Radiation protection in dental radiology – Recent advances and future directions

Optimizing radiation safety in dentistry: Clinical recommendations and regulatory considerations

BACKGROUND

The value of dental radiographs to oral health care decision making must be balanced with radiation safety to minimize patient exposure and occupational risk of oral health care providers. This review summarizes recommendations and regulatory guidance regarding dental radiography and cone-beam computed tomography. An expert panel presents recommendations on radiation safety, appropriate imaging practices, and reducing radiation exposure.

TYPES OF STUDIES REVIEWED

A systematic search run in Ovid MEDLINE, Embase, and Cochrane Database of Systematic Reviews identified relevant topical systematic reviews, organizational guidelines, and regulatory reviews published in the peer-reviewed literature since 2010. A supplemental search of the gray literature (eg, technical reports, standards, and regulations) identified topical nonindexed publications. Inclusion criteria required relevance to primary oral health care (ie, general or pediatric dentistry).

RESULTS

A total of 95 articles, guidance documents, and regulations met the inclusion criteria. Resources were characterized as applicable to all modalities, operator and occupational protection, dose reduction and optimization, and quality assurance and control.

PRACTICAL IMPLICATIONS

Understanding factors affecting imaging safety and applying fundamental principles of radiation protection consistent with federal, state, and local requirements are essential for limiting patient ionizing radiation exposure, in conjunction with implementing optimal imaging procedures to support prudent use of dental radiographs and cone-beam computed tomographic imaging. The regulatory guidance and best practice recommendations summarized in this article should be followed by dentists and other oral health care providers.

Magnetic resonance imaging in dental implant surgery: a systematic review

PURPOSE

To comprehensively assess the existing literature regarding the rapidly evolving in vivo application of magnetic resonance imaging (MRI) for potential applications, benefits, and challenges in dental implant surgery.

METHODS

Electronic and manual searches were conducted in PubMed MEDLINE, EMBASE, Biosis, and Cochrane databases by two reviewers following the PICOS search strategy. This involved using medical subject headings (MeSH) terms, keywords, and their combinations.

RESULTS

Sixteen studies were included in this systematic review. Of the 16, nine studies focused on preoperative planning and follow-up phases, four evaluated image-guided implant surgery, while three examined artifact reduction techniques. The current literature highlights several MRI protocols that have recently investigated and evaluated the in vivo feasibility and accuracy, focusing on its potential to provide surgically relevant quantitative and qualitative parameters in the assessment of osseointegration, peri-implant soft tissues, surrounding anatomical structures, reduction of artifacts caused by dental implants, and geometric accuracy relevant to implant placement. Black Bone and MSVAT-SPACE MRI, acquired within a short time, demonstrate improved hard and soft tissue resolution and offer high sensitivity in detecting pathological changes, making them a valuable alternative in targeted cases where CBCT is insufficient. Given the data heterogeneity, a meta-analysis was not possible.

CONCLUSIONS

The results of this systematic review highlight the potential of dental MRI, within its indications and limitations, to provide perioperative surgically relevant parameters for accurate placement of dental implants.

Impact of dental imaging on pregnant women and recommendations for fetal radiation safety: A systematic review

Purpose

This study was conducted to investigate the safety of dental imaging in pregnant women with respect to fetal health.

Materials and Methods

Searches were conducted of the PubMed, Scopus, and Web of Science databases in May 2023. The inclusion criteria encompassed cross-sectional and longitudinal studies that focused on the analysis of diagnostic dental imaging in pregnant women, as well as studies utilizing phantoms to simulate imaging examinations. The exclusion criteria consisted of reviews, letters to the editor, book chapters, and abstracts from scientific conferences and seminars.

Results

A total of 3,913 articles were identified. Based on a review of the titles and abstracts, 3,892 articles were excluded, leaving 21 articles remaining for full-text review. Of these, 18 were excluded, and 4 additional articles were included as cross-references. Ultimately, 7 articles underwent quantitative-qualitative analysis. Three retrospective studies were focused on pregnant women who underwent dental imaging procedures. The remaining 4 studies utilized female phantoms to simulate imaging examinations and represent the radiation doses absorbed by the uterus or thyroid.

Conclusion

Few dental radiology studies have been conducted to determine the safe radiation threshold for pregnant women. Additionally, the reviewed articles did not provide numbers of dental examinations, by type, corresponding to this dose. Dental imaging examinations of pregnant women should not be restricted if clinically indicated. Ultimately, practitioners must be able to justify the examination and should adhere to the "as low as diagnostically acceptable, being indication-oriented and patient-specific" (ALADAIP) principle of radioprotection.

Preoperative imaging in third molar surgery - A prospective comparison of X-ray-based and radiation-free magnetic resonance orthopantomography

This study aimed to compare preoperative data relevant to third molar surgery based on radiographic orthopantomography (OPG) and orthopantomogram-like MR images (MR-OPG), using five different MR protocols. X-ray-based OPG and OPG-like MRI reconstructions from DESS, SPACE-STIR, SPACE-SPAIR, T1-VIBE-Dixon, and UTE sequences were acquired in 11 patients undergoing third molar surgery, using a 15-channel mandibular coil. Qualitative (image quality, susceptibility to artifacts, positional relationship, contact/non-contact of the inferior alveolar nerve (IAN), relationship to maxillary sinus, IAN continuity, root morphology) and quantitative (tooth length, retromolar distance, distance to the IAN, and distance to the mandible margin) parameters of the maxillary and mandibular third molars were assessed regarding inter-reader agreement and quantitative discrepancies by three calibrated readers. Radiation-free MR-OPGs generated within clinically tolerable acquisition times, which exhibited high image quality and low susceptibility to artifacts, showed no significant differences compared with X-ray-based OPGs regarding the assessment of quantitative parameters. UTE MR-OPGs provided radiographic-like images and were best suited for assessing qualitative preoperative data (positional relationship, nerve contact/non-contact, and dental root morphology) relevant to third molar surgery. For continuous and focal nerve imaging, DESS MR-OPG was superior. MR-OPGs could represent a shift towards indication-specific and modality-oriented perioperative imaging in high-risk oral and maxillofacial surgery.

Imaging in Third Molar Surgery: A Clinical Update

Third molar surgery is one of the most common surgical procedures performed in oral and maxillofacial surgery. Considering the patient's young age and the often-elective nature of the procedure, a comprehensive preoperative evaluation of the surgical site, relying heavily on preoperative imaging, is key to providing accurate diagnostic work-up, evidence-based clinical decision making, and, when appropriate, indication-specific surgical planning. Given the rapid developments of dental imaging in the field, the aim of this article is to provide a comprehensive, up-to-date clinical overview of various imaging techniques related to perioperative imaging in third molar surgery, ranging from panoramic radiography to emerging technologies, such as photon-counting computed tomography and magnetic resonance imaging. Each modality's advantages, limitations, and recent improvements are evaluated, highlighting their role in treatment planning, complication prevention, and postoperative follow-ups. The integration of recent technological advances, including artificial intelligence and machine learning in biomedical imaging, coupled with a thorough preoperative clinical evaluation, marks another step towards personalized dentistry in high-risk third molar surgery. This approach enables minimally invasive surgical approaches while reducing inefficiencies and risks by incorporating additional imaging modality- and patient-specific parameters, potentially facilitating and improving patient management.

Genotoxic and Cytotoxic Effects of Cone Beam Computed Tomography and Multidetector Computed Tomography on Exfoliated Buccal Epithelial Cells

Background

Cone beam computed tomography (CBCT) and multidetector computed tomography (MDCT) are frequently used in dental and maxillofacial problems. This study aimed to assess the genotoxicity and cytotoxicity effects of CBCT and MDCT radiographies on exfoliated buccal epithelial cells during dental examinations.

Methods

This prospective experimental study was conducted at Babol University of Medical Sciences (Babol, Iran) from March 2021 to April 2021. Buccal mucosa smears were collected bilaterally pre-exposure and 12 days after CBCT or MDCT examinations. To compare the frequency of micronuclei and other cytotoxic cellular changes such as pyknosis, karyolysis, and karyorrhexis, the paired sample t test and Wilcoxon test were used. In addition, independent sample t test, Mann-Whitney, and Chi square tests were used to investigate the differences between the imaging methods and between men and women. All statistical analyses were performed using the SPSS software, and P≤0.05 was considered statistically significant.

Results

The current study included 60 adult patients (30 patients in each group), ranging in age from 21 to 50 years. The micronuclei and the other cytotoxic cellular changes increased significantly after CBCT and MDCT radiographic examinations on the 12th day compared to the pre-exposure results (P<0.001). MDCT had statistically higher cytotoxic and genotoxic effects than CBCT (9.4%, 23.1%, and 40% higher values in micronucleus frequency, the mean frequency of micronuclei, and other cytotoxic changes, respectively). There were no significant differences between men and women in the two examination methods (P=0.46 and P=0.49, respectively).

Conclusion

Dental examinations with CBCT and MDCT can increase cytotoxicity and chromosomal damage in both men and women. Due to its lower radiation toxicities, CBCT can be recommended as an alternative to MDCT for dental examinations.

MR-orthopantomography in operative dentistry and oral and maxillofacial surgery: a proof of concept study

This prospective study aimed to present, compare, and evaluate the suitability of five different magnetic resonance imaging (MRI) protocols (3D double-echo steady-state (DESS), 3D fast spin echo short-tau inversion recovery (SPACE-STIR), 3D fast spin echo spectral attenuated inversion recovery (SPACE-SPAIR), volumetric interpolated breath-hold examination (T1-VIBE-Dixon), and ultrashort echo time (UTE)) and for orthopantomogram (OPG)-like MRI reconstructions using a novel mandibular coil. Three readers assessed MR-OPGs of 21 volunteers regarding technical image quality (4, excellent; 0, severely reduced), susceptibility to artifacts (3, absence; 0, massive), and visualization of anatomical structures in the oral cavity and surrounding skeletal structures (4, fine details visible; 0, no structures visible). Average image quality was good (3.29 ± 0.83) for all MRI protocols, with UTE providing the best image quality (3.52 ± 0.62) and no to minor artifacts (2.56 ± 0.6). Full diagnostic interpretability of the osseous structures is best in VIBE-Dixon and UTE MR-OPGs. DESS provided excellent visualization of the finest details of the nervous tissue (3.95 ± 0.22). Intra-reader and inter-reader agreement between the readers was good to excellent for all protocols (ICCs 0.812-0.957). MR-OPGs provide indication-specific accurate imaging of the oral cavity and could contribute to the early detection of pathologies, staging, and radiological follow-up of oral and maxillofacial diseases.

Magnetic resonance imaging for preoperative diagnosis in third molar surgery: a systematic review

In recent years, magnetic resonance imaging (MRI) has made great strides through various technical improvements and new sequences, which have made it one of the most promising and leading imaging techniques in the head and neck region. As modern imaging techniques in dentistry aim to reduce radiation exposure, this systematic review evaluated the possibilities, advantages, and disadvantages of advanced imaging diagnostics using dental MRI and its evidence for clinical indications and limitations relevant to mandibular third molar (MTM) surgery. Two reviewers performed multiple database searches (PubMed MEDLINE, EMBASE, Biosis, and Cochrane databases) following the PICOS search strategy using medical subject headings (MeSH) terms, keywords, and their combinations. Ten studies were included in this systematic review. By providing high spatial resolution and excellent soft tissue contrast, black bone MRI sequences such as 3D Double Echo Steady State (DESS) and 3D Short Tau Inversion Recovery (STIR) imaging protocols have the potential to become a valuable alternative to cone-beam computed tomography (CBCT) in future dental clinical routines. Overall, radiation-free MRI represents another step toward personalized dentistry and improved decision-making that avoids ineffectiveness and minimizes risks in oral surgery by taking into account additional patient-side factors such as comorbidity, anatomical norm variations, and imaging biomarkers.

Effect of field of view (FOV) positioning and shielding on radiation dose in paediatric CBCT

OBJECTIVE

To investigate the effect of two different large field of view (FOV) positions in the vertical dimension and shielding (thyroid collar and eyeglasses) on the effective dose and the local doses of various sites of the craniofacial complex.

METHODS

Organ doses and effective doses were calculated based on the measured doses using 27 pairs of thermoluminescent dosemeters in a paediatric tissue-equivalent of a 10-year-old anthropomorphic phantom. The large FOV of the 3D Accuitomo F170 CBCT scanner was used to image parts of the craniofacial complex. Six protocols were performed: (A) cranial position without shielding; (B) cranial position with shielding; (C) caudal position without shielding; (D) caudal position with shielding, (E) similar to C with 3600 rotation and (F) similar to D with 360° rotation. Measurements were obtained in duplicate, and the relative δ value (%) was applied to compare the average doses between the protocols.

RESULTS

Changing the FOV position from cranial to caudal without using shielding resulted in an increase of the effective dose of 18.8%. Use of shielding in the caudal position reduced the dose by 31.6%. Local absorbed dose of the thyroid had the most relevant impact on calculation of the effective dose, followed by oesophagus, bone marrow and bone surfaces, especially when comparing the different protocols.

CONCLUSIONS

Application of shielding devices for thyroid in combination with a most caudal positioning of FOV led to the lowest local absorbed doses as well as the effective dose in a child phantom model.

Evaluating the X-ray-Shielding Performance of Graphene-Oxide-Coated Nanocomposite Fabric

Exposure to ionizing radiation (IR) during diagnostic medical procedures brings certain risks, especially when experiencing recurrent exposures. The fabrication of nano-based composites, doped with different nanoparticles, have been suggested as effective shielding materials to replace conventional lead-based ones in material sciences and nanotechnology. In this study, commercially available fabrics, used to produce scrubs and gowns for clinical staff, are modified utilizing graphene oxide (GO) nanoparticles using a layer-by-layer (LBL) technique. GO was obtained from graphite through environmentally friendly technology by using a modified-improved Hummers' method without NaNO₃. Lightweight, flexible, air- and water-permeable shielding materials are produced that are wearable in all-day clinical practice. The nanoparticles are kept to a minimum at 1 wt%; however, utilizing the LBL technique they are distributed evenly along the fibers of the fabrics to achieve as much shielding effect as possible. The evaluation of samples is accomplished by simulating real-time routine clinical procedures and the radiographic programs and devices used daily. The GO-coated nanocomposite fabrics demonstrated promising results for X-ray shielding.

Knowledge, attitude, and behavior of Turkish dentists about radiation protection and radiation safety

OBJECTIVES

Dentists use dental imaging methods frequently in the diagnosis and treatment of dental diseases. This study aimed to determine dentists' knowledge, attitudes, and behaviors about radiation protection during dental imaging procedures.

METHODS

Dentists from two major dental health centres in İzmir province were asked to participate in this study. The participants replied to a questionnaire that consisted of questions on the use of radiographic devices, knowledge on the radiation protection of patients and staff, and attitudes and behaviors regarding radiation protection. The questionnaire also included questions about the socio-demographic characteristics of the participants. Descriptive statistics of data were performed using the SPSS software program.

RESULTS

Sixty-six dentists participated in the survey. The mean knowledge score of dentists on dental imaging, radiation, and radiation protection was 8.3 ± 2.6 out of 17, while the mean attitude and behavior score was 8.3 ± 2.1 out of 27.97% of the participants stated that medical imaging technicians should carry out imaging procedures. The use of rectangular collimators was 9.1%, and using E/F film was 56.3% among dentists. 23.3% of participants stated that they applied the bisecting angle technique during dental imaging, 23.8% stated that they wear a lead apron during imaging, and 37.8% stated that they always used thyroid shields on the patients. In addition, 37.2% of the dentists stated that the patient holds the film during preapical radiography, and 81.5% used the same imaging parameters for adult and pediatric patients. 62% of dentists stated that they question the pregnancy of female patients before imaging.

CONCLUSION

Findings of the study suggest that the knowledge of dentists about dental imaging procedures and radiation protection needs to be improved. The implementation and the follow-up of quality training programs in accordance with the standards set by the national authority will be of great importance.

Diagnostic Accuracy of Cystic Lesions Using a Pre-Programmed Low-Dose and Standard-Dose Dental Cone-Beam Computed Tomography Protocol: An Ex Vivo Comparison Study

Background: This study aimed to analyze the diagnostic reliability of radiographic assessment of cystic lesions using a pre-set, manufacturer-specific, low-dose mode compared to a standard-dose dental cone-beam computed tomography (CBCT) imaging protocol. Methods: Forty pig mandible models were prepared with cystic lesions and underwent both CBCT protocols on an Orthophos SL Unit (Dentsply-Sirona, Bensheim, Germany). Qualitative and quantitative analysis of CBCT data was performed by twelve investigators independently in SIDEXIS 4 (Dentsply-Sirona) using a trial-specific digital examination software tool. Thereby, the effect of the two dose types on overall detectability rate, the visibility on a scale of 1 (very low) to 10 (very high) and the difference between measured radiographic and actual lesion size was assessed. Results: Low-dose CBCT imaging showed no significant differences considering detectability (78.8% vs. 81.6%) and visibility (9.16 vs. 9.19) of cystic lesions compared to the standard protocol. Both imaging protocols performed very similarly in lesion size assessment, with an apparent underestimation of the actual size. Conclusion: Low-dose protocols providing confidential diagnostic evaluation with an improved benefit–risk ratio according to the ALADA principle could become a promising alternative as a primary diagnostic tool as well as for radiological follow-up in the treatment of cystic lesions.

Comparison of Preoperative Cone-Beam Computed Tomography and 3D-Double Echo Steady-State MRI in Third Molar Surgery

We investigated the reliability of assessing a positional relationship between the inferior alveolar nerve (IAN) and mandibular third molar (MTM) based on CBCT, 3D-DESS MRI, and CBCT/MRI image fusion. Furthermore, we evaluated qualitative parameters such as inflammatory processes and imaging fusion patterns. Therefore, two raters prospectively assessed in 19 patients with high-risk MTM surgery cases several parameters for technical image quality and diagnostic ability using modified Likert rating scales. Inter- and intra-reader agreement was evaluated by performing weighted kappa analysis. The inter- and intra-reader agreement for the positional relationship was moderate (κ = 0.566, κ = 0.577). Regarding the detectability of inflammatory processes, the agreement was substantial (κ = 0.66, κ = 0.668), with MRI providing a superior diagnostic benefit regarding early inflammation detection. Independent of the readers’ experience, the agreement of judgment in 3D-DESS MRI was adequate. Black bone MRI sequences such as 3D-DESS MRI providing highly confidential preoperative assessment in MTM surgery have no significant limitations in diagnostic information. With improved cost and time efficiency, dental MRI has the potential to establish itself as a valid alternative in high-risk cases compared to CBCT in future clinical routine.

Visualization of the Inferior Alveolar Nerve and Lingual Nerve Using MRI in Oral and Maxillofacial Surgery: A Systematic Review

We evaluate the preoperative visualization of the inferior alveolar nerve (IAN) and lingual nerve (LN) as reported using radiation-free magnetic resonance imaging (MRI). An accurate visualization shall minimize the postoperative risk for nerve injuries in oral and maxillofacial surgery. PubMed MEDLINE, EMBASE, Biosis, and Cochrane databases were selected for the PICOS search strategy by two reviewers using medical subject headings (MeSH) terms. Thirty studies were included in the systematic review. Based on these studies’ findings, the use of black bone MRI sequences, especially 3D short-tau inversion recovery (STIR), provides superior soft-tissue resolution and high sensitivity in detecting pathological changes. Due to the implementation variability regarding scan parameters and the use of different magnetic field strengths, studies with well-designed protocols and a low risk of bias should be conducted to obtain stronger evidence. With improved cost and time efficiency and considering the benefit–risk ratio, MRI is a promising imaging modality that could become part of routine clinical practice in the future.

Occupational and patients effective radiation doses in dental imaging

Ionizing radiation exposure from medical applications is increasing annually worldwide. It was estimated that 325 million dental procedures were performed in the United States. Radiation exposure from dental radiography consists of intraoral, panoramic, and 3D imaging cone-beam computed tomography (CBCT) imaging. Recent studies reported an association between dental imaging procedures and increased cancer probability of brain and thyroid. Previous studies showed that some dental imaging practices exposed patients and staff to unnecessary radiation doses due to incorrect image acquisition and insufficient radiation protection measures. This study aims to (i) measure the occupational and patients doses during dental procedures and (ii) assess the current imaging techniques and radiation protection practices. Two hundred fourteen patients were evaluated for periapical, bitewing, cephalometric, occlusal, and panoramic procedures. Organ equivalent doses were quantified for the breast, eye lens, and thyroid gland during CBCT procedure. Occupational and ambient dose assessment were assessed using calibrated thermoluminescent dosimeters (TLD-100(LiF: Mg. Ti). Ambient doses were measure at different locations at the department using TLDs. Patients' radiation doses were quantified using kerma area product (PKA (mGy.cm) and the entrance surface air kerma (ESAK (mGy). Fixed tube voltage (65 kVp) and tube current-time product (7 mAs) were used. The overall mean, sd, and range of patients dose values during intraoral (mGy), panoramic and CBCT examinations were 4.6 ± 0.7 (1.4-7.1), 135 ± 45 (75.2-168.5), and 215 ± 165 (186-2115), respectively. The mean and range of the annual occupational doses (mSv) were 1.4 (0.6-3.7), which below the annual dose limits for radiation workers (20 mSv/y). The study showed that inadequate radiation protection for patients existed in terms of the use of the thyroid shield, the technologist's presence inside the room during radiation exposure. Patients' radiation doses were comparable with the international diagnostic reference level (DRL). Staff education and training in radiation protection aspects are highly recommended.

Dental cone beam CT: An updated review

Cone beam computed tomography (CBCT) is a diverse 3D x-ray imaging technique that has gained significant popularity in dental radiology in the last two decades. CBCT overcomes the limitations of traditional two-dimensional dental imaging and enables accurate depiction of multiplanar details of maxillofacial bony structures and surrounding soft tissues. In this review article, we provide an updated status on dental CBCT imaging and summarise the technical features of currently used CBCT scanner models, extending to recent developments in scanner technology, clinical aspects, and regulatory perspectives on dose optimisation, dosimetry, and diagnostic reference levels. We also consider the outlook of potential techniques along with issues that should be resolved in providing clinically more effective CBCT examinations that are optimised for the benefit of the patient.

Backscatter factors calculation for intraoral dental radiology

The dosimetry of intraoral radiography procedures is of great interest since dental examinations are among the most numerous radiological procedures. Usually, the surveys are performed using measurements free in air. The entrance surface air kerma (K_e) can be estimated from measurements of incident air kerma and the use of backscatter factors (BSF). The purpose of this work is to calculate BSF values suitable for intraoral radiography. In addition to specific intraoral radiography, a comprehensive reassessment of internationally recommended BSF values was performed through Monte Carlo simulations. Moreover, theK_ewas estimated using the calculated BSF values for a sample of 44 intraoral radiography systems. The interpolation of intraoral radiography BSF values from reference data can lead to an overestimation of up to 10% and 6% in comparison with the values calculated in this work for monoenergetic photons and x-ray spectra, respectively. Such discrepancy may be relevant when defining diagnostic reference levels (DRLs) or performing quality control tests. The calculations for a sample of 44 intraoral radiography systems showed that the majority of the equipment operates with an entrance surface air kerma higher than 3.5 mGy. In the case of adopting a single value to estimateK_e, the use of BSF equal to 1.2 results in less dispersion compared to calculated values in this work and the use of 1.1 can underestimateK_evalues up to 12%.

ESTIMATING RADIATION DOSE TO MAJOR ORGANS IN DENTAL X-RAY EXAMINATIONS: A PHANTOM STUDY

The radiation doses absorbed by major organs of males and females were studied from three types of dental X-ray devices. The absorbed doses from cone-beam computed tomography (CBCT), panoramic and intraoral X-ray machines were in the range of 0.23-1314.85 μGy, and were observed to be high in organs and tissues located in or adjacent to the irradiated area, there were discrepancies in organ doses between male and female. Thyroid, salivary gland, eye lens and brain were the organs that received higher absorbed doses. The organ absorbed doses were considerably lower than the diagnostic reference level for dental radiography in China. The calculated effective radiation doses for males and females were 56.63, 8.15, 2.56 μSv and 55.18, 8.99, 2.39 μSv, respectively, when using CBCT, the panoramic X-ray machine and intraoral X-ray machine. The effective radiation dose caused by CBCT was much higher than those of panoramic and intraoral X-ray machines.

X-ray dose reduction using additional copper filtration for dental cone beam CT

This study aims to quantitatively evaluate the effect of additional copper-filters (Cu-filters) on the radiation dose and contrast-to-noise ratio (CNR) in a dental cone beam computed tomography (CBCT). The Cu-filter thickness and tube voltage of the CBCT unit were varied in the range of 0.00-0.20 mm and 70-90 kV, respectively. The CBCT images of a phantom with homogeneous materials of aluminum, air, and bone equivalent material (BEM) were acquired. The CNRs were calculated from the voxel values of each homogeneous material. The CTDI_vol was measured using standard polymethyl methacrylate CTDI test objects. We evaluated and analyzed the effects of tube current and various radiation qualities on the CNRs and CTDI_vol. We observed a tendency for higher CNR at increasing tube voltage and tube current in all the homogeneous materials. On the other hand, the CNR reduced at increasing Cu-filter thickness. The tube voltage of 90 kV showed a clear advantage in the tube current-CNR curves in all the homogeneous materials. The CTDI_vol increased as the tube voltage and tube current increased and decreased with the increase in the Cu-filter thickness. When the CNR was fixed at 9.23 of BEM at an exposure setting of 90 kV/5 mA without a Cu-filter, the CTDI_vol at 90 kV with Cu-filters was 8.7% lower compared with that at 90 kV without a Cu-filter. The results from this study demonstrate the potential of adding a Cu-filter for patient dose reduction while ensuring the image quality.

Dental MRI: a road beyond CBCT

KEY POINTS

• Three-dimensional (3D) imaging coupled with computer-guided surgery planning is the core of the contemporary dental implant practice.• Magnetic resonance (MR)-based dental implant planning can achieve results comparable to those with cone beam computed tomography (CBCT)-based planning.• MR-based dental implant planning without radiation dose could be a potential alternative to CBCT-based planning.

The missing link in image quality assessment in digital dental radiography

Digital radiography is gaining popularity among general dental practitioners. It includes digital intraoral radiography, digital panoramic radiography, digital cephalography, and cone-beam computed tomography. In this study, we focused on the methods to assess image quality of these techniques, except for digital cephalography, in the light of historical issues. We stressed on the importance of the development of a standardized phantom and quantitative analysis of diagnostic image quality using it, especially in the aspect of psychophysical properties of these digital systems. There is no missing link in the image quality assessment in digital intraoral radiography and cone-beam computed tomography in dental use. However, there are missing links between physical and diagnostic image qualities in panoramic radiography. The development of a semi-standardized phantom and the corresponding quantitative analysis method for image quality may be required in digital panoramic radiography. Quantitative image quality assessment using a standardized phantom will also be promising in the future artificial intelligence era.

Photogrammetry as an alternative for acquiring digital dental models: A proof of concept

Photogrammetry is a mathematical technique that generates three-dimensional coordinates of specific points identified from multiple images of the same object obtained at different angles. This technique may be a low-cost alternative for traditional scanning. The objective of this proof of concept was to evaluate the accuracy and precision in obtaining digital models (DM) from a plaster model (PM) using photogrammetry. Five DM were generated from 50 photographs taken surrounding the PM. The photographs were taken by a single operator on five consecutive days using natural light. The images obtained were processed on 3DF Zephyr Free software. The height and width of all teeth were recorded on both PM and DM, as well as the distance between the canine cusps (C-C) and between the mesiobuccal cusps of the first molars (1 M-1 M). For the PM the measurements were taken with a digital caliper, whereas the DM was measured using the software Blender. The DM and PM measurements presented a limit of agreement between -0.433 and 0.611 mm. The accuracy of DM measurements showed a SD of ±0.171 mm and a repeatability coefficient of 0.474. In the superimposition of all DM, it was possible to notice a greater discrepancy in the posterior region of the arch and palate, but this difference decreased when the region was segmented. It can be concluded that photogrammetry appears to be a viable technique for the digitization of dental models. Further studies need to be performed to evaluate its clinical application.

Investigation of radiation-protection knowledge, attitudes, and practices of North Queensland dentists

AIM

Queensland has current radiation-protection guidelines; however, with the absence of data exploring compliance and implementation, the efficacy is unknown. The aim of the present study was to investigate the knowledge and attitudes on radiation protection among private North Queensland (NQ) dentists.

METHODS

A quantitative methodology was employed in an observational and descriptive study using questionnaires for data collection.

RESULTS

Of the 154 questionnaires distributed, 63 were completed and returned. The respondents' knowledge concerning the technical details of their equipment was limited, with 31.5% and 47% not knowing the tube voltage and current utilized for their machines, respectively. In total, 23.8% of dentists had limited knowledge about the speed of the conventional film they used, 90.5% of respondents agreed that the role of imaging in dentistry is important, and 75.8% dentists reported the thyroid as the most important organ to protect during dental radiography. Their knowledge regarding position-distance rule was reasonably adequate; 80.3% of the dental practices appeared to follow the Australian Radiation Protection and Nuclear Safety Agency guidelines, 95.2% preferred taking radiographs if it was only urgent, and 69.8% identified a need for spreading awareness regarding radiation protection.

CONCLUSIONS

An opportunity and need for further continuing education was identified among NQ dentists to ensure safety of patients.

Patient radiation doses in intraoral and panoramic X-ray examinations in Sudan

Radiation doses were measured for the first time in intraoral and panoramic dental radiology at Sudanese hospitals. Doses were determined using various exposure settings for adults and children in 8 intraoral and 6 panoramic X-ray devices. The study sample was equally divided between devices using a digital image receptor (DR) and those using conventional screen film (SF). Radiation doses are reported in terms of incident air kerma (IAK) (intraoral radiology) and kerma area product (P_KA) (panoramic radiology). IAK values in intraoral radiology were: 1.45 mGy (DR), 4.45 mGy (SF), and 3.01 mGy (combined). For panoramic radiology, P_KA values ranged: from 35.8 to 103.2 mGy cm² (average: 70.4 mGy cm²) for children and from 65.7 to 151.4 mGy cm² (average: 103.4 mGy cm²) for adults. The results showed that the downward trend in patient doses can be achieved using digital imaging. The study revealed important concerns surrounding radiation protection, such as the lack of regular quality assurance programs and the use of circular collimators.

22nd International Conference on Medical Physics 2016, Bangkok, Thailand; Medical physics propelling global health

As medical technology evolves and patient needs increase, the need for well-trained and highly professional medical physicists (MPs) becomes even more urgent. The roles and responsibilities of MPs in various departments within the hospital are diverse and demanding. It is obvious that training, continuing education and professional development of MPs have become essential. One of the ways for an MP to advance his or her knowledge is to participate in conferences and congresses. Last year, the 22nd International Conference of Medical Physics (ICMP 2016) took place in Bangkok, Thailand. The event attracted 584 delegates with most of the participants coming from Asia. It attracted also delegates from 42 countries. The largest delegations were from Thailand, Japan and South Korea. ICMP 2016 included 367 oral presentations and e-posters, most of these being in the fields of Radiation Therapy, Medical Imaging and Radiation Safety. All abstracts were published as an e-book of Abstracts in a supplement to the official IOMP Journal. Many companies had exhibition stands at ICMP2016, thus allowing the participants to see the latest developments in the medical physics-related industry. The conference included 42 mini-symposia, part of the first "IOMP School" activity, covering various topics of importance for the profession and this special issue follows from the success of the conference.