European consensus on patient contact shielding

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.

Exceeding radiation thresholds for cataract induction in diagnostic imaging: a paediatric case report

This case report investigates the radiation dose received by a paediatric patient with a ventricular assist device who underwent four non-contrast brain computed tomography (CT) scans, two brain perfusion CT scans and two head angiographic CT scans. The total estimated absorbed dose to the lens of the eye is above the 500 mGy radiation-induced cataract threshold. It is recommended that this patient and those with similar imaging histories have routine follow-up with an ophthalmologist. It is also recommended that radiation dose tracking and an electronic medical alert program be implemented to allow the identification of patients who may exceed tissue reaction thresholds.

Is the use of gonad protection protectors necessary during infants chest radiography?

INTRODUCTION AND OBJECTIVES

To compare gonad doses with and without a gonad protector and to optimize the use of gonadal protectors in infants thorax radiography.

MATERIALS AND METHODS

Two pediatric anthropomorphic phantoms are used: an X-ray system for KXO-50SS/DRX-3724HD, and a digital radiography system for CALNEO Smart C12, with and without a gonad protector during infants thorax radiography. A real time skin dosimeter is placed on the X-ray system, and a real time skin dosimeter is inserted on the front side of the mammary gland, the front and back sides of the true pelvis level, and on the ovaries and testes. The X-ray system is irradiated 15 times using phantoms with and without a gonad protector. The measured entrance patient doses values of for the real time skin dosimeter are compared for each phantom, with and without the gonad protector.

RESULTS

The medium of measured entrance patient doses values for front side dose of the true pelvis level with and without the protector are 10.00 and 5.00 μGy at newborn, and 10.00 and 0.00μGy at one year, respectively. The medium of measured entrance patient doses values for the back side dose of the true pelvis level with and without the protector are 0.00 and 0.00 μGy at both newborn one year, respectively. The measured entrance patient doses cannot be detected in the ovaries and testes with or without the protector. No significant differences are observed in the measured entrance patient doses values for the front and back side doses of the pelvis, ovaries, and testes at newborn and one year, with and without the protector (p>0.05).

CONCLUSIONS

No significant difference was observed in gonad dose measurements with and without the gonad protector during infants chest radiography. We believe that gonadal protector wearing is not necessary.

Initial Imaging of Pregnant Patients in the Trauma Bay-Discussion and Review of Presentations at a Level-1 Trauma Centre

Trauma is the leading non-obstetric cause of maternal and fetal mortality and affects an estimated 5-7% of all pregnancies. Pregnant women, thankfully, are a small subset of patients presenting in the trauma bay, but they do have distinctive physiologic and anatomic changes. These increase the risk of certain traumatic injuries, and the gravid uterus can both be the primary site of injury and mask other injuries. The primary focus of the initial management of the pregnant trauma patient should be that of maternal stabilization and treatment since it directly affects the fetal outcome. Diagnostic imaging plays a pivotal role in initial traumatic injury assessment and should not deviate from normal routine in the pregnant patient. Radiographs and focused assessment with sonography in the trauma bay will direct the use of contrast-enhanced computed tomography (CT), which remains the cornerstone to evaluate the potential presence of further management-altering injuries. A thorough understanding of its risks and benefits is paramount, especially in the pregnant patient. However, like any other trauma patient, if evaluation for injury with CT is indicated, it should not be denied to a pregnant trauma patient due to fear of radiation exposure.

Is It Appropriate to Completely Eliminate Contact Shielding during CT Examination? A Discourse Based on Experimental Findings

OBJECTIVE

Through the integration of experimental data and literature, this study examines whether complete elimination of contact shielding during CT examination is warranted, with a particular focus on potential impacts to children's thyroid and pregnant women, as well as limitations associated with contact shielding. Methods: The thermoluminescent dosimeter (TLD) tablets were inserted into the phantom's five organs and tissues. Select fixed exposure, automatic exposure control (AEC), and use contact shielding combined into four experimental modes, with scanning of the phantom's four parts. Obtain the absorbed dose measurements within or outside the FOV. Statistical analysis was conducted using SPSS software. Results: (1) The AEC significantly reduces dose within and outside the FOV, with a dose reduction of 40%-60%. (2) The application of contact shielding outside the FOV significantly reduced the dose adjoin the FOV. (3) Both the use of AEC mode and contact shielding can effectively minimize the dose, with a reduction of 50-80%. (4) The shielding within the FOV may introduce image artifacts or interfere with AEC, the implementation of contact shielding outside FOV provides little reduction in radiation exposure risk through previous literature. (5) Contact shielding exhibits certain drawbacks in all aspects. Conclusion: The utilization of AEC mode in clinical CT should be widely adopted to minimize patient radiation exposure. In general, contact shielding both inside and outside the FOV should be avoided during exposure. However for children under 12 years old with thyroid gland examination, contact shielding could maximally reduce external radiation and may be appropriate. Pregnant women require careful evaluation when considering the use of contact shielding. Contact shielding should not be entirely abandoned.

Bismuth Shielding in Head Computed Tomography-Still Necessary?

Introduction: Cranial CT scans are associated with radiation exposure to the eye lens, which is a particularly radiosensitive organ. Children are more vulnerable to radiation than adults. Therefore, it is essential to use the available dose reduction techniques to minimize radiation exposure. According to the European Consensus on patient contact shielding by the IRCP from 2021, shielding is not recommended in most body areas anymore. This study aims to evaluate whether bismuth shielding as well as its combination with other dose-saving technologies could still be useful. Methods: Cranial CT scans of a pediatric anthropomorphic phantom were performed on two up-to-date MDCT scanners. Eye lens dose measurements were performed using thermoluminescent dosimeters. Furthermore, the impact of BS and of the additional placement of standoff foam between the patient and BS on image quality was also assessed. Results: Bismuth shielding showed a significant lens dose reduction in both CT scanners (GE: 41.50 ± 4.04%, p < 0.001; Siemens: 29.75 ± 6.55%, p = 0.00). When combined with AEC, the dose was lowered even more (GE: 60.75 ± 3.30%, p < 0.001; Siemens: 41.25 ± 8.02%, p = 0.00). The highest eye dose reduction was achieved using BS + AEC + OBTCM (GE: 71.25 ± 2.98%, p < 0.001; Siemens: 58.75 ± 5.85%, p < 0.001). BS caused increased image noise in the orbital region, which could be mitigated by foam placement. Eye shielding had no effect on the image noise in the cranium. Conclusions: The use of BS in cranial CT can lead to a significant dose reduction, which can be further enhanced by its combination with other modern dose reduction methods. BS causes increase in image noise in the orbital region but not in the cranium. The additional use of standoff foam reduces image noise in the orbital region.

Laparoscopic Cholecystectomy in Pregnancy: A Seven-Year Retrospective Study From an Australian Tertiary Center

Background Cholecystectomy is the second most common non-obstetric indication for surgery during pregnancy; however, there is little recent literature specifically exploring perioperative care approaches, and a paucity of Australian data exists. This study investigates the incidence of laparoscopic cholecystectomy (LC) during pregnancy, peri-operative management, and post-operative outcomes in a single Australian tertiary center. Methods A retrospective analysis of LCs performed on pregnant patients between the ages of 16 and 50 years at a tertiary hospital between 2016 and 2023 was completed. Results Twenty-three patients underwent LC. The median gestational age was 17+4 weeks (4+3-30+6). Cases were performed in all three trimesters, with the majority in the second trimester (n=12, 52.2%). Surgery indications were recurrent biliary colic (n=11, 47.8%), acute cholecystitis (n=8, 34.8%), and gallstone pancreatitis (n=4, 17.4%). Obstetrics and Gynecology (O&G) consultations occurred in 56.5% (n=13) of cases. Fetal heart rate (FHR) was recorded perioperatively in 82.6% (n=19) of cases. Preoperative steroids were given to 40% of eligible patients. An intraoperative cholangiogram was performed in 12 (52.2%) cases, of which eight (66.7%) utilized abdominal shielding. There was no perioperative maternal mortality nor fetal loss. Surgical morbidities were pancreatitis (n=1), bile leak (n=1), and intraoperatively recognized bile duct injury (n=1). Two threatened preterm labors and five (26.3%) preterm deliveries occurred. Conclusion Performing LC in pregnancy does carry a risk of major morbidity; however, there was no mortality or fetal loss across all trimesters. The decision to perform abdominal shielding during an intraoperative cholangiogram should be approached sensitively in a case-by-case manner, given recent paradigm shifts in radiology. A multidisciplinary approach with standardized local perioperative care policies regarding procedures such as O&G consultation, perioperative steroid use, and FHR monitoring is strongly recommended.

The effect of contact radiation shielding on breast dose during CT abdomen-pelvis: a phantom study

This study aims to investigate if contact shielding reduces breast radiation dose during computed tomography (CT) abdomen-pelvis examinations using automatic tube current modulation to protect one of the four most radiosensitive organs during CT examinations. Dose measurements were taken with and without contact shielding across the anterior and lateral aspects of the breasts and with and without organ dose modulation (ODM) to quantify achievable dose reductions. Although there are no statistically significant findings, when comparing with and without shielding, the mean breast surface dose was reduced by 0.01 μSv without ODM (1.92-1.91 μSv, p = 0.49) and increased by 0.03 μSv with ODM (1.53-1.56 μSv, p = 0.44). Comparing with and without ODM, the mean breast surface dose was reduced by 0.35 μSv with shielding (1.91-1.56 μSv, p = 0.24) and by 0.39 μSv without shielding (1.92-1.53 μSv, p = 0.17). The addition of contact shielding does not provide significant breast surface radiation dose reduction during CT abdomen-pelvis.

Exploring radiographers' perceptions and knowledge about patient lead shielding: a cross-sectional study in Greece and Cyprus

The present study aimed to explore radiographers' knowledge, clinical practice and perceptions regarding the use of patient lead shielding in Greece and Cyprus. Qualitative data were analyzed using conceptual content analysis and through the classification of findings into themes and categories. A total of 216 valid responses were received. Most respondents reported not being aware of the patient shielding recommendations issued by the American Association of Physicists in Medicine (67%) or the guidance issued by the British Institute of Radiology (69%). Shielding-related training was generally not provided by radiography departments (74%). Most of them (85%) reported that they need specific guidance on lead shielding practices. Also, 82% of the respondents said that lead shielding should continue to be used outside the pelvic area when imaging pregnant patients. Pediatric patients are the most common patient category to which lead shielding was applied. Significant gaps in relevant training have been identified among radiographers in Greece and Cyprus, highlighting the need for new protocols and provision of adequate training on lead shielding practices. Radiography departments should invest in appropriate shielding equipment and adequately train their staff.

Effectiveness of protective thyroid shield in chest X-ray imaging

Chest X-ray imaging is the most common X-ray imaging method for diagnosing coronavirus disease. The thyroid gland is one of the most radiation-sensitive organs of the body, particularly in infants and children. Therefore, it must be protected during chest X-ray imaging. Yet, because it has benefits and drawbacks, using a thyroid shield as protection during chest X-ray imaging is still up for debate.Therefore, this study aims to clarify the need for using a protective thyroid shield during chest X-ray imaging. This study was performed using different dosimeters (silica beads as a thermoluminescent dosimeter and an optically stimulated luminance dosimeter) embedded in an adult male ATOM dosimetric phantom. The phantom was irradiated using a portable X-ray machine with and without thyroid shielding. The dosimeter readings indicated that a thyroid shield reduced the radiation dose to the thyroid gland by 69% ± 18% without degrading the obtained radiograph. The use of a protective thyroid shield during chest X-ray imaging is recommended because its benefits outweigh the risks.

European survey on the use of patient contact shielding during radiological examinations

OBJECTIVES

Contact shielding (CS) of patients during X-ray studies has been used for decades to protect radiosensitive organs. This practice has not changed much despite increasing evidence that CS is not useful in many cases. The Gonad And Patient Shielding (GAPS) group-founded by representatives of the main European bodies involved in radiology-promoted this survey to assess the current practice of CS among European radiology departments and the attitude towards a non-shielding policy.

METHODS

Over a four-month period (15 May-15th September 2021) European Society of Radiology and European Society of Paediatric Radiology radiologist members were invited to respond to a web-based questionnaire consisting of 59 questions.

RESULTS

225 centres from 35 countries responded to this survey. CS was routinely applied in at least one radiological modality in 49.2% of centres performing studies in adults, 57.5% of centres performing studies in children, and 47.8% of centres performing studies on pregnant women. CS was most frequently used in conventional radiography, where the most frequently shielded organs were the gonads, followed by thyroid, female breasts, and eye lens. 83.6% respondents would follow European recommendations on the use of CS when provided by the main European bodies involved in radiology.

CONCLUSIONS

This review shows that CS is still largely used across Europe. However, a non-shielding policy could be adopted in most departments if European professional societies provided recommendations. In this regard, a strong commitment by European and national professional societies to educate and inform practitioners, patients and carers is paramount.

CLINICAL RELEVANCE STATEMENT

According to this survey expectations of patients and carers, and skepticism among professionals about the limited benefits of CS are the most important obstacles to the application of a no-shielding policy. A strong commitment from European and national professional societies to inform practitioners, patients and carers is fundamental.

The effect of breast shielding outside the field of view on breast entrance surface dose in axial X-ray examinations: a phantom study

PURPOSE

The purpose of this study was to evaluate the effect of outside-field-of-view (FOV) lead shielding on the entrance surface dose (ESD) of the breast on an anthropomorphic X-ray phantom for a variety of axial skeleton X-ray examinations.

METHODS

Using an anthropomorphic phantom and radiation dosimeter, the ESD of the breast was measured with and without outside-FOV shielding in anterior-posterior (AP) abdomen, AP cervical spine, occipitomental 30° (OM30) facial bones, AP lumbar spine, and lateral lumbar spine radiography. The effect of several exposure parameters, including a low milliampere-seconds technique, grid use, automatic exposure control use, wraparound lead (WAL) use, trolley use, and X-ray table use, on the ESD of the breast with and without outside-FOV shielding was investigated. The mean ESD (μSv) and standard deviation for each radiographic protocol were calculated. A one-tailed Student's t-test was carried out to evaluate whether ESD to the breast was reduced with the use of outside-FOV shielding.

RESULTS

A total of 920 breast ESD measurements were recorded across the different protocol parameters. The largest decrease in mean ESD of the breast with outside-FOV shielding was 0.002 μSv (P = 0.084), recorded in the AP abdomen on the table with a grid, OM30 on the table with a grid, OM30 standard protocol on the trolley, and OM30 on the trolley with WAL protocols. This decrease was found to be statistically non-significant.

CONCLUSION

This study found no significant decrease in the ESD of the breast with the use of outside-FOV shielding for the AP abdomen, AP cervical spine, OM30 facial bones, AP lumbar spine, or lateral lumbar spine radiography across a range of protocols.

[Use of patient radiation shielding in diagnostic and interventional radiology]

The use of patient contact shielding provides an opportunity to reduce patient radiation exposure. Recently, the use has been the subject of controversy. The Radiation Protection Committee has published a recommendation on the use of patient radiation shields by considering the recent findings on dose savings but also the risks of incorrect use. In this article, a specification for the more frequently used types of X‑ray examination is given, which describes whether and which radiation contact shielding should be used. This is accompanied by a rationale for the use or non-use of patient radiation protection agents. Problems and possible errors are explained, as well as how to deal with special situations such as pregnant women and children.

AWARENESS OF PAEDIATRIC RADIOLOGICAL PROTECTION AND IMAGING PARAMETERS AMONG GROUP OF SRI LANKAN RADIOGRAPHERS

The present survey evaluated the level of awareness of radiological protection concepts and imaging parameters among Sri Lankan radiographers for the first time. The data were collected using an electronic questionnaire of 22 questions on demographic data, awareness of radiation protection concepts and imaging parameters. Only 84 out of 122 (68.8%) requested radiographers to return the questionnaire. More than 85% had ≥3 years of experience in the radiography field. The average scores for questions on best practices, imaging parameters and radiation protection were 75, 75.8 and 70.2%, respectively, with an overall score of 73.4%. Significant confusion existed on protective shielding, paediatric consenting capability, use of grids and excess X-ray field during paediatric radiography. Although the overall knowledge and awareness of participants on studied concepts were satisfactory, a continuous professional development credit system and implementation of a code of practice are required to improve the quality of radiography practice.

RADIATION DOSE OF THE EYE LENS IN CT EXAMINATIONS OF THE BRAIN IN CLINICAL PRACTICE-THE EFFECT OF RADIOGRAPHER TRAINING TO OPTIMISE GANTRY TILT AND SCAN LENGTH

Lenses are always exposed to radiation in brain computed tomography (CT) scans. However, the lens dose can be reduced by excluding lens from scanning area by optimising gantry tilt and scan length. The object of this study is to retrospectively analyse if the optimisation by gantry tilt and scan length have been adequate in the CT scan of the brain, and to prospectively analyse the effect of radiographer training to the quality of the CT examinations. This study was conducted in two parts. In all, 329 brain CTs performed in the Tampere University Hospital from 2017 to 2019 were revised retrospectively. The prospective part included 51 brain CT studies conducted in October 2021. Dose to the eye of the lens was modelled using CT-Expo using zero-degree beam angle and scan lengths to expose the lens either to the primary or scattered radiation. Non-zero gantry tilt had been used in a large proportion of the CT examinations in the retrospective setting, 84.8%. However, the lenses were successfully excluded from the scan area in only 1.8% of the examinations. In the prospective part, the gantry tilt was used in 98% of the studies and the proportion of successful examinations rose from 1.8 to 11.8%. The lens dose decreased significantly when the eyes were excluded from the imaging area. The modelled lens dose in the large retrospective part was 25.9 mGy (17.8-49.2 mGy) when the eyes were included and 1.5 mGy (0.4-1.9 mGy) when the eyes were excluded. The lens dose was similar in the small prospective part. Despite the gantry tilt is widely used, unnecessary lens irradiation occurs extensively because of suboptimal gantry tilt and scan length. The training of radiographers reduces the radiation exposure to the lens by more optimal gantry tilt and scan length.

Paediatric CT made easy

Paediatric computed tomography (CT) imaging has always been associated with challenges. Although the technical background of CT imaging is complex, it is worth considering the baseline aspects of radiation exposure to prevent unwanted excess radiation in paediatric patients. In this review, we discuss the most relevant factors influencing radiation exposure, and provide a simplified and practical approach to optimise paediatric CT.

EFFECT OF PELVIC LEAD SHIELD ON ORGAN DOSES IN POSTERO-ANTERIOR CHEST RADIOGRAPHY

Lead shields are commonly used in X-ray imaging to protect radiosensitive organs and to minimise patient's radiation dose. However, they might also complicate or interfere with the examination, and even decrease the diagnostic value if they are positioned incorrectly. In this study, the radiation dose effect of waist half-apron lead shield was examined via Monte Carlo simulations of postero-anterior (PA) chest radiography examinations using a female anthropomorphic phantom. Relevant organs for dose determination were lungs, breasts, liver, kidneys and uterus. The organ dose reductions varied depending on shield position and organ but were negligible for properly positioned shields. The shield that had the largest effective dose reduction (9%) was partly positioned inside the field of view, which should not be done in practice. Dose reduction was practically 0% for properly positioned shields. Therefore, the use of lead shield in the pelvic region during chest PA examinations should be discontinued.

Breast Shielding Combined With an Optimized Computed Tomography Pulmonary Angiography Pregnancy Protocol: A Special Use-Case for Shielding?

OBJECTIVES

To determine the impact of breast shields on breast dose and image quality when combined with a low-dose computed tomography pulmonary angiography (CTPA) protocol for pregnancy.

METHODS

A low-dose CTPA protocol, with and without breast shields, was evaluated by anthropomorphic phantom and 20 prospectively recruited pregnant participants from January to October 2019. Thermoluminescent dosimeters measured surface and absorbed breast dose in the phantom and surface breast dose in participants. The Monte-Carlo method estimated the absorbed breast dose in participants. Image quality was assessed quantitatively by regions of interest analysis and subjectively by the Likert scale. Doses and image quality for CTPA alone were compared with CTPA with breast shields.

RESULTS

Mean surface and absorbed breast dose for CTPA alone were 1.3±0.4 and 2.8±1.5 mGy in participants, and 1.5±0.7 and 1.6±0.6 mGy in the phantom. Shielding reduced surface breast dose to 0.5±0.3 and 0.7±0.2 mGy in the phantom (66%) and study participants (48%), respectively. Absorbed breast dose reduced to 0.9±0.5 mGy (46%) in the phantom.Noise increased with breast shields at lower kV settings (80 to 100 kV) in the phantom; however, in study participants there was no significant difference between shield and no-shield groups for main pulmonary artery noise (no-shield: 34±9.8, shield: 36.3±7.2, P =0.56), SNR (no-shield: 11.2±3.7, shield: 10.8±2.6, P =0.74) or contrast-to-noise ratio (no-shield: 10.0±3.3, shield: 9.3±2.4, P =0.6). Median subjective image quality scores were comparable (no-shield: 4.0, interquartile range: 3.5 to 4.4, shield: 4.3, interquartile range: 4.0 to 4.5).

CONCLUSION

Combining low-dose CTPA with breast shields confers additional breast-dose savings without impacting image quality and yields breast doses approaching those of low-dose scintigraphy, suggesting breast shields play a role in protocol optimization for select groups.

Gonad contact shielding in digital radiography: A questionnaire survey

PURPOSE

The use of gonad contact shielding (GCS) in radiology departments has varied across countries, possibly because, until recently, there was no agreed consensus with mixed evidence supporting its use. This study aims to explore radiographers' use and opinion on GCS in digital radiography (DR) and to evaluate whether radiographers' use of GCS is associated with their gender, highest educational qualification, and/or years of experience.

METHOD

An online survey was sent via email to potential participants through the Society of Medical Radiographers Malta (SRM) as well as social media posts on local radiography pages. Descriptive and inferential statistics were used to analyse the collected data.

RESULTS

Almost half of the registered radiographers working in radiology departments in Malta (n = 101/203) completed the survey (49.7 % response rate). 61.4 % of participating radiographers indicated they 'often' use GCS in some patients, with 56.4 % stating they perceive GCS as an effective tool to protect the gonads from radiation exposure in DR. Equally, 56.4 % claimed that GCS use is guided by local rules and/or departmental protocols. While 58.4 % indicated that patients' gender does not impact their use of GCS, patients' age does influence their use. No statistically significant association was noted between radiographers' likeliness of using GCS and their gender, highest educational qualification, and/or years of experience.

CONCLUSIONS

Some misconceptions and uncertainties among radiographers concerning the benefits and risks of using GCS were noted. Local radiology departments should look into their protocols and assess the need for an update aligned with the latest recommendations.

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.

Using barium as an internal radioprotective shield for pregnant patients undergoing CT pulmonary angiography: A retrospective study

PURPOSE

The purpose of our retrospective study was to assess the effect of barium sulfate contrast medium on radiation dose and diagnostic quality of CT Pulmonary Angiography (CTPA) in an in-vivo study of pregnant patients.

METHODS

Our retrospective study included 33 pregnant patients who underwent CTPA to exclude pulmonary embolism. The patients received oral 40% w/v barium solution just prior to the acquisition of their planning radiograph. All CTPA were performed on 64-slice, single-source CT scanners with AEC with noise index = 28.62-31.64 and the allowed mA range of 100-450. However, only 5/33 patients had mA modulation (AEC 100-450 mA range), while 28/33 patients had mA maxed out at the set maximum mA of 450 over the entire scan range. We recorded CTDIvol (mGy), DLP (mGy.cm) and scan length. The same information was recorded in weight-and scanner-matched, non-pregnant patients. Statistical tests included descriptive data (median and interquartile range) and Mann-Whitney test.

RESULTS

There were no significant differences in CTDIvol and DLP between the barium and control group patients (p > 0.1). The median mA below the diaphragm was significantly higher in each patient with barium compared to the weight and scanner-matched patient without barium. Evaluation of lung and subsegmental lower lobe pulmonary arteries was limited in 85% barium group. Due to thin prospective section thickness (1.25 mm), most patients were scanned at maximum allowed mA for AEC.

CONCLUSION

Use of AEC with thick barium in pregnant patients undergoing CTPA as an internal radioprotective shield produces counterproductive artifacts and tube current increments.

Three-Dimensional Distance Mapping Method to Evaluate Mandibular Symmetry and Morphology of Adults with Unilateral Premolar Scissors Bite

(1) Objective: This study aimed to evaluate the association between unilateral premolar scissors bite and mandibular symmetry of adults via the 3D distance mapping method. (2) Methods: A total of 53 cone-beam computed tomography (CBCT) images of adults with unilateral premolar scissors bite were set as study samples. A total of 53 age- and sex-matched samples without scissors bite were in the control group. Three-dimensional mandibular models and seven mandibular functional units, including condylar process (Co), coronoid process (Cr), mandibular ramus (Ra), mandibular angle (Ma), alveolar process (Ap), mandibular body (Mb), and chin process (Ch) were constructed and mirrored. After superimposition of the original and the mirrored models, 3D distance maps and deviation analysis were performed to evaluate the mandibular symmetry and morphology. (3) Results: In the study group, the matching percentages of the entire mandible (50.79 ± 10.38%), Ap (67.00 ± 12.68%), Mb (66.62 ± 9.44%), Ra (62.52 ± 11.00%), Ch (80.75 ± 9.86%), and Co (62.78 ± 13.56) were lower than that of the entire mandible (58.60 ± 5.52) (p < 0.01), Ap (73.83 ± 8.88%) (p < 0.01), Mb (72.37 ± 8.69%) (p < 0.01), Ra (68.60 ± 7.56%) (p < 0.01), Ch (85.23 ± 6.80%) (p < 0.01), and Co (67.58 ± 10.32%) (p < 0.05) in the control group. However, Cr and Ma showed no significant difference (p > 0.05). (4) Conclusions: The 3D distance mapping method provided a qualitative and quantitative mandibular symmetry and morphology assessment. Mandibular asymmetry was found in adults with unilateral premolar scissors bites. Mandibular functional units, including the alveolar process, mandibular body, mandibular ramus, chin process, and condylar process, showed significant differences, while no significant difference was observed in the coronoid process and mandibular angle.

Impact of thyroid gland shielding on radiation doses in dental cone beam computed tomography with small and medium fields of view

OBJECTIVE

The purpose of this study was to evaluate the impact of thyroid gland shielding on radiation doses in dental cone beam computed tomography (CBCT) with small and medium fields of view (FOVs).

STUDY DESIGN

Six CBCT protocols were investigated by exposing an adult anthropomorphic male phantom head without and with thyroid shielding, using 4 small (4 × 5 cm) and 2 medium (10 × 6 cm) FOVs. Twenty metal oxide semiconductor field-effect transistor dosimeters were placed in the phantom head to measure absorbed doses and calculate equivalent doses at 11 sites. Effective doses were calculated based on the tissue weighting factors in International Commission on Radiological Protection Publication 103. The data were analyzed using the independent samples t test.

RESULTS

Thyroid gland shielding led to significant equivalent dose reductions in many tissues for all protocols. Equivalent dose reductions to the thyroid were significant in all 6 protocols (P ≤ .037). Significant reduction depended on the FOV and ranged between 24.5% and 42.6% for the thyroid gland and 4.9% and 34.5% for other tissues and organs. Effective doses were significantly lower in all protocols (P ≤ .016).

CONCLUSIONS

Thyroid gland shielding protects the thyroid gland and other organs and should be utilized with all CBCT examinations where feasible.