Radiobiological risks following dentomaxillofacial imaging: should we be concerned?

Optimization of orofacial cleft imaging protocols using device-specific low-dose cone-beam computed tomography

OBJECTIVE

The aim of this study was to present optimized device-specific low-dose cone-beam computed tomography (CBCT) protocols with sufficient image quality for pre-surgical diagnostics and three-dimensional (3D) modelling of cleft defects.

METHODS

Six paediatric skulls were acquired, and an artificial bony cleft was created. A high-resolution CBCT scan acted as a reference standard (Accuitomo 170, Morita, Kyoto, Japan) for comparing eight low-dose protocols of Newtom VGi-evo (QR Verona, Cefla, Verona, Italy), which included Eco and Regular protocols with different field of views (FOVs). Delineation of lamina dura, cementoenamel junction (CEJ), trabecular bone and bony bridge were assessed. A 3D model of the defect was also evaluated.

RESULT

The dose area product of low-dose protocols ranged from 31 to 254 mGy*cm2. Despite the dose difference of up to eight times between applied protocols, trabecular bone and CEJ exhibited appropriate image quality in all scans. However, Regular small FOV protocols (5 × 5 and 8 × 5 cm2), for both lamina dura and bony bridge, demonstrated a significant improvement in image quality compared to Eco FOV counterparts. Based on 3D defect analysis, no significant difference existed between low-dose protocols and the reference standard.

CONCLUSION

The findings highlight the possibility of achieving a considerable reduction (up to eight times) in the radiation dose using low-dose CBCT protocols while maintaining sufficient image quality for assessing anatomical structures and 3D modelling in cleft cases.

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.

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.

Creation of Dimicleft radiological cleft phantom skulls using reversed virtual planning technique

OBJECTIVES

The aim of this technical report was to develop customized pediatric phantoms for cone-beam computed tomography (CBCT)-related research in cleft patients.

METHODS

Six human pediatric skulls (age: 5-10 years) were recruited. A cone-beam computed tomography (CBCT) scan was taken for each skull, followed by virtual modeling through the process of segmentation. An artificial cleft was designed and printed to be applied onto the skull for the creation of an artificial cleft. The skulls were covered with non-radiopaque tape and immersed in melted Mix-D soft tissue equivalent material. The resulting phantoms covered with Mix-D were assessed radiologically by two expert radiologists. These phantoms were referred to as Dimicleft pediatric skull phantoms.

RESULTS

Dimicleft phantoms were able to appropriately mimic in vivo circumstances. No gaps existed between Mix-D and bony tissue. Virtual planning allowed the optimal designing of an artificial cleft onto the phantom. The artificially created cleft was suitable to determine the size, location, and extent of the cleft.

CONCLUSIONS

Dimicleft phantoms could act as a viable alternative to other commercially available options for assessing image quality and optimizing CBCT protocols in cleft patients for diagnostics and three-dimensional treatment planning.

Cumulative exposure and lifetime cancer risk from diagnostic radiation in patients undergoing orthognathic surgery: a cross-sectional analysis

Radiation doses in dentomaxillofacial imaging are typically very low. However, diagnostic and follow-up protocols in orthognathic surgery result in a patient-specific risk in effective dose. Estimating the cancer risks from these exposures remains abstract for many maxillofacial surgeons. In this study, 40 orthognathic patients were randomly sampled and their cumulative effective dose (ED) calculated. The lifetime attributable risk of cancer (LAR) was calculated based on the standard radiological protocol for orthognathic surgery follow-up using methods described in the BEIR VII report and RadRAT. The mean cumulative ED of the 40 sampled patients at the end of their 2-year follow-up period was 1.91 ± 0.58 mSv. The LAR at the end of follow-up was 17.65 (90% confidence interval 6.46-32.90) per 100,000 person-years for male orthognathic patients and 13.93 (90% confidence interval 6.27-25.24) per 100,000 person-years for female orthognathic patients. This represents 0.70% and 0.68%, respectively, of the baseline cancer risk for oral, thyroid, and brain cancer combined. Although theoretical, these results provide a framework for interpreting radiation doses and cancer risks in patients undergoing orthognathic surgery. Considering the increased radiation sensitivity in children and adolescents, indication-oriented and patient-specific imaging protocols should be advised.

Moving toward patient specificity for devising cone-beam computed tomography field-of-views: A normative maxillary skeletal dimensional analysis

BACKGROUND

A lack of evidence exists comprehensively assessing skeletal dimensions in a Caucasian population group at different ages.

AIM

To provide age- and gender-specific normative skeletal dimensional measurements of the maxillary region using cone-beam computed tomography (CBCT) imaging.

DESIGN

Cone-beam computed tomography images of Caucasian patients were acquired and divided into different age groups ranging from 8 to 20 years. Linear measurements were taken to evaluate seven distance-based variables, which included anterior nasal spine-posterior nasal spine (ANS-PNS) distance, bilateral maxillary first molar's central fossae (CF) distance, palatal vault depth (PVD), bilateral palatal cementoenamel junction (PCEJ) distance, bilateral vestibular CEJ (VCEJ) distance, bilateral jugulare distance (Jug) and arch length (AL).

RESULTS

A total of 529 patients (243 male, 286 female) were selected. ANS-PNS and PVD showed the highest change in dimensions from 8 to 20 years of age. On the contrary, AL had the least variability in all age groups. Male patients had larger dimensions and showed a significant change in all dimensional measurements (p < .001) than female patients.

CONCLUSION

The maxillary linear dimensions varied across different age groups. The presented maxillary normative data could serve as a reference guide for devising patient-specific CBCT field of views.

Feasibility of photon-counting computed tomography as a novel imaging modality for challenging endodontic diagnostic tasks

Photon-counting computed tomography (PCCT) is an innovative technological advancement in relation to x-ray detectors which offers ultra-high-resolution images. The current study aimed to evaluate the visualization ability of PCCT compared to cone-beam computed tomographic (CBCT) devices for challenging endodontic diagnostic tasks. A reference image of an anthropomorphic phantom was acquired using an industrial micro-CT device. Thereafter, the phantom was scanned with three imaging devices, which included PCCT scanner (NAEOTOM Alpha) and two CBCT devices (3D Accuitomo 170 and NewTom VGi evo) having standard and high-resolution acquisition protocols. The diagnostic tasks involved visualizing fine endodontic structures (apical delta, narrow canal, and isthmus) and root cracks. Three experienced examiners assessed the images and were blinded to the PCCT and CBCT devices. Each image was rated according to a three-grade scale (appropriate, acceptable, or inappropriate) for the diagnostic tasks. In relation to fine endodontic structures grouped together, PCCT showed similar diagnostic performance compared to the reference image (p > 0.05). As for the CBCT devices, an excellent performance was only observed with the 3D Accuitomo 170 device at a high-resolution acquisition mode (p > 0.05). The visualization of root cracks was also better with 3D Accuitomo 170 compared to other devices (p < 0.05). Overall, PCCT and 3D Accuitomo 170 at a high-resolution setting showed similar performance for visualizing fine endodontic structures. In addition, the high-resolution CBCT protocol was superior for visualizing root cracks compared to both PCCT and other standard- and high-resolution CBCT protocols.

Monitoring cone-beam CT radiation dose levels in a University Hospital

OBJECTIVE

To present patient dose levels for different CBCT scanners, acquired by a dose monitoring tool in a University Hospital, as a function of field of view (FOV), operation mode, and patient age.

METHODS

An integrated dose monitoring tool was used to collect radiation exposure data [type of CBCT unit, dose-area product (DAP), FOV size, and operation mode] and patient demographic information (age, referral department) performed on a 3D Accuitomo 170 and a Newtom VGI EVO unit. Effective dose conversion factors were calculated and implemented into the dose monitoring system. For each CBCT unit, the frequency of examinations, clinical indications, and effective dose levels were obtained for different age and FOV groups, and operation modes.

RESULTS

A total of 5163 CBCT examinations were analyzed. Surgical planning and follow-up were the most frequent clinical indications. For the standard operation mode, effective doses ranged from 35.1 to 300 µSv and 9.26-117 µSv using 3D Accuitomo 170 and Newtom VGI EVO, respectively. In general, effective doses decreased with increasing age and FOV size reduction.

CONCLUSIONS

Effective dose levels varied notably between systems and operation modes.Operation mode selection and FOV size were indication-oriented, with larger FOV sizes election serving surgical planning and follow-up. Seeing the influence of FOV size on effective dose levels, manufacturers could be advised to move toward patient-specific collimation and dynamic FOV selection. Systematically monitoring patient doses could be recommended for steering future CBCT optimization.

Genotoxicity and cytotoxicity effects of x-rays on the oral mucosa epithelium at different fields of view: A cone beam computed tomography technique

Background

Cone beam computed tomography (CBCT) is considered a common examination for dentistry problems. Cellular biology can be affected by exposure to ionizing radiations procedures. In this study, we aimed to assess the genotoxicity and cytotoxicity effects of CBCT dental examinations at two different fields of view (FOVs) in exfoliated buccal epithelial cells.

Methods

Sixty healthy adults participated in the current study. They were divided into two identical groups; CBCT with FOV of 6*6 cm2 and 8*11 cm2. Exfoliated oral mucosa cells were prepared immediately before and after 10-12 days of CBCT exposure. The cytological smears were stained with the Papanicolaou technique. The amounts of micronuclei and other cytotoxicity cellular changes (Pyknosis, Karyolysis, and Karyorrhexis) were evaluated. The variables of the parameters before and after CBCT examination in the two investigated FOVs were performed using Wilcoxon test and paired-samples t-test in SPSS software.

Results

The micronuclei and other cytotoxic changes parameters before and after CBCT exposure for both FOVs (6*6 and 8*11 cm2) increased significantly (p<0.001). Furthermore, a significant difference (p<0.05) was observed between the investigated parameters at the two FOVs. Notably, the FOV of 8*11 cm2 had more side effects than that of 6*6 cm2. There were no statistically significant among males and females for both FOVs.

Conclusion

CBCT examinations of dental disorders would increase the risks of inducing genetic damage. The cytotoxicity and chromosomal damage were considered in males and females in both investigated FOVs (6*6 and 8*11 cm2). In this regard, the use of CBCT must be following the ALARA principle.

Low-Dose Gamma Radiation Modulates Liver and Testis Tissues Response to Acute Whole Body Irradiation

Aim

This work aims to investigate whether the pre-exposure to low dose/low dose rate (40 mGy, 2.2 mGy/hour) γ-radiation as a priming dose can produce a protective effect against the subsequent high one (4 Gy, .425 Gy/minute).

Methods

Rats were divided into Group I (control), Group II (L); exposed to 40 mGy, Group III (H); exposed to 4 Gy, and Group IV (L+H); exposed to 40 mGy 24 hours before the exposure to 4Gy. The molecular and biochemical changes related to oxidative stress, DNA damage, apoptosis, and mitochondrial activity in the liver and testis were studied 4 hours after irradiation.

Results

Exposure to 40 mGy before 4 Gy induced a significant increase in the levels of Nrf2, Nrf2 mRNA, TAC, and mitochondrial complexes I & II accompanied by a significant decrease in the levels of LPO, 8-OHdG, DNA fragmentation, TNF-α, caspase-3, and caspase-3 mRNA compared with H group.

Conclusion

Exposure to low-dose γ-radiation before a high dose provides protective mechanisms that allow the body to survive better after exposure to a subsequent high one via reducing the oxidative stress, DNA damage, and apoptosis-induced early after irradiation. However, further studies are required to identify the long-term effects of this low dose.