Evidence on radiation dose reduction using rectangular collimation: a systematic review

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.

Exposure and protection protocols of dentomaxillofacial imaging applied by paediatric dentists in Europe

OBJECTIVES

Evaluate exposure and protection practices regarding dentomaxillofacial imaging among pediatric dentists in Europe and determine the effect of different clinician specific characteristics on their implementation.

METHODS

A cross-sectional study involving an electronic questionnaire addressed to paediatric dentists, participating in a seminar on dental radiology organized by the European Academy of Paediatric Dentistry. Participants were asked to respond to questions regarding dentomaxillofacial imaging in terms of applied radiation dose, adoption of radiation protection techniques, and different patterns of radiographic studying and exchange between patients and colleagues. Data analysis was performed and distribution of responses was tested using chi-square and Fisher's exact tests.

RESULTS

A total of 151 paediatric dentists, 119 females and 32 males, with a mean chronological age of 42.8 years (s.e. 11.3 years), successfully completed the questionnaire (response rate = 82%). Regardless of the type of radiograph, majority of respondents (68%), reported that they perform the radiographs themselves, while 21% reported that they refer the patients. Half of the respondents (51%), indicated requesting a small (localized) field of view (FOV) when referring for a cone beam computed tomography (CBCT) with only a small proportion (11%) reporting a large (maxillofacial) FOV. Thyroid collars and optimizing exposure settings were the most commonly reported patient protection measures used. Lastly, paediatric dentists have adopted the latest technological capacities for the study of dental images.

CONCLUSIONS

Dentomaxillofacial imaging protection and exposure protocols used are common among paediatric dentists with none of their specific characteristics having a significant effect.

Development of an open project rectangular collimator for use with intraoral dental X-ray unit

In this work, an open beam-limiting device, consisting of a rectangular collimator to be coupled to an intraoral dental X-ray device, was made using recycled lead sheets as a radiation-absorbing element. The collimator was designed for 3D printing, and using Spektr 3.0 software, the number of lead sheets needed to absorb excess radiation was calculated. The rectangular collimator reduced the radiation dose to patients by 65% when using four layers of recycled lead sheets (saturating with a 70% reduction in radiation dose at the limit of eight or more sheets of lead). The rectangular collimator does not negatively impact the quality of the radiological image, is available as an open design for 3D printing, and can be built with materials that are easily accessible to the dentist, facilitating its use in clinical practice and reducing the patient's exposure to ionizing radiation.

Influence of the Tube Angle on the Measurement Accuracy of Peri-Implant Bone Defects in Rectangular Intraoral X-ray Imaging

BACKGROUND

Intraoral radiography in the right-angle technique is the standard procedure to examine the peri-implant bone level in implant follow-up and implant-related studies. For the implementation of the right-angle or parallel technique, mostly ready-made image receptor holders are used. The aim of this experimental study is to analyze changes in the measurement of standardized peri-implant defects caused by a deviation in the position of the image receptor.

METHODS

Eleven Xive® implants (Dentsply Sirona, Bensheim, Germany) were placed in bovine bone, and peri-implant defects of varying depths were created. The preparations were fixed in a specially made test stand, and intraoral radiographs were taken using the right-angle technique with standard film holders at various horizontal and vertical projection angles. Defect measurement was carried out with the imaging software Sidexis 4 V 4.3 (Dentsply Sirona, Bensheim, Germany).

RESULTS

With increasing angular deviation, larger deviations between the measured and the real extent of the defect occurred. Vertical tilting caused significant distortion, while horizontal rotation showed less effect.

CONCLUSION

Intraoral radiography only provides a valid representation of the peri-implant bone level for follow-up or as a tool in implant-related studies if a reproducible projection direction is assured.

Stray radiation dose reduction using a backscatter shield and a rectangular collimator for a handheld intraoral X-ray unit

The objective of this study was to study the dose reduction effect on occupational exposure of operators and public exposure other than operators when a backscatter shield and a rectangular collimator are used in conjunction with a handheld intraoral X-ray unit. The occupational exposure was reduced to 40% when the backscatter shield was attached to the cone-tip, to 13% when the rectangular collimator was attached and to 7.7% when the backscatter shield and rectangular collimator were used together. On the other hand, the public exposure was reduced to 20% when the rectangular collimator was attached, but the backscatter shield was not effective in reducing the public exposure. Attaching a backscatter shield is effective in reducing the occupational exposure, and a rectangular aperture is effective in reducing the occupational exposure, as well as the public exposure.

Evaluating cone cut in rectangular collimation in intraoral radiography: application of ALADA and radiation stewardship

OBJECTIVE

Rectangular collimation is a popular method used in intraoral radiography to reduce patient exposure to ionizing radiation. One of the perceived drawbacks of rectangular collimation is the possibility of an increase in cone cut errors ultimately impacting the diagnostic value of the radiographs. Thus, the aim of this study was to explore the frequency of cone cut errors in radiographs taken using a rectangular collimator.

MATERIALS AND METHODS

Radiographs taken using PSP plates at Academic Center for Dentistry Amsterdam in the Netherlands by staff and students from January to December 2015 were assessed for cone cut errors. The radiographs were grouped as bitewings, front teeth, inferior premolars and molars, and superior premolars and molars and categorized as no cone cut, cone cut but diagnostically usable, and cone cut but diagnostically not usable. The results were entered into Microsoft Excel and analyzed thereafter.

RESULTS

A total of 53,684 radiographs were assessed, 79% had no cone cut errors and consequently 21% had some degree of cone cut. However, the diagnostic value was unaffected in 18% of the radiographs with cone cut. Only 3% of the radiographs were deemed diagnostically unusable due to cone cut. The most common area of cone cut was in the premolar and molar areas while cone cut in the front teeth was least likely to be diagnostically unusable.

CONCLUSION

Cone cut from the use of a rectangular collimator does not seem to result in an increase of diagnostically unusable radiographs. Thus, rectangular collimation should be preferred as it decreases the amount of radiation exposure to the patient while producing diagnostically usable radiographs and thus allowing the dental professional to adhere to the ALADA principle and practice radiation stewardship.

CLINICAL RELEVANCE

Scientific rationale for the study: rectangular collimation is a method used to reduce patient exposure to ionizing radiation; however, this benefit is negligible if radiographs must be retaken due to cone cut errors that make the radiograph diagnostically unusable. Therefore, the aim of this study was to explore the frequency of cone cut in radiographs taken using a rectangular collimator.

PRINCIPAL FINDINGS

cone cut was observed in 21% of the radiographs; however, only 3% of the radiographs were considered diagnostically unusable.

PRACTICAL IMPLICATIONS

rectangular collimation does not result in a high number of diagnostically unusable radiographs and should be used to reduce patient exposure to ionizing radiation.

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.

Estimation of Surface Radiation Dosage to Thyroid Gland and Lower Abdomen While Using Intraoral Periapical Radiography: A Phantom Study

Background and objective

Every dose of radiation has the potential to cause biological harm. Quantitative assessment of radiation doses to radiosensitive organs can aid dental professionals in taking the appropriate protective measures against radiation. This data may also be used among the general public to alleviate fears of radiation exposure in dental radiography. This study aimed to estimate the surface radiation dose at the level of the thyroid and lower abdomen during intraoral periapical radiography (IOPAR).

Materials and methods

A total of 80 calcium sulfate (CaSO₄) discs were utilized in this cross-sectional in vitro study to estimate the surface radiation dose at the level of thyroid and lower abdomen on a phantom model while using an IOPAR. After exposure, the discs were submitted to the Radiation Laboratory's "Personnel Monitoring Service" to measure the surface radiation dose. Mean and standard deviations were calculated using descriptive statistics for continuous variables. The Mann-Whitney U test was used to compare bi-variate samples of independent groups. All statistical analyses were performed using SPSS Statistics version 21.0 (IBM, Armonk, NY).

Results

The results showed a statistically significant difference in radiation exposure between the maxillary anterior and mandibular anterior regions when the thermoluminescent dosimeter (TLD) was placed in the lower abdomen (p=0.000). When the maxillary and mandibular posterior regions were compared, there was a statistically significant difference in radiation exposure when the TLD was placed in the lower abdomen (p=0.000).

Conclusion

When the cone was positioned in the maxillary region, there was an increase in surface radiation dosage to the lower abdomen and thyroid.

Reject Rates of Radiographic Images in Dentomaxillofacial Radiology: A Literature Review

This report surveyed the image reject rates of intra-oral, extra-oral, and cone-beam computed tomography (CBCT) imaging in the academic literature. PubMed, Web of Science, and Scopus databases were queried in mid-April 2021. Manual screening of the reference lists of the identified publications was performed to identify papers missed from the database search. All publications returned by the searches were initially included. Exclusion criteria included irrelevance, no reporting of reject rate, no access to the article, and not original article. The total number of images and the number of rejects were recorded for each type of radiographic images. Factors and commonest errors associated with the rejects were recorded. Twenty-six original articles were identified and reviewed. The average reject rate was 11.25% for bitewings, 16.38% for periapicals, 4.10% for panoramics, 6.08% for lateral cephalography, and 2.77% for CBCT. Positioning error and patient movement were two common reasons for the rejects. The average reject rates computed from data pooled across studies should form the reference values for quality assurance programs to follow. Future reject analysis studies should report more radiographic parameters such as type of collimation for intra-oral radiography and patient posture for CBCT.

Women's awareness regarding the use of dental imaging during pregnancy

Background

There is often anxiety among pregnant women about dental imaging during pregnancy. This may hinder some women from seeking dental treatment during pregnancy and consequently, may negatively affect the oral health of the mother and fetus. This study was conducted to assess women’s awareness regarding the use of dental imaging during pregnancy.

Methods

In this cross-sectional study, the electronic distribution of structured questionnaires was done via social media. The self-administered questionnaires contained questions related to women’s knowledge regarding the radiation protection measures during dental imaging, the safest period for dental imaging, the type of radiographs that can be acquired during pregnancy, and the possibility of radiation-induced malignancy and fetal malformation as a result of dental imaging.

Results

In total, 410 completed questionnaires were received and analyzed. More than half of the participants were 30–49 years of age. The majority of the participants (91%) demonstrated poor knowledge concerning dental imaging. Only 4% reported that pregnant women can have dental imaging during any trimester. The majority believed that panoramic images and cone-beam computed tomography should not be acquired during pregnancy. The majority also believed there is a high risk of congenital malformation due to dental imaging and were unsure about the oncogenic risks.

Conclusions

Our study suggests that there is insufficient knowledge about dental imaging safety during pregnancy. This misconception may have a direct impact on the attitude toward seeking dental care. Therefore, community awareness initiatives aimed at informing our society about radiation exposure, safety, and required protection measures are critical.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01726-6.

Awareness and practice of 2D and 3D diagnostic imaging among dentists in Hong Kong

Aims To investigate the awareness and practice of 2D and 3D diagnostic imaging, including respective equipment, specifications, number of images acquired, indications for CBCT scans, preference between 2D and 3D imaging, and the confidence in acquiring and interpreting radiographic images among dentists in Hong Kong.Materials and methods A citywide survey was performed with an online questionnaire that was sent via the local dental association to registered dentists in Hong Kong. The anonymous survey focused on: their dental background; number, type and age of their intra-oral, panoramic devices; CBCT indications, field-of-view and consideration of low-dose protocols; and their confidence in taking and interpreting these images.Results From the feedback collected, 65% of dentists used digital intra-oral systems. Around 70% of respondents who perform CBCTs utilised low-dose protocols to reduce radiation dose. Age and years of practising dentistry were significant influencing factors in determining dentists' utilisation of low-dose protocols for CBCT devices. Male dentists and dentists with higher qualifications generally reported being more confident in taking and interpreting CBCT images. Dentists who were older and had more years of practising dentistry were generally more confident in interpreting CBCT images.Conclusion Only half of the dentists feel confident in taking and interpreting CBCT images, and there seems to be a limited knowledge of radiation dose-related risks. Therefore, continuous professional education should specifically focus on the potential of digital imaging and training in CBCT modalities, radiation dose protection and image interpretation.

Outcomes of different radioprotective precautions in children undergoing dental radiography: a systematic review

PURPOSE

To evaluate the effectiveness of all radioprotective measures in underage patients who undergo a dental radiodiagnostic examination.

METHODS

A systematic review was performed including randomised controlled trials (RCTs), or cluster trials, cohort studies, cross-sectional studies, case-control studies and comparative in vitro research. These studies examined the healthy underage human population (below 18 years) undergoing a dental radiodiagnostic examination. All radioprotective measures were included except for justification as an intervention. The primary outcomes were in vivo mortality and morbidity. Some surrogate or indirect outcomes such as in vitro effective dose and organ absorbed doses were also accepted. Secondary outcomes with regards to image quality and therapeutic value were also analysed.

RESULTS

Eighteen papers were eligible for implementation. Fifteen studies underwent narrative synthesis. Regression analysis was performed on three studies.

CONCLUSION

The following radioprotective measures can reduce the exposure dose. For lateral cephalometry: collimation, filtration, the fastest receptor type and circumstantial thyroid shielding. For oblique lateral radiographs: the shortest exposure time, a smaller horizontal angulation, a longer focus to skin distance. For intraoral radiography: rectangular collimation, the fastest image receptor speed and thyroid shielding when the thyroid gland is in line of or very close to the primary beam. For panoramic radiographs: collimation, the fastest receptor type and the use of automatic exposure control (AEC) or manual adjustment of intensity. For cone-beam computed tomography: collimation, the largest voxels size in relation to the treatment need, change in image settings such as ultra-low dose settings, shorter exposure time, a lower amount of projections, lower beam intensity, reduction of the potential, use of a thyroid shield except in two situations and the use of AEC. All of the changes in exposure parameters should be performed while maintaining a sufficient therapeutic value on an individual and indication-based level.

Feasibility of ultra-low radiation dose digital subtraction angiography: Preliminary study in a simplified cerebral angiography phantom

INTRODUCTION

The objective of this article is to evaluate the feasibility of cerebral digital subtraction angiography (DSA) using ultra-low radiation dose settings in a simplified cerebral angiography phantom.

MATERIALS AND METHODS

We created a silicone phantom capable of producing a simplified cerebral DSA. A total of 18 DSA sets were obtained with gradual six-step reduction of the detector entrance dose (DED) from 1.82 to 0.08 μGy per frame, while standard, postprocessing algorithm (PPA) and copper filter (0.3 mm) with PPA (CwP) algorithm reconstruction protocols were applied. We quantitatively compared their signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) and qualitatively analyzed the images' qualities in terms of image sharpness, contrast, and noise as investigated by five observers.

RESULTS

The SNR and CNR, which decreased with lowering of the DED in the standard protocol group, were significantly compensated by using the PPA. The values were approximately double in the PPA (11.5 ± 2.9) and CwP (11.0 ± 2.5) groups compared with the standard (5.4 ± 1.1) group in the DED of 0.24 μGy per frame as well as in the other values. The total scores of the observers according to the protocols showed a tendency to decrease as the DED lowered. On average, the PPA (96.3 ± 34.6) and CwP (91.3 ± 29.9) groups yielded higher results than the standard protocol (83.7 ± 46.7).

CONCLUSION

Given that the current DED ranges from 1.82 to 3.60 μGy per frame for routine cerebral DSA, our results indicate that DED can be decreased to 15%-30% of the current dose level in vessels 2-4 mm in diameter if image-improvement algorithms are applied.