image; and
a central processing unit (CPU), for executing the following steps:
obtaining the medical image;
establishing an upper airway model according to the medical image;
defining a narrowest cross-section having a smallest cross-sectional area orthogonal to a skull axis in the upper airway model and defining a nasopharyngeal boundary cross-section orthogonal to the skull axis in the upper airway model in the direction of the skull axis;
calculating a cross-sectional area of the narrowest cross-section and a cross-sectional area of the nasopharyngeal boundary cross-section;
calculating a stenosis rate according to the cross-sectional area of the narrowest cross-section and the cross-sectional area of the nasopharyngeal boundary cross-section;
generating an internal mesh data of the upper airway model;
setting a boundary condition comprising an inlet region, an outlet region, and a respiratory gas amount ;
performing a respiratory flow field simulation according to the upper airway model, the internal mesh data, and the boundary condition, so as to obtain a flow field pressure distribution of the upper airway model;
calculating an upper airway pressure difference according to the flow field pressure distribution; and
establishing a first relation curve between the stenosis rate and the upper airway pressure difference, for aiding determination.
13. The computer for aiding determination of OSA according to claim 12 , wherein the medical image is obtained according to a computed tomography scan (CT scan) of a part of the upper airway.
14. The computer for aiding determination of OSA according to claim 12 , wherein the medical image is a file of Digital Imaging and Communications in Medicine (DICOM).
15. The computer for aiding determination of OSA according to claim 12 , wherein the upper airway model is a three dimensional (3D) model.
16. The computer for aiding determination of OSA according to claim 15 , wherein the step of establishing the upper airway model according to the medical image comprises:
processing the medical image in a thresholding segmentation means to obtain an upper airway image segmentation region; and
establishing the upper airway model corresponding to the upper airway image segmentation region with a Marching Cubes algorithm.
17. The computer for aiding determination of OSA according to claim 12 , wherein the stenosis rate is
1.0
-
(
the
cross
-
sectional
area
of
the
narrowest
cross
-
section
the
cross
-
sectional
area
of
the
nasopharyngeal
boundary
cross
-
section
)
.
18. The computer for aiding determination of OSA according to claim 12 , wherein the CPU further executes the following step:
determining whether the stenosis rate is larger than a stenosis threshold.
19. The computer for aiding determination of OSA according to claim 12 , wherein the CPU further executes a following step:
determining whether the upper airway pressure difference is larger than a pressure difference threshold.
20. The computer for aiding determination of OSA according to claim 12 , wherein the upper airway pressure difference is obtained according to respiratory flow resistance information generated by the flow field simulation.
21. The computer for aiding determination of OSA according to claim 12 , wherein the upper airway pressure difference is obtained according to a mean pressure on surfaces of the inlet region and the outlet region.
22. The computer for aiding determination of OSA according to claim 12 , comprising:
establishing a second relation curve between the stenosis rate and apnea hypopnea indexes, for aiding determination.