What are the risks from medical X-rays and other low dose radiation?

Radiation exposure and estimated risk of radiation-induced cancer from thoracic and abdominal radiographs in 1307 neonates

OBJECTIVE

This study examined radiation exposure and the possible risk of radiation-induced cancer in a large sample of newborn and premature patients.

MATERIAL AND METHODS

In this retrospective study, we included all hospitalised neonates treated at our university hospital who received at least one X-ray examination from 1 January 2013 to 31 December 2018. We evaluated the dose area product (DAP), effective dose (ED), and estimated risk. The International Commission on Radiological Protection Publication 60 defines values (2.8-13 × 10-2 Sv-1) to calculate the estimated risk in relation to the ED.

RESULTS

Of the 3843 patients (aged 241.1 ± 35.45 days) treated in the neonatal care unit, 1307 (34%) received at least one X-ray. The mean number of X-ray examinations per patient was 3.19 and correlated negatively with birth weight. The mean cumulative DAP was 5.9 mGy*cm2, and the cumulative ED was 23.7 µSv per hospital stay. Patients with a birth weight of < 1000 g showed the highest cumulative ED and DAP (p < 0.001). Patients with a birth weight of < 2500 g had the highest ED and DAP per image (p < 0.001). The highest radiation exposure (ED/DAP) occurred for thoracic/abdominal examinations, especially for neonates < 500 g (p < 0.001).

CONCLUSION

There is a strong correlation between immaturity, the number of X-ray examinations, and radiation exposure. The total exposure was minimal, and the number of X-rays per patient has been decreasing in recent years.

CLINICAL RELEVANCE

Possible risks to newborns and premature infants caused by ionising X-rays are often the subject of scientific and clinical discussion. Nevertheless, conventional X-ray imaging remains a frequently used tool, and total exposure remains at a very low level.

KEY POINTS

The number of X-rays per patient has been decreasing in a large university hospital. Half of all patients received only one X-ray; most had a birth weight over 1500 g. This radiation risk can be classified as 'minimal' for patients with a birth weight of < 500 g and as 'negligible' for others.

Assessment of radiation exposure risks in patients undergoing elastic stable intramedullary nailing: Insights from intraoperative fluoroscopy

INTRODUCTION

Elastic stable intramedullary nailing (ESIN) is a well-defined and appropriate treatment of choice for long bone fractures. Despite its benefits, the risk of cancer from imaging devices is of particular concern for younger adults. So, this survey was conducted to estimate the doses administered to patients undergoing ESIN of long bone fractures utilizing a 2-dimensional (2D) C-arm fluoroscopy machine during surgery, as well as the carcinogenic risk associated with the use of the machine.

METHODS

This study was conducted on 147 patients who required ESIN for long-bone fractures. Patients' demographic data, surgical data and imaging information were collected. For each patient, the organ doses and the effective doses were computed with the Monte Carlo PCXMC 2.0 simulation software. The cancer risk models proposed in the Biological Effects of Ionizing Radiation VII (BEIR VII) Phase 2 report were used to evaluate the risk of exposure-induced cancer death (REID) values.

RESULTS

For all patients, the highest organ dose was delivered to the gonads. The mean effective dose was 0.026 ± 0.015 mSv and 1.3E-04 ± 1E-04 mSv for ESIN of femur and tibia fractures, respectively. Males had a mean REID of 1 per million, while females had a mean REID of 0.19 per million. The younger males had considerably higher REID values. The effective dose was significantly correlated with age, gender, and irradiation time.

CONCLUSION

Low levels of effective doses and cancer risks associated with the utilization of the fluoroscopy machine in current practice were found in ESIN treatment of long-bone fractures.

IMPLICATIONS FOR PRACTICE

This outcome will help to raise surgeons' awareness of radiation risks and encourage them to initiate measures to keep radiation dose and exposure time as low as reasonably achievable.

Red flags to screen for vertebral fracture in people presenting with low back pain

BACKGROUND

Low back pain is a common presentation across different healthcare settings. Clinicians need to confidently be able to screen and identify people presenting with low back pain with a high suspicion of serious or specific pathology (e.g. vertebral fracture). Patients identified with an increased likelihood of having a serious pathology will likely require additional investigations and specific treatment. Guidelines recommend a thorough history and clinical assessment to screen for serious pathology as a cause of low back pain. However, the diagnostic accuracy of recommended red flags (e.g. older age, trauma, corticosteroid use) remains unclear, particularly those used to screen for vertebral fracture.

OBJECTIVES

To assess the diagnostic accuracy of red flags used to screen for vertebral fracture in people presenting with low back pain. Where possible, we reported results of red flags separately for different types of vertebral fracture (i.e. acute osteoporotic vertebral compression fracture, vertebral traumatic fracture, vertebral stress fracture, unspecified vertebral fracture).

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 26 July 2022.

SELECTION CRITERIA

We considered primary diagnostic studies if they compared results of history taking or physical examination (or both) findings (index test) with a reference standard test (e.g. X-ray, magnetic resonance imaging (MRI), computed tomography (CT), single-photon emission computerised tomography (SPECT)) for the identification of vertebral fracture in people presenting with low back pain. We included index tests that were presented individually or as part of a combination of tests.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data for diagnostic two-by-two tables from the publications or reconstructed them using information from relevant parameters to calculate sensitivity, specificity, and positive (+LR) and negative (-LR) likelihood ratios with 95% confidence intervals (CIs). We extracted aspects of study design, characteristics of the population, index test, reference standard, and type of vertebral fracture. Meta-analysis was not possible due to heterogeneity of studies and index tests, therefore the analysis was descriptive. We calculated sensitivity, specificity, and LRs for each test and used these as an indication of clinical usefulness. Two review authors independently conducted risk of bias and applicability assessment using the QUADAS-2 tool.

MAIN RESULTS

This review is an update of a previous Cochrane Review of red flags to screen for vertebral fracture in people with low back pain. We included 14 studies in this review, six based in primary care, five in secondary care, and three in tertiary care. Four studies reported on 'osteoporotic vertebral fractures', two studies reported on 'vertebral compression fracture', one study reported on 'osteoporotic and traumatic vertebral fracture', two studies reported on 'vertebral stress fracture', and five studies reported on 'unspecified vertebral fracture'. Risk of bias was only rated as low in one study for the domains reference standard and flow and timing. The domain patient selection had three studies and the domain index test had six studies rated at low risk of bias. Meta-analysis was not possible due to heterogeneity of the data. Results from single studies suggest only a small number of the red flags investigated may be informative. In the primary healthcare setting, results from single studies suggest 'trauma' demonstrated informative +LRs (range: 1.93 to 12.85) for 'unspecified vertebral fracture' and 'osteoporotic vertebral fracture' (+LR: 6.42, 95% CI 2.94 to 14.02). Results from single studies suggest 'older age' demonstrated informative +LRs for studies in primary care for 'unspecified vertebral fracture' (older age greater than 70 years: 11.19, 95% CI 5.33 to 23.51). Results from single studies suggest 'corticosteroid use' may be an informative red flag in primary care for 'unspecified vertebral fracture' (+LR range: 3.97, 95% CI 0.20 to 79.15 to 48.50, 95% CI 11.48 to 204.98) and 'osteoporotic vertebral fracture' (+LR: 2.46, 95% CI 1.13 to 5.34); however, diagnostic values varied and CIs were imprecise. Results from a single study suggest red flags as part of a combination of index tests such as 'older age and female gender' in primary care demonstrated informative +LRs for 'unspecified vertebral fracture' (16.17, 95% CI 4.47 to 58.43). In the secondary healthcare setting, results from a single study suggest 'trauma' demonstrated informative +LRs for 'unspecified vertebral fracture' (+LR: 2.18, 95% CI 1.86 to 2.54) and 'older age' demonstrated informative +LRs for 'osteoporotic vertebral fracture' (older age greater than 75 years: 2.51, 95% CI 1.48 to 4.27). Results from a single study suggest red flags as part of a combination of index tests such as 'older age and trauma' in secondary care demonstrated informative +LRs for 'unspecified vertebral fracture' (+LR: 4.35, 95% CI 2.92 to 6.48). Results from a single study suggest when '4 of 5 tests' were positive in secondary care, they demonstrated informative +LRs for 'osteoporotic vertebral fracture' (+LR: 9.62, 95% CI 5.88 to 15.73). In the tertiary care setting, results from a single study suggest 'presence of contusion/abrasion' was informative for 'vertebral compression fracture' (+LR: 31.09, 95% CI 18.25 to 52.96).

AUTHORS' CONCLUSIONS

The available evidence suggests that only a few red flags are potentially useful in guiding clinical decisions to further investigate people suspected to have a vertebral fracture. Most red flags were not useful as screening tools to identify vertebral fracture in people with low back pain. In primary care, 'older age' was informative for 'unspecified vertebral fracture', and 'trauma' and 'corticosteroid use' were both informative for 'unspecified vertebral fracture' and 'osteoporotic vertebral fracture'. In secondary care, 'older age' was informative for 'osteoporotic vertebral fracture' and 'trauma' was informative for 'unspecified vertebral fracture'. In tertiary care, 'presence of contusion/abrasion' was informative for 'vertebral compression fracture'. Combinations of red flags were also informative and may be more useful than individual tests alone. Unfortunately, the challenge to provide clear guidance on which red flags should be used routinely in clinical practice remains. Further research with primary studies is needed to improve and consolidate our current recommendations for screening for vertebral fractures to guide clinical care.

Diagnostic accuracy of ultra-low-dose CT compared to standard-dose CT for identification of non-displaced fractures of the shoulder, knee, ankle, and wrist

OBJECTIVES

To compare the performance of ultra-low-dose computed tomography (ULD-CT) with standard-dose computed tomography (SD-CT) for the diagnosis of non-displaced fractures of the shoulder, knee, ankle, and wrist.

METHODS

This prospective study enrolled 92 patients receiving conservative treatment for limb joint fractures who underwent SD-CT followed by ULD-CT at a mean interval of 8.85 ± 1.98 days. Fractures were characterized as displaced or non-displaced. Objective (signal-to-noise ratio, contrast-to-noise ratio) and subjective CT image quality were evaluated. Observer performance for ULD-CT and SD-CT detecting non-displaced fractures was estimated by calculating the area under the receiver operating characteristic (ROC) curve (A_z).

RESULTS

The effective dose (ED) for the ULD-CT protocol was significantly lower than the ED for the SD-CT protocol (F = 422.21~2112.25, p < 0.0001); 56 patients (65 fractured bones) had displaced fractures, and 36 patients (43 fractured bones) had non-displaced fractures. Two non-displaced fractures were missed by SD-CT. Four non-displaced fractures were missed by ULD-CT. Objective and subjective CT image quality was significantly improved for SD-CT compared to ULD-CT. The sensitivity, specificity, PPV, NPV, and diagnostic accuracy of SD-CT and ULD-CT for non-displaced fractures of the shoulder, knee, ankle and wrist were similar: 95.35% and 90.70%; 100% and 100%; 100% and 100%; 99.72% and 99.44%; and 99.74% and 99.47%, respectively. The A_z was 0.98 for SD-CT and 0.95 for ULD-CT (p = 0.32).

CONCLUSION

ULD-CT has utility for the diagnosis of non-displaced fractures of the shoulder, knee, ankle, and wrist and can support clinical decision-making.

Paced breathing and respiratory movement responses evoked by bidirectional constant current stimulation in anesthetized rabbits

Objective: Diaphragm pacing (DP) is a long-term and effective respiratory assist therapy for patients with central alveolar hypoventilation and high cervical spinal cord injury. The existing DP system has some limitations, especially high price, inconvenience preoperative evaluation methods and diaphragm fatigue easily. Our objective was to develop a DP system and evaluated reliability through hardware testing and animal experiments. Methods: A DP system with bidirectional constant current was designed, manufactured and tested. Effects of a wide range of stimulus amplitudes (range: .5-2.5 mA) and frequencies (range: 10-250 Hz) on airflow and corresponding inspired volume were investigated during DP. Differences in airflow characteristics under various stimulation parameters were evaluated using power function. ECG interference in diaphragm electromyography (EMGdi) was filtered out using stationary wavelet transform to obtain pure EMGdi (EMGdi_p). 80-min period with a tendency for diaphragm fatigue by root mean square (RMS) and centroid frequency (f _c ) of EMGdi_p was studied. Results: The increase of stimulus frequency and amplitude in animals resulted in different degrees of increase in envoked volume. Significant difference in Airflow Index (b) between anesthesia and DP provided a simple, non-invasive and feasible solution for phrenic nerve conduction function test. Increased stimulation duration with the developed DP system caused less diaphragm fatigue. Conclusion: A modular, inexpensive and reliable DP was successfully developed. Its effectiveness was confirmed in animal experiments. Significance: This study is useful for design of future implantable diaphragmatic pacemakers for improving diaphragm fatigue and convenient assessment of respiratory activity in experiments.

Pilot study to determine whether reduced-dose photon-counting detector chest computed tomography can reliably display Brody II score imaging findings for children with cystic fibrosis at radiation doses that approximate radiographs

BACKGROUND

The Brody II score uses chest CT to guide therapeutic changes in children with cystic fibrosis; however, patients and providers are often reticent to undergo chest CT given concerns about radiation.

OBJECTIVE

We sought to determine the ability of a reduced-dose photon-counting detector (PCD) chest CT protocol to reproducibly display pulmonary disease severity using the Brody II score for children with cystic fibrosis (CF) scanned at radiation doses similar to those of a chest radiograph.

MATERIALS AND METHODS

Pediatric patients with CF underwent non-contrast reduced-dose chest PCD-CT. Volumetric inspiratory and expiratory scans were obtained without sedation or anesthesia. Three pediatric radiologists with Certificates of Added Qualification scored each scan on an ordinal scale and assigned a Brody II score to grade bronchiectasis, peribronchial thickening, parenchymal opacity, air trapping and mucus plugging. We report image-quality metrics using descriptive statistics. To calculate inter-rater agreement for Brody II scoring, we used the Krippendorff alpha and intraclass correlation coefficient (ICC).

RESULTS

Fifteen children with CF underwent reduced-dose PCD chest CT in both inspiration and expiration (mean age 8.9 years, range, 2.5-17.5 years; 4 girls). Mean volumetric CT dose index (CTDI_vol) was 0.07 ± 0.03 mGy per scan. Mean effective dose was 0.12 ± 0.04 mSv for the total examination. All three readers graded spatial resolution and noise as interpretable on lung windows. The average Brody II score was 12.5 (range 4-19), with moderate inter-reader reliability (ICC of 0.61 [95% CI=0.27, 0.84]). Inter-rater reliability was moderate to substantial for bronchiectasis (0.52), peribronchial thickening (0.55), presence of opacity (0.62) and air trapping (0.70) and poor for mucus plugging (0.09).

CONCLUSION

Reduced-dose PCD-CT permits diagnostic image quality and reproducible identification of Brody II scoring imaging findings at radiation doses similar to those for chest radiography.

Comparison of Concordance between Chuna Manual Therapy Diagnostic Methods (Palpation, X-ray, Artificial Intelligence Program) in Lumbar Spine: An Exploratory, Cross-Sectional Clinical Study

Before Chuna manual therapy (CMT), a manual therapy applied in Korean medicine, CMT spinal diagnosis using palpation or X-ray is performed. However, studies on the inter-rater concordance of CMT diagnostic methods, concordance among diagnostic methods, and standard CMT diagnostic methods are scarce. Moreover, no clinical studies have used artificial intelligence (AI) programs for X-ray image-based CMT diagnosis. Therefore, this study sought a feasible and standard CMT spinal diagnostic method and explored the clinical applicability of the CMT-AI program. One hundred participants were recruited, and the concordance within and among different diagnostic modalities was analyzed by dividing them into manual diagnosis (MD), X-ray image-based diagnosis (XRD) by experts and non-experts, and XRD using a CMT-AI program by non-experts. Regarding intra-group concordance, XRD by experts showed the highest concordance (used as a gold standard when comparing inter-group concordance), followed by XRD using the AI program, XRD by non-experts, and then MD. Comparing diagnostic results between the groups, concordance with the gold standard was the highest for XRD using the AI program, followed by XRD by non-experts, and MD. Therefore, XRD is a more reasonable CMT diagnostic method than MD. Furthermore, the clinical applicability of the CMT-AI program is high.

Patterns and trends of population radiation exposure and projected the risk of exposure-induced death from gamma camera examinations in Yazd Province

INTRODUCTION

The use of nuclear medicine examinations as imaging modalities has recently increased. This study aimed to assess the radiation dose delivered to patients from common diagnostic nuclear medicine examinations and estimate the risk of exposure-induced death (REID). In addition, the frequency of nuclear medicine procedures were evaluated from 2015-2018.

MATERIALS AND METHODS

The data were collected from adult patients who had undergone cardiac, skeletal, renal, lacrimal, and thyroid imaging. For each patient, the effective dose was calculated using dose conversion factors, and REID was estimated using PCXMC. The frequency of examinations between 2015 and 2018 was obtained from the hospital information system (HIS).

RESULTS

The highest estimated effective dose was attributed to the scans of myocardial stress (8.09 ± 1.28 mSv), myocardial rest (5.59 ± 1.27 mSv), and thyroid imaging (3.93 ± 0.55 mSv). In addition, cardiac stress examination had the highest REID values for solid cancers (212.5 ± 67.5) and bone scans had the highest REID values for leukemia (11.5 ± 2.5). A large increase in the number of myocardial perfusion scans was a significant contributor to an increase in collective effective dose from 23.37 man-Sv in 2015 to 49.47 man-Sv in 2018, a compound annual growth rate (CAGR) of 26%.

CONCLUSION

Although the annual frequency and per capita effective dose of nuclear medicine procedures in Yazd Province increased continuously, they were comparably lower than those reported for other countries. Despite this, the cancer risks of nuclear medicine scans at the individual level are negligible (around 0.01% excess fatal cancer risk), yet the increasing tendency for these examinations could be of concern.

Virtual fracture clinic reduces patient X-ray volume for common wrist and ankle fractures

Background

Virtual fracture clinics (VFC) have been widely adopted worldwide as part of the changes in healthcare delivery during the COVID-19 pandemic. They have been shown to be a safe and effective method of delivering trauma care for injuries which do not require immediate intervention or specialist management, whilst maintaining high levels of patient satisfaction.

Aims

Our aim was to evaluate whether VFCs reduce the volume of X-rays performed for common fractures of the wrist and ankle.

Methods

A retrospective cohort review was performed. The pre-VFC group consisted of 168 wrist and 108 ankle referrals from March to September 2019. The VFC group included 75 wrist and 68 ankle referrals, during the period March to September 2020. The total number of X-ray images, carried out within a 3-month period for each fracture was summated, with statistical analysis performed following fracture pattern classification.

Findings

A statistically significant decrease in mean X-rays was observed for isolated stable fracture patterns, such as non-displaced distal radius, − 0.976 (p = 0.00025), and Weber A ankle fractures, − 0.907 (p = 0.000013). A reduction was also observed for more complex fracture patterns such as dorsally displaced distal radius, − 0.701 (p = 0.129) and Weber B ankle fractures, − 0.786 (p = 0.235), though not achieving statistical significance.

Conclusions

Virtual fracture clinics can reduce X-ray frequency for common stable wrist and ankle fractures, with resultant benefits for both patients and healthcare systems. These benefits may be sustained in patient care beyond the current COVID-19 pandemic.

Association of Lumbar Spine Radiographic Changes With Severity of Back Pain-Related Disability Among Middle-aged, Community-Dwelling Women

IMPORTANCE

Previous studies, using mostly cross-sectional data, provide conflicting evidence of an association between lumbar spine radiographic changes and the severity of back pain-related disability. Such conflicting evidence may be associated with widely unnecessary diagnostic imaging of the lumbar spine.

OBJECTIVE

To examine both cross-sectional and longitudinal associations between lumbar spine radiographic changes and the severity of back pain-related disability among middle-aged, community-dwelling women.

DESIGN, SETTING, AND PARTICIPANTS

This population-based prospective cohort study used data from the Chingford 1000 Women Study. Analyses included data collected from year 6 (1994-1996; physical activity was measured), year 9 (1997-1999; treated as baseline), and year 15 (2003-2005), with a total length of follow-up for longitudinal analyses of 6 years. Data were analyzed from April 17 to November 3, 2020.

EXPOSURES

Primary exposure was lumbar spine radiographic changes, defined using the Kellgren-Lawrence (K-L) grade. Secondary exposures were defined using presence of osteophytes and disc space narrowing. The composite score combined the number of lumbar spine segments with definite changes detected on radiographic images (ie, radiographic changes) (K-L grade ≥2, which means at least definite osteophyte and possible narrowing of disc space are present; osteophyte and disc space narrowing grade ≥1, which means at least mild or definite changes are present).

MAIN OUTCOMES AND MEASURES

Self-reported back pain-related disability measured in years 9 and 15 assessed by the St Thomas disability questionnaire.

RESULTS

Among 650 women (mean [SD] age, 61.3 [5.9] years) in cross-sectional analyses and 443 women (mean [SD] age, 60.6 [6.0] years) in longitudinal analyses, there was no evidence to support an association between higher number of lumbar segments with radiographic changes (K-L grade, osteophytes, and disc space narrowing) and more severe back pain-related disability (eg, cross-sectional analyses using the K-L grade; 1 segment vs 0 segment: adjusted odds ratio, 1.22 [95% CI, 0.76-1.96]). No interactions were found of an association between lumbar spine radiographic changes and the severity of back pain-specific disability with age, body mass index, or smoking status.

CONCLUSIONS AND RELEVANCE

In this cohort of middle-aged, community-dwelling women, there was no evidence to support an association between a higher number of lumbar segments with radiographic changes (K-L grade, osteophytes, and disc space narrowing) and more severe back pain-related disability cross-sectionally or over time. These findings provide further evidence against routinely using diagnostic imaging of the lumbar spine.

EVALUATION OF IRRADIATION DOSES DELIVERED TO PATIENTS IN COMPUTED TOMOGRAPHY EXAMINATIONS IN 10 RADIOLOGY DEPARTMENTS IN DOUALA-CAMEROON

Computed tomography (CT) scan is currently the most irradiating radio diagnostic procedure for the patients. The effective dose delivered by a CT-scan exploration corresponds to 1-20 years of natural irradiation of an individual. Hence, there is need to evaluate this medical exposure, in order to provide indicators and propose guidelines for its daily practice. The purpose of this work was to assess patient exposure levels due to CT-scan exams and propose a local diagnostic reference levels for the most common CT examinations performed in the radiology units of Douala/Cameroon. Data from 1775 CT scans, amongst which 10 different types of common CT examinations on adults and children, were collected, of which 1378 were adult CT scans and 397 were pediatric CT scans. The dose-length product (DLP) values in the adult population for head, abdomen-pelvic and lumber spine CT scans were high as compared to the Institute for Radiological Protection and Nuclear Safety recommendations and previous local DRL with an increase of 36, 15 and 23%, respectively. A general decrease of the DLP for CT-scans examinations in the pediatric population was observed.

Intramedullary fixation versus anatomically contoured plating of unstable ankle fractures: a randomized control trial

AIM

This study compared functional outcomes between anatomical shaped fibular plates and intramedullary nail fixation of adult patients who sustained unstable ankle fractures.

METHODS

A prospective randomized control trial was conducted between November 2013 and December 2016 on patients that presented with an unstable ankle fractures. They were randomized into a plate-and-screw group and a fibula nail group. At each post-operative visit the wounds were reviewed, and specific outcome measures were recorded, which included (i) the patient reported outcome measure (PROM) Olerud and Molander functional score, (ii) the Grimby score, (iii) swelling around the malleoli, (iv) plantar flexion, (v) dorsiflexion, (vi) inversion, and (vi) eversion.

RESULTS

Significant differences were observed in scar size (p < 0.001) and screening time (p < 0.001) whilst no differences were observed in functional and PROM measures. Although not statistically significant, of clinical value is one deep infection that occurred in the plate group, whilst no infections occurred in the nail group.

CONCLUSION

Both fixation methods yielded very similar functional results with differences only in scar size, screening time and swelling. Although none of these warrant a change in surgical decision-making processes, taken together, these factors potentially influence the decisions made in terms of surgical modalities used.

How common is imaging for low back pain in primary and emergency care? Systematic review and meta-analysis of over 4 million imaging requests across 21 years

Objectives

To (1) estimate the proportion of patients seeking care for low back pain (LBP) who are imaged and (2) explore trends in the proportion of patients who received diagnostic imaging over time. We also examined the effect of study-level factors on estimates of imaging proportion.

Data sources

Electronic searches of MEDLINE, Embase and CINAHL databases from January 1995 to December 2017.

Eligibility criteria for selecting studies

Observational designs and controlled trials that reported imaging for patients presenting to primary care or emergency care for LBP. We assessed study quality and calculated pooled proportions by care setting and imaging type, with strength of evidence assessed using the GRADE system.

Results

45 studies were included. They represented 19 451 749 consultations for LBP that had resulted in 4 343 919 imaging requests/events over 21 years. Primary care: moderate quality evidence that simple imaging proportion was 16.3% (95% CI 12.6% to 21.1%) and complex imaging was 9.2% (95% CI 6.2% to 13.5%). For any imaging, the pooled proportion was 24.8% (95% CI 19.3%to 31.1%). Emergency care: moderate quality evidence that simple imaging proportion was 26.1% (95% CI 18.2% to 35.8%) and high-quality evidence that complex imaging proportion was 8.2% (95% CI 4.4% to 15.6%). For any imaging, the pooled proportion was 35.6% (95% CI 29.8% to 41.8%). Complex imaging increased from 7.4% (95% CI 5.7% to 9.6%) for imaging requested in 1995 to 11.4% (95% CI 9.6% to 13.5%) in 2015 (relative increase of 53.5%). Between-study variability in imaging proportions was only partially explained by study-level characteristics; there were insufficient data to comment on some prespecified study-level factors.

Summary/conclusion

One in four patients who presented to primary care with LBP received imaging as did one in three who presented to the emergency department. The rate of complex imaging appears to have increased over 21 years despite guideline advice and education campaigns.

Trial registration number

CRD42016041987.

Healthcare Workers Occupationally Exposed to Ionizing Radiation Exhibit Altered Levels of Inflammatory Cytokines and Redox Parameters

Studies have shown an increased risk for a variety of cancers, specifically brain cancer, in healthcare workers occupationally exposed to ionizing radiation. Although the mechanisms mediating these phenomena are not fully understood, ionizing radiation-mediated elevated levels of reactive oxygen species (ROS), oxidative DNA damage, and immune modulation are likely involved. A group of 20 radiation exposed workers and 40 sex- and age-matched non-exposed control subjects were recruited for the study. We measured superoxide (O₂•⁻) levels in whole blood of healthcare workers and all other measurements of cytokines, oxidative DNA damage, extracellular superoxide dismutase (EcSOD) activity and reduced/oxidized glutathione ratio (GSH/GSSG) in plasma. Levels of O₂•⁻ were significantly higher in radiation exposed workers compared to control. Similarly, a significant increase in the levels of interleukin (IL)-6, IL-1α and macrophage inflammatory protein (MIP)-1α in radiation exposed workers compared to control was observed, while there was no significance difference in the other 27 screened cytokines. A significant positive correlation was found between MIP-1α and O₂•⁻ levels with no correlation in either IL-6 or IL-1α. Further, a dose-dependent relationship with significant O₂•⁻ production and immune alterations in radiation exposed workers was demonstrated. There was no statistical difference between the groups in terms of oxidative DNA damage, GSH/GSSG levels, or EcSOD activity. Although the biologic significance of cytokines alterations in radiation exposed workers is unclear, further studies are needed for determining the underlying mechanism of their elevation.

The Association of Coloproctology of Great Britain and Ireland consensus guidelines in surgery for inflammatory bowel disease

AIM

There is a requirement of an expansive and up to date review of surgical management of inflammatory bowel disease (IBD) that can dovetail with the medical guidelines produced by the British Society of Gastroenterology.

METHODS

Surgeons who are members of the ACPGBI with a recognised interest in IBD were invited to contribute various sections of the guidelines. They were directed to produce a procedure based document using literature searches that were systematic, comprehensible, transparent and reproducible. Levels of evidence were graded. An editorial board was convened to ensure consistency of style, presentation and quality. Each author was asked to provide a set of recommendations which were evidence based and unambiguous. These recommendations were submitted to the whole guideline group and scored. They were then refined and submitted to a second vote. Only those that achieved >80% consensus at level 5 (strongly agree) or level 4 (agree) after 2 votes were included in the guidelines.

RESULTS

All aspects of surgical care for IBD have been included along with 157 recommendations for management.

CONCLUSION

These guidelines provide an up to date and evidence based summary of the current surgical knowledge in the management of IBD and will serve as a useful practical text for clinicians performing this type of surgery.

Diagnostic concordance between skeletal cephalometrics, radiograph-based soft-tissue cephalometrics, and photograph-based soft-tissue cephalometrics

Objective

This study aims to investigate the diagnostic concordance between skeletal cephalometrics and soft-tissue cephalometrics in identifying facial lower third characteristics.

Materials and methods

We compared a skeletal cephalometric analysis (SCA) to a soft-tissue analysis performed on cephalometric radiographs (rSTCA) and to one performed on profile photograph (pSTCA). Ninety-six pre-treatment digital lateral cephalometric radiographs and 96 digital profile photographs were randomly selected for this study (patients' mean age: 18.33, SD: 3.38, age range: 14-29). Inclusion criteria were as follows: no skeletal asymmetry, well-aligned upper and lower dental arches, no history of orthodontic treatment, prosthodontic treatment, facial surgery and trauma, patient's age between 14 and 30 years, high-resolution images, exams taken with natural head position. Kruskas-Wallis and post hoc pairwise comparisons tests were used to find differences among the considered cephalometric methods. The diagnostic performance of the three methods was also assessed using the receiver-operating characteristic (ROC) curve analysis.

Results

Significant differences were found between SCA and rSTCA and between SCA and pSTCA in defining sagittal and vertical facial lower third characteristics (P < 0.05). No differences were found between rSTCA and pSTCA (P > 0.05) for the same facial characteristics. For each parameters investigated, pSTCA showed an area under the curve much closer to the perfect value of 1.00.

Conclusion

Poor diagnostic concordance was found between SCA and rSTCA and between SCA and pSTCA. pSTCA is a reliable method for evaluating the soft-tissue profile characteristics compared to that performed on cephalograms.

Current evidence for spinal X-ray use in the chiropractic profession: a narrative review

The use of routine spinal X-rays within chiropractic has a contentious history. Elements of the profession advocate for the need for routine spinal X-rays to improve patient management, whereas other chiropractors advocate using spinal X-rays only when endorsed by current imaging guidelines. This review aims to summarise the current evidence for the use of spinal X-ray in chiropractic practice, with consideration of the related risks and benefits. Current evidence supports the use of spinal X-rays only in the diagnosis of trauma and spondyloarthropathy, and in the assessment of progressive spinal structural deformities such as adolescent idiopathic scoliosis. MRI is indicated to diagnose serious pathology such as cancer or infection, and to assess the need for surgical management in radiculopathy and spinal stenosis. Strong evidence demonstrates risks of imaging such as excessive radiation exposure, overdiagnosis, subsequent low-value investigation and treatment procedures, and increased costs. In most cases the potential benefits from routine imaging, including spinal X-rays, do not outweigh the potential harms. The use of spinal X-rays should not be routinely performed in chiropractic practice, and should be guided by clinical guidelines and clinician judgement.

Health Impacts of Low-Dose Ionizing Radiation: Current Scientific Debates and Regulatory Issues

Health impacts of low-dose ionizing radiation are significant in important fields such as X-ray imaging, radiation therapy, nuclear power, and others. However, all existing and potential applications are currently challenged by public concerns and regulatory restrictions. We aimed to assess the validity of the linear no-threshold (LNT) model of radiation damage, which is the basis of current regulation, and to assess the justification for this regulation. We have conducted an extensive search in PubMed. Special attention has been given to papers cited in comprehensive reviews of the United States (2006) and French (2005) Academies of Sciences and in the United Nations Scientific Committee on Atomic Radiation 2016 report. Epidemiological data provide essentially no evidence for detrimental health effects below 100 mSv, and several studies suggest beneficial (hormetic) effects. Equally significant, many studies with in vitro and in animal models demonstrate that several mechanisms initiated by low-dose radiation have beneficial effects. Overall, although probably not yet proven to be untrue, LNT has certainly not been proven to be true. At this point, taking into account the high price tag (in both economic and human terms) borne by the LNT-inspired regulation, there is little doubt that the present regulatory burden should be reduced.

Diagnosis and treatment planning of orthodontic patients with 3-dimensional dentofacial records

INTRODUCTION

Cephalometrics has been the foundation of orthodontic diagnosis for many years. However, for many orthodontic patients, a lateral cephalogram might not be necessary. The aim of this study was to compare the diagnosis and treatment planning agreement between standard records and nonradiographic 3-dimensional (3D) dentofacial photogrammetry records.

METHODS

Twenty patients had standard orthodontic records taken for their treatment as well as extraoral and intraoral 3D images. Twelve evaluators examined the standard records and then completed diagnosis and treatment planning questionnaires. They repeated the process 4 to 6 weeks later by using 3D photographic images along with the panoramic radiographs. Each evaluator also evaluated 2 random orthodontic cases twice with each method to evaluate consistency within each method. At the end of study, each evaluator was asked to complete a survey to document his or her experiences with the 3D photogrammetry method. Descriptive and kappa statistics were used to determine the agreement.

RESULTS

Most diagnosis parameters had fair agreement between the methods and within each method. Skeletal and dental relationships had excellent agreement between and within the methods as well as most treatment decisions such as the need for extractions and surgery. Most evaluators (91.7%) thought that cephalometric x-rays would be needed only some of the time in diagnosis and treatment planning. Most evaluators (83.33%) thought that cephalometric radiographs are not needed in patients with a Class I ± a quarter cusp with crowding or spacing.

CONCLUSIONS

Most diagnostic decisions had fair agreement within and between the 2 methods. The decision to extract and the need for orthognathic surgery had excellent agreement between the cephalometric and photogrammetric methods. The majority of examiners agreed that patients with Class I malocclusions ± a quarter cusp with no obvious skeletal discrepancy can be diagnosed and planned without a cephalometric radiograph.

Effects of Medical Diagnostic Low-dose X Rays on Human Lymphocytes: Mitochondrial Membrane Potential, Apoptosis and Cell Cycle

Low-dose radiation is widely used across the world for the diagnosis of many diseases by means of a variety of imaging technologies. However, the harmful effects of exposure to low-dose radiation during medical examination remain controversial. The authors studied the effects of medical diagnostic low-dose x rays (i.e., 0.03, 0.05, or 0.1 mGy) after an in vitro exposure of human lymphocytes. Cells with no irradiation served as the non-irradiated control group. Three biological indicators were used to determine the effects of medical diagnostic low-dose x rays at 4, 8, 24, 48, and 72 h post-irradiation. These biological endpoints were mitochondrial membrane potential (ΔΨm), cell cycle, and apoptosis. Results indicated no changes in the ΔΨm, number of apoptotic cells, and cell cycle in lymphocytes exposed to these low doses of radiation, as compared to the corresponding non-irradiated lymphocytes at all harvest time-points. These results suggested that there were no harmful effects of the diagnostic low-dose x rays when human lymphocytes were exposed in an in vitro condition.

Measured Head CT/CTA Skin Dose and Intensive Care Unit Patient Cumulative Exposure

BACKGROUND AND PURPOSE

Estimates of cumulative CT/CTA radiation dose based on volumetric CT dose index have raised concern that neurological intensive care unit patient exposures may reach thresholds for deterministic skin injury. Because the accuracy of volumetric CT dose index for this purpose in unknown, we set out to directly measure head CT and CTA peak skin dose, assess the relationship of volumetric CT dose index to measured peak skin dose, and determine whether multiple CT/CTA exposures in typical patients in the neurological intensive care unit produce cumulative doses approaching or exceeding single-dose deterministic thresholds for skin injury.

MATERIALS AND METHODS

In a prospective study from 2011-2013, nanoDot optical stimulated luminescence dosimeters were used to measure head CT/CTA peak skin dose in 52 patients (28 female, 24 male; mean age, 63 years) divided equally between 2 CT scanners. Volumetric CT dose index and dose-length product were recorded for each examination. Peak skin dose was also measured on an acrylic skull phantom in each scanner. A 2-tailed, unpaired t test was used to compare mean patient skin doses between the 2 scanners. The measured peak skin doses were then used to calculate cumulative peak skin dose in 4 typical patients in intensive care units who received multiple CT/CTA scans.

RESULTS

Head CT/CTA peak skin dose agreed between scanners in patients and phantoms: (scanner 1 CT/CTA: patients, 39.2 ± 3.7 mGy and 98.9 ± 5.3 mGy, respectively, versus phantom, 40.0 mGy and 105.4 mGy, respectively; scanner 2 CT/CTA: patients, 42.9 ± 9.4 mGy and 98.8 ± 7.4 mGy, respectively, versus phantom, 37.6 mGy and 95.2 mGy, respectively). Volumetric CT dose index overestimated peak skin dose by a factor of 1.4-1.9 depending on examination and CT scanner. Cumulative doses in 4 patients in the intensive care unit estimated from measured CT/CTA peak skin dose ranged from 1.9-4.5 Gy.

CONCLUSIONS

Directly measured radiation skin doses from head CT/CTA patient examinations are substantially lower than volumetric CT dose index. Measured peak skin dose confirms that multiple head CT/CTA examinations in representative patients in the neurological intensive care unit may produce cumulative doses exceeding the single-dose deterministic threshold for skin injury.

Optimizing Radiotherapy with Immunotherapeutic Approaches

Several factors must be considered to successfully integrate immunotherapy with radiation into clinical practice. One such factor is that concepts arising from preclinical work must be tested in combination with radiation in preclinical models to better understand how combination therapy will work in patients; examples include checkpoint inhibitors, tumor growth factor-beta (TGF-β) inhibitors, and natural killer (NK) cell therapy. Also, many radiation fields and fractionation schedules typically used in radiation therapy had been standardized before the introduction of advanced techniques for radiation planning and delivery that account for changes in tumor size, location, and motion during treatment, as well as uncertainties introduced by variations in patient setup between treatment fractions. As a result, radiation therapy may involve the use of large treatment volumes, often encompassing nodal regions that may not be irradiated with more conformal techniques. Traditional forms of radiation in particular pose challenges for combination trials with immunotherapy. This chapter explores these issues in more detail and provides insights as to how radiation therapy can be optimized to combine with immunotherapy.

Computed tomography and patient risk: Facts, perceptions and uncertainties

Since its introduction in the 1970s, computed tomography (CT) has revolutionized diagnostic decision-making. One of the major concerns associated with the widespread use of CT is the associated increased radiation exposure incurred by patients. The link between ionizing radiation and the subsequent development of neoplasia has been largely based on extrapolating data from studies of survivors of the atomic bombs dropped in Japan in 1945 and on assessments of the increased relative risk of neoplasia in those occupationally exposed to radiation within the nuclear industry. However, the association between exposure to low-dose radiation from diagnostic imaging examinations and oncogenesis remains unclear. With improved technology, significant advances have already been achieved with regards to radiation dose reduction. There are several dose optimization strategies available that may be readily employed including omitting unnecessary images at the ends of acquired series, minimizing the number of phases acquired, and the use of automated exposure control as opposed to fixed tube current techniques. In addition, new image reconstruction techniques that reduce radiation dose have been developed in recent years with promising results. These techniques use iterative reconstruction algorithms to attain diagnostic quality images with reduced image noise at lower radiation doses.

JOURNAL CLUB: Scatter Radiation Dose From Digital Screening Mammography Measured in a Representative Patient Population

OBJECTIVE

The purpose of this study was to quantify the amount of scatter radiation received at the skin surface overlying the thyroid gland, salivary gland, lens of the eye, sternum, and uterus during a routine screening digital mammographic examination measured in a representative patient population.

SUBJECTS AND METHODS

The subjects were 207 women without symptoms with varied body mass indexes who underwent annual screening mammography while wearing six optically stimulated luminescence dosimeters placed at the bridge of the nose, right submandibular gland, right and left thyroid lobes, mid sternum, and 2 cm caudal to the umbilicus to assess scatter radiation dose to the skin.

RESULTS

The average scatter radiation doses at the skin surface during digital screening mammography in the representative population of women were as follows: overlying the right lobe of the thyroid, 0.24 mGy; left lobe of the thyroid, 0.25 mGy; salivary gland, 0.2 mGy; bridge of the nose, 0.025 mGy; sternum, 0.87 mGy; and umbilicus, 0.011 mGy. The scatter radiation doses at the umbilicus and the bridge of the nose were too low to measure with statistical confidence. Scatter radiation dose increased with increasing body mass index and increasing breast compression thickness.

CONCLUSION

Scatter radiation dose at the skin overlying organs of interest is a small fraction of the entrance skin dose to the breast. The low levels of scatter radiation measured do not support delaying clinically indicated mammography during early pregnancy.

Caries Experience among Adults Exposed to Low to Moderate Doses of Ionizing Radiation in Childhood - The Tinea Capitis Cohort

While the impact of therapeutic levels of ionizing radiation during childhood on dental defects has been documented, the possible effect of low doses on dental health is unknown. The study aim was to assess the association between childhood exposure to low-moderate doses of therapeutic radiation and caries experience among a cohort of adults 50 years following the exposure. The analysis was based on a sample of 253 irradiated (in the treatment of tinea capitis) and 162 non-irradiated subjects. The decayed, missing, and filled teeth (DMFT) index was assessed during a clinical dental examination and questions regarding dental care services utilization, oral hygiene behavior, current self-perceived mouth dryness, socio-demographic parameters, and health behavior variables were obtained through a face-to-face interview. An ordered multivariate logistic regression model was used to assess the association of the main independent variable (irradiation status) and other relevant independent variables on the increase in DMFT. Mean caries experience levels (DMFT) were 18.6 ± 7.5 for irradiated subjects compared to 16.4 ± 7.2 for the non-irradiated (p = 0.002). Controlling for gender, age, education, income, smoking, dental visit in the last year, and brushing teeth behavior, irradiation was associated with a 72% increased risk for higher DMFT level (95% CI: 1.19-2.50). A quantification of the risk by dose absorbed in the salivary gland and in the thyroid gland showed adjusted ORs of 2.21 per 1 Gy (95% CI: 1.40-3.50) and 1.05 per 1 cGy (95% CI: 1.01-1.09), respectively. Childhood exposure to ionizing radiation (0.2-0.4 Gy) might be associated with late outcomes of dental health. In line with the guidelines of the American Dental Association, these results call for caution when using dental radiographs.

Imaging for Urinary Stones: Update in 2015

CONTEXT

Imaging is essential for the diagnosis and the clinical decision-making process of patients with urinary stones.

OBJECTIVE

To assess the benefits and limitations of various imaging techniques by specifically focusing on different phases of stone patients' management.

EVIDENCE ACQUISITION

PubMed and Web of Science databases were used to identify studies published in the last 10 yr on this argument. Search terms included 'urolithiasis', nephrolithiasis', or 'urinary stones' in combination (AND) with the terms 'imaging', 'computer tomography', 'ultrasonography', 'intravenous pyelogram', or 'radiation exposure'. Study selection was based on an independent peer-review process of all the authors after the structured data search.

EVIDENCE SYNTHESIS

Noncontrast-enhanced computer tomography (CT) provides the highest value of diagnostic accuracy for urinary stones. Stone composition can be specifically assessed through the use of dual-energy CT. When information about the anatomy of the renal collecting system is required or alternative pathologies are suspected, CT with contrast injection is recommended. Low-dose protocols allowed a drastic reduction of the effective dose administered to the patient, thus limiting the biological risk due to ionising radiations. Other strategies to contain the radiation exposure include the dual-split bolus dual energy CT and the adaptive statistical image reconstruction. Abdomen ultrasound may be a valid alternative as an initial approach since it does not change the outcome of patients compared with CT, and should be the imaging of choice in children and pregnant women.

CONCLUSIONS

Noncontrast-enhanced CT is the most accurate imaging technique to identify urinary stones. Abdomen ultrasound seems to be a valid alternative in the initial evaluation of urinary colic. New low-dose protocols and strategies have been developed to contain radiation exposure, which is a major issue especially in specific circumstances.

PATIENT SUMMARY

Noncontrast-enhanced computer tomography has been increasingly used for the diagnosis and management of urinary stones. Low-dose protocols as well as alternative imaging should be considered by clinicians in specific circumstances to minimise radiation exposure.

Long-Term Effects of Exposure to Ionizing Irradiation on Periodontal Health Status - The Tinea capitis Cohort Study

Studies among long-term survivors of childhood cancer who had received high-dose irradiation therapy of 4–60 Gy, demonstrated acute and chronic dental effects, including periodontal diseases. However, the possible effects of low to moderate doses of radiation on dental health are sparse. The aim of this study is to investigate the association between childhood exposure to low–moderate doses of ionizing radiation and periodontal health following 50 years since exposure. The study population included 253 irradiated subjects (treated for Tinea capitis in the 1950s) and, 162 non-irradiated subjects. The estimated dose to the teeth was 0.2–0.4 Gy. Dental examination was performed according to the community periodontal index (CPI). Socioeconomic and health behavior variables were obtained through a personal questionnaire. Periodontal disease was operationally defined as “deep periodontal pockets.” A multivariate logistic regression model was used for the association of irradiation status and other independent variables with periodontal status. The results showed that among the irradiated subjects, 23%, (95% CI 18–28%) demonstrated complete edentulousness or insufficient teeth for CPI scoring as compared to 13% (95% CI 8–19%) among the non-irradiated subjects (p = 0.01). Periodontal disease was detected among 54% of the irradiated subjects as compared to 40% of the non-irradiated (p = 0.008). Controlling for education and smoking, the ORs for the association between radiation and periodontal disease were 1.61 (95% CI 1.01–2.57) and 1.95 (95% CI 1.1–3.5) for ever never and per 1 Gy absorbed in the salivary gland, respectively. In line with other studies, a protective effect for periodontal diseases among those with high education and an increased risk for ever smokers were observed. In conclusion, childhood exposure to low-moderate doses of ionizing radiation might be associated with later outcomes of dental health. The results add valuable data on the long-term health effects of exposure to ionizing radiation and support the implementation of the ALARA principle in childhood exposure to diagnostic procedure involving radiation.

Radiation exposure from abdominal imaging studies in patients with intestinal Behçet disease

Background/Aims

Recently, several studies have revealed that diagnostic imaging can result in exposure to harmful levels of ionizing radiation in inflammatory bowel disease patients. However, the extent of radiation exposure in intestinal Behcet disease (BD) patients has not been documented. The aim of this study was to estimate the radiation exposure from abdominal imaging studies in intestinal BD patients.

Methods

Patients with a diagnosis of intestinal BD established between January 1990 and March 2012 were investigated at a single tertiary academic medical center. The cumulative effective dose (CED) was calculated retrospectively from standard tables and by counting the number of abdominal imaging studies performed. High exposure was defined as CED >50 mSv.

Results

In total, 270 patients were included in the study. The mean CED was 41.3 mSv, and 28.1% of patients were exposed to high levels of radiation. Computed tomography (CT) accounted for 81.7% of the total effective dose. In multivariate analyses, predictors of high radiation exposure were azathioprine/6-mercaptopurine use, surgery, and hospitalization.

Conclusions

Approximately a quarter of intestinal BD patients were exposed to harmful levels of diagnostic radiation, mainly from CT examination. Clinicians should reduce the number of unnecessary CT examinations and consider low-dose CT profiles or alternative modalities such as magnetic resonance enterography.

Current knowledge on tumour induction by computed tomography should be carefully used

Risks associated to ionising radiation from medical imaging techniques have focused the attention of the medical society and general population. This risk is aimed to determine the probability that a tumour is induced as a result of a computed tomography (CT) examination since it makes nowadays the biggest contribution to the collective dose. Several models of cancer induction have been reported in the literature, with diametrically different implications. This article reviews those models, focusing on the ones used by the scientific community to estimate CT detriments. Current estimates of the probability that a CT examination induces cancer are reported, highlighting its low magnitude (near the background level) and large sources of uncertainty. From this objective review, it is concluded that epidemiological data with more accurate dosimetric estimates are needed. Prediction of the number of tumours that will be induced in population exposed to ionising radiation should be avoided or, if given, it should be accompanied by a realistic evaluation of its uncertainty and of the advantages of CTs. Otherwise they may have a negative impact in both the medical community and the patients. Reducing doses even more is not justified if that compromises clinical image quality in a necessary investigation. Key Points • Predictions of radiation-induced cancer should be discussed alongside benefits of imaging. • Estimates of induced cancers have noticeable uncertainties that should always be highlighted. • There is controversy about the acceptance of the linear no-threshold model. • Estimated extra risks of cancer are close to the background level. • Patients should not be alarmed by potential cancer induction by CT examinations.

Effects of radiation and vitamin C treatment on metronidazole genotoxicity in mice

The impact of exposure to low dose radiation (LDR) on human health is not clear. Besides, cross adaptation or sensitization with pharmaceutical agents may modify the risk of LDR. In the present study, we analyzed the interaction of radiation and metronidazole (MTZ) in inducing chromosome aberration (CA) and micronucleus (MN) in the bone marrow cells of Balb/C mice in vivo. Further, we evaluated the efficacy of vitamin C to reduce MTZ induced genotoxicity. We found that 10, 20 and 40mg/kg of MTZ induced dose dependent increase in the frequency of CA (r=0.9923, P<0.01) as well as MN (r=0.9823, P<0.05) in polychromatic erythrocytes. However, MTZ did not affect the ratio of polychromatic erythrocytes to normochromatic erythrocytes indicating lack of cytotoxicity. Supplementation with vitamin C prior to MTZ treatment significantly reduced the frequency of CA (P<0.001) as well as MN (P<0.001). Radiation (0.5Gy) exposure prior to MTZ treatment produced a less than additive (for CA) to additive (for MN) effects. However, radiation exposure following MTZ treatment produced additive (for CA) and synergistic (for MN) effects. Further, vitamin C pre-treatment also reduced the genotoxicity indices following the combined treatment of MTZ and radiation. Our findings suggest that MTZ may sensitize bone marrow cells to radiation exposure and enhances genotoxicity. We recommend more studies on the interaction of LDR and marketed pharmaceuticals to minimize possible harmful outcomes through appropriate precautionary measures.

Effect of low dose radiation on differentiation of bone marrow cells into dendritic cells

Low dose radiation has been shown to be beneficial to living organisms using several biological systems, including immune and hematopoietic systems. Chronic low dose radiation was shown to stimulate immune systems, resulting in controlling the proliferation of cancer cells, maintain immune balance and induce hematopoietic hormesis. Since dendritic cells are differentiated from bone marrow cells and are key players in maintaining the balance between immune activation and tolerance, it may be important to further characterize whether low dose radiation can influence the capacity of bone marrow cells to differentiate into dendritic cells. We have shown that bone marrow cells from low dose-irradiated (γ-radiation, 0.2Gy, 15.44mGy/h) mice can differentiate into dendritic cells that have several different characteristics, such as expression of surface molecules, cytokine secretion and antigen uptake capacity, when compared to dentritic cells differentiated from the control bone marrow cells. These differences observed in the low dose radiation group can be beneficial to living organisms either by activation of immune responses to foreign antigens or tumors, or maintenance of self-tolerance. To the best of our knowledge, this is the first report showing that total-body low dose radiation can modulate the capacity of bone marrow cells to differentiate into dendritic cells.

Risk of leukaemia mortality from exposure to ionising radiation in US nuclear workers: a pooled case-control study

OBJECTIVE

To follow-up on earlier studies of the leukaemogenicity of occupational ionising radiation exposure.

METHODS

We conducted a nested case-control analysis of leukaemia mortality in a pooled cohort of US nuclear workers followed through 2005. Each case was matched to four controls on attained age. Exposures were estimated from available records. General relative risk models were used to estimate the excess relative risk (ERR) of leukaemia, excluding chronic lymphocytic (CLL), acute myeloid leukaemia, chronic myeloid leukaemia and CLL while controlling for potential confounders. Preferred exposure lags and time-windows of risks were calculated using joint maximum likelihood. Dose-response was also examined using linear, linear-quadratic, categorical and restricted cubic spline models.

RESULTS

There were 369 leukaemia deaths in 105 245 US nuclear workers. The adjusted ERR for non-CLL leukaemia was 0.09 (95% CI -0.17 to 0.65) per 100 mGy. Elevated non-CLL risks were observed from exposures occurring 6-14 years prior to attained age of cases (ERR per 100 mGy=1.9; 95% CI <0 to 8.0). Lagged models indicated non-linearity of risk at very low (<10 mGy) and high (>100 mGy) doses, which contributed to the imprecision of results in linear models. Similar risk attenuation was not evident in time-windows-based models.

CONCLUSIONS

Risk estimates were in reasonable agreement with previous estimates, with the temporality of non-CLL leukaemia risk as a dominant factor in dose-response analyses. Future research should focus on methods that improve evaluations of the dose-response, particularly in the low-dose range.

Integrated molecular analysis indicates undetectable change in DNA damage in mice after continuous irradiation at ~ 400-fold natural background radiation

BACKGROUND

In the event of a nuclear accident, people are exposed to elevated levels of continuous low dose-rate radiation. Nevertheless, most of the literature describes the biological effects of acute radiation.

OBJECTIVES

DNA damage and mutations are well established for their carcinogenic effects. We assessed several key markers of DNA damage and DNA damage responses in mice exposed to low dose-rate radiation to reveal potential genotoxic effects associated with low dose-rate radiation.

METHODS

We studied low dose-rate radiation using a variable low dose-rate irradiator consisting of flood phantoms filled with 125Iodine-containing buffer. Mice were exposed to 0.0002 cGy/min (~ 400-fold background radiation) continuously over 5 weeks. We assessed base lesions, micronuclei, homologous recombination (HR; using fluorescent yellow direct repeat mice), and transcript levels for several radiation-sensitive genes.

RESULTS

We did not observe any changes in the levels of the DNA nucleobase damage products hypoxanthine, 8-oxo-7,8-dihydroguanine, 1,N6-ethenoadenine, or 3,N4-ethenocytosine above background levels under low dose-rate conditions. The micronucleus assay revealed no evidence that low dose-rate radiation induced DNA fragmentation, and there was no evidence of double strand break-induced HR. Furthermore, low dose-rate radiation did not induce Cdkn1a, Gadd45a, Mdm2, Atm, or Dbd2. Importantly, the same total dose, when delivered acutely, induced micronuclei and transcriptional responses.

CONCLUSIONS

These results demonstrate in an in vivo animal model that lowering the dose-rate suppresses the potentially deleterious impact of radiation and calls attention to the need for a deeper understanding of the biological impact of low dose-rate radiation.

Theoretical increase of thyroid cancer induction from cervical spine multidetector computed tomography in pediatric trauma patients

BACKGROUND

The trend of increasing cervical spine multidirectional computed tomography (MDCT) imaging of pediatric trauma patients is characteristic of the overall dramatic increase in computed tomography utilization in the United States. The purpose of this study is to compare the amount of radiation a pediatric trauma patient absorbs to the thyroid from plain radiographs and MDCT of the cervical spine and to express risk by calculation of theoretical thyroid cancer induction.

METHODS

A retrospective evaluation of pediatric trauma patients admitted from October 1, 2004, to October 31, 2009, was performed at an academic, Level I trauma center. Inclusion criteria were Level I/II trauma patients, cervical spine imaging performed at our institution, and age <18 years. Absorbed thyroid radiation was calculated for patients receiving plain radiographs or MDCT. Thyroid cancer risk was calculated using the 2006 Biological Effects on Ionizing Radiation VII report.

RESULTS

Six hundred seventeen patients met inclusion criteria: 224 received cervical spine radiographs and 393 received cervical spine MDCT. The mean thyroid radiation absorbed from radiographs was 0.90 mGy for males and 0.96 mGy for females compared with 63.6 mGy (males) and 64.2 mGy (females) receiving MDCT (p < 0.001). The median excess relative risk of thyroid cancer induction from one cervical spine MDCT in males was 13.0% and females was 25.0%, compared with 0.24% (males) and 0.51% (females) for radiographs (p < 0.001).

CONCLUSIONS

The significant difference in radiation that MDCT delivers to the pediatric trauma patient when compared with plain radiographs should temper routine use of computed tomography in pediatric cervical spine clearance algorithms.

Database of radiogenic cancer in experimental animals exposed to low doses of ionizing radiation

For decades, there have been debates regarding the nature of the relationship between exposure to low doses of ionizing radiation and cancer risk. Under the linear no-threshold hypothesis, which serves as a theoretical basis for current radiation protection standards, the risk of cancer at low levels of exposure is presumed to be directly proportional to dose. Opponents of this hypothesis claim that there are threshold doses for radiation carcinogenesis, or even a reduction in cancer risk at low doses (a phenomenon referred to as "radiation hormesis"). Epidemiological, animal, molecular, and cellular studies were conducted to resolve this controversy, although each of these study types has its strengths and limitations. Although the results of animal experiments are not directly applicable to humans, data can substantially add to our knowledge on the form of relationship between radiation dose and cancer risk in a wide range of doses. Laboratory animals are a homogeneous population with little biological variability; animal experiments are conducted under controlled conditions with good estimates of radiation doses. In order to address the question of whether or not the dose-response curve for radiation carcinogens is linear at low doses, a comprehensive database of animal carcinogenesis experiments was assembled involving exposure to different types of ionizing gradation. The database includes virtually all publicly accessible data on the induction of radiogenic cancer in laboratory mammals. This review provides a descriptive overview of the experiments included in the database, along with a qualitative assessment of the shape of the dose-response relationship for radiation carcinogenesis at low doses in experimental animals.