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                     DENTAL RADIOLOGY
                     VOLUME, ASYMMETRY AND RECIPROCAL
 Original Articles
                     RELATIONSHIPS BETWEEN PARANASAL SINUSES:
                     A 3D SEGMENTATION STUDY ON HEAD CT-SCANS
                     Giulia Andrea Guidugli1,2a , Daniele Maria Gibelli1b , Michaela Cellina3c                           , Antonio Giancarlo Oliva3d,
                     Luisa Barni1e , Patrizia Sartori1f , Chiarella Sforza1g*
                     1
                      Department of Biomedical Sciences for Health, University of Milan, I-20133 Milan, Italy
                     2
                      Department of Orthopedics and Traumatology, Lugano Regional Hospital, CH-6900 Lugano, Switzerland
                     3
                      Department of Radiology, Fatebenefratelli Hospital, ASST Fatebenefratelli Sacco, I- 20157 Milan, Italy

                     a
                       MD; e-mail: giulia.a.guidugli@hotmail.it; ORCIDiD: https://orcid.org/0000-0002-3473-9888
                     b
                       MD, PhD; e-mail: daniele.gibelli@unimi.it; ORCIDiD: https://orcid.org/0000-0002-9591-1047
                     c
                       MD; e-mail: michaela.cellina@asst-fbf-sacco.it; ORCIDiD: https://orcid.org/0000-0002-7401-1971
                     d
                       MD; e-mail: linforisonanza@gmail.com;
                     e
                       BSc, PhD; e-mail: luisa.barni@unimi.it; ORCIDiD: https://orcid.org/0000-0002-2414-408X
                     f
                      BSc, PhD; e-mail: patrizia.sartori@unimi.it; ORCIDiD: https://orcid.org/0000-0002-4806-2337
                     g
                       MD, Professor; e-mail: chiarella.sforza@unimi.it; ORCIDiD: https://orcid.org/0000-0001-6532-6464

                     ABSTRACT                                                                                   https://doi.org/10.25241/stomaeduj.2020.7(1).art.3

                     Introduction Very little is known about the morphology of paranasal sinuses, especially with respect to
                     symmetry.
                     Methodology The head CT-scans of 100 patients (50 male, 50 female) were retrospectively analyzed. The
                     volume segmentation of frontal, sphenoid and maxillary sinuses was performed through semi-automatic
                     segmentation. An asymmetry index was extracted, and differences according to sex and side were assessed
                     through ANOVA test (p<0.05). Pearson test was applied to verify possible correlation between age and
                     volume and asymmetry index in different paranasal sinuses and sexes (p<0.05).
                     Results On average, male sinuses were larger in volume than female ones (p<0.01). Generally, volumes
                     of the three sinuses were significantly related each other in both sexes (correlation coefficients ranging
                     between 0.34 and 0.58). In both sexes, the maxillary sinus was less asymmetric than the other two types,
                     without significant sex-related differences (p>0.05). Significant inverse correlations between sinus volume
                     and asymmetry index were found for the sphenoid and maxillary sinuses in males, and for the maxillary sinus
                     in females. No correlation of sinus volume or asymmetry index with age was found, with the exception of
                     maxillary volume/age in females.
                     Conclusion The present results may find practical applications in planning surgical procedures involving
                     paranasal sinuses.
                     KEYWORDS
                     Anatomy; CT-Scan; Segmentation; Paranasal Sinuses; Surgery.

                     1. INTRODUCTION                                                                     the most variable of all the anatomical structures of
                                                                                                         the entire body [3,4]. Genetic diseases, infectious
                     The paranasal sinuses are air-filled anatomical                                     and environmental conditions may influence these
                     structures inside the skull and facial bones forming                                variations [5]. A detailed knowledge of anatomy
                     a complex interconnected system communicating                                       and anatomic variations of paranasal sinuses has
                     with the nasal cavities through an ostium [1,2]. There                              become mandatory in the recent years due to
                     are four paired paranasal sinuses: the maxillary,                                   advances in imaging technology and in functional
                     frontal and sphenoid sinuses, and the ethmoid cells,                                endoscopic sinus surgery (FESS) which represents
                     with great inter- and intra-individual variations.                                  the current standard treatment for chronic paranasal
                     Shape and size of the paranasal sinuses are probably                                sinus pathology [6]. To detect sinus pathologies,

                                    OPEN ACCESS This is an Open Access article under the CC BY-NC 4.0 license.
                                    Peer-Reviewed Article
                         Citation: Guidugli GA, Gibelli DM, Cellina M, Oliva AG, Barni L, Sartori P, Sforza C. Volume, asymmetry and reciprocal relationships between paranasal
                         sinuses: a 3D segmentation study on head CT-scans. Stoma Edu J. 2020;7(1):20-27.
                         Received: January 13, 2020; Revised: February 07, 2020; Accepted: February 10, 2020; Published: February 11, 2020
                         *Corresponding author: Prof. Chiarella Sforza, MD, Department of Biomedical Sciences for Health, University of Milan, Via Luigi Mangiagalli, 31, I-20133
                         Milano, MI, Italy
                         Tel/Fax: +39 02 5031 5384,
                         e-mail: chiarella.sforza@unimi.it
                         Copyright: © 2020 the Editorial Council for the Stomatology Edu Journal.




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Metrical characteristics of paranasal sinuses
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                                                                                                                                        Original Articles
Figure 1. Example of 3D segmentation on CT-scan: in the lower left box, the 3D models of frontal, sphenoid and maxillary sinuses.


determine therapy, plan endonasal surgeries and                             height and width of frontal sinuses continue to
avoid careless manipulation, detailed knowledge of                          increase until the age of 20 related to the growth
their morphology has a crucial clinical value [7].                          pattern and grade of craniofacial structures [11,12].
Despite the great importance of this topic, the                             During the sinus development, struts, structural com-
morphological characteristics of paranasal sinuses                          ponents and bony deposition are crucial to protect
are incompletely known. Most of the studies per-                            against external physical forces. Several inter-
formed on adults analyzed the maxillary sinuses,                            individual differences in shape and behavior
and very few investigations considered the                                  patterns can be noticed. According to Kim et al.
maxillary, frontal and sphenoid sinuses together,                           [8], three different explanations can be considered.
and especially their symmetry [8]. The development                          The first one is that the incessant conflict between
of the paranasal sinuses starts in the late embryonic                       epithelial expansion (formation of cavities) and
period and continues into young adulthood [8].                              bony deposition (protection from the external
The maxillary sinus is the first sinus to appear and                        environment) can undergo different patterns, and
starts from ectodermal cells between the 7th and                            produces a great variability. The second and third
10th week of development and grows until 17 years                           hypotheses try to explain differences between
of life. It develops from a shallow groove expanding                        individuals through heredity: for the second one
from the primitive infundibulum to the maxilla.                             pneumatization is genetically determined and for
After birth, the growth of the maxillary sinus is                           the latter hypothesis the degree of pneumatization
biphasic: the first spurt occurs during the first                           also depends on the pathological involvement
three years then again between the ages of 7–12.                            during childhood [8]. In recent years, the three-
After the age of 12, the growth slowly continues                            dimensional segmentation of medical image data
until adulthood. The sphenoid sinus develops as                             has been largely applied to the morphological
evagination of the spheno-ethmoidal recess about                            evaluation of the upper airways, included the para-
the 3rd intrauterine month and reaches full size at                         nasal sinuses. The volume of air cavities is the simplest
the age of 7. In extreme cases of pneumatization                            and most significant parameter for the evaluation
the optic nerve and internal carotid artery may lie                         of the paranasal sinuses [13]. Several investi-
naked within the sinus cavity [9]. The frontal sinus                        gations analyzed the volume of paranasal sinuses
is the most variable; its development begins during                         [8,10,14-17], but little is known about their
the 16th prenatal week as a direct continuation of                          symmetry, and the calculation of asymmetry indices
the embryonic infundibulum and frontal recess                               has been performed only in forensic contexts
superiorly, or by upward migration of anterior eth-                         [17,18]. In the present study, we segmented CT-
moidal air cells to penetrate the inferior aspect of                        scan images to create three-dimensional models
the frontal bone between its outer and inner tables.                        of the maxillary, frontal and sphenoid sinuses, and
The right and left sides of the frontal sinuses develop                     calculated their volume. The aim of the study was
independently as a result of bone resorption and                            to investigate inter and intra-individual variations
septations [10]. It remains as a cul de sac within the                      and possible correlations of the sinuses’ volume
frontal bone till 2 years of age. The pneumatization                        and pneumatization in a large sample of adults.
process continues till the age of 9, but the volume,                        The results will improve knowledge concerning the


Stoma Edu J. 2020;7(1): 20-27                                                                    pISSN 2360-2406; eISSN 2502-0285          21
                     Guidugli GA. et al.
www.stomaeduj.com


 Original Articles    Table 1. Volume of paranasal sinuses in 100 healthy subjects (mean±SD).

                                                  Frontal sinuses                             Sphenoid sinuses                               Maxillary sinuses

                                        Right              Left            Total      Right           Left            Total         Right              Left          Total

                         Males        4.2 ± 2.2        5.4 ± 3.6     9.6 ± w5.04     5.4 ± 3.6      5.6 ± 3.4      10.9 ± 5.3     16.4 ± 5.1        15.9 ± 5.6    32.3 ± 10.4

                       Females        2.2 ± 1.4        2.7 ± 1.8       4.9 ± 2.8     4.4 ± 2.6      3.9 ± 2.2      8.3 ± 2.9      13.2 ± 3.8        13.1 ± 3.6    26.3 ± 6.9

                         M+F          3.2 ± 2.1        4.0 ± 3.1       7.2 ± 4.7     4.9 ± 3.2      4.7 ± 2.9      9.6 ± 4.4      14.8 ± 4.8        14.9 ± 4.9    29.3 ± 9.3

                     All values are expressed in cm3

                      Table 2. Correlation coefficients among                       Table 3. Correlation coefficients among age, sinus volumes and a
                     sinus volumes.                                                symmetry indices.
                                   Frontal Sphenoid Maxillary                                                      Volume                             Asymmetry
                       Frontal                    0.34*           0.36**                      Sex      Frontal Sphenoid Maxillary        Frontal       Sphenoid     Maxillary
                      Sphenoid      0.58**                        0.36**            Age    Females      -0.02       -0.04       -0.07       -0.14        -0.06        0.29*
                      Maxillary      0.23         0.47**                            Age     Males        -0.13       -0.21      -0.24       0.14         -0.14        0.16
                     Female values are in italics; *p<0.05; **p<0.01               Female values are in italics; *p<0.05


                     morphological characteristics of paranasal sinuses.                             (Fig. 1) [19]. Volume was automatically calculated
                                                                                                     through VAM® (Vectra Analysis Module, version
                     2. METHODS AND MATERIALS                                                        2.8.3, Canfield Scientific Inc., USA) [20].
                                                                                                     Intra-operator repeatability of segmentation through
                     2.1. Sample                                                                     ITK-SNAP had already been tested: no significant
                     For this study, 100 head CT-scans were selected                                 differences between repeated segmentations and
                     from the database of a hospital in Northern Italy and                           volume measurements were found, with a random
                     analyzed retrospectively. The CT-scans were anony-                              error explaining less than 1% of sample variance [21].
                     mized according to local and international ethic                                The sinus side prevalence was assessed for every pair
                     rules. The study followed the guidelines of the                                 of sinuses, and an asymmetry index was calculated
                     Helsinki Declaration and was approved by the local                              as follows:
                     ethical committee (7331/2019). The mean age of the                              |(volumer - volumel) / (volumer + volumel) x 100 |
                     male patients was 49.32 ± 18.9 years (range, 21-91
                     years), while the mean age of the female patients was                           Where volumer is the volume of the right sinus,
                     57.1 ± 22.8 years (range, 20-91 years). No differences                          volumel the volume of the left sinus. The index
                     were found in the age distribution between males                                ranges from 0 (perfect symmetry) to 100 (totally
                     and females (Student’s t test, p>0.05). The most                                asymmetrical).
                     frequent clinical requests for CT-scan were screening
                     for fractures in case of trauma (57.3%), suspected                              2.4. Statistical analysis
                     sinusitis (20.0%), neurological symptoms (12.7%).                               The normal distribution and homoscedasticity
                     Subjects with paranasal sinuses aplasia, chronic                                for volumes and asymmetry index were assessed
                     paranasal sinus pathology, edentulism, maxillofacial                            respectively through Jarque-Bera test and Bartlett
                     fractures or congenital craniofacial abnormalities,                             tests. Tests were run through the MATLAB statistic
                     or any pathological conditions involving paranasal                              toolbox. Possible statistically significant differences
                     sinuses were excluded from the study.                                           in volume and asymmetry index according to sex
                                                                                                     and type of sinus were assessed through the two-
                     2.2. CT-scan acquisition                                                        way ANOVA test. In case of statistically significant
                     All CT-scans were acquired through the same                                     differences according to type of sinus, post-hoc
                     instrument, a second generation dual-source sca-                                tests were performed through the Tukey’s Honestly
                     nner, Somatom Definition Flash (Siemens, Forchheim,                             Significant Difference (HSD), separately for males
                     Germany). The acquisition parameters were: kV: 120;                             and females. Pearson correlation coefficients
                     mAs: 320; collimation: 40 x 0.6 mm; tube rotation: 1                            were calculated between age, sinus volume and
                     sec; reconstruction thickness: 3 mm; reconstruction                             asymmetry index.
                     filters: H21s smooth for soft tissues and H60 sharp                             A p value of 0.05 or less was considered significant.
                     for bone.
                                                                                                     3. RESULTS
                     2.3. Data collection
                     Volume segmentation from the DICOM files was                                    The volume measurements are listed in Table 1. On
                     performed by a single operator using a semi-auto-                               average, male sinuses were larger in volume than
                     matic segmentation with the freeware ITK-SNAP                                   female ones (F=38.87, p<0.0001), with the maxillary



    22               Stoma Edu J. 2020;7(1):20-27                                                                            pISSN 2360-2406; eISSN 2502-0285
Metrical characteristics of paranasal sinuses
                                                                                                                                                       www.stomaeduj.com




                                                                                                                                                     Original Articles
                                                                                                    Figure 2. Distribution of side prevalence in
                                                                                                   the analyzed patients (M, males; F, females).


 Table 4. Asymmetry indices in the analyzed paranasal
sinuses (mean±SD).

                      Frontal        Sphenoid           Maxillary
   Males            22.28 ± 18.36   36.96 ± 26.00       7.47 ± 8.40

  Females           28.69 ± 18.59   37.89 ± 27.89       8.11 ± 8.51

    M+F             25.48 ± 18.66   37.43 ± 26.83       7.79 ± 8.42

All values are %.


sinus being about three (sphenoid sinus) and four
(frontal sinus) times larger than the other ones
(F=387.75; p<0.0001). Post-hoc HSD tests found
that both the frontal and sphenoid sinuses were
significantly smaller than the maxillary one in both
males and females (p<0.01); in addition, in females
also the difference between frontal and sphenoid
sinuses was significant (p<0.01). No significant sex
x sinus interaction was found (F=1.96, p=0.1427).                      Figure 3. Correlation between maxillary sinus volume (X axis) and
The volumes of the three sinuses were significantly                   asymmetry index (Y axis) in males (open circles, continuous line) and in
                                                                      females (closed circles, interrupted line). Both regressions are significant
related to each other in both sexes, except for the                   (p = 0.01).
maxillary and frontal sinuses volumes in males (Table
2). However, in all cases the correlation coefficients                more asymmetric than the maxillary one (p<0.01
were generally low, ranging between 0.34 and 0.58.                    for both comparisons in both sexes), while the
No correlation of sinus volume with age was found                     difference between the frontal and sphenoid
(Table 3).The side prevalence was assessed for every                  sinuses was significant only in males (p<0.01). No
pair of sinuses (Fig. 2). In both males and females the               significant sex differences (F=1.4, p=0.2377) and sex
left frontal sinus was prevailing in about two-thirds                 x sinus interactions were found (F=0.7, p=0.4974).
of patients (68% males and 66% females). For the                      No correlations of sinus asymmetry with age were
sphenoid sinus, the larger volume was in the right                    found, except for the maxillary sinus in females:
side in 52% of patients (both males and females). The                 older women had more asymmetric sinuses (Table
right maxillary sinus was prevalent in 60% of males                   3).Significant inverse correlations between the sinus
and in 48% of females. Only 26% of subjects had the                   volume and asymmetry index were found for the
same side prevailing for all sinuses (17% left side and               sphenoid (r= -0.28, p<0.05) and maxillary (r= -0.39,
9% right side). The asymmetry indices calculated                      p<0.01) sinuses in males, and for the maxillary sinus
for the three pairs of sinuses and according to sex                   in females (r= -0.37, p<0.01): in all occasions, larger
are reported in Table 4. In both sexes, the maxillary                 sinuses were less asymmetric (Fig. 3).
sinus was the less asymmetric of the other two, its
asymmetry index being approximately one third of                      4. DISCUSSION
the frontal sinus and one fifth of the sphenoid sinus
(F=58.53, p<0.0001). Post hoc tests found that both                   The morphology of paranasal sinuses represents
the frontal and sphenoid sinuses were significantly                   a long-time debated issue. In the last decades,


Stoma Edu J. 2020;7(1): 20-27                                                              pISSN 2360-2406; eISSN 2502-0285                             23
                     Guidugli GA. et al.
www.stomaeduj.com



                                                                                                                                                                                                                       [17]. In addition, very few studies used an asymmetry
 Original Articles    Table 4. Paranasal sinuses volume in literature (mean±SD).
                     All values are cm3.                                                                                                                                                                               index in order to evaluate the side prevalence for
                                                                                                                                                                                                                       every pair of sinuses [8,22,23]. Only Kim et al. [8]
                                                                                                                                                                                                                       and Yoshino et al. [24] provided some calculations




                                                                                                                                                                                                       29.3±9.3
                                                                                           18.0±6.0
                                                                                                                                                                                                                       of the frontal sinus asymmetry but within forensic
                                           Total




                                                                                                            41.6
                                                                                                                                                                                                                       contexts. They proposed a “bilateral asymmetry
                                                                                                                                                                                                                       index” (BAI) calculated dividing the smaller sinus
                                                                                                                                                                                                                       by the larger one multiplied by 100 and used it for




                                                                                                                                                                                                       26.3±6.9
                                                                                           16.0±5.0
                                                           21.8±7.8

                                                                           22.7±9.8
                                           Females



                                                                                                                                                                                                                       classification purposes. This index maximizes the



                                                                                                            34.6
                       Maxillary sinuses




                                                                                                                                                                                                                       asymmetry values, and it was considered useful for
                                                                                                                                                                                                                       individual identification, but it has not been applied




                                                                                                                                                                                                       32.3±10.4
                                                                           31.0±11.4


                                                                                                                                                                                                                       to surgery. As far as sinus volumes are concerned,
                                                                                           19.8±6.3
                                                           32.0±9.0




                                                                                                                                                                                                                       the comparison with existing literature highlights
                                           Males




                                                                                                            43.7
                                                                                                                                                                                                                       differences in values according to authors: these
                                                                                                                                                                                                                       discordances may be explained by ethnic variations
                                                                                                                                                                                                                       and by discrepancies in defining cranial structure.




                                                                                                                                                                                                       9.6±4.5
                                           Total




                                                                                                                                                                                                                       As far as the Italian population is concerned, values
                                                                                                            13.7




                                                                                                                                                                                                                       for sphenoid volume are well in line with those
                                                                                                                                                                                                                       already published in a previous publication [25].
                                                                                                                                                                        6.09±3.63

                                                                                                                                                                                           7.07±3.72
                                                                           7.88±3.0




                                                                                                                                                                                                                       Interestingly, different authors reporting data from
                                           Females




                                                                                                                                                                                                       8.3±2.9
                                                                                           6.1±3.2
                                                           8.7±2.4




                                                                                                                                                                                                                       the same population show discordances in volume
                                                                                                            10.6
                       Sphenoid sinuses




                                                                                                                                                                                                                       measurements [10,14,15]; this detail may confirm
                                                                                                                                                                                                                       the importance of ethnic variability which may be
                                                                                                                                                                                                                       extended also to geographical location of different
                                                                                                                                                                                                       10.9±5.3
                                                                                                                                                                        6.1±3.4

                                                                                                                                                                                           7.4±3.5
                                                                                           7.7±4.0
                                                           9.7±2.6

                                                                           8.5±4.2
                                           Males




                                                                                                                                                                                                                       population groups. Another possible variant which
                                                                                                            14.7




                                                                                                                                                                                                                       may explain discordances in literature is the variety
                                                                                                                                                                                                                       of techniques for volume extraction: however,
                                                                                                                                       3.4±2.7

                                                                                                                                                         4.1±2.7




                                                                                                                                                                                                       7.2±4.7
                                                                                           5.8±4.1




                                                                                                                                                                                                                       Karakas and Kavakli found results similar to those
                                           Total




                                                                                                                                                                                                                       of the present study for all three pairs of sinuses,
                                                                                                            6.8




                                                                                                                                                                                                                       although they used the Cavalieri principle to extract
                                                                                                                                                                                                                       volume, and not a segmentation software (Table
                                           Females




                                                                                                                                                                                                                       5). On the other side, the Cavalieri principle was
                                                                                                                                                                                                       4.9±2.8
                                                                                           4.1±2.9
                                                           3.5±3.1

                                                                           3.5±2.4




                                                                                                                                                                                                                       also used by Emirzeoglu et al. [15] to estimate the
                                                                                                            4.4
                       Frontal sinuses




                                                                                                                                                                                                                       sinus volume, obtaining slightly different results
                                                                                                                                                                                                                       from those currently calculated with semi-automatic
                                                                                                                                                                                                                       segmentation for frontal and sphenoidal sinuses,
                                                                                                                                                                                                       9.6±5.0
                                                           8.8±4.5

                                                                           8.4±4.0

                                                                                           7.5±4.3
                                           Males




                                                                                                                                                                                                                       and smaller values for the maxillary sinus. The use of
                                                                                                            7.6




                                                                                                                                                                                                                       the Cavalieri principle for the paranasal sinuses has
                                                                                                                                                                                                                       been criticized because of the complex morphology
                                           Age/side


                                                           21-25 y




                                                                                                                                                                                                                       of these organs. The method estimates the organ
                                                                           >25 y




                                                                                                                                       Right



                                                                                                                                                                        Right



                                                                                                                                                                                                       Total
                                                                                           Total

                                                                                                            Total



                                                                                                                                                         Left



                                                                                                                                                                                           Left




                                                                                                                                                                                                                       volume starting from a sample of cross sections, but
                                                                                                                                                                                                                       they may not be sufficiently representative for the
                                           Population




                                                                                                                                                                                                                       organ shape, thus producing unreliable results.
                                                                                                                                                                               Brazilian
                                                                                                                                              Turkish
                                                                                           Turkish
                                                                 Turkish




                                                                                                            Korean




                                                                                                                                                                                                                       Nonetheless, even if Kim et al. [18] used a segmen-
                                                                                                                                                                                                       Italian




                                                                                                                                                                                                                       tation software similar to that applied in the
                                                                                                                                                                                                                       current study, their results are pretty different,
                                                                                                                                                                   Oliveira et al., 2017
                                                                                                            Kim et al., 2010 (8)
                                                                                                                                   Yuksel et al., 2016




                                                                                                                                                                                                                       with somewhat smaller values for the frontal sinus,
                                                                                       Emirzeoglu et al.,




                                                                                                                                                                                                       Present Study




                                                                                                                                                                                                                       and larger for the sphenoidal and maxillary ones.
                                                        Karakas et al.,




                                                                                                                                                                                                                       Moreover, also the segmentation protocol used by
                                                                                       2007 (14)
                                                        2005 (1)




                                                                                                                                                                                                                       Oliveira et al. [16] in their analysis of the sphenoid
                                                                                                                                                                   (15)




                                                                                                                                                                                                                       sinus morphology was similar to the present one, but
                                                                                                                                   (9)




                                                                                                                                                                                                                       they obtained 1.2-1.6 larger volumes in both sexes.
                     the technological improvements and widening                                                                                                                                                       Therefore, possible differences due to the segmen-
                     of applications of paranasal sinuses surgery have                                                                                                                                                 tation method cannot be excluded, although its
                     required further investigations to clarify some aspects                                                                                                                                           influence cannot be clearly separated from the
                     still unexplored, such as the asymmetry of these                                                                                                                                                  ethnic variability. Anyway, but for the differences in
                     structures. To the best of our knowledge, several                                                                                                                                                 volumetric measurements, all studies are concordant
                     studies have assessed the volume of the paranasal                                                                                                                                                 on the sexual dimorphism of paranasal sinuses, with
                     sinuses but very few studies have considered the                                                                                                                                                  male structures always larger than the female ones
                     frontal, maxillary and sphenoid sinuses together                                                                                                                                                  [10,14,15]. An interesting result from the present



    24               Stoma Edu J. 2020;7(1):20-27                                                                                                                                                                                     pISSN 2360-2406; eISSN 2502-0285
Metrical characteristics of paranasal sinuses
                                                                                                                                                      www.stomaeduj.com



study concerns the correlation between the volumes                           tigations measuring the volume of paranasal




                                                                                                                                                    Original Articles
of different paranasal sinuses: Emirzeoglu et al. [15]                       sinuses, the systematic study of their asymmetry has
found a high correlation between the volumes                                 been neglected so far. The asymmetry index applied
of the maxillary-frontal and maxillary-ethmoidal                             in the current study is of easy calculation, and can
sinuses for female subjects, while in the male group                         complement the analysis of sinus volumes.
the volumes of all sinuses correlated well with each
other except for the frontal-sphenoid sinuses. These                         5. CONCLUSIONS
data confirm that paranasal sinuses are somehow
linked one type to another: generally, the similarities                      The current results show that paranasal sinuses
in size of different types of paranasal sinuses may                          in the single individual share some similarities
be explained by genetic variables involved in their                          in size possibly explained by underling genetic
development [8]. However, although statistically                             characteristics modulated by local modification
significant, the correlation coefficient is low (under                       due to environmental and acquired factors. Aging
0.70) in all cases; this additional information                              does not seem to be a key factor in explaining sinus
seems to demonstrate that other factors (probably                            dimensions and asymmetry, at least in healthy
acquired and/or environmental) may be involved                               adults, but the two aspects are significantly related,
in sinuses development. Finally, the present study                           with a larger asymmetry in small sinuses.
provided novel data concerning the morphological                             The present data may provide a contribution
characteristics of paranasal sinuses: first, both their                      for improving our knowledge concerning the
volume and asymmetry seem not to be related to                               development of paranasal sinuses and possible
age, with the exception of maxillary sinus volume                            factors involved in this process. Also, surgical
in females. Cohen et al. explored the same topic                             treatments involving paranasal sinuses should
and found that both maxillary and sphenoid                                   consider these characteristics to better plan complex
sinuses volumes are related with age (they decrease                          interventions.
with age) in both sexes [17]. These discordances
may be explained in different ways: with respect                             CONFLICT OF INTEREST
to the maxillary sinuses, possible alterations of
the upper dental profile may represent a bias in                             The authors declare no conflict of interest.
assessing volumetric differences. On the other
side, differences in sphenoid volume need to be                              AUTHORS CONTRIBUTIONS
explained, although the ethnic variable may have
a role. Another innovative information concerns                              GG: conception and design of the study, data acquisition, data
the significant correlation between the asymmetry                            analysis, drafting the article, final approval. DG: conception
index and volume (the smallest the sinuses, the most                         and design of the study, data analysis, data interpretation,
asymmetric). This has not been reported in literature                        drafting the article, revising the article, final approval. MC: data
yet, and proves that asymmetry and volume are                                acquisition, data analysis, drafting the article, final approval.
somehow linked. However, again the coefficients                              AO: data interpretation, revising the article, final approval. LB:
are too small to exclude other possible variables in                         data acquisition, revising the article, final approval. PS: data
determing paranasal sinuses morphology. In the                               interpretation, revising the article, final approval. CS: conception
present study the volume segmentation of frontal,                            and design of the study, data interpretation, revising the article,
sphenoid and maxillary sinuses was performed using                           final approval.
semi-automatic segmentation with the freeware
ITK-SNAP. Although literature reports several inves-                         Drs. Guidugli and Gibelli equally contributed to this work.



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                                                                                                    Giulia Andrea GUIDUGLI
                                                                                                                            MD
                                                                                     Department of Orthopedics and Traumatology
                                                                                                        Lugano Regional Hospital
                                                                                                    CH-6900 Lugano, Switzerland


                     CV
                     Dr. Giulia Andrea Guidugli is a medical doctor currently attending a Residency program in Orthopedics and Traumatology
                     (Lugano Regional Hospital, Switzerland). Her fields of research are the morphological and metrical assessment of anatomical
                     characteristics of bones, paranasal sinus and upper airways, including the analysis of facial anatomy in both healthy and
                     pathological conditions through the study of CT and 3D reconstruction of the upper airways.




                                                                                                        Daniele Maria GIBELLI
                                                                                                                   MD, PhD
                                                       LAFAS-Laboratory of Functional Anatomy of the Stomatognathic System
                                                                               Department of Biomedical Sciences for Health
                                                                                                         University of Milan
                                                                                                         I-20133 Milan, Italy

                     CV
                     Dr. Daniele Maria Gibelli is a senior researcher in Human Anatomy in Department of Biomedical Sciences for Health, University
                     of Milan, Italy. His fields of research are the morphological and metrical assessment of anatomical characteristics of bones
                     and teeth, including anatomical dimorphism, their modification with age, ethnic variability and the analysis of individualizing
                     characteristics. He also deals with the analysis of facial anatomy both in healthy and pathological conditions, for studies
                     concerning the assessment of facial symmetry, modifications with mimicry and anatomical uniqueness of facial structures.




    26               Stoma Edu J. 2020;7(1):20-27                                                              pISSN 2360-2406; eISSN 2502-0285
Metrical characteristics of paranasal sinuses
                                                                                             www.stomaeduj.com




Questions




                                                                                           Original Articles
1. When does the development of paranasal sinuses start?
qa. Childhood;
qb. Fetal period;
qc. Puberty;
qd. Adult age

2. On average, the volume of paranasal sinuses:
qa. Is higher in females than in males;
qb. Is equal in males and females;
qc. Is higher in males than in females;
qd. Cannot be analysed through 3D segmentation

3. Which paranasal sinus is the least asymmetric?
qa. Frontal sinus;
qb. Sphenoid sinus;
qc. Maxillary sinus;
qd. Ethmoid cells.

4. For which paranasal sinus a positive correlation was found between volume and age?
qa. Frontal sinus;
qb. Sphenoid sinus;
qc. Maxillary sinus;
qd. None.




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