# A Review of Doses for Dental Imaging in 2010–2020 and Development of a Web Dose Calculator

Authors: Hawon Lee; Andreu Badal
Journal: Radiology Research and Practice
 (2021)

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## Abstract

Dental imaging is one of the most common types of diagnostic radiological procedures in modern medicine. We introduce a comprehensive table of organ doses received by patients in dental imaging procedures extracted from literature and a new web application to visualize the summarized dose information. We analyzed articles, published after 2010, from PubMed on organ and effective doses delivered by dental imaging procedures, including intraoral radiography, panoramic radiography, and cone-beam computed tomography (CBCT), and summarized doses by dosimetry method, machine model, patient age, and technical parameters. Mean effective doses delivered by intraoral, 1.32 (0.60–2.56)μSv, and panoramic, 17.93 (3.47–75.00) μSv, procedures were found to be about1% and 15% of that delivered by CBCT, 121.09 (17.10–392.20) μSv, respectively. In CBCT imaging, child phantoms received about 29% more effective dose than the adult phantoms received. The effective dose of a large field of view (FOV) (>150 cm2) was about 1.6 times greater than that of a small FOV (<50 cm2). The maximum CBCT effective dose with a large FOV for children, 392.2 μSv, was about 13% of theeffective dose that a person receives on average every year from natural radiation, 3110 μSv. Monte Carlo simulations of representative cases of the three dental imaging procedures were then conducted to estimate and visualize the dose distribution within the head. The user-friendly interactive web application (available at http://dentaldose.org) receives user input, such as the number of intraoral radiographs taken, and displays total organ and effective doses, dose distribution maps, and a comparison with other medical and natural sources of radiation. The web dose calculator provides a practical resource for patients interested in understanding the radiation doses delivered by dental imaging procedures.


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## Body

## 1. Introduction

Dental imaging is one of the most common types of diagnostic radiological procedures taken by the average person. Popular dental imaging procedures include intraoral radiography, which has the longest history of use, followed by panoramic radiography, and more recently, cone-beam computed tomography (CBCT) [1]. Intraoral radiography, a simple two-dimensional (2D) projection imaging, is often used to detect periodontal disease and cavities at regular dental check-ups. Panoramic radiography, a more comprehensive 2D image that combines a series of narrow 2D images, has been widely used to provide a wide range of information about the dentition and jaws. Introduced in the late 1990s, three-dimensional (3D) imaging technology, CBCT, offers a comprehensive set of cross-sectional images, the ability of vertical scanning, and real-time intraoperative assessment. All three procedures expose different portions of the head, from small parts of the teeth to the whole lower head, to ionizing radiation. There are concerns about the increasing use of imaging procedures as well as the resulting radiation dose, especially for pediatric patients [2, 3].Absorbed dose is defined as the energy deposited to a given volume divided by the mass (measured in gray, Gy, in the International System of Units) [4]. Equivalent dose (measured in sieverts, Sv) is derived from the absorbed dose multiplied by the radiation weighting factor, which represents the effectiveness of the biological damage to the exposed tissue. Effective dose (measured in sieverts, Sv) is then derived by adding all equivalent doses multiplied by tissue weighting factors and provides a relative measure of the risk of stochastic effects that might result from irradiation. The most fundamental dose quantity, organ dose, of dental imaging can be obtained through two methods: measurement and computer simulation. First, organ doses can be physically measured with dosimeters placed within anatomy models, called physical human phantoms, that are exposed to dental radiation. Second, organ doses can be calculated through computer simulations where the simulation model of an imaging device is combined with digital anatomy models, called computational human phantoms [5]. Different types of pediatric and adult computational human phantoms are available for dose calculations. Many studies report organ doses from dental imaging procedures estimated by measurement or simulation. However, there are few resources that summarize a variety of data and present the radiation dose with a user-friendly interface.The current study was intended to provide a practical resource for patients interested in understanding the radiation doses delivered by dental imaging procedures for the period of 2010–2020 and comparison with other radiation sources that are commonly faced in daily life. We established a comprehensive table of organ doses for dental imaging procedures by extracting data from literature and developed a user-friendly web application to present the summarized information.


## 2. Materials and Methods

We obtained articles from PubMed, published after 2010, on organ and effective doses delivered by dental imaging procedures including intraoral radiography, panoramic radiography, and CBCT, and summarized doses by dosimetry method, machine model, patient age, and technical parameters. Monte Carlo simulations of representative cases of the three dental imaging procedures were conducted to estimate and visualize the dose distribution within the head. Finally, we developed an interactive web-based dose calculator to provide easy access to the dental doses and to compare them with other radiation sources commonly faced in daily life.


### 2.1. Literature Search

We searched for articles on organ and effective doses delivered by dental imaging in PubMed (https://pubmed.ncbi.nlm.nih.gov, National Library of Medicine, National Center for Biotechnology Information) available on October 1, 2020, using the following keywords:(i)
“dental intraoral organ dose” (for intraoral)(ii)
“dental panoramic organ dose” (for panoramic)(iii)
“dental cone beam CT organ dose” (for CBCT)These keywords brought up 41, 49, and 54 papers (144 in total) for intraoral, panoramic, and CBCT procedures, respectively. We selected papers published after 2010:a total of 81 papers (14, 20, and 47 papers for intraoral, panoramic, and CBCT, respectively) out of 144 papers. The papers that were not written in English (except for non-English articles with dose tables in English) or did not include the dose to bone marrow, brain, salivary glands, and thyroid and effective doses were excluded from the review process. After the exclusion, we finally used 3, 9, and 11 papers providing organ and effective doses for intraoral, panoramic, and CBCT procedures, respectively.


### 2.2. Data Collection

The following data were extracted from the papers:(i)
Dosimetry methods: simulation or measurement(ii)
Imaging machine model(iii)
Age represented by physical (measurement) or computational (simulation) phantoms: we denoted the age of 35 as the minimum age for all adult phantoms, which is the International Commission on Radiological Protection (ICRP) reference age of adults [6](iv)
Dose calculation program for simulation studies or dosimeter type for measurement studies(v)
Beam rotation angle (only for CBCT)(vi)
Imaging protocol(vii)
Dose area product (DAP) (mGy-cm2) (for intraoral and CBCT)(viii)
Tube potential (kVp)(ix)
The width and height of field of view (FOV) (cm) (for intraoral and CBCT)(x)
Effective dose (E) (μSv)(xi)
Doses to the bone marrow, brain, salivary glands, and thyroid (μGy)When a single paper provided multiple dose data in multiple categories, the dose in each category was considered a separate dose set. Simulation and measurement data were analyzed separately when both were reported in a single paper. When an effective dose was missing but organ doses were reported, an effective dose was derived from the organ doses using tissue weighting factors from ICRP Publication 103 [4]: 0.12 (bone marrow), 0.01 (brain), 0.01 (salivary glands), and 0.04 (thyroid). We assumed zero doses for other organs outside the head region in the calculation of the effective dose. The extracted data were tabulated in three detailed tables for intraoral, panoramic, and CBCT, respectively.To efficiently analyze the doses, we averaged the organ and effective doses over different data sources. As for CBCT, which had more available data for different phantom ages and FOVthan intraoral and panoramic, we further arranged organ and effective doses by phantom age group (children and adults) and/or the area (heightx width) of FOV (small <50 cm2, medium 50–150 cm2, and large >150 cm2).


### 2.3. Monte Carlo Simulation of Dental Imaging Procedures

We conducted Monte Carlo simulations of intraoral, panoramic, and CBCT imaging procedures by using a computational human head phantom and multimodal imaging-based detailed anatomical (MIDA) [7]combined with a Monte Carlo radiation transport code, MC-GPU [8]. The voxel resolution of the head phantom was 0.5 × 0.5 × 0.5 mm3. Key technical parameters for Monte Carlo simulations that were collected from literature are summarized in Table 1. In the case of panoramic imaging, a simplified image acquisition was modeled by concatenating 9,153 simulations with a 1-pixel-wide field of view of 10 × 0.05 cm2 instead of the realistic field of view of 10 × 0.2 cm2 since the image overlap in real machines could not be reliably simulated. Our simulations had two purposes: to evaluate the proportion of the dose distribution among different tissues during the three imaging modalities and to visualize dose distribution across the head anatomy in the web program.Table 1
Technical parameters for intraoral, panoramic, and cone-beam computed tomography collected from literature, which were used for Monte Carlo simulations conducted using MC-GPU to estimate dose distribution within the head.
ParametersIntraoralPanoramicCone-beam computed tomographyX-ray energy (kVp)607390Filtration (mm Al)3.52.52.8FOV (cm2)4 × 310 × 0.210 × 10SRD1 (cm)753550Rotation angle per view (degree)02240360Number of views per acquisition19153360Number of X-rays per simulated view10115 × 1075 × 109Total simulation time (min)3331437601Source-to-rotation axis distance. 2The rectangular field was rotated 30° cranially. 3Simulation run in an NVIDIA GeForce GTX 1080 GPU.


### 2.4. Development of a Web-Based Dose Calculator

After the summary dose tables were established, we developed a web-based dose calculation program to allow for convenient access to the organ and effective doses and comparison of the dental doses with doses from other radiation sources.The web program was designed to allow an input from the user for the following parameters: type of imaging modalities, number of image sets, patient age group (child or adult), and size of imaging region, which is the area of the FOV (small <50 cm2, medium 50–150 cm2, and large >150 cm2). The last two parameters were only used for CBCT dose as the dose data for intraoral and panoramic imaging were not enough to be stratified by age and FOV. The user has the option of “I do not know” for the patient age group and FOV, in which case the average dose of the age groups and/or the size of FOV were presented.Based on the input data from a user, the web application presents the following information:(i)
Dose delivered to the bone marrow, brain, salivary glands, and thyroid and effective dose; the doses are calculated by multiplying the dose per imaging by the number of image sets inputted by a user. Limited pediatric data points were available for intraoral and panoramic, andonly a total of 22 pediatric data points were extracted for CBCT. Since the data points were not enough to derive age dependency of dose for finer age resolution, we combined the 22 data points for CBCT into the pediatric age group. In the case of CBCT, when the user selects both age group and FOV, age and FOV dependent doses are displayed. FOV-averaged doses are displayed when a user selects “I do not know” for FOV. Age-averaged dose is displayed when a user selects “I do not know” for age.(ii)
2D and 3D dose distribution for the selected imaging procedures and the fraction of dose delivered to different tissues(iii)
Comparison of the total effective dose (effective dose multiplied by the number of image sets) with that from other radiation sources: 37μSv (London-to-New York flight), 100 μSv (chest X-ray) and 3110 μSv (annual natural background) [9]The web dose calculator was developed using the commercial cross-platform language, Xojo (Xojo, Inc., Austin, TX). The Xojo development tool provides a graphical user interface-based programming environment to develop multiplatform apps for macOS, Windows, Linux, and Web. We used the web application platform to develop our web-based dose calculator. We created two versions of the web interface for web browsers on a personal computer and a smart phone to account for differences in screen size. The web application was deployed through Xojo Cloud hosting, which was connected to the domain namehttp://dentaldose.org. Figure 1 shows the workflow of the web program, where the user input data and output data are described.Figure 1
Flowchart of the web application for dental radiation dose calculations and dose display.


## 2.1. Literature Search

We searched for articles on organ and effective doses delivered by dental imaging in PubMed (https://pubmed.ncbi.nlm.nih.gov, National Library of Medicine, National Center for Biotechnology Information) available on October 1, 2020, using the following keywords:(i)
“dental intraoral organ dose” (for intraoral)(ii)
“dental panoramic organ dose” (for panoramic)(iii)
“dental cone beam CT organ dose” (for CBCT)These keywords brought up 41, 49, and 54 papers (144 in total) for intraoral, panoramic, and CBCT procedures, respectively. We selected papers published after 2010:a total of 81 papers (14, 20, and 47 papers for intraoral, panoramic, and CBCT, respectively) out of 144 papers. The papers that were not written in English (except for non-English articles with dose tables in English) or did not include the dose to bone marrow, brain, salivary glands, and thyroid and effective doses were excluded from the review process. After the exclusion, we finally used 3, 9, and 11 papers providing organ and effective doses for intraoral, panoramic, and CBCT procedures, respectively.


## 2.2. Data Collection

The following data were extracted from the papers:(i)
Dosimetry methods: simulation or measurement(ii)
Imaging machine model(iii)
Age represented by physical (measurement) or computational (simulation) phantoms: we denoted the age of 35 as the minimum age for all adult phantoms, which is the International Commission on Radiological Protection (ICRP) reference age of adults [6](iv)
Dose calculation program for simulation studies or dosimeter type for measurement studies(v)
Beam rotation angle (only for CBCT)(vi)
Imaging protocol(vii)
Dose area product (DAP) (mGy-cm2) (for intraoral and CBCT)(viii)
Tube potential (kVp)(ix)
The width and height of field of view (FOV) (cm) (for intraoral and CBCT)(x)
Effective dose (E) (μSv)(xi)
Doses to the bone marrow, brain, salivary glands, and thyroid (μGy)When a single paper provided multiple dose data in multiple categories, the dose in each category was considered a separate dose set. Simulation and measurement data were analyzed separately when both were reported in a single paper. When an effective dose was missing but organ doses were reported, an effective dose was derived from the organ doses using tissue weighting factors from ICRP Publication 103 [4]: 0.12 (bone marrow), 0.01 (brain), 0.01 (salivary glands), and 0.04 (thyroid). We assumed zero doses for other organs outside the head region in the calculation of the effective dose. The extracted data were tabulated in three detailed tables for intraoral, panoramic, and CBCT, respectively.To efficiently analyze the doses, we averaged the organ and effective doses over different data sources. As for CBCT, which had more available data for different phantom ages and FOVthan intraoral and panoramic, we further arranged organ and effective doses by phantom age group (children and adults) and/or the area (heightx width) of FOV (small <50 cm2, medium 50–150 cm2, and large >150 cm2).


## 2.3. Monte Carlo Simulation of Dental Imaging Procedures

We conducted Monte Carlo simulations of intraoral, panoramic, and CBCT imaging procedures by using a computational human head phantom and multimodal imaging-based detailed anatomical (MIDA) [7]combined with a Monte Carlo radiation transport code, MC-GPU [8]. The voxel resolution of the head phantom was 0.5 × 0.5 × 0.5 mm3. Key technical parameters for Monte Carlo simulations that were collected from literature are summarized in Table 1. In the case of panoramic imaging, a simplified image acquisition was modeled by concatenating 9,153 simulations with a 1-pixel-wide field of view of 10 × 0.05 cm2 instead of the realistic field of view of 10 × 0.2 cm2 since the image overlap in real machines could not be reliably simulated. Our simulations had two purposes: to evaluate the proportion of the dose distribution among different tissues during the three imaging modalities and to visualize dose distribution across the head anatomy in the web program.Table 1
Technical parameters for intraoral, panoramic, and cone-beam computed tomography collected from literature, which were used for Monte Carlo simulations conducted using MC-GPU to estimate dose distribution within the head.
ParametersIntraoralPanoramicCone-beam computed tomographyX-ray energy (kVp)607390Filtration (mm Al)3.52.52.8FOV (cm2)4 × 310 × 0.210 × 10SRD1 (cm)753550Rotation angle per view (degree)02240360Number of views per acquisition19153360Number of X-rays per simulated view10115 × 1075 × 109Total simulation time (min)3331437601Source-to-rotation axis distance. 2The rectangular field was rotated 30° cranially. 3Simulation run in an NVIDIA GeForce GTX 1080 GPU.


## 2.4. Development of a Web-Based Dose Calculator

After the summary dose tables were established, we developed a web-based dose calculation program to allow for convenient access to the organ and effective doses and comparison of the dental doses with doses from other radiation sources.The web program was designed to allow an input from the user for the following parameters: type of imaging modalities, number of image sets, patient age group (child or adult), and size of imaging region, which is the area of the FOV (small <50 cm2, medium 50–150 cm2, and large >150 cm2). The last two parameters were only used for CBCT dose as the dose data for intraoral and panoramic imaging were not enough to be stratified by age and FOV. The user has the option of “I do not know” for the patient age group and FOV, in which case the average dose of the age groups and/or the size of FOV were presented.Based on the input data from a user, the web application presents the following information:(i)
Dose delivered to the bone marrow, brain, salivary glands, and thyroid and effective dose; the doses are calculated by multiplying the dose per imaging by the number of image sets inputted by a user. Limited pediatric data points were available for intraoral and panoramic, andonly a total of 22 pediatric data points were extracted for CBCT. Since the data points were not enough to derive age dependency of dose for finer age resolution, we combined the 22 data points for CBCT into the pediatric age group. In the case of CBCT, when the user selects both age group and FOV, age and FOV dependent doses are displayed. FOV-averaged doses are displayed when a user selects “I do not know” for FOV. Age-averaged dose is displayed when a user selects “I do not know” for age.(ii)
2D and 3D dose distribution for the selected imaging procedures and the fraction of dose delivered to different tissues(iii)
Comparison of the total effective dose (effective dose multiplied by the number of image sets) with that from other radiation sources: 37μSv (London-to-New York flight), 100 μSv (chest X-ray) and 3110 μSv (annual natural background) [9]The web dose calculator was developed using the commercial cross-platform language, Xojo (Xojo, Inc., Austin, TX). The Xojo development tool provides a graphical user interface-based programming environment to develop multiplatform apps for macOS, Windows, Linux, and Web. We used the web application platform to develop our web-based dose calculator. We created two versions of the web interface for web browsers on a personal computer and a smart phone to account for differences in screen size. The web application was deployed through Xojo Cloud hosting, which was connected to the domain namehttp://dentaldose.org. Figure 1 shows the workflow of the web program, where the user input data and output data are described.Figure 1
Flowchart of the web application for dental radiation dose calculations and dose display.


## 3. Results

We tabulated technical parameters and doses for a total of 4, 18, and 51 dose sets for intraoral (Table2), panoramic (Table 3), and CBCT (Table 4) procedures, respectively.Table 2
Dosimetry method, machine model, phantom age, technical parameters, and effective and organ (bone marrow, brain, salivary gland, and thyroid) doses for intraoral imaging procedures. No simulation-based doses are reported.
MethodMachine modelAgeDosimeterPhantomImaging protocolsDAP (mGy × cm2)kVpFOV width (cm)FOV height (cm)Effective dose (uSv)Organ dose (uGy)ReferenceBone marrowBrainSalivary glandThyroidMeasurementGendex Oralix DC35TLDARTBitewing single image603.54.50.850.500.0027.002.00Granlund et al. 2015 [10]MeasurementGendex Oralix DC35TLDARTFull-mouth single image603.54.50.830.330.0025.112.94Granlund et al. 2015 [10]MeasurementProstyle10Gafchromic filmATOM 706CPeriapical lateral7.42664.55.50.601.200.305.500.00Kadesjo et al. 2018 [11]MeasurementProstyle10Gafchromic filmATOM 706CPeriapical central7.42664.55.50.700.000.000.010.00Kadesjo et al. 2018 [11]MeasurementFocus35TLDCDP-R1Maxillary premolar left704.53.52.560.556.1245.2524.47Li et al. 2020 [12]MeasurementFocus35TLDCDP-R1Maxillary premolar left704.53.52.391.197.7633.8818.38Li et al. 2020 [12]DAP, dose area product; FOV, field of view.Table 3
Dosimetry methods, machine model, phantom age, technical parameters, and effective and organ (bone marrow, brain, salivary gland, and thyroid) doses for panoramic imaging procedures.
MethodMachine modelAge (year)Dosimeter/MC codePhantomImaging protocolskVpEffective dose (uSv)Organ dose (uGy)ReferenceBone marrowBrainSalivary glandThyroidMeasurementAZ300035TLDRANDOTemporomandibular7011.003.3029.50549.9029.80Matsuo et al. 2011 [13]MeasurementOP-20035TLDART6610.739.9410.03311.7827.89Han et al. 2013 [14]MeasurementORTHOPHOS CD35TLDART7114.3310.749.41419.1767.87Han et al. 2013 [14]MeasurementORTHOPHOS XG Plus35TLDART6919.0615.9918.41604.0554.60Han et al. 2013 [14]MeasurementProMax35TLDART6626.2614.5315.12939.5554.95Han et al. 2013 [14]MeasurementCranex Tome Ceph35TLDARTJaw6619.0011.0026.001028.0040.00Granlund et al. 2015 [10]MeasurementCranex Tome Ceph35TLDARTDental6622.0010.0010.001182.0048.00Granlund et al. 2015 [10]MeasurementVeraviewepocs35TLDARTJaw6623.0013.0010.00869.0053.00Granlund et al. 2015 [10]MeasurementVeraviewepocs35TLDARTDental6630.0018.005.00939.0052.00Granlund et al. 2015 [10]MeasurementScanora35TLDARTJaw6675.0054.0018.002887.00126.00Granlund et al. 2015 [10]MeasurementScanora35TLDARTDental6649.0038.0019.002428.00111.00Granlund et al. 2015 [10]MeasurementOP-2005TLDATOM 705Long collimator P16611.401.9043.0094.0037.00Davis 2015 [15]MeasurementOP-2005TLDATOM 705Short collimator P2667.701.5019.00103.0030.00Davis et al. 2015 [15]MeasurementOP-10035TLDRANDO737.155.0072.00109.0024.00Lee et al. 2016 [16]SimulationOP-10035PCXMCORNL739.3910.009.00299.0020.00Lee et al. 2016 [16]MeasurementProMax 2D10Gafchromic filmATOM 706C624.101.800.00160.0017.00Kadesjo et al. 2018 [11]MeasurementORTHOPHOSXG/Cep35TLDRANDO6413.0024.0037.00622.00256.00Qiang et al. 2019 [17]MeasurementOP-1005TLDATOM 705-D663.8538.3355.6454.4035.85Lee et al. 2019 [18]SimulationOP-1005PCXMCORNL663.4710.5120.004.3213.29Lee et al. 2019 [18]MeasurementPP135TLDCDP-R1Maxillofacial738.158.0833.10113.3054.31Li et al. 2020 [12]MeasurementPP135TLDCDP-R1Maxillofacial738.998.3429.59148.5563.90Li et al. 2020 [12]Table 4
Dosimetry methods, machine model, phantom age, technical parameters, and effective and organ (bone marrow, brain, salivary gland, and thyroid) doses for cone-beam computed tomography procedures.
MethodMachine modelAgeDosimeter/MC codePhantomRotation (degree)Imaging protocolsDAP (mGy × cm2)kVpFOV width (cm)FOV height (cm)Effective dose (uSv)Organ dose (uGy)ReferenceBone marrowBrainSalivary glandThyroidMeasurementGalileos35TLDARTMaxillofacial85151584.0082.00124.002104.00380.00Pauwels et al. 2012 [19]Measurementi-CAT35TLDARTMaxillofacial120161383.00116.00375.001830.00355.00Pauwels et al. 2012 [19]MeasurementIluma Elite35TLDARTMaxillofacial1202114368.00660.003415.007225.001230.00Pauwels et al. 2012 [19]MeasurementKodak 950035TLDARTMaxillofacial902018136.00206.001205.002676.00585.00Pauwels et al. 2012 [19]MeasurementNewTom VG35TLDARTMaxillofacial110151083.00115.00251.001690.00354.00Pauwels et al. 2012 [19]MeasurementNewTom VGi35TLDARTMaxillofacial1101515194.00186.00605.002855.002045.00Pauwels et al. 2012 [19]MeasurementScanora 3D35TLDARTMaxillofacial8514.513.568.0086.00255.001568.00296.00Pauwels et al. 2012 [19]MeasurementSkyView35TLDARTMaxillofacial90171787.00134.00719.001582.00474.00Pauwels et al. 2012 [19]Measurement3D Accuitomo 17035TLDARTMaxilla9010554.00112.00189.002138.00148.00Pauwels et al. 2012 [19]Measurementi-CAT NG35TLDARTMandible12016645.0033.0046.00973.00251.00Pauwels et al. 2012 [19]MeasurementKodak 950035TLDARTDentoalveolar9015892.0085.0091.002166.00541.00Pauwels et al. 2012 [19]MeasurementNewTom VGi35TLDARTDentoalveolar110128265.00294.00431.006372.001293.00Pauwels et al. 2012 [19]MeasurementPicasso trio35TLDARTDentoalveolar85127123.00126.00134.002982.00551.00Pauwels et al. 2012 [19]MeasurementPicasso trio35TLDARTDentoalveolar8512781.0062.0039.001837.00583.00Pauwels et al. 2012 [19]MeasurementProMax 3D35TLDARTDentoalveolar8488122.0088.0053.002576.001021.00Pauwels et al. 2012 [19]MeasurementProMax 3D35TLDARTDentoalveolar848828.0027.0028.00596.00202.00Pauwels et al. 2012 [19]MeasurementScanora 3D35TLDARTDentoalveolar85107.546.0042.0045.001285.00148.00Pauwels et al. 2012 [19]MeasurementScanora 3D35TLDARTMandible85107.547.0034.0025.001052.00352.00Pauwels et al. 2012 [19]MeasurementScanora 3D35TLDARTMaxilla85107.545.0037.0031.001117.00240.00Pauwels et al. 2012 [19]MeasurementVeraviewepocs 3D35TLDARTDentoalveolar708873.0055.0040.001956.00330.00Pauwels et al. 2012 [19]Measurement3D Accuitomo 17035TLDARTLower jaw, molar region904443.0037.0037.002120.00195.00Pauwels et al. 2012 [19]MeasurementKodak 9000 3D35TLDARTUpper jaw, front region7053.719.0021.0018.00523.0030.00Pauwels et al. 2012 [19]MeasurementKodak 9000 3D35TLDARTLower jaw, molar region7053.740.0078.00290.00709.00251.00Pauwels et al. 2012 [19]MeasurementPax-Uni3D35TLDARTUpper jaw, front region855544.0047.0028.001073.00209.00Pauwels et al. 2012 [19]MeasurementProMax 3D35MOSFETRANDO RAN10220057488153.0025.004.3032.0032.00Koivisto et al. 2012 [20]SimulationProMax 3D35PCXMCORNL Phantom20057488131.006.902.8041.008.40Koivisto et al. 2012 [20]Simulationi-CAT35EGS4ICRP ADULT360556161366.0050.00590.001270.0080.00Morant et al. 2013 [21]Simulationi-CAT35EGS4ICRP ADULT360476161158.0040.00310.001230.0080.00Morant et al. 2013 [21]Simulationi-CAT35EGS4ICRP ADULT360415161053.0030.00190.001150.0070.00Morant et al. 2013 [21]SimulationAccuitomo 1705EGSnrcIn-house360Standard resolution9066172.261052.0089.002965.00387.00Stratis et al. 2016 [22]SimulationAccuitomo 1705EGSnrcIn-house360Standard resolution9088297.971478.00181.004204.001919.00Stratis et al. 2016 [22]SimulationAccuitomo 1708EGSnrcIn-house360Standard resolution9066119.35518.0092.002623.00751.00Stratis et al. 2016 [22]SimulationAccuitomo 1708EGSnrcIn-house360Standard resolution9088228.32986.00181.003831.001747.00Stratis et al. 2016 [22]SimulationAccuitomo 17012EGSnrcIn-house360Standard resolution9066111.76607.0042.001862.00497.00Stratis et al. 2016 [22]SimulationAccuitomo 17012EGSnrcIn-house360Standard resolution9088250.95913.0090.002961.002772.00Stratis et al. 2016 [22]SimulationAccuitomo 17035EGSnrcICRP AF360Standard resolution906681.54376.00112.002830.00175.00Stratis et al. 2016 [22]SimulationAccuitomo 17035EGSnrcICRP AF360Standard resolution9088126.68565.00224.004308.00339.00Stratis et al. 2016 [22]Simulationi-CAT35PCXMCORNL Phantom360120161330.9942.90269.58738.2946.97Yeh and Chen 2018 [23]SimulationProMax 3D5EGSnrcIn-houseCanine XS/ND964.25.5134.90200.00152.003558.00214.00Marcu et al. 2018 [24]SimulationProMax 3D5EGSnrcIn-houseMolars XS/ND964.25.5155.90222.00170.004352.00256.00Marcu et al. 2018 [24]SimulationProMax 3D5EGSnrcIn-houseMolars XS/ND9655.5220.2023.8015.80336.3067.90Marcu et al. 2018 [24]SimulationProMax 3D5EGSnrcIn-houseMolars XS/ND9610968.6077.7062.701400.60315.30Marcu et al. 2018 [24]SimulationProMax 3D5EGSnrcIn-houseMolars XS/ND96105.555.7045.0028.601211.00308.80Marcu et al. 2018 [24]SimulationProMax 3D5EGSnrcIn-houseMolars XS/ND96131675.60149.60948.201453.60206.60Marcu et al. 2018 [24]SimulationProMax 3D5EGSnrcIn-houseS/ND962326178.40614.004324.001596.002677.00Marcu et al. 2018 [24]SimulationProMax 3D8EGSnrcIn-houseCanine XS/ND964.25.5124.6085.00126.003080.00157.00Marcu et al. 2018 [24]SimulationProMax 3D8EGSnrcIn-houseMolars XS/ND964.25.5128.6093.00141.003458.00187.00Marcu et al. 2018 [24]SimulationProMax 3D8EGSnrcIn-houseMolars XS/ND9655.517.1015.2014.40419.0038.60Marcu et al. 2018 [24]SimulationProMax 3D8EGSnrcIn-houseMolars XS/ND9610960.8054.3048.701389.00290.90Marcu et al. 2018 [24]SimulationProMax 3D8EGSnrcIn-houseMolars XS/ND96105.547.9031.70219.001028.00270.60Marcu et al. 2018 [24]SimulationProMax 3D8EGSnrcIn-houseMolars XS/ND96131664.70104.70772.201319.00202.60Marcu et al. 2018 [24]SimulationProMax 3D8EGSnrcIn-houseS/ND962326392.20518.004247.004007.002908.00Marcu et al. 2018 [24]SimulationProMax 3D35EGSnrcICRP AM962326256.10362.804653.004378.00294.00Marcu et al. 2018 [24]SimulationCranex3Dx35MCNP6.1ZUBAL Head180Maxillary first molar/SR168905540.00375.00105.001154.00139.00Kralik et al. 2018 [25]SimulationCranex3Dx35MCNP6.1ZUBAL Head180Mandibular dental arch/SR280906.17.875.00370.0055.001278.001252.00Kralik et al. 2018 [25]SimulationCranex3Dx35MCNP6.1ZUBAL Head180Both dental arches338907.87.874.00578.001155.002045.00535.00Kralik et al. 2018 [25]SimulationCranex3Dx35MCNP6.1ZUBAL Head180Mandible/SR528907.815142.00564.0096.002275.002465.00Kralik et al. 2018 [25]SimulationCranex3Dx35MCNP6.1ZUBAL Head180Viscerocranium/SR755901315170.001034.00552.002847.002370.00Kralik et al. 2018 [25]SimulationCranex3Dx35MCNP6.1ZUBAL Head360Maxillary first molar/SR168905537.00335.0078.00592.00104.00Kralik et al. 2018 [25]SimulationCranex3Dx35MCNP6.1ZUBAL Head360Mandibular dental arch/SR280906.17.8105.00400.0049.001161.00789.00Kralik et al. 2018 [25]SimulationCranex3Dx35MCNP6.1ZUBAL Head360Both dental arches338907.87.892.00621.00153.001559.00789.00Kralik et al. 2018 [25]SimulationCranex3Dx35MCNP6.1ZUBAL Head360Mandible/SR528907.815184.00607.0087.002035.003533.00Kralik et al. 2018 [25]SimulationCranex3Dx35MCNP6.1ZUBAL Head360Viscerocranium/SR755901315214.001005.00523.002371.003384.00Kralik et al. 2018 [25]MeasurementProMax 3D10TLDATOM 706C360510904588.00130.00510.001800.00200.00Kadesjo et al. 2018 [11]MeasurementNewTom5G10TLDATOM 706C360108011066172.00270.00760.003800.00340.00Kadesjo et al. 2018 [11]MeasurementGalileos35TLDRANDOMaxillofacial851515203.00278.00636.007775.008727.00Qiang et al. 2019 [17]SimulationCS930035PCXMCORNL Phantom360Facial251901713.5160.90180.00460.004570.00450.00Lee et al. 2020 [26]SimulationCS930035PCXMCORNL Phantom360Dual jaw9190101094.40100.00230.001950.00580.00Lee et al. 2020 [26]SimulationRAYSCAN35PCXMCORNL Phantom360Large jaw177801610198.00200.00220.005360.00320.00Lee et al. 2020 [26]SimulationRAYSCAN35PCXMCORNL Phantom360Jaw91801010195.20190.00280.004700.00410.00Lee et al. 2020 [26]MeasurementCS930035OSLDATOM 702C360Facial251901713.5181.4020.001020.003160.001210.00Lee et al. 2020 [26]MeasurementCS930035OSLDATOM 702C360Dual jaw9190101090.7010.00230.001950.00580.00Lee et al. 2020 [26]MeasurementRAYSCAN35OSLDATOM 702C360Large jaw177801610228.5010.00380.004540.001680.00Lee et al. 2020 [26]MeasurementRAYSCAN35OSLDATOM 702C360Jaw91801010213.8010.00570.003930.001500.00Lee et al. 2020 [26]MeasurementKaVo 3D eXami35TLDCDP-R1Maxillofacial12014.58.556.6315.22427.821177.24476.04Li et al. RPD 2020 [12]MeasurementKaVo 3D eXami35TLDCDP-R1Maxillofacial12014.58.555.1811.63494.501314.85452.68Li et al. RPD 2020 [12]DAP, dose area product; FOV, field of view.


### 3.1. Technical Parameters and Methods Used in Dosimetry Studies

About 56% (n = 57) of the dose sets were from measurements, and the remaining 44% (n = 44) were from simulation studies. In the measurement studies, different types of dosimeters were used: the thermoluminescent dosimeter (TLD) (86%), the optically stimulated luminescent dosimeter (OSLD) (7%), the Gafchromic film (5%), and the metal-oxide-silicon field-effect transistor (MOSFET) (2%). The physical head phantoms used for measurements included the Alderson Radiation Therapy (ART) phantom (Radiology Support Devices Inc., Long Beach, CA) (70%), the ATOM adult and child phantoms (CIRS, Norfolk, VA) (20%), and CDP-R1 (Chengdu Fangtuo Simulation Technology Company Limited, China) (10%). In the simulation studies, the EGS program [27] produced about 60% of all dose sets followed by MCNP [28] (22%) and PCXMC [29] (STUK, Helsinki, Finland) (18%). A variety of computational head phantoms were used for the simulation studies: in-house head phantoms developed from patient CT images (44%), the Zubal head phantom [30] (22%), the Oak Ridge National Laboratory (ORNL)-stylized phantoms (18%), and the ICRP adult phantoms [31] (16%). The tube potential for intraoral imaging ranged from 60 to 70 kVp. The panoramic and CBCT scans used 62–73 kVp and 70–120 kVp, respectively. In the case of CBCT, the width and height of the FOV ranged from about 4 to 26 cm and the area (width × height) ranged from about 15 [11] to 600 [24] cm2. The beam rotation angle for CBCT was between 180° and 360°. The DAP for CBCT ranged from 91 to 1080 mGy-cm2.


### 3.2. Organ and Effective Doses

The organ and effective doses reported in the literature are summarized in Table5. Mean effective doses delivered by intraoral, 1.32 (0.60–2.56) μSv, and panoramic, 17.93 (3.47–75.00) μSv, procedures are about 1% and 15% of that delivered by CBCT, 121.09 (17.10–392.20) μSv. Among the three imaging modalities, the salivary glands received the greatest dose: 22.79 μGy (intraoral), 660.24 μGy (panoramic), and 2333.95 μGy (CBCT). Among the four organs of interest, the smallest dose was delivered to the bone marrow, except for intraoral where the brain received the smallest dose.Table 5
Minimum, mean, and maximum values of effective and organ (bone marrow, brain, salivary gland, and thyroid) doses from intraoral, panoramic, and cone-beam computed tomography procedures reported in the selected publications.
ProceduresEffective dose (μSv)Organ dose (μGy)Bone marrowBrainSalivary glandThyroidIntraoral (n = 6)Mean1.320.632.3622.797.97Min0.600.000.000.010.00Max2.561.207.7645.2524.47Panoramic (n = 21)Mean17.9314.6623.28660.2457.93Min3.471.500.004.3213.29Max75.0054.0072.002887.00256.00Cone-beam computed tomography (n = 76)Mean121.09254.78471.652333.95811.16Min17.106.902.8032.008.40Max392.201478.004653.007775.008727.00In CBCT imaging, the child phantoms tended to receive greater doses compared with the adult phantoms, except for the salivary glands and thyroid doses (Table6). The child phantoms received about 29% greater effective dose than the adult phantoms. The bone marrow dose of the child phantoms was about 80% greater than that of the adult phantom.Table 6
Minimum, mean, and maximum values of effective and organ (bone marrow, brain, salivary gland, and thyroid) doses from cone-beam computed tomography procedures by age group (children and adults) reported in the selected publications.
Age groupEffective dose (μSv)Organ dose (μGy)Bone marrowBrainSalivary glandThyroidChildren (n = 22)Mean143.9372.2600.72393.3759.7Min17.115.214.4336.338.6Max392.21478.04324.04352.02908.0Adults (n = 54)Mean111.8207.0419.12309.7832.1Min19.06.92.832.08.4Max368.01034.04653.07775.08727.0The effective dose for the larger FOV in CBCT is greater than that for the smaller FOV (Table7). The effective dose for the large FOV (greater than 150 cm2) is about 1.6 times greater than that for the small FOV (less than 50 cm2). The brain dose for the large FOV is about eight times greater than that for the small FOV.Table 7
Minimum, mean, and maximum values of effective and organ (bone marrow, brain, salivary gland, and thyroid) doses from cone-beam computed tomography procedures by field-of-view area (FOV width × height, cm2) reported in the selected publications.
FOV area (cm2)Effective dose (μSv)Organ dose (μGy)Bone marrowBrainSalivary glandThyroidSmall (<50) (n = 20)Mean96.5262.8144.21984.7312.0Min17.115.214.4336.338.6Max220.21052.0760.04352.01252.0Medium (50–150) (n = 32)Mean113.7246.4184.92137.2780.7Min28.06.92.832.08.4Max298.01478.01155.04700.03533.0Large (>150) (n = 24)Mean151.4259.31126.82887.31267.7Min31.010.0124.0738.347.0Max392.21034.04653.07775.08727.0Table8 shows the age- and FOV size-dependent organ and effective doses. A similar trend by age group shown in Table 6 (child’s dose is greater than adult’s dose) and by FOV size shown in Table 7 (large FOV gives greater dose than small FOV) is also observed.Table 8
Minimum, mean, and maximum values of effective and organ (bone marrow, brain, salivary gland, and thyroid) doses from cone-beam computed tomography procedures by age group (children and adults) and field-of-view area (FOV width × height, cm2) reported in the selected publications.
FOV area (cm2) age groupEffective dose (μSv)Organ dose (μGy)Bone marrowBrainSalivary glandThyroidSmall (<50)Children (n = 11)Mean131.3292.4192.02568.5281.4Min17.115.214.4336.338.6Max220.21052.0760.04352.0751.0Adults (n = 9)Mean53.8226.685.81271.1349.3Min19.021.018.0523.030.0Max105.0400.0290.02830.01252.0Medium (50–150)Children (n = 7)Mean144.3512.2115.92289.21089.1Min47.931.728.61028.0270.6Max298.01478.0219.04204.02772.0Adults (n = 25)Mean105.2172.0204.32094.7694.4Min28.06.92.832.08.4Max265.0621.01155.06372.03533.0Large (>150)Children (n = 4)Mean177.7346.62572.92093.91498.6Min64.7104.7772.21319.0202.6Max392.2614.04324.04007.02908.0Adults (n = 20)Mean146.1241.9837.63046.01221.5Min31.010.0124.0738.347.0Max368.01034.04653.07775.08727.0


### 3.3. Monte Carlo Dose Distribution

2D dose distribution at the level of the center of the lower teeth for intraoral, panoramic, and CBCT calculated by MC-GPU simulations are presented in Figure2. The angles of radiation incidence to the head phantom used in the simulations (Table 1) are visible on the head anatomy: 30° from the patient’s front for intraoral; 240° rotation behind the patient’s head for panoramic; and 360° rotation for CBCT. Movie clips presenting a rotating 3D dose distribution for panoramic and CBCT were created and included in the web dose calculator.Figure 2
Dose distribution at the level of the lower teeth generated by MC-GPU simulations for (a) intraoral radiography, (b) panoramic radiography, and (c) cone-beam computed tomography.
(a)(b)(c)The fraction of dose in different tissues (brain, muscle, bone, skin, soft tissue, cerebrospinal, blood, and eye lens) out of the total dose for intraoral, panoramic, and CBCT is shown in Figure3. A larger portion of the radiation dose is delivered to the bone (55%) in intraoral imaging compared with panoramic and CBCT, each of which contributes about 35% of the total radiation dose to the bone. The dose delivered to the brain is nearly zero in intraoral but slightly increased to 1% in panoramic and 2% in CBCT. The dose delivered to skin and soft tissue remarkably increases from 12% (soft tissue) and 10% (skin) in intraoral to 26% (soft tissue) and 12% (skin) in panoramic and 22% (soft tissue) and 11% (skin) in CBCT.Figure 3
Percent fraction of radiation dose for the different tissues in the head derived from the MC-GPU simulation of the human head phantom exposed to (a) intraoral radiography, (b) panoramic radiography, and (c) cone-beam computed tomography.
(a)(b)(c)


### 3.4. Web Dose Calculator

A user-friendly interactive web program was developed for a user to input the following: the type of imaging procedure, the number of image sets, age group, and FOV size (Figure 4(a)). The web interface displays organ and effective doses (Figure4(b)), dose fraction in tissues and 2D and 3D dose distributions in the head (Figure 4(c)), and dose comparison with other radiation sources (Figure 4(d)).Figure 4
Web interfaces for (a) user input, (b) organ (brain, salivary gland, bone marrow, thyroid) and effective doses, (c) the fraction of dose in different tissues and 2D and 3D dose distributions, and (d) dose comparison with other radiation sources.
(a)(b)(c)(d)


## 3.1. Technical Parameters and Methods Used in Dosimetry Studies

About 56% (n = 57) of the dose sets were from measurements, and the remaining 44% (n = 44) were from simulation studies. In the measurement studies, different types of dosimeters were used: the thermoluminescent dosimeter (TLD) (86%), the optically stimulated luminescent dosimeter (OSLD) (7%), the Gafchromic film (5%), and the metal-oxide-silicon field-effect transistor (MOSFET) (2%). The physical head phantoms used for measurements included the Alderson Radiation Therapy (ART) phantom (Radiology Support Devices Inc., Long Beach, CA) (70%), the ATOM adult and child phantoms (CIRS, Norfolk, VA) (20%), and CDP-R1 (Chengdu Fangtuo Simulation Technology Company Limited, China) (10%). In the simulation studies, the EGS program [27] produced about 60% of all dose sets followed by MCNP [28] (22%) and PCXMC [29] (STUK, Helsinki, Finland) (18%). A variety of computational head phantoms were used for the simulation studies: in-house head phantoms developed from patient CT images (44%), the Zubal head phantom [30] (22%), the Oak Ridge National Laboratory (ORNL)-stylized phantoms (18%), and the ICRP adult phantoms [31] (16%). The tube potential for intraoral imaging ranged from 60 to 70 kVp. The panoramic and CBCT scans used 62–73 kVp and 70–120 kVp, respectively. In the case of CBCT, the width and height of the FOV ranged from about 4 to 26 cm and the area (width × height) ranged from about 15 [11] to 600 [24] cm2. The beam rotation angle for CBCT was between 180° and 360°. The DAP for CBCT ranged from 91 to 1080 mGy-cm2.


## 3.2. Organ and Effective Doses

The organ and effective doses reported in the literature are summarized in Table5. Mean effective doses delivered by intraoral, 1.32 (0.60–2.56) μSv, and panoramic, 17.93 (3.47–75.00) μSv, procedures are about 1% and 15% of that delivered by CBCT, 121.09 (17.10–392.20) μSv. Among the three imaging modalities, the salivary glands received the greatest dose: 22.79 μGy (intraoral), 660.24 μGy (panoramic), and 2333.95 μGy (CBCT). Among the four organs of interest, the smallest dose was delivered to the bone marrow, except for intraoral where the brain received the smallest dose.Table 5
Minimum, mean, and maximum values of effective and organ (bone marrow, brain, salivary gland, and thyroid) doses from intraoral, panoramic, and cone-beam computed tomography procedures reported in the selected publications.
ProceduresEffective dose (μSv)Organ dose (μGy)Bone marrowBrainSalivary glandThyroidIntraoral (n = 6)Mean1.320.632.3622.797.97Min0.600.000.000.010.00Max2.561.207.7645.2524.47Panoramic (n = 21)Mean17.9314.6623.28660.2457.93Min3.471.500.004.3213.29Max75.0054.0072.002887.00256.00Cone-beam computed tomography (n = 76)Mean121.09254.78471.652333.95811.16Min17.106.902.8032.008.40Max392.201478.004653.007775.008727.00In CBCT imaging, the child phantoms tended to receive greater doses compared with the adult phantoms, except for the salivary glands and thyroid doses (Table6). The child phantoms received about 29% greater effective dose than the adult phantoms. The bone marrow dose of the child phantoms was about 80% greater than that of the adult phantom.Table 6
Minimum, mean, and maximum values of effective and organ (bone marrow, brain, salivary gland, and thyroid) doses from cone-beam computed tomography procedures by age group (children and adults) reported in the selected publications.
Age groupEffective dose (μSv)Organ dose (μGy)Bone marrowBrainSalivary glandThyroidChildren (n = 22)Mean143.9372.2600.72393.3759.7Min17.115.214.4336.338.6Max392.21478.04324.04352.02908.0Adults (n = 54)Mean111.8207.0419.12309.7832.1Min19.06.92.832.08.4Max368.01034.04653.07775.08727.0The effective dose for the larger FOV in CBCT is greater than that for the smaller FOV (Table7). The effective dose for the large FOV (greater than 150 cm2) is about 1.6 times greater than that for the small FOV (less than 50 cm2). The brain dose for the large FOV is about eight times greater than that for the small FOV.Table 7
Minimum, mean, and maximum values of effective and organ (bone marrow, brain, salivary gland, and thyroid) doses from cone-beam computed tomography procedures by field-of-view area (FOV width × height, cm2) reported in the selected publications.
FOV area (cm2)Effective dose (μSv)Organ dose (μGy)Bone marrowBrainSalivary glandThyroidSmall (<50) (n = 20)Mean96.5262.8144.21984.7312.0Min17.115.214.4336.338.6Max220.21052.0760.04352.01252.0Medium (50–150) (n = 32)Mean113.7246.4184.92137.2780.7Min28.06.92.832.08.4Max298.01478.01155.04700.03533.0Large (>150) (n = 24)Mean151.4259.31126.82887.31267.7Min31.010.0124.0738.347.0Max392.21034.04653.07775.08727.0Table8 shows the age- and FOV size-dependent organ and effective doses. A similar trend by age group shown in Table 6 (child’s dose is greater than adult’s dose) and by FOV size shown in Table 7 (large FOV gives greater dose than small FOV) is also observed.Table 8
Minimum, mean, and maximum values of effective and organ (bone marrow, brain, salivary gland, and thyroid) doses from cone-beam computed tomography procedures by age group (children and adults) and field-of-view area (FOV width × height, cm2) reported in the selected publications.
FOV area (cm2) age groupEffective dose (μSv)Organ dose (μGy)Bone marrowBrainSalivary glandThyroidSmall (<50)Children (n = 11)Mean131.3292.4192.02568.5281.4Min17.115.214.4336.338.6Max220.21052.0760.04352.0751.0Adults (n = 9)Mean53.8226.685.81271.1349.3Min19.021.018.0523.030.0Max105.0400.0290.02830.01252.0Medium (50–150)Children (n = 7)Mean144.3512.2115.92289.21089.1Min47.931.728.61028.0270.6Max298.01478.0219.04204.02772.0Adults (n = 25)Mean105.2172.0204.32094.7694.4Min28.06.92.832.08.4Max265.0621.01155.06372.03533.0Large (>150)Children (n = 4)Mean177.7346.62572.92093.91498.6Min64.7104.7772.21319.0202.6Max392.2614.04324.04007.02908.0Adults (n = 20)Mean146.1241.9837.63046.01221.5Min31.010.0124.0738.347.0Max368.01034.04653.07775.08727.0


## 3.3. Monte Carlo Dose Distribution

2D dose distribution at the level of the center of the lower teeth for intraoral, panoramic, and CBCT calculated by MC-GPU simulations are presented in Figure2. The angles of radiation incidence to the head phantom used in the simulations (Table 1) are visible on the head anatomy: 30° from the patient’s front for intraoral; 240° rotation behind the patient’s head for panoramic; and 360° rotation for CBCT. Movie clips presenting a rotating 3D dose distribution for panoramic and CBCT were created and included in the web dose calculator.Figure 2
Dose distribution at the level of the lower teeth generated by MC-GPU simulations for (a) intraoral radiography, (b) panoramic radiography, and (c) cone-beam computed tomography.
(a)(b)(c)The fraction of dose in different tissues (brain, muscle, bone, skin, soft tissue, cerebrospinal, blood, and eye lens) out of the total dose for intraoral, panoramic, and CBCT is shown in Figure3. A larger portion of the radiation dose is delivered to the bone (55%) in intraoral imaging compared with panoramic and CBCT, each of which contributes about 35% of the total radiation dose to the bone. The dose delivered to the brain is nearly zero in intraoral but slightly increased to 1% in panoramic and 2% in CBCT. The dose delivered to skin and soft tissue remarkably increases from 12% (soft tissue) and 10% (skin) in intraoral to 26% (soft tissue) and 12% (skin) in panoramic and 22% (soft tissue) and 11% (skin) in CBCT.Figure 3
Percent fraction of radiation dose for the different tissues in the head derived from the MC-GPU simulation of the human head phantom exposed to (a) intraoral radiography, (b) panoramic radiography, and (c) cone-beam computed tomography.
(a)(b)(c)


## 3.4. Web Dose Calculator

A user-friendly interactive web program was developed for a user to input the following: the type of imaging procedure, the number of image sets, age group, and FOV size (Figure 4(a)). The web interface displays organ and effective doses (Figure4(b)), dose fraction in tissues and 2D and 3D dose distributions in the head (Figure 4(c)), and dose comparison with other radiation sources (Figure 4(d)).Figure 4
Web interfaces for (a) user input, (b) organ (brain, salivary gland, bone marrow, thyroid) and effective doses, (c) the fraction of dose in different tissues and 2D and 3D dose distributions, and (d) dose comparison with other radiation sources.
(a)(b)(c)(d)


## 4. Discussion

Dental imaging is one of the most common radiological imaging procedures. Although the dose level is known to be relatively low, it is still important to monitor the trend of dental dose in different dental imaging modalities. We evaluated the radiation dose received from dental imaging practices by extracting data from literature published after 2010. To efficiently present the results of the study, an interactive web-based dose calculator was created.We compared our results from intraoral imaging with those published by Fontana et al. [32], which report the dose to the brain, salivary gland, and thyroid delivered by imaging conducted from 1940 to 2009, with the increment of ten years. To simplify the comparison, we averaged their doses in three time periods: 1940–1969, 1970–1989, and 1990–2009. The period 2010–2020 adopted in our study follows the end of their study period. A clear dose reduction was observed in the brain dose by period. Compared with the organ doses reported for the earliest period (1940–1969), the doses to the brain, salivary gland, and thyroid resulted from our study were smaller by 77%, 93%, and 93%, respectively. Compared with the latest period, 1990–2009, in Fontana et al., our organ doses were smaller by 7%, 64%, and 62% for the brain, salivary gland, and thyroid, respectively. The dose reduction may be due to the change in technical parameters and the improvement in imaging quality with the same amount of radiation.The average effective dose from CBCT, delivering the greatest dose compared with intraoral and panoramic, was more than 92 times greater than that from intraoral and seven times greater than that from panoramic (Table4). However, the maximum CBCT effective dose, with a large FOV, for children, 392.2 μSv [5], is about 13% of the dose from the natural radiation that a person receives on average every year, 3110 μSv [9], disregarding the radiation received from occupations and medical procedures.We are aware of the following limitations in the current study. First, without dose calibration using measurements from clinical machines, absolute doses could not be estimated with our Monte Carlo simulations, so only relative dose distributions were obtained and analyzed. Future work may involve accurate dose measurements to provide absolute doses for a comprehensive library of technical parameters for panoramic and CBCT procedures. Second, we found that pediatric dose data were relatively limited in literature compared with those of adults, so we grouped age-dependent dose data into pediatric (age <20) and adult (age ≥ 20) for CBCT only,for which a total of 22 pediatric data points were available. Since a clear age dependency for those limited data points was not observed, possibly due to large variability, we categorized the pediatric ages into a single group. Considering the higher potential risk in pediatric patients, due to increased radiosensitivity and longer expected life span after the irradiation event, it is important to more accurately evaluate the doses delivered to them once additional dose data are available in the future. Lastly, our literature search was limited to one bibliographic database, PubMed, to the keywords we defined, and to the papers written in English.


## 5. Conclusion

A comprehensive table of the organ and effectives doses delivered by intraoral, panoramic, and CBCT dental imaging procedures was established from previously published articles collected from PubMed. We found that organ and effective doses from intraoral and panoramic radiography are substantially smaller than those from CBCT, and the maximum CBCT effective dose is about 13% of the dose from annual natural radiation. Our dose summary should be useful for comparison among doses from different dental imaging methods as well as comparison with doses from other radiation sources. The user-friendly, interactive web application (http://dentaldose.org) allows for receiving user input and displaying doses, dose distribution maps, and dose comparison with other radiation sources.



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