Impact du grossissement de l'image sur l'exactitude des mesures verticales effectuées sur des radiographies panoramiques numériques

Thesis

Reference

Impact du grossissement de l'image sur l'exactitude des mesures verticales effectuées sur des radiographies panoramiques

numériques

EL HAGE, Marc

Abstract

L'objet de cette étude est d'évaluer l'impact du grossissement de l'image sur l'exactitude des mesures verticales effectuées dans la région mandibulaire postérieure sur des radiographies panoramiques numériques. A l'aide de trois logiciels d'imagerie, et sous trois grossissements de l'image à l'écran, deux observateurs ont effectué des mesures de longueur d'implants dentaires insérés dans un modèle en résine. L'erreur entre la valeur mesurée et la longueur réelle était proche de zéro pour tous les grossissements et logiciels. Le pourcentage de mesures égales à la longueur réelle était le plus élevé (83.3%) avec le fort grossissement (10 :1) et en dessous de 30% avec le faible grossissement (1.9 :1). Les grossissements forts et moyens ont permis d'effectuer des mesures verticales exactes, avec les trois logiciels d'imagerie. Le faible grossissement ne devrait pas être utilisé pour les mesures verticales sur les orthopantomogrammes lors de la planification d'implants mandibulaires postérieurs.

EL HAGE, Marc. Impact du grossissement de l'image sur l'exactitude des mesures verticales effectuées sur des radiographies panoramiques numériques. Thèse de doctorat : Univ. Genève, 2016, no. Méd. dent. 744

URN : urn:nbn:ch:unige-877733

DOI : 10.13097/archive-ouverte/unige:87773

Available at:

http://archive-ouverte.unige.ch/unige:87773

Disclaimer: layout of this document may differ from the published version.

Clinique Universitaire de Médecine Dentaire

Département de Réhabilitation Oro-faciale

Unité de Radiologie dento- maxillo-faciale

Thèse préparée sous la responsabilité du Docteur Lydia Vazquez et du Professeur Anselm Wiskott

« Impact du grossissement de l’image sur l’exactitude des mesures verticales effectuées sur des

radiographies panoramiques numériques. »

Thèse

présentée à la Faculté de Médecine de l’Université de Genève

pour obtenir le grade de Docteur en médecine dentaire par

Marc Philippe EL HAGE du

Liban

Thèse n° 744

Genève

2016

Remerciements

Mes sincères remerciements s’adressent…

... Au Docteur Lydia Vazquez pour ses précieux conseils ainsi que sa grande disponibilité et son respect sans faille des délais serrés de relecture.

... Au Professeur Anselm Wiskott pour la confiance qu'il m'a accordée en acceptant de s’associer à ce travail.

... Au Professeur Jean-Pierre Bernard qui a été à l’origine de ce travail doctoral, et qui n’a jamais manqué de m’encourager durant sa préparation.

… A ma femme et mes filles, Ines, Lila, et Kira pour leur patience et leur amour inconditionnel.

... A mes parents pour le soutien infaillible.

Remerciements

Mes sincères remerciements s’adressent…

... Au Docteur Lydia Vazquez pour ses précieux conseils ainsi que sa grande disponibilité et son respect sans faille des délais serrés de relecture.

... Au Professeur Anselm Wiskott pour la confiance qu'il m'a accordée en acceptant de s’associer à ce travail.

… A ma femme et mes filles, Ines, Lila, et Kira pour leur patience et leur amour inconditionnel.

... A mes parents pour le soutien infaillible.

Résumé

L'objet de cette étude est d'évaluer l’impact du grossissement de l’image sur l’exactitude des mesures verticales effectuées dans la région mandibulaire postérieure sur des radiographies panoramiques numériques. A l’aide de trois logiciels d'imagerie, et sous trois grossissements de l’image à l’écran, deux observateurs ont effectué des mesures de longueur d’implants dentaires insérés dans un modèle en résine. L'erreur entre la valeur mesurée et la longueur réelle était proche de zéro pour tous les grossissements et logiciels. Le pourcentage de mesures égales à la longueur réelle était le plus élevé (83.3%) avec le fort grossissement (10 :1) et en dessous de 30% avec le faible grossissement (1.9 :1). Les grossissements forts et moyens ont permis d’effectuer des mesures verticales exactes, avec les trois logiciels d'imagerie. Le faible grossissement ne devrait pas être utilisé pour les mesures verticales sur les orthopantomogrammes lors de la planification d'implants mandibulaires postérieurs.

Table des matières

Introduction ... 2

Publication originale ... 6

Conclusions ... 24

Bibliographie ... 25

Introduction

Les implants dentaires ont des taux élevés de succès à long terme et sont largement utilisés en médecine dentaire pour remplacer une ou plusieurs dents manquantes.^{1, 2} Lors de la planification de la pose d’implants dentaires, l’examen clinique avec palpation de la région édentée ainsi que l’examen radiologique préopératoire, permettent d’évaluer la disponibilité ainsi que la morphologie de l’os alvéolaire. Les examens radiologiques à but diagnostic sont une source croissante d’exposition de la population générale à des rayonnements ionisants.^{3, 4} Le praticien devrait connaître les dangers potentiels liés à l’utilisation de rayons X, et être en mesure de produire des radiographies de bonne qualité pour le diagnostic, tout en maintenant la dose à laquelle est exposée le patient au niveau le plus bas qu’il soit raisonnablement possible d’atteindre (As Low As Reasonably Achievable ou principe ALARA).⁵ Il existe un risque augmenté de cancer radio-induit (cancer du cerveau, de la glande thyroïdienne et des glandes salivaires) lié à la prise de clichés dentaires, bien que les doses liées aux radiographies dentaires soient faibles.^6-8 Les techniques d’imagerie en 2 dimensions (intra-orale, panoramique, céphalométrie), traditionnellement préconisées en chirurgie implantaire, ont une dose effective comprise entre 1 et 26 microSievert (µSv).^9-11 Les techniques d’imagerie en 3 dimensions telles que la tomodensitométrie et la tomographie volumique à faisceau conique (CBCT), sont également utilisées, mais les doses d’irradiation sont plus élevées (36 à 1410 µSv).¹²

Lors de la planification d’implants dentaires dans les segments postérieurs de la mandibule, il est important de localiser le trajet du canal mandibulaire au niveau du futur site implantaire (Figure 1) afin d’éviter de léser le nerf alvéolaire inférieur lors du forage et/ou de la pose de l’implant.¹³ Kiyak et coll.¹⁴ ont rapporté que, dans 43,5% des cas, une paresthésie labiale inférieure était présente deux semaines après la pose d’implants mandibulaires; Bartling et coll.¹⁵ ont rapporté que 8,5% des patients se plaignaient d’une altération des sensations de l’hémi-lèvre inférieure

et/ou du menton, et Ellies¹⁶ a enregistré, dans un questionnaire rétrospectif concernant les modifications sensorielles, 37% de sensations altérées un mois après la pose de l'implant.

Figure 1. Evaluation de la hauteur osseuse disponible au dessus du canal mandibulaire sur une radiographie panoramique numérique.

(a) hauteur osseuse disponible (distance entre le bord supérieur du canal mandibulaire et le sommet de la crête osseuse) (b) Le foramen mentonnier ainsi que le trajet du canal mandibulaire gauche.

Les radiographies panoramiques sont couramment utilisées en implantologie.^{15, 17} Bien que la nécessité de techniques d’imageries en coupe a été fortement recommandée,^18-23 la radiographie panoramique est considérée comme l'examen standard pour la planification du traitement implantaire car elle occasionne une faible dose d’irradiation tout en révélant les données radiologiques nécessaires au traitement implantaire.^17,23,25 Vazquez et coll.¹³ ont déterminé l'incidence de la survenue de paresthésies labiales inférieures après la pose d’implants dans le segment mandibulaire postérieur, en utilisant une radiographie panoramique argentique comme seul examen préopératoire. Ils ont conclu que la radiographie panoramique peut être considérée

comme un outil d'évaluation préopératoire sûr pour la pose d’implants dans le secteur mandibulaire postérieur. De plus, il s’agit d’un examen simple, rapide, économique qui n’occasionne qu’une faible dose d’irradiation. Ces auteurs confirment que lorsqu’une distance de sécurité d'au moins 2 mm au-dessus du canal mandibulaire est respectée, la radiographie panoramique semble être suffisante pour évaluer la hauteur osseuse disponible avant l'insertion d'implants dans les secteurs mandibulaires postérieurs. Ces mêmes auteurs ont ensuite montré que les radiographies panoramiques numériques permettent d’effectuer des mesures verticales avec une précision et une reproductibilité adéquates dans les segments prémolaires et molaires mandibulaires et peuvent donc elles aussi être utilisées dans la planification pré-implantaire.^{25, 26} Divers logiciels d’imagerie numérique ainsi que les visionneuses Digital Imaging and Communication in Medicine (DICOM) sont utilisés par les cliniciens dans leur pratique quotidienne. Les avantages de ces logiciels d'imagerie comprennent l'archivage et le partage des images, la manipulation des propriétés radiologiques tels que le contraste, la luminosité et la netteté ainsi que des outils numériques de mesures. Plusieurs auteurs ont examiné l’exactitude des mesures linéaires sur des images acquises par CBCT.^27-32 Gaia et coll.³³ ont utilisé deux logiciels d'imagerie afin de comparer la précision ainsi que l’exactitude des mesures linéaires sur les images de CBCT réalisées avant une ostéotomie maxillaire de Le Fort I. Vazquez et coll. ont analysé l’impact de logiciels d’imagerie et l’impact d’artéfacts métalliques liés à la présence d’implants dentaires sur l’exactitude des mesures verticales dans les segments mandibulaires postérieurs.³⁴

En revanche, l’exactitude des mesures verticales linéaires sur les radiographies panoramiques numériques évaluées avec différents logiciels d'imagerie dentaire n'a pas été rapportée dans la littérature. De plus, sur leur écran d'ordinateur, les praticiens utilisent la fonction du grossissement d’image qu'ils considèrent comme étant la plus adaptée pour leur pratique quotidienne. Pour la radiographie panoramique numérique, aucune étude dans la littérature n’a

évalué, avec différents logiciels d'imagerie, l'impact du grossissement de l'image radiologique à l’écran sur la précision des mesures verticales linéaires dans la région mandibulaire postérieure.

L'objet de cette étude in vitro est d'évaluer l’impact de trois agrandissements de l'image radiologique à l’écran sur l’exactitude des mesures verticales, effectuées dans la région mandibulaire postérieure sur des radiographies panoramiques numériques, à l’aide de trois logiciels d'imagerie : Kodak Dental Imaging Software (KDIS) (version 6.12.32.0; Kodak Dental Systems, Carestream Health, Rochester, NY), le logiciel web Weasis (version 1.2.5; Weasis Team, Genève, Suisse) et la visionneuse libre DICOM OsiriX (version 1.2 64-bit; Pixmeo, Genève, Suisse).

Publication originale

Marc EL HAGE, Jean-Pierre BERNARD, Christophe COMBESCURE, Lydia VAZQUEZ.

Impact of digital panoramic radiograph magnification on vertical measurement accuracy.

Int J Dent. 2015;2015:452413. doi: 10.1155/2015/452413. Epub 2015 Oct 19.

Impact of digital panoramic radiograph magnification on vertical measurement accuracy.

(Short title: impact of image magnification on measurement accuracy)

AUTHORS: Marc EL HAGE, DDS, MS^*, Jean-Pierre BERNARD, MD^**, Christophe COMBESCURE, PhD^***, Lydia VAZQUEZ, MD, DMD^****

* Lecturer, Oral Surgery and Implantology Unit, Division of Oral and Maxillofacial Surgery, Department of Surgery, Faculty of Medicine, Geneva University Hospitals, Geneva, Switzerland; Medical Director, Ardentis Clinique Dentaire Lausanne SA, Swiss Dental Clinics Group, Switzerland

** Professor and former Dean, Dept. of Oral Surgery, Oral Medicine, Oral and Maxillofacial Radiology, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland

*** Biostatistician, Department of Health and Community Medicine, Center of Clinical Research and Division of Clinical Epidemiology, Faculty of Medicine, Geneva University Hospitals, Geneva, Switzerland

**** Assistant Professor, Department of Orofacial Rehabilitation, Oral and Maxillofacial Radiology, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland

Disclosure: The authors declare that there is no conflict of interest regarding the publication of this manuscript.

Reprint requests and correspondence to: Marc El Hage, DDS, MS, Oral Surgery and Implantology Unit, Division of Oral and Maxillofacial Surgery, Department of Surgery, Faculty of Medicine, Geneva University Hospitals, 19 Rue Barthélémy-Menn, 1205 Geneva, Switzerland. Phone: 41 (22) 3794026, Fax: 41 (22) 3794082, Email: marc.hage.el@gmail.com

ABSTRACT

Objectives: The purpose of this panoramic radiography study was to assess the impact of image magnification on the accuracy of vertical measurements in the posterior mandible. Methods: Six dental implants, inserted in the posterior segments of a resin model, were used as reference objects. Two observers performed implant length measurements using a proprietary viewer with two pre-set image magnifications: the low (1.9:1) and the medium (3.4:1) image magnification.

They also measured the implant lengths in two Digital Imaging Communications in Medicine viewers set at low (1.9:1), medium (3.4:1) and high (10:1) image magnifications. Results: The error between the measured and the real implant length was close to zero for all three viewers and image magnifications. The percentage of measurements equal to the real implant length was the highest (83.3.%) for the high image magnification and below 30% for all viewers with the low image magnification. Conclusions: The high and medium image magnifications used in this study allowed accurate vertical measurements, with all three imaging programs, in the posterior segments of a mandibular model. This study suggests that a low image magnification should not be used for vertical measurements on digital panoramic radiographs when planning an implant in the posterior mandible.

KEY WORDS: dental implant; panoramic; radiographic magnification; accuracy.

INTRODUCTION

Panoramic radiography, a standard examination tool for planning of posterior mandibular dental implants, provides adequate radiographic evaluation with a low radiation dose.^1-5 In routine dental practice, proprietary dental imaging software programs as well as Digital Imaging Communications in Medicine (DICOM) viewers are used by clinicians for measurements on two and three-dimensional images. Several authors have reported on the accuracy of linear measurements on cone beam computed tomography (CBCT) images.^6-9 Gaia et al.⁹ used two imaging software programs to compare the precision and accuracy of linear measurements on CBCT images performed for Le Fort I osteotomy. Schulze et al.¹⁰ examined the precision and accuracy of measurements on digital panoramic radiography under two image magnifications.

The authors did the measurements with a single software program and concluded that high image magnification (2:1) lowered the measurement accuracy.

Clinicians use the image magnification setting on their computer screen that they perceive as being the most adapted for their daily practice. To the best of our knowledge, no studies on digital panoramic radiography have assessed, with different imaging software programs, the impact of image magnification on the accuracy of on-screen linear vertical measurements in the posterior mandible.

The purpose of this in vitro digital panoramic radiography study was to assess, with three imaging software programs, the impact of image magnification on the accuracy of vertical measurements in the posterior mandible.

MATERIAL AND METHODS:

Reference object

Eight standard diameter (4.1 mm) regular neck Straumann® dental implants (Straumann AG, Basel, Switzerland) were inserted bilaterally in a radiopaque custom-made resin model, duplicated from a Straumann® mandibular model, into sites corresponding to the canine, first and second premolar and first molar position. The implants were used as reference objects and their length was 8mm or 10mm alternatively (Fig. 1).

Fig. 1. The custom-made resin model.

Radiographic examination

The panoramic radiographic examination was performed in a digital panoramic unit (CS 9300C, Carestream Health, Rochester, NY, USA). Exposure parameters were set at 60 kV, 2.5 mA and a 180° rotation (14.3 s scan).

Measurements

Implants in the canine position were excluded, as this in vitro study required only implants in the posterior segments. Two trained oral surgeons, experienced in interpreting panoramic radiographs, did all the measurements. The 6 implants were measured twice randomly, 1 week apart, by the two observers on 3 imaging software programs: proprietary Kodak Dental Imaging Software (KDIS) (version 6.12.32.0; Kodak Dental Systems, Carestream Health, Rochester, NY, USA), open-source DICOM viewer OsiriX (version 1.2 64-bit; Pixmeo, Geneva, Switzerland), and web-based DICOM viewer Weasis (version 1.2.5; Weasis Team, Geneva, Switzerland).

Radiological implant length evaluation

Each observer measured twice randomly the radiological length of the 6 implants in the posterior mandibular region. For the vertical measurements, both image magnifications pre-set by the KDIS proprietary viewer were used and were labeled K-medium (3.4:1) and K-low (1.9:1). With Weasis and OsiriX viewers, three image magnifications were used. W-medium and O-medium were equal to K-medium (3.4:1), W-low and O-low were equal to K-low (1.9:1) and a higher image magnification (labeled W-high and O-high) was set to 10:1. For each magnification setting, 24 measurements were performed.

Statistical analysis

The error for each measurement (measured value minus real implant length) was assessed and its distribution was graphically represented by boxplot and described by mean, standard deviation, and minimal and maximal values. The percentage of measurements with a null error was reported and compared between magnification settings with McNemar’s test. The inter- and intraobserver agreements were analyzed using Bland and Altman analysis. Mean and standard deviation of error (between observers and between sessions) and limits of agreement were reported. The maximum tolerated difference was set at 0.3 mm. Standard deviations compared the magnification settings with a Morgan-Pitman procedure.^11,12 Statistical analysis was performed using S-PLUS 8.0 (Insightful Corp, Seattle, WA).

Implant length values measured in Weasis and OsiriX viewers were rounded to the nearest tenth for comparison with the values measured in KDIS viewer as the authors of the present study agreed that a precision of more than a tenth of a millimeter was clinically irrelevant in dental implant planning. Statistical analysis confirmed that results were identical for rounded and non- rounded values.

RESULTS Error description

The error between the measured and the real implant length was close to zero for all three viewers and image magnifications (Table 1): the mean errors ranged from -0.13 mm (O-low) to +0.05 mm (W-low). Distribution of errors is shown in Figure 2. The percentage of measurements equal to the real implant length was the highest for O-high (83.3%) and below 30% for all viewers with the low image magnification. Globally, this percentage increased significantly with

magnification of the image (McNemar, O-high vs O-medium: χ²=7.56, df=1, p=0.006; O-high vs O-low: χ²=11.08, df=1, p=0.0009, K-low vs K-medium: χ²=5.82, df=1, p=0.02, W-medium vs W-low: χ²=6.75, df=1, p=0.009).

Table 1: Measurement error description. SD: standard deviation.

Magnification Mean error in mm (SD)

Median error in mm [min-max]

% of measurements with a null error K-low 1.9:1 -0.02 (0.16) 0.00 [-0.30 ;0.20] 5/24 (20.8%) K-medium 3.4:1 0.02 (0.07) 0.00 [-0.10 ;0.20] 14/24 (58.3%)

W-low 1.9:1 0.05 (0.13) 0.10 [-0.10 ;0.30] 4/24 (16.7%) W-medium 3.4:1 0.04 (0.06) 0.00 [-0.10 ;0.20] 14/24 (58.3%)

W-high 10:1 0.03 (0.06) 0.00 [-0.10 ;0.10] 14/24 (58.3%) O-low 1.9:1 -0.13 (0.13) -0.10 [-0.30 ;0.20] 7/24 (29.2%) O-medium 3.4:1 -0.02 (0.10) 0.00 [-0.20 ;0.10] 8/24 (33.3%) O-high 10:1 0.00 (0.04) 0.00 [-0.10 ;0.10] 20/24 (83.3%)

Fig. 2. Distribution of the error in mm (box plots). The white horizontal line represents the median, the grey rectangle the interquartile range, and the lower and upper limits are the minimums and maximums.

Inter- and intraobserver agreements

The difference between values measured during both sessions (intraobserver difference) was analyzed. The mean difference was close to zero for all viewers and image magnifications (Table 2). The Bland and Altman plots are represented in Figure 3. For all viewers, the limits of agreement were smaller than ±0.30 mm with the medium or high image magnifications but not with the low image magnification. Intraobserver differences were closer to zero with the high image magnification than with the low image magnification (Morgan-Pitman, W: t=7.27, df=10, p<0.0001; O: t=4.23, df=10, p=0.002). Intraobserver differences were also closer to zero with the

-0.3-0.2-0.10.00.10.20.3

K-low K-medium W-low W-medium W-high O-low O-medium O-high

Error (mm)

high than with the medium image magnification (Morgan-Pitman, W: t=3.80, df=10, p=0.004;

O: t=2.50, df=10, p=0.03). No difference was detected between low and medium magnification settings.

The Bland and Altman plots representing the differences between observers (interobserver difference) are shown in Figure 4. The interpretation of the interobserver agreement was similar to the intraobserver agreement.

Table 2: Intra- and interobserver differences and limits of agreement. SD: standard deviation.

Difference (mm) Limit of agreement (mm)

Mean (SD)

Median

[min-max] Lower Upper

Intraobserver difference

K-low 0.05 (0.17) 0.0 [-0.2 ;0.4] -0.29 0.39

K-medium -0.03 (0.11) 0.0 [-0.3 ;0.1] -0.25 0.20

W-low -0.04 (0.16) 0.0 [-0.3 ;0.3] -0.35 0.26

W-medium 0.01 (0.10) 0.0 [-0.1 ;0.2] -0.19 0.20

W-high 0.02 (0.04) 0.0 [0.0 ;0.1] -0.06 0.09

O-low 0.00 (0.18) -0.05 [-0.3 ;0.3] -0.35 0.35

O-medium 0.00 (0.11) 0.0 [-0.2,0.2] -0.22 0.22

O-high 0.00 (0.06) 0.0 [-0.1,0.1] -0.12 0.12

Interobserver difference

K-low -0.17 (0.23) -0.3 [-0.5 ;0.1] -0.61 0.28

K-medium -0.03 (0.08) 0.0 [-0.1;0.1] -0.17 0.12

W-low 0.06 (0.16) 0.0 [-0.2 ;0.3] -0.26 0.38

W-medium -0.03 (0.11) 0.0 [-0.2,0.2] -0.23 0.18

W-high -0.02 (0.07) 0.0 [-0.1,0.1] -0.16 0.12

O-low 0.05 (0.17) 0.05 [-0.4;0.3] -0.29 0.39

O-medium 0.00 (0.12) 0.0 [-0.2;0.2] -0.24 0.24

O-high -0.02 (0.06) 0.0 [-0.1;0.1] -0.13 0.10

Fig. 3. Intraobserver reproducibility (Bland and Altman plots). The straight horizontal line represents the mean difference between sessions and the dashed horizontal lines the limits of agreements.

K-low

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5 12.0

-0.40.00.4

K-medium

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.40.00.4

W-low

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.40.00.4

W-medium

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.40.00.4

W-high

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.40.00.4

O-low

Mean (mm)

Difference (mm)

9.5 10.0 10.5 11.0 11.5

-0.40.00.4

O-medium

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.40.00.4

O-high

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.40.00.4

Fig. 4. : Interobserver reproducibility (Bland and Altman plots). The straight horizontal line represents the mean difference between observers and the dashed horizontal lines the limits of agreements.

DISCUSSION

Digital radiographic imaging systems have become widely available, allowing the use of digital panoramic radiographs for dental implant treatments. This quick, simple, low-cost and low-dose diagnostic tool allows evaluation of the available bone height before placement of posterior mandibular implants.^4,5 A safety margin of at least 2 mm between the implant’s tip and the mandibular canal is recommended.⁴ Proprietary software-based measurements tools are commonly used for vertical measurements in premolar and molar mandibular segments on digital panoramic radiographs.^13-17 Precision and accuracy of measurements in digital panoramic

K-low

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5 12.0

-0.60.00.4

K-medium

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5 12.0

-0.60.00.4

W-low

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.60.00.4

W-medium

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.60.00.4

W-high

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.60.00.4

O-low

Mean (mm)

Difference (mm)

9.5 10.0 10.5 11.0 11.5

-0.60.00.4

O-medium

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.60.00.4

O-high

Mean (mm)

Difference (mm)

10.0 10.5 11.0 11.5

-0.60.00.4

radiography using a single measurement software program have been examined under two magnification settings.¹⁰ To our knowledge, no digital panoramic radiography studies have assessed impact of image magnification on the accuracy of measurements using various imaging software programs, including DICOM viewers. Yet, DICOM and other software programs have been used to examine the accuracy of CBCT measurements.^6,8,9,18 Gaia et al.⁹ compared linear measurements in CBCT images using Vitrea 3.8.1 (Vital Images Inc., Plymouth, MN) viewer, and the same open-source DICOM viewer OsiriX 1.2 64-bit (Pixmeo, Geneva, Switzerland) as the one used in the present in vitro study. Vitrea software showed measurements closer to the dry skull values (gold standard) than measurements obtained with OsiriX.⁹ The same authors concluded that measurements with Vitrea were precise and accurate whereas the OsiriX viewer was not successful in producing accurate linear measurements for Le Fort I osteotomy. In the present study, the high image magnification (10:1) used to measure reference objects might explain why our results do not support the conclusions of Gaia et al.⁹ regarding the precision of OsiriX software program. Furthermore, OsiriX software has been used in another study to evaluate the accuracy and reliability of measurements on 3D computed tomography images of pig femur.¹⁹ Differences between real and OsiriX measurements were less than 0.1 mm and the authors concluded that OsiriX software was very reliable for measurements purposes. In the present study, measurements performed with OsiriX under the high image magnification (O- high) showed the lowest error value. In addition, the percentage of measurements equal to the real implant length was the highest for O-high (83.3%). Furthermore, the present study demonstrated that there were no statistically significant differences between the three software programs (proprietary and DICOM viewers) when measuring vertical linear distances on panoramic radiographs. Our results corroborate other studies using various proprietary measurement software programs on digital panoramic radiographs in premolar and molar mandibular segments.^{15-17, 20}

Agreements between observers and between measurement sessions appeared to be optimal when a high (10:1) image magnification was used for on-screen vertical measurements in the posterior segments of a mandibular model. Standard deviations were significantly lower with the high than with the low image magnification. The high and medium image magnifications used in this in vitro study allowed accurate vertical measurements with all three imaging programs. Our results contradict Schulze et al.¹⁰ reporting that measurements with a high image magnification (2:1) were less accurate than with a lower magnification (1:1); the authors recommended that digital measurements should not be performed on magnified images. The same authors mention the reason for this; the pixel size was a limiting factor for larger magnifications since high magnification resulted in a relatively diffuse image on the screen, which made it increasingly difficult to identify the borders of any object shown on the screen. In the present study, the observers were not confronted with such a problem, and this is a result of high initial image resolution and small pixel size, features that are common to the current panoramic digital image acquisition systems and imaging software programs.

Certain limitations do exist in the present study. This study was limited to measurements on 8mm and 10mm implants which may have underpowered measurement inaccuracies. When analyzing the percentages of measurements with a null error, a higher image magnification globally improved the accuracy. With the sample size of our study, the statistical power was 80%

to detect a difference around 30% in the proportion of measurements without error between two image magnifications, and certain specific differences below 10% (such as the difference between O-low and O-medium) were not statistically significant. Furthermore, the single panoramic acquisition of parallel mandibular implants placed in the center of the resin crest may have positively impacted the measurements. Moreover, another limitation was that a static model

was used for measurements. Susceptibility to patient movement during acquisition and error of head positioning were not analyzed, knowing that these factors could affect the measurements.²¹ Our results nevertheless showed good measurement accuracy on a static model with three imaging programs and three image magnifications. Results might also have been positively impacted by the observers’ experience in interpreting panoramic images whereas clinicians with different experiences in measurements on a screen would have been better representative of routine clinical practice.

CONCLUSION

The high and medium image magnifications used in this in vitro study allowed, with all three imaging programs, accurate vertical measurements in the posterior segments of a mandibular model. This study suggests that a low image magnification should not be used for vertical measurements on digital panoramic radiographs when planning an implant in the posterior mandible.

REFERENCES

1. Dula K, Mini R, van der Stelt PF, Buser D. The radiographic assessment of implant patients:

decision-making criteria. Int J Oral Maxillofac Implants. 2001;16:80–89.

2. Harris D, Buser D, Dula K, Grondahl K, Haris D, Jacobs R, et al. EAO Guidelines for the use of diagnostic imaging in implant dentistry. A consensus workshop organized by the European Association for Osseointegration in Trinity College Dublin. Clin Oral Implants Res.

2002;13:566–570.

3. Frei C, Buser D, Dula K. Study on the necessity for cross-section imaging of the posterior mandible for treatment planning of standard cases in implant dentistry. Clin Oral Implants Res.

2004;15:490–497.

4. Vazquez L, Saulacic N, Belser U, Bernard JP. Efficacy of panoramic radiographs in the preoperative planning of posterior mandibular implants: a prospective clinical study of 1527 consecutively treated patients. Clin Oral Implants Res. 2008;19:81–85.

5. Vazquez L, Nizam Al Din Y, Belser UC, Combescure C, Bernard JP. Reliability of the vertical magnification factor on panoramic radiographs: clinical implications for posterior mandibular implants. Clin Oral Impl Res. 2011;22:1420–1425.

6. Kobayashi K, Shimoda S, Nakagawa Y, Yamamoto A. Accuracy in measurement of distance using limited cone-beam computerized tomography. Int J Oral Maxillofac Implants.

2004;19:228–231.

7. Marmulla R, Wortche R, Muhling J, Hassfeld S. Geometric accuracy of the NewTom 9000 Cone Beam CT. Dentomaxillofac Radiol. 2005;34:28–31.

8. Lascala CA, Panella J, Marques MM. Analysis of the accuracy of linear measurements obtained by cone beam computed tomography (CBCT-NewTom). Dentomaxillofac Radiol.

2004;33:291–294.

9. Gaia BF, Pinheiro LR, Umetsubo OS, Costa FF, Cavalcanti MG. Comparison of precision and accuracy of linear measurements performed by two different imaging software programs and obtained from 3D-CBCT images for Le Fort I osteotomy. Dentomaxillofac Radiol.

2013;42:20120178.

10. Schulze R, Krummenauer F, Schalldach F, d'Hoedt B. Precision and accuracy of measurements in digital panoramic radiography. Dentomaxillofac Radiol. 2000;29:52-56.

11. Morgan WA. A test for the significance of the difference between the two variances in a sample from a normal bivariate population. Biometrika. 1939;31:13-19

12. Pitman EJG. A note on normal correlation. Biometrika. 1939;31:9-12.

13. Alhassani AA, AlGhamdi AS. Inferior alveolar nerve injury in implant dentistry: diagnosis, causes, prevention, and management. J Oral Implantol. 2010;36:401-7.

14. Park JB. The evaluation of digital panoramic radiographs taken for implant dentistry in daily practice. Med Oral Patol Oral Cir Bucal. 2010;15:e663–666.

15. Kim YK, Park JY, Kim SG, Kim JS, Kim JD. Magnification rate of digital panoramic radiographs and its effectiveness for pre-operative assessment of dental implants.

Dentomaxillofac Radiol. 2011;40:76–83.

16. Machtei EE, Zigdon H, Levin L, Peled M. Novel ultrasonic device to measure the distance from the bottom of the osteotome to various anatomic landmarks. J Periodontol. 2010;81:1051–

1055.

17. Vazquez L, Nizamaldin Y, Combescure C, Nedir R, Bischof M, Dohan Ehrenfest DM, et al.

Accuracy of vertical height measurements on direct digital panoramic radiographs using posterior mandibular implants and metal balls as reference objects. Dentomaxillofac Radiol.

2013;42:20110429.

18. Santana RR, Lozada J, Kleinman A, Al-Ardah A, Herford A, Chen JW. Accuracy of cone beam computerized tomography and a three-Dimensional stereolithographic model in identifying the anterior loop of the mental nerve: A study on cadavers. J Oral Implantol. 2012;38:668-76.

19. Kim G, Jung HJ, Lee HJ, Lee JS, Koo S, Chang SH. Accuracy and reliability of length measurements on three-dimensional computed tomography using open-source OsiriX software. J Digit Imaging. 2012;25:486-491.

20. Haghnegahdar A, Bronoosh P. Accuracy of linear vertical measurements in posterior mandible on panoramic view. Dent Res J (Isfahan). 2013;10:220-224.

21. Peretz B, Gotler M, Kaffe I. Common errors in digital panoramic radiographs of patients with mixed dentition and patients with permanent dentition. International Journal of Dentistry.

vol. 2012, Article ID 584138, 7 pages, 2012. doi:10.1155/2012/584138.

Conclusions

Cette étude in vitro réunit les domaines de la radiologie dento-maxillo-faciale et de l’implantologie orale. Elle avait pour but d'évaluer l’impact du grossissement de l’image sur l’exactitude des mesures verticales effectuées sur des radiographies panoramiques numériques dans la région mandibulaire postérieure. Elle a permis d’évaluer l’exactitude de trois logiciels d’imagerie, utilisés fréquemment par les praticiens, sous différents grossissements d’image lors de la planification de traitements implantaires. Il est essentiel en chirurgie implantaire, et en particulier dans les régions postérieures de la mandibule, d’utiliser des outils logiciels de mesure qui permettent, à l’écran et sous diverses conditions de visualisation d’une image radiologique, une estimation verticale exacte afin de sélectionner correctement la longueur de l’implant dentaire.

Les conclusions qui peuvent être tirées de ce travail sont les suivantes. Les grossissements moyens (3.4 :1) et forts (10 :1) utilisés dans cette étude ont permis d’obtenir, avec les trois logiciels d'imagerie, des mesures verticales exactes dans les segments postérieurs d'un modèle mandibulaire en résine. Cette étude suggère que le faible grossissement (1.9 :1) ne devrait pas être utilisé pour les mesures verticales sur les radiographies panoramiques numériques lors de la planification d'un implant au niveau des segments mandibulaires postérieurs. En respectant une marge de sécurité d'au moins 2 mm afin d’écarter tout risque de lésion du nerf alvéolaire inférieur, les trois logiciels utilisés sous de moyens et forts grossissements peuvent donc être recommandés pour la planification d'implants dans la région mandibulaire postérieure.

Bibliographie

1. Astrand P, Ahlqvist J, Gunne J, Nilson H. Implant treatment of patients with edentulous jaws: a 20-year follow-up. Clin Implant Dent Relat Res. 2008;10: 207-217.

2. Chappuis V, Buser R, Brägger U, Bornstein MM, Salvi GE, Buser D. Long-term outcomes of dental implants with a titanium plasma-sprayed surface: A 20-year prospective case series study in partially edentulous patients. Clin Implant Dent Relat Res. 2013;15:780-790.

3. Strahlenschutz und Überwachung der Radioaktivität in der Schweiz: Ergebnisse 2013.

Strahlenschutz BAG; Jahresbericht 2013 (Radioprotection et surveillance de la radioactivité en Suisse: Résultats 2013. Radioprotection OFSP; rapport annuel 2013). www.bag.admin.ch 4. United Nations Scientific Committee on the Effects of Atomic Radiation Sources and

Effects of Ionizing Radiation, UNSCEAR Report Volume 1, United Nations, New York.

www.unscear.org/unscear/en/publications/2000_1.html. 2000.

5. Berkhout WE. The ALARA-principle. Backgrounds and enforcement in dental practices.

Ned Tijdschr Tandheelkd. 2015;122:263-70.

6. Preston-Martin S, Thomas DC, White SC, Cohen D. Prior exposure to medical and dental x- rays related to tumors of the parotid gland. J Natl Cancer Inst. 1988;80:943–949.

7. Preston-Martin S & White SC. Brain and salivary gland tumors related to prior dental radiography: implications for current practice. J Am Dent Assoc. 1990;120:151-158.

8. Memon A, Godward S, Williams D, Siddique I, Al-Saleh K. Dental x-rays and the risk of thyroid cancer: a case-control study. Acta Oncol. 2010;49: 447-453.

9. Ludlow JB, Davies-Ludlow LE, White SC. Patient risk related to common dental radiographic examinations: the impact of 2007 International Commission on Radiological Protection recommendations regarding dose calculation. J Am Dent Assoc. 2008;139:1237- 1243.

10. Lecomber AR, Yoneyama Y, Lovelock DJ, Hosoi T, Adams AM. Comparison of patient dose from imaging protocols for dental implant planning using conventional radiography and computed tomography. Dentomaxillofac Radiol. 2001;30: 255-259.

11. Ludlow JB, Davies-Ludlow LE, Brooks SL. Dosimetry of two extraoral direct digital imaging devices: NewTom cone beam CT and Orthophos Plus DS panoramic unit.

Dentomaxillofac Radiol. 2003;32: 229-234.

12. The Sedentexct project. Radiation protection: cone beam CT for dental and maxillofacial radiology. Evidence based guidelines. Geneva, Switzerland: European Commission.

http://wwwsedentexcteu/guidelines. 2011.

13. Vazquez L, Saulacic N, Belser U, Bernard JP. Efficacy of panoramic radiographs in the preoperative planning of posterior mandibular implants: a prospective clinical study of 1527 consecutively treated patients. Clin Oral Implants Res. 2008;19: 81–85.

14. Kiyak HA, Beach BH, Worthington P, Taylor T, Bolender C, Evans J. Psychological impact of osseointegrated dental implants. Int J Oral Maxillofac Implants. 1990;5:61–69.

15. Bartling R, Freeman K, Kraut RA. The incidence of altered sensation of the mental nerve after mandibular implant placement. J Oral Maxillofac Surg. 1999;57:1408–1412.

16. Ellies LG. Altered sensation following mandibular implant surgery: a retrospective study. J Prosthet Dent. 1992;68:664–671.

17. Dula K, Mini R, van der Stelt PF, Buser D. The radiographic assessment of implant patients:

decision-making criteria. Int J Oral Maxillofac Implants. 2001;16:80–89.

18. Lindh C, Petersson A, Klinge B. Measurements of distances related to the mandibular canal in radiographs. Clin Oral Implants Res. 1995;6:96–103.

19. Bolin A, Eliasson S, von Beetzen M. Radiographic evaluation of mandibular posterior implant sites: correlation between panoramic and tomographic determinations. 1996;7:354–

359.

20. Bou Serhal C, Jacobs R, Persoons M, Hermans R, van Steenberghe D. The accuracy of spiral tomography to assess bone quantity for the preoperative planning of implants in the posterior maxilla. Clin Oral Implants Res. 2000;11:242–247.

21. Tyndall AA, Brooks SL. Selection criteria for dental implant site imaging: a position paper of the American Academy of Oral and Maxillofacial radiology. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2000:89:630–637.

22. Schropp L, Wenzel A, Kostopoulos L. Impact of conventional tomography on prediction of the appropriate implant size. Oral Surg Oral Med Oral Pathol Oral Radiol Endod.

2001;92:458–463.

23. Harris D, Buser D, Dula K, Grondahl K, Haris D, Jacobs R, Lekholm U, Nakielny R, van Steenberghe D, van der Stelt P. EAO Guidelines for the use of diagnostic imaging in implant dentistry. A consensus workshop organized by the European Association for Osseointegration in Trinity College Dublin. Clin Oral Implants Res. 2002;13: 566–570.

24. Frei C, Buser D, Dula K. Study on the necessity for cross-section imaging of the posterior mandible for treatment planning of standard cases in implant dentistry. Clin Oral Implants Res. 2004;15: 490–497.

25. Vazquez L, Nizam Al Din Y, Belser UC, Combescure C, Bernard JP. Reliability of the vertical magnification factor on panoramic radiographs: clinical implications for posterior mandibular implants. Clin Oral Impl Res. 2011;22: 1420–1425.

26. Vazquez L, Nizamaldin Y, Combescure C, Nedir R, Bischof M, Dohan Ehrenfest DM, Carrel JP, Belser UC. Accuracy of vertical height measurements on direct digital panoramic radiographs using posterior mandibular implants and metal balls as reference objects.

Dentomaxillofac Radiol. 2013;42:20110429.

27. Kobayashi K, Shimoda S, Nakagawa Y, Yamamoto A. Accuracy in measurement of distance using limited cone-beam computerized tomography. Int J Oral Maxillofac

Implants. 2004;19: 228–231.

28. Marmulla R, Wortche R, Muhling J, Hassfeld S. Geometric accuracy of the NewTom 9000 Cone Beam CT. Dentomaxillofac Radiol. 2005;34: 28–31.

29. Loubele M, Maes F, Schutyser F, Marchal G, Jacobs R, Suetens P. Assessment of bone segmentation quality of cone-beam CT versus multislice spiral CT: a pilot study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2006;102: 225–234.

30. Gerlach NL, Meijer GJ, Maal TJ, Mulder J, Rangel FA, Borstlap WA, Bergé SJ.

Reproducibility of 3 different tracing methods based on cone beam computed tomography in determining the anatomical position of the mandibular canal. J Oral Maxillofac Surg.

2010;68: 811–817.

31. Lascala CA, Panella J, Marques MM. Analysis of the accuracy of linear measurements obtained by cone beam computed tomography (CBCT-NewTom). Dentomaxillofac Radiol.

2004;33: 291–294.

32. Torres MG, Campos PS, Segundo NP, Navarro M, Crusoé-Rebello I. Accuracy of linear measurements in cone beam computed tomography with different voxel sizes. Implant Dent.

2012;21:150-5.

33. Gaia BF, Pinheiro LR, Umetsubo OS, Costa FF, Cavalcanti MG. Comparison of precision and accuracy of linear measurements performed by two different imaging software programs and obtained from 3D-CBCT images for Le Fort I osteotomy. Dentomaxillofac Radiol.

2013;42:20120178.

34. Vazquez L, Srinivasan M, Khouja F, Combescure C, Carrel JP. Influence of image viewers and artifacts on implant length measurements in Cone-Beam Computed Tomography: an in vitro study (submitted).