Remodeling of living human nasal cavity under the assistance of acoustic rhinometry technique

doi:10.4236/jbm.2013.12007

Paper Menu >>

Journal Menu >>

Journal of Biosciences and Medicines, 2013, 1, 28-32 JBM

http://dx.doi.org/10.4236/jbm.2013.12007 Published Online October 2013 (http://www.scirp.org/journal/jbm/)

OPEN ACCESS

Remodeling of livin g human nasal cavity under the

assistance of acoustic rhinometry technique*

Jun Zhang

Advanced Technology of Transportation Vehicle Key Laboratory of Liaoning Province, Dalian Jiaotong University, Dalian, China

Email: [email protected]

Received 2013

ABSTRACT

Acoustic rhinometry could numerically describe up-

per airway condition of air draft by drawing a graph

plotting the distance from the nostril vs. the cross-

sectional area. Some d ecreases on the graph corres-

pond to the typical anatomic structures of human

nasal cavity. The 3-dimensional, computing fluid dy-

namic model of the same person was developed based

on computed tomography scans. The veracity of the

CFD model was valued by contrasting the relevant

areas of stenosis site between the model and the AR

graph. The aim in this study is to make clear how to

use an AR to help improve and enrich the CFD model

with the information of graph acquired from the

measurement. The combination of AR and CT can be

used to establish a living human nasal cavity model

with higher significant information content.

Keywords: Acoustic Rhinometry; Nasal Cavity;

Computed Tomography; 3-Dimensional Reconstruction;

Computing Fluid Dynamic Model

1. INTRODUCTION

The human nose is the first line of defense that every-

body has to protect itself from outer invasion all one’s

life. With the currently development of research towards

the pathogenic mechanism and the application of iatrical

apparatus such as endoscopes, it has been gradually

proved that many diseases such as rhinitis or nasosinusi-

tis are related to the nasal anatomy [1]. Abnormal nasal

structure leads to abnormal nasal function and conse-

quently, the abnormal nasal function causes further ab-

normalities of nasal structure. Many rhino-diseases so

occur. By simulating the structure and function of the

nasal cavity with 3-dimensional reconstruction theory

with a computer, we can profoundly explore the outbreak,

treatment and prevention of nasal diseases. Nowadays,

there is a focus on the quantificational study of the rela-

tionship between environmental stimulus and body re-

modeling [2] which is called self-adaptation by estab-

lishing of computing fluid dynamic (CFD) models and

analyzing the results with inversion methods. In this pa-

per, the 3-dimensional model was reconstructed based on

computed tomography (CT) images. More instruments

should be applied to help adjust the model. Acoustic ref-

lectometry is a helpful tool that can measure the coronal

section information of the nasal cavity.

Acoustic reflectometry, which generally include

acoustic rhinometry (AR) and acoustic pharyngometry

(AP) i n the ear-nose-throat (ENT) department clinic, is a

relatively new modality of evaluating the construction

and function of the nasal cavities, and the technique can

quantify upper airway airing status [3]. A computer

draws a graph (Figure 1 show an AR report in detail).

under corresponding AR analysis system plotting the

distance from the nostril relative to the CSA. In this

graph, the x-axis represents the distance into the nasal

cavity, and the y-axis represents the 2-dimensional area

relative to distance. Most subjects demonstrate some

sudden decreases, which look like a series of valleys on

the graph. The valleys appear at ar ound 2 cm, 4 cm, 6 cm

and 8 cm, which are termed the minimal CSA 1 to 4 [4].

Numerical studies using realistic nasal geometries

have not been possible until recent advances in both

computer hardware and software. Up to the present,

many researchers have conducted numerical simulations

of human nasal airflow. Among them, Ravi P. Subrama-

niam et al.’s [5] is the most detailed of these studies. In

their numerical work, they studied airflow through the

whole human nose in a three-dimensional model and

used computational fluid dynamics simulations to re-

search the nasal airflow field for steady-state inspiration

in an anatomically accurate computer reconstruction of

both sides of the human nasal passages. And the project

included the posterior nasal airway and nasopharynx.

The model simulated in this study contains the whole

nasal region from nostril till to nasopharynx (see Figure

2) include maxillary sinus. The volunteers were asked for

acoustic rhinometry examine soon af ter CT scans. Acous-

*Project of Liaoning Province Education Department, LS2010030.

J. Zhang / Journal of Biosciences and Medicines 1 (2013) 28-32

Figure 1. AR report. Label a, b, c and d refer to MCSA1,

MCSA2, MCSA3 and MCSA4 respectively.

Figure 2. Lateral view of the left human nose.

Labels a-g mark locations of the coronal sections

in Figu re 1.

tic rhinometry was widely used in clinic and research

ever since it was invented. Bulent Mamikoglu and Ste-

ven M. Houser [6,7] used it to diagnose nasal septal dev-

iation and mild sleep apnea respectively which are the

main diseases it can diagnose.

2. NASAL ANATOMY

The nasal passages have a complex geometry [8]. A lat-

eral outline of the human nasal passages with various

sections labeled is shown in Fig ure 2. We assume a

standing position in this discussion of the nasal anatomy

and in our model simulations and acoustic rhinometry

measurements. The anterior three-quarter of the nose is

divided into two enantiomorphic parts by the nasal sep-

tum. Entrance to these two cavities is through the nostrils,

which are slightly slanted with respect to the hard palate

about 45˚. The nasal vestibule is a funnel-shaped region

extending abou t 1 - 2 cm from the anterior tip of the nose

and includes the nostril section. The vestibule leads to

the constricted nasal valve region, the posterior boundary

of which is roughly presumed to be the anterior limit of

the inferior turbinate [9]. The nasal valve, which has

been conventionally defined as the site of narrowest

cross-sectional area of the nasal passage posterior to the

nostril opening, accounts for more than half of the total

nasal resistance [10]. Here, we define the exact location

and orientation of the nasal valve follow the tradition

opinion [9,11] in referring broadly to the nasal valve

region. The nasal vestibule and valve region form a flow-

limiting structure that is liable to disturb when the pres-

sure difference between the ambient and the respired air

in this portion of the airway exceeds a critical value. In

our research, we assume the boundary of the nasal air-

way to be rigid throughout. In contrast with this rigid

characterization, the nasal airway is, in fact, a dynami-

cally changing structure. Most individuals demonstrate a

coordinated nasal cycle where the nasal passages on one

side of the nose are occluded to various degrees due to

tissue congestion for a certain period of time [12]. This

physiological effect will lead to dynamically changing

differences in the airflow profiles on the two sides of the

nose. Here we ignored that effect.

At the constriction around the nasal valve region, the

airway undergoes a right-angled bend toward the nasal

floor, with a sudden increase in the coronal cross-sec-

tional area of the passages [9]. As a consequence, airflow

in humans has been reported to become turbulent in this

region [12]. The region between the nasal valve region

and the nasopharynx is referred to as the main nasal air-

way.

3. METHODS

Thirty volunteers (15 males and 15 females) were ran-

domly selected for our study. These patients were fully

evaluated by nasal anterior rhinoscopy and endoscopy.

Our initial physical examination allowed us to qualita-

tively designate a patient’s septum as having no devia-

tion or being mildly, moderately, severely, or markedly

severely deviated. All CT studies were done for evalua-

tion of each patient’s sinus problems and for the final

3-parameter reconstruction. The layer thickness was 3

mm to make the model more accurate. The CT scans and

AR graphs were concentratively obtained in one day. The

ages of the patients ranged from 25 to 55 years (median

30 years).

AR testing was carried out without a vasoconstrictor

and 15 minutes when the computer been steady running.

The test was performed in an acoustically adequate en-

vironment, with control of the following factors accord-

ing to the Standards of the International Committee on

AR [13] in order to guarantee the accuracy of the test: a)

the patients remained in the air-conditioned room for 30

minutes before the measurement, b) temperature and

humidity were kep t at 21˚C and 50% - 6 0% respectively,

c) stabilization of the patients’ heads: All volunteers were

examined in the sitting position on a straight-back

J. Zhang / Journal of Biosciences and Medicines 1 (2013) 28-32

chair with head support during measuring, d ) position of

the wave tube: wave tube was placed horizontally paral-

lel to the ground. Volunteers were requested to fix their

gaze at a point on the opposite wall straight ahead to the

gaze level. e) Use of Vaseline to prevent leakage, selec-

tion of proper silica gel coupler and f) training the con-

trol of respiration. All AR studies were performed by the

same examiner when measurement was performing. In

order to guarantee the accuracy of the test, at least three

curves were obtained for each examination. After each

measurement, the nasal adaptor was removed from the

nostril and after a few seconds reconnected. A new mea-

surement was then obtained. The results were considered

to be adequate when the coefficient of variation was less

than 10% [14]. A mean curve for each nostril was then

constructed for each volunteer based on the recorded

curves.

The 3-dimensional, finite-element models were de-

veloped from CT scans of the noses of those volunteers.

The scans provided 37 - 43 contiguous coronal images of

each nose at intervals of 3 mm. The points, which were

on the edge of the nasal cavity to the nasal wall, were

first picked up from the gray-scaled CT images. Then the

airway perimeters traced from the images appeared. Se-

condly, connecting the points on the perimeters, we con-

structed the 2-dimensional, finite-element lines of each

coronal slice. After every piece of perimeters was deli-

neated, the third step is to link the lines of one piece to

next together to form the 3-dimensional, finite-element

closed area of the nasal airways. At last, we formed the

columns with the closed area. Thus, the 3-dimensional,

finite-element model of the nasal airways was finished.

The reconstruction utilized commercial software AN-

SYS6.1 (ANSYS Inc., USA). The finite-element models

used 190,000 - 300,000 3D FLOTRAN elements, com-

prising 34,000 - 63,000 nodes. The following conditions

were imposed on the spatial boundaries of the flow field:

a) a no-slip condition was imposed at the surface of the

nasal airway walls (vs = 0 m/s); b) a str ess-free condition

was established at the outlet. This condition is satisfied if

the normal velocity gradients are set to zero at the outlet

(v = constant); c) at the nostril surface (the flow inlet),

stationary pressure, which equal to atmosphere pressure

in numerical value (p = 101325 Pa) were specified. We

applied the finite-element method (FEM) using the

commercial fluid dynamics solution package of AN-

SYS6.1 to solve the equations of motion for airflow. The

FEM obtains solutions to th e full Navier-Stokes and con-

tinuity equations within each element of the fin iteele-

ment mesh.

4. RESULTS

Thirty cases were performed in this study and here we

take one for illustration. The volunteer was a healthy,

26-year-old, nonsmoking northeast China male. The vo-

lunteer’s septum was no deviation and sinus was normal.

The FEM model contained 42 layers of CT images, and

was meshed into 271,168 elements with 59,382 nodes

after reconstruction. The AR offered numerical value of

CSA each 0.24 cm from the anterior nostril between −7.5

and 20 cm inwards. Connecting the discrete points with

smooth curve, we got the AR graph. Here we intercepted

the curve from −4 - 12 cm for analysis.

The FEM model and the AR graph of the same nasal

cavity are paralleling which is shown in Figure 3. The

longitudinal curve-axis across the nasal airway passage

from the nostril to the nasopharynx referred to the spread

direction of the sound waves and it was corresponding to

the X-axis of the AR graph below. We set a coordinate

point each two centimeter (0, 2, 4, 6, 8, and 10 cm) on

the curve. From the AR graph, we can see four valleys

appear at the positions of about 2, 4, 6 and 8cm. They

correspond to the classical anatomic sites of nasal cavity

as declared above and the corresponding sectional pat-

terns at each point of the model are shown in Figure 4.

The patterns meet the description of valleys. Similarly,

we can get the pattern and area of any cross -section of

nasal cavity.

5. DISCUSSIO N

In the present clinical studies, d eviation of the nasal sep-

tum (DNS) is one of the most common diagnoses in

otorhinolaryngology practice. AR has been extensively

used in the otorhinolaryngologic clinic to diagnose DNS

since it was introduced to medical field. Furthermore, th e

diseases relation to the function and structure of upper

airway such as obstructive sleep apnea (OSA), adenoids

hypertrophy (AH) of children and so on can all be diag-

nosed by AR. The acoustic reflection technique is repro-

ducible, noninvasive, and free from potential side effects.

The good correlation between AR graph and nasal area

Figure 3. Meshed model of human nasal cavity

and its AR graph.

J. Zhang / Journal of Biosciences and Medicines 1 (2013) 28-32

Figure 4. Sectional pattern of nasal cavity model at 2, 4, 6, 8

and 10 cm along the direction of sound waves.

adds to the potential of this technique. Integrated with

some other tools, such as rhinomanameter, AR could be

applied to more extensive fields.

This study describes how to use the AR technique to

assess a 3-dimensional model of nasal cavity. The me-

thod of 3-dimensional construction based on CT scans in

this paper is widely used in the medical model construc-

tion. CT detects the nasal cavity wall with transmitted

technique, while AR does with reflected technique. The

AR and the CT technique are complementary to each

other. Their testing results can be compared to assess if

the nasal model is acceptable. Moreover, the results be-

tween CFD simulations of the airflow profile and the AR

graph can also examine the quality of the model. In this

way, we can receive more amount of objective informa-

tion from the model of the nasal cavity. In brief, they all

offer objective documentation, however, are all useful in

the reconstruction of nasal cavity by combined of each

other.

Knowledge of airflow in the human nose is important

for understanding many aspects of the biology and pa-

thology of the respiratory tract. We get to know that ab-

normal nasal structure leads to abnormal nasal function

and as a consequence, abnormal nasal function causes

further abnormalities of nasal structure. Simulating the

relationship between structure and function of nasal cav-

ity with 3-dimensional reconstruction theory and CFD

analysis by a computer, we can deeply research the prin-

ciple of the outbreak, treatment and prevention of nasal

diseases. Nowadays, there is a focus on the quantifica-

tional study of the relationship between environmental

stimulus and body remodeling by inversion methods and

establishing of CFD models. In this paper, the 3-dime n -

sional model was reconstructed based on CT images. AR

scan was applied to help value the model. It shows that

the combination of AR and CT is helpful and offers

another way for the modelin g of living human nasal cav-

ity.

6. CONCLUSION

AR is a relatively new technique that quantifies upper

airway condition of obstruction. It may provide the re-

searcher with objective coronal CSA data of nasal cavity

beyond that of any other physical examination. A com-

puter draws a graph plotting the distance from the nostril

relative to the cross-sectional area; thus the 3-dime n -

sional nasal cavity is projected into a 2-dimensional

graph. In this graph, some sudden decreases emerge,

which look like a series of valleys. Such segments on the

graph correspond to the typical anatomic structures of

human nasal cavity, where sudden changes of air pres-

sure and flow velocity occur because of the changes of

nasal airway status. The 3-dimensional, CFD models are

developed based on CT scans. Connecting the contours

from CT images by their position to a closed volume, a

3-dimensional nasal passage model is then reconstructed.

The airflow can be simulated under commercial software

or some other programs. CT and AR are complementary

techniques since CT acquires boundary information by

the transmission of X-rays, while AR does it by the ref-

lection of sound waves. We can value the veracity of the

CFD model by contrasting the relevant areas of stenosis

site between the model and AR graph. The aim in this

study was to make clear how to use an AR to help im-

prove and enrich the CFD model with the information of

graph acquired from the measurement. It is proved that

the combination of AR technique and CT is a way for the

establishing of a living human nasal cavity model to be

of more amount of information.

REFERENCES

[1] Uliyanov, Y.P. (1997) Surgical reconstruction of nasal

serodynamics. XVI World Congress of Otolaryngology

Head and Neck Surgery, Sydney, 1591-1595.

[2] Wenzhi, Z. (2004) Experimental study on the stress and

remodeling adaptation of vivo bone tissue and its biolog-

ical model. Doctoral Dissertation of Dalian University of

Technology, Dalian.

[3] Corey, J.P., Gungor, A. and Nelson, R. (1998) Normative

standards for nasal cross sectional area by race as meas-

ured by acoustic rhinometry. Otolaryngology Head and

Neck Surgery, 119, 389-393.

http://dx.doi.org/10.1016/S0194-5998(98)70085-3

[4] Corey, J.P., Kemker, B.J. and Nelson, R. (1997) Evalua-

tion of the nasal cavity by acoustic rhinometry in normal

and allergic subjects. Otolaryngology Head and Neck

Surgery, 117, 8-22.

http://dx.doi.org/10.1016/S0194-5998(97)70201-8

[5] Subramaniam, R.P., Richardson, R.B. and Morgan, K.T.

(1998) Computational fluid dynamics simulations of in-

spiratory airflow in the human nose and nasopharynx.

Inhalation Toxicology, 10, 91-120.

http://dx.doi.org/10.1080/089583798197772

[6] Mamikoglu, B., Houser, S.M. and Akbar, I. (2000) Acou-

stic rhinometry and computed tomography scans for the

diagnosis of nasal septal deviation, with clinical correla-

tion. Otolaryngology Head and Neck Surgery, 123, 61-68.

http://dx.doi.org/10.1067/mhn.2000.105255

[7] Houser, S.M., Mamikoglu, B. and Aquino, B.F. (2000)

Acoustic rhinometry findings in patients with mild sleep

apnea. Otolaryngology He ad and Neck Surgery , 126,

J. Zhang / Journal of Biosciences and Medicines 1 (2013) 28-32

475-480. http://dx.doi.org/10.1067/mhn.2002.124848

[8] Negus, V. (1958) The comparative anatomy and physi-

ology of the nose and paranasal sinuses. Livingstone,

London.

[9] Proctor, D.F. (1982) The upper airway. Nose, Uppe r Air-

way Physiology and the Atmospheric Environment, 23-

43.

[10] Haight, S.J. and Cole, P. (1983) Site and function of the

nasal valve. Laryngoscope, 49-55.

[11] Lanza, D.C. and Clerico, D.M. (1995)Anatomy of the hu-

man nasal passages. Handbook of Olfaction and Gusta-

tion, 53-73.

[12] Cole, P. (1982) Upper respiratory airflow. Nose, Upper

Airway Physiology and the Atmospheric Environment,

163-183.

[13] Hilberg, O.F. and Pedersen, (2000) Acoustic rhinometry:

Recommendations for technical specifications and stan-

dard operating procedures. Rhinology, 16, 3-17.

[14] Brown, I.G., Zamel, N. and Hoffstein, V. (1986) Pharyn-

geal crosssectional area in normal men and women. Jour-

nal of Applied Physiology, 61, 890-895.