Effect of Variations of Field of View (FOV) and Milliampere (mA) on Metal Artifacts Produced by Dental Implants in Cone Beam Computed Tomography Image Quality. (In-vitro Study)
Conditions: Metal Artifacts, Implant
Sponsor: Cairo University

 
 
 
 
 
Official Title of the Study: 
Effect of variations of Field of view (FOV) and milliampere (mA) on metal artifacts in 
Cone Beam Computed Tomography. (In vitro study) 
NCT Number: NCT04935944 
 
Date of Document: July 15, 2021 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
I. Administrative information: 
1. Title: 
Effect of variations of Field of view (FOV) and milliampere (mA) on metal artifacts produced by dental 
implants 
in 
Cone 
Beam 
Computed 
Tomography 
image 
quality.  
(In-vitro study) 
2. Protocol registration:  
DOI: 10.21203/rs.3.pex-1575/v1 ( https://www.nature.com/protocolexchange/ ) 
3. Protocol version:  
6 Jul 2021 Protocol. 
Version number: 1 
4. Funding: 
No financial support, self-funding. 
5. Roles and responsibilities: 
Investigator: 
 
Roshan Adel Ahmed 
Master degree student 
Oral and maxillofacial Radiology Department 
Faculty of Dentistry 
Cairo University 
Responsibility: 
She is responsible for: 
• Recruitment of bio models and dental implants. 
• CBCT image analysis. 
• Interpretation of data. 
• Writing the protocol. 
• Writing final report of the research. 
• Responsible for Thesis writing. 
 
 
 

 
Main supervisor: 
Dr. Noha Issa 
Associate Professor of Oral and Maxillofacial Radiology 
Faculty of Dentistry, 
Cairo University 
Responsibility: 
Main supervisor. 
The one responsible for: 
• Study selection 
• Data managing, 
• Monitoring and auditing 
• Analysis of CBCT images. 
• Thesis revision. 
 
Co-supervisor: 
 
Dr. Walaa Samir Abdelfatah 
Associate Professor of Oral and Maxillofacial Radiology 
Faculty of Dentistry 
Beni Suef University 
Responsibility: 
Co-supervisor 
The one responsible for: 
• CBCT image analysis. 
• Data monitoring and auditing. 
• Interpretation of data. 
• Revision of final report of the research. 
• Responsible for Thesis revision. 
 
 
 
 
 
 
 
 
 
 

 
II. Introduction:   
Cone Beam Computed Tomography (CBCT) is considered an important valuable imaging technique in the 
diagnosis and treatment planning in oral and maxillofacial surgery  as well as  implant dentistry by means 
of three dimensional images which provide extra information about the buccolingual dimension of the 
alveolar bone with more details for bone anatomy and inclination (Venkatesh & Elluru, 2017). 
 
To make an accurate diagnosis and treatment planning, we have to obtain images with more details, good 
resolution and quality which could be achieved by CBCT. However, there are some issues in scanned areas 
that can affect their quality such as presence of metals (metallic restorations, orthodontic appliances, dental 
implants, crowns) which result in artifacts which can be considered as an important cause of poor image 
quality which will lead to poor diagnosis (Bechara et al., 2012). 
There are many types of artifacts which can be observed on CBCT images. Beam hardening artifact is 
considered a common one which occurs when an x-ray beam comprised of polychromatic energies passes 
through an object, resulting in selective attenuation of lower energy photons. The effect is conceptually 
similar to a high-pass filter, in that only higher energy photons are left to contribute to the beam and thus 
the mean beam energy is increased ("hardened") (Shokri et al., 2019). 
 
Research question: 
Can change of milliampere (mA) and field of view (FOV) reduce the metallic artifacts in CBCT that result 
from metallic structures? 
 
The aim of this study is to evaluate the effect of exposure parameters as milliampere (mA) and field of 
view (FOV) in CBCT on metal artifact of dental implant. 
 
Review of literature: 
Databases used: PubMed – Google scholar – Cochrane. 
 
Keywords: CBCT - Metal artifacts - Beam hardening artifact - Dental Implants - MAR–Metal artifacts 
reduction- metal artifact reduction protocols – mAs - FOV 
 
The first development of Cone beam Computed tomography (CBCT) was originally in 1982 for medical 
use specially for angiography (Patcas et al., 2012). 
 
Then in 1998 the CBCT was introduced for craniofacial scanning, moreover it generates 3D image with a 
lower cost and lower radiation doses than that in Computed Tomography. The technique of CBCT is 
depending on a cone-shaped beam of x-ray which is centered on a 2D detector and rotates around the 
object,  providing hundreds of 2D scans of a defined volume of anatomy instead of the slice by slice 
scanning which was carried out in conventional Computed Tomography (Alshehri et al., 2012). 

 
CBCT offers more options for image quality improvement by more than one software and most of these 
are user- friendly and easy to use with 3D imaging tools.   Third party software are available at a wide 
range of cost, which offer a lot of tools for easy and good diagnosis, analyzing and making appropriate 
treatment plan. Moreover, third party software are also of help in virtual studying, preparing surgical guides 
,etc.… (Venkatesh & Elluru, 2017). 
 
The use of CBCT became more common in implant treatment planning as it provides help in minimizing 
implant complications due to its injury of anatomical structures by offering more accurate details about 
them (Alawaji et al., 2018). 
 
Implant placement has now become part of everyday dental practice and CBCT makes it easier and 
quicker by providing more accurate detailed images for preoperative treatment planning and evaluation of 
alveolar ridge morphology (height and width), quality (according to the density of the remaining structure 
of the bone) and quantity of the available bone for proper implant placement in the most appropriate 
position to achieve optimum phonetic, esthetic, and masticatory function. Also, CBCT can provide 
accurate diagnosis of lesions and anatomical structures (inferior alveolar canal, mental foramen, nasal fossa 
and maxillary sinus) that may limit the placement of osseous implant (Albelbeisi et al., 2016). 
  
Despite all advantages of CBCT over multi-slice CT, there are some disadvantages that can interfere with 
the diagnosis and accurate vision of the images produced. Artifacts can be considered as one of the most 
important disadvantages of CBCT and when we talk about CBCT and implant we must consider metal 
artifacts that result from titanium implants in radiation path which can deteriorate the diagnostic image 
quality significantly (Parsa et al., 2014). 
 
Image artifact defined as a visualized structure in reconstructed data which is not visible in the object under 
investigation. Which interfere with the final diagnostic process, so must know about these artifacts and 
how to reduce them. These artifacts include extinction artifacts, beam hardening artifacts (metal artifact 
and cupping artifacts), partial volume effect, aliasing artifacts, ring artifacts and motion artifacts 
(misalignment artifacts) (Jaju et al., 2013). 
 
Beam hardening is considered as one of the most encountered sources of artifacts that are produced when 
lower-energy photons in the polychromatic x-ray beam are absorbed by a higher attenuating or radiopaque 
material in preference to high energy photons. The attenuated x-ray beam exits this material with a higher 
mean energy than the incident or primary beam as it becomes harder or more intense when it reaches the 
detector. This results in distortion of the attenuated x-ray beam because of differential absorption by the 
material and produces streaks and dark bands on the image (Jaju et al., 2013). 
 
So, beam hardening considered as two different artifacts on the reconstructed images, the appearance of 
streaks or dark bands and a cupping artifact. Cupping artifacts resulted from passing of x-rays through the 
large object center which become harder that through the edges due to the greater amount of material that 

 
the beam has to penetrate. So, the final profile of linear attenuation coefficients appears as a cup. But the 
dark streaks and bands between dense objects which can be seen between two implants in close relation to 
each other as the beam becomes harder when it passes through both objects than when it passes through 
only one object (Jaju et al., 2013). 
 
Metallic objects in the dental field as implants can produce dark artifacts, induced by scattering, and streak 
artifacts, making anatomical structures mysterious and affecting the contrast between adjacent areas at 
region of interest. As this metallic material highly attenuates the x-ray beam, the attenuation values of 
objects behind the object are incorrectly high. Due to the cone shaped beam of CBCT, the metallic streak 
artifacts occur in all directions from the high attenuation object (Parsa et al., 2014). 
 
Many types of software and imaging protocols have been developed trying to solve the problem of the 
effect of the artifacts on the final CBCT image. So, manufacturers tried to minimize beam hardening by 
using filtration, anti-scatter grids, calibration correction, and beam hardening correction software. (Jaju et 
al., 2013). 
 
A lot of parameters such as X-ray beam quantity and quality, rotation arc, field of view (FOV) and pixel 
size can affect the CBCT image quality and image characteristics that may include artifacts, contrast 
resolution and noise. Metal artifact is considered as one of the most factors that degrading the image quality 
(Panjnoush et al., 2016). 
 
Field of view is one of the most important hardware tools that must be determined carefully to get more 
reliable and accurate measurements (Abdelkarim, 2019). 
 
FOV must be determined according to the needs of the case. 
Small FOV devices range normally from 5 to 10 cm, which give a 3D view of a single tooth unit and its 
surrounding anatomy. They are used for individual tooth assessment (e.g; impacted teeth, root morphology, 
supernumeraries, sites for placement of dental implants, and temporary anchorage devices). Medium FOV 
provides single jaw anatomy, whereas the maxillomandibular FOV gives the clinician an understanding of 
two-jaw anatomy, temporomandibular joint (TMJ), and occlusion.  They are used for more information on 
facial asymmetries, bilateral TMJ evaluations and occlusal relationships. 
In addition, Large or craniofacial FOVs include the cranial base, cranium and all associated structures. The 
large FOVs involve most of the whole head which help clinicians to assess relationships between skeletal 
bases, between teeth and skeletal bases, and also can be significant for anomalies in patients requiring 
orthognathic surgery or those with craniofacial anomalies (Kau and Ortho, 2014). 
In a study done by Shokri et al, to evaluate the effect of exposure parameters of milliampere (mA) and 
field of view (FOV) of CBCT image on a metal artifact of dental implants by using of 27 bone blocks with 
different densities (nine were type 1, nine were types 2 and 3, and nine were type 4). These blocks were 
placed in mandibular wax models. Then scanned after drilling and implant placement using Cranex3D 
imaging system with a 4 × 6 cm2and 6 × 8 cm2 FOV and 4 and 10 mA. Gray value of the bone blocks was 

 
recorded before and after placement of implants. And the result was that the amount of artifacts was 
lower in small FOV compared to large FOV (P < 0.05). Change of mA had no effect on metal artifacts (P 
> 0.05). Artifacts in type 4 bone were greater than in other bone types (P < 0.05). Difference between type 
1 and types 2 and 3 was not significant (P > 0.05). 
 
Study objectives and hypotheses: 
 
Study objectives: 
The objective of this study will be the evaluation of the effect of variation of the exposure parameters FOV 
& mA on the produced metallic artifact induced by dental implants that affect the CBCT image using linear 
measurements of dental implant dimensions.   
 
Study hypotheses: 
Is the variation of Field of view (FOV) and milliampere (mA) can affect the CBCT image quality with 
metal artifacts? 
 
III. Methods 
A) Samples, intervention and outcomes 
7. Calculated sample size 
A power analysis was designed to have adequate power to apply a statistical test of the null hypothesis that 
there is no difference between tested groups. By adopting an alpha level of (0.05) a beta of (0.2) i.e., 
power=80% and an effect size (f) of (0.38) calculated based on the results of a previous study1; the 
predicted sample size (n) was a total of (80) cases. Sample size calculation was performed using G*Power 
version 3.1.9.72 
8. Description of study sample 
• 4 dry human mandibles will be obtained from faculty of medicine from Cairo University. 
• Layers of dental wax for soft tissue stimulation from dental store of El-Kasr El-Einy, faculty of 
dentistry, Cairo University. 
• 8 dental implants will be obtained from Roots Company. 
• 
Each dry human mandible with implant will be scanned in the Oral and Maxillofacial Radiology 
Department, Faculty Dentistry, Cairo University using CBCT machine Planmeca ProMax® 3D Mid. 
• Produced CBCT images will be analyzed by using Romexis ® software (planmeca Helsinki-
Finland) for measuring dental implant dimensions (length and width) using linear measurements 
on software and real measurements of dental implants as a reference standard. 
 
 
 
 

 
9. Intervention for each group  
• Each mandible will be prepared and drilled for implant placement at the middle of the bone at the 
area of interest 
• Two layers of wax will be applied over them for soft tissue stimulation. 
• Then each mandible will be scanned by using CBCT machine Planmeca ProMax® 3D Mid in the 
Oral and Maxillofacial Radiology Department, Faculty Dentistry, Cairo University 4 times with 4 
different protocols of FOV (40 × 50 mm & 100 × 60 mm) and mA (8 and 10) by the following: 
➢ First:   
o mA 8 and FOV 40 × 50 
o mA 8 and FOV 100 × 60 
o mA 10 and FOV 40 × 50 
o mA 10 and FOV 100 × 60 
➢ Second: 
o mA 8 and FOV 40 × 50 
o mA 8 and FOV 100 × 60 
o mA 10 and FOV 40 × 50 
o mA 10 and FOV 100 × 60 
 
➢ Third: 
o mA 8 and FOV 40 × 50 
o mA 8 and FOV 100 × 60 
o mA 10 and FOV 40 × 50 
o mA 10 and FOV 100 × 60 
 
➢ Fourth: 
o mA 8 and FOV 40 × 50 
o mA 8 and FOV 100 × 60 
o mA 10 and FOV 40 × 50 
o mA 10 and FOV 100 × 60 
 
• Each CBCT image Produced will be analyzed for metal artifact by using Romexis ® software 
(planmeca Helsinki-Finland) for measuring dental implant dimensions (length and width) using 
linear measurements  
 
 
 
 
 
 

 
10. Outcomes  
The primary outcome of this study will be the assessment of Implants dimensions measurements that will 
be measured by using linear measurement on Romexis® software (Planmeca-Helsinki-Finland) for each 
scan to evaluate the effect of FOV and mA on artifacts induced by dental implamts. 
 
Prioritization 
of 
Outcome 
Method 
of 
Measurement  
Unit 
of 
Measurement  
Assessment of 
implants dimensions 
measurements 
accuracy 
Linear 
measurements 
Millimetres 
(mm) 
  
B) Assignment to intervention 
The randomization will applicable. 
11. Sequence generation 
Mechanism used to implement the random allocation sequence is that mandibles will be sequentially 
numbered. 
12. Allocation concealment  
Opaque sealed envelopes will be used to conceal the sequence until intervention is assigned. 
12. Implementation: 
The main supervisor will be responsible for the random allocation sequence and enrolling mandibles, but 
the co-supervisor and the researcher will be responsible for assignment for intervention. 
C) Blinding 
14. Blinding 
The Co-supervisor and investigator will be blinded. 
 
 

 
D) Statistical methods  
Handling of numerical/ quantitative variables: 
Numerical data will be explored for normality by checking the data distribution, calculating the mean and 
median values and using Kolmogorov-Smirnov and Shapiro-Wilk tests. If the data was found to be 
normally distributed, it will be presented as mean and standard deviation values. If the assumption of 
normality was found to be violated, the data will be presented as median and range values. 
Handling of categorical/ qualitative variables: 
Categorical data will be represented as frequency (n) and percentage (%). 
Statistical methods: 
Categorical data will be represented as frequency (n) and percentage (%) and will be analyzed using chi 
square test. Numerical data will be explored for normality by checking the data distribution, calculating 
the mean and median values and using Kolmogorov-Smirnov and Shapiro-Wilk tests. If the data was found 
to be normally distributed, it will be presented as mean and standard deviation values and one-way 
ANOVA followed by Tukey’s post hoc test will be used for the analysis.  
If the assumption of normality was found to be violated; the data will be presented as median and range 
values and will be analyzed using Kruskal Wallis test followed by multiple Mann-Whitney U tests with 
Bonferroni correction.  
The significance level will be set at p ≤0.05 for all tests. Statistical analysis will be performed with IBM® 
SPSS® Statistics Version 26 for Windows. 
 
 
 
 
 
 
 
 
 

 
IV- Ethics: 
16. Research ethics approval 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
V- References: 
• Alawaji, Y., Macdonald, D. S., & Ford, N. L. (2018). Optimization of cone beam computed 
tomography image quality in implant dentistry. October, 268–278.  
 
• Albelbeisi, T. M., Khtob, A. R., & Hassan, N. E. (2016). Cone-Beam Computed Tomography 
Versus Digital Orthopantomography in Treatment Planning for Mandibular Dental Implants. 
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• Alshehri, A. M. A., Alamri, H., Alshalhoob, M., Arabia, S., & Cam, C. A. D. (2012). CBCT 
applications in dental practice : A literature review. General Dentistry, 60(4), 390–400. 
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