Effects of low level radiation-what's new?

Radiation-targeted immunotherapy: A new perspective in cancer radiotherapy

In contemporary oncology, radiation therapy and immunotherapy stand as critical treatments, each with distinct mechanisms and outcomes. Radiation therapy, a key player in cancer management, targets cancer cells by damaging their DNA with ionizing radiation. Its effectiveness is heightened when used alongside other treatments like surgery and chemotherapy. Employing varied radiation types like X-rays, gamma rays, and proton beams, this approach aims to minimize damage to healthy tissue. However, it is not without risks, including potential damage to surrounding normal cells and side effects ranging from skin inflammation to serious long-term complications. Conversely, immunotherapy marks a revolutionary step in cancer treatment, leveraging the body's immune system to target and destroy cancer cells. It manipulates the immune system's specificity and memory, offering a versatile approach either alone or in combination with other treatments. Immunotherapy is known for its targeted action, long-lasting responses, and fewer side effects compared to traditional therapies. The interaction between radiation therapy and immunotherapy is intricate, with potential for both synergistic and antagonistic effects. Their combined use can be more effective than either treatment alone, but careful consideration of timing and sequence is essential. This review explores the impact of various radiation therapy regimens on immunotherapy, focusing on changes in the immune microenvironment, immune protein expression, and epigenetic factors, emphasizing the need for personalized treatment strategies and ongoing research to enhance the efficacy of these combined therapies in cancer care.

Long-term LDR exposure may induce cognitive impairments: A possible association through targeting gut microbiota-gut-brain axis

Environmental and occupational low-dose radiation (LDR) exposure may be harmful for health but the previous reports regarding effect of LDR on cognition are contradictory. Here we investigated the effect of long-term LDR exposure on cognition. In this study, male Balb/c mice' cognitive functions were tested at 15 weeks after being exposed to 0.5 Gy LDR in 10 fractions at each dose of 0.05 Gy. The results demonstrated that long-term LDR exposure increases escape latency and the time spent in finding exits in mice compared with non LDR exposure. Meanwhile, the inflammation-related proteins including NFκB and p38 also increased. Lipopolysaccharide (LPS) increased and short-chain fatty acid (SCFA) levels decreased following long term LDR exposure. Treatment with microbiota-derived LPS and SCFAs reversed these effects in mice. Furthermore, the gut barrier integrity was damaged in a time-dependent manner with the decreased expression of intestinal epithelial-related biomarkers such as ZO-1 and occludin. Mechanistically, long after exposure to LDR, increased LPS levels may cause cognitive impairment through the regulation of Akt/mTOR signaling in the mouse hippocampus. These findings provide new insight into the clinical applications of LDR and suggest that the gut microbiota-plasma LPS and SCFAs-brain axis may underlie long-term LDR-induced cognition effects.

Estimated Atherosclerotic Cardiovascular Disease Risk: Disparities and Severe COVID-19 Outcomes (from the National COVID Cohort Collaborative)

Although cardiovascular disease risk factors relate to COVID-19, the association of estimated atherosclerotic cardiovascular disease (ASCVD) risk with severe COVID-19 is not established. We examined the relation of the pooled-cohort ASCVD risk score to severe COVID-19 among 28,646 subjects from the National COVID Cohort Collaborative database who had positive SARS-CoV-2 test results from April 1, 2020 to April 1, 2021. In addition, 10-year ASCVD risk scores were calculated, and subjects were stratified into low-risk (<5%), borderline-risk (5% to <7.5%), intermediate-risk (7.5% to <20%), and high-risk (>=20%) groups. Severe COVID-19 outcomes (including death, remdesivir treatment, COVID-19 pneumonia, acute respiratory distress syndrome, and mechanical ventilation) occurring during follow-up were examined individually and as a composite in relation to ASCVD risk group across race and gender. Multiple logistic regression, adjusted for age, gender, and race, examined the relation of ASCVD risk group to the odds of severe COVID-19 outcomes. Our subjects had a mean age of 59.4 years; 14% were black and 57% were female. ASCVD risk group was directly related to severe COVID-19 prevalence. The adjusted odds ratio of the severe composite COVID-19 outcome by risk group (vs the low-risk group) was 1.8 (95% confidence interval 1.5 to 2.2) for the borderline-risk, 2.7 (2.3 to 3.2) for the intermediate-risk, and 4.6 (3.7 to 5.6) for the high-risk group. Black men and black women in the high-risk group showed higher severe COVID-19 prevalence compared with nonblack men and nonblack women. Prevalence of severe COVID-19 outcomes was similar in intermediate-risk black men and high-risk nonblack men (approximately 12%). In conclusion, although further research is needed, the 10-year ASCVD risk score in adults ages 40 to 79 years may be used to identify those who are at highest risk for COVID-19 complications and for whom more intensive treatment may be warranted.

Unenhanced computed tomography for non-invasive diagnosis of hepatic steatosis with low tube potential protocol

Background

Lowering kVp affects the image contrast and computed tomography (CT) attenuation values of low kVp CT is different from those of conventional 120-kVp scans. The purpose of this study is to determine the diagnostic performance and to establish the reference range of low-kVp unenhanced CT for the assessment of hepatic steatosis in liver transplantation donors using magnetic resonance (MR) spectroscopy as a reference standard.

Methods

This retrospective study included 165 potential donors (male:female =114:51, 36.5±12.0 years old) who underwent 100-kVp single-slice unenhanced CT scan and MR spectroscopy. The difference between hepatic and splenic attenuation (CT_L-S) and liver-to-spleen attenuation ratio (CT_L/S) were calculated. Reference standard was the fat signal fraction measured by MR spectroscopy. Limits of agreement between CT measurements and the reference standard were calculated. Areas under receiver operating characteristic curves (AUROCs) of CT_L-S and CT_L/S were compared for the diagnosis of moderate to severe steatosis. Cut-off values of CT_L-S and CT_L/S that provided a balance between sensitivity and specificity and the highest specificity using the lower limit of the reference range were calculated.

Results

Eighty-seven subjects had a non-steatotic liver. Sixty-one subjects had mild steatosis and 17 subjects had moderate to severe steatosis based on MR spectroscopy. CT_L-S and CT_L/S values were negatively correlated with the fat signal fraction (P<0.001) and limits of agreement were -8.4% to 8.4% for CT_L-S and -9.6% to 9.6% for CT_L/S. AUROCs of CT_L-S and CT_L/S for diagnosing moderate to severe steatosis were 0.956 and 0.957, respectively. Cut-off values of CT_L-S and CT_L/S for diagnosis of moderate to severe steatosis by the Youden index were -0.5 HU for CT_L-S and 0.99 for CT_L/S. Reference ranges of non-steatotic liver were -6.90 to 31.40 HU for CT_L-S and 0.89 to 1.77 for CT_L/S. Using -6.9 HU for CT_L-S and 0.89 for CT_L/S as cut-off values, the sensitivity and specificity for diagnosing moderate to severe steatosis were 70.59% and 90.54% (CT_L-S) and 76.47% and 90.54% (CT_L/S), respectively.

Conclusions

Measurements from a low-kVp unenhanced CT scan were negatively correlated with the degree of hepatic steatosis. Low-kVp unenhanced CT is a robust technique with reduced radiation exposure for diagnosing moderate to severe hepatic steatosis.

Ionizing Radiation Protein Biomarkers in Normal Tissue and Their Correlation to Radiosensitivity: A Systematic Review

Background and objectives: Exposure to ionizing radiation (IR) has increased immensely over the past years, owing to diagnostic and therapeutic reasons. However, certain radiosensitive individuals show toxic enhanced reaction to IR, and it is necessary to specifically protect them from unwanted exposure. Although predicting radiosensitivity is the way forward in the field of personalised medicine, there is limited information on the potential biomarkers. The aim of this systematic review is to identify evidence from a range of literature in order to present the status quo of our knowledge of IR-induced changes in protein expression in normal tissues, which can be correlated to radiosensitivity. Methods: Studies were searched in NCBI Pubmed and in ISI Web of Science databases and field experts were consulted for relevant studies. Primary peer-reviewed studies in English language within the time-frame of 2011 to 2020 were considered. Human non-tumour tissues and human-derived non-tumour model systems that have been exposed to IR were considered if they reported changes in protein levels, which could be correlated to radiosensitivity. At least two reviewers screened the titles, keywords, and abstracts of the studies against the eligibility criteria at the first phase and full texts of potential studies at the second phase. Similarly, at least two reviewers manually extracted the data and accessed the risk of bias (National Toxicology Program/Office for Health Assessment and Translation—NTP/OHAT) for the included studies. Finally, the data were synthesised narratively in accordance to synthesis without meta analyses (SWiM) method. Results: In total, 28 studies were included in this review. Most of the records (16) demonstrated increased residual DNA damage in radiosensitive individuals compared to normo-sensitive individuals based on γH2AX and TP53BP1. Overall, 15 studies included proteins other than DNA repair foci, of which five proteins were selected, Vascular endothelial growth factor (VEGF), Caspase 3, p16^INK4A (Cyclin-dependent kinase inhibitor 2A, CDKN2A), Interleukin-6, and Interleukin-1β, that were connected to radiosensitivity in normal tissue and were reported at least in two independent studies. Conclusions and implication of key findings: A majority of studies used repair foci as a tool to predict radiosensitivity. However, its correlation to outcome parameters such as repair deficient cell lines and patients, as well as an association to moderate and severe clinical radiation reactions, still remain contradictory. When IR-induced proteins reported in at least two studies were considered, a protein network was discovered, which provides a direction for further studies to elucidate the mechanisms of radiosensitivity. Although the identification of only a few of the commonly reported proteins might raise a concern, this could be because (i) our eligibility criteria were strict and (ii) radiosensitivity is influenced by multiple factors. Registration: PROSPERO (CRD42020220064).

Double-layered fiber for lightweight flexible clothing providing shielding from low-dose natural radiation

Natural and medical radiation are the most frequent sources of daily low-dose radiation exposure for the general public, but these radiation levels are generally acceptable. Among various occupations, aviation crew members and medical workers are exposed to high levels of radiation from scattered rays. This study focused on developing clothing for shielding aviation crew members from natural radiation during air travel. Materials were selected considering their radiation-shielding properties. A tungsten double-layered composite yarn and a polyethylene terephthalate (PET) fiber fabric containing BaSO4 were manufactured. The characteristics and shielding performances of the products were analyzed. Prototypes of a protective scarf (for shielding the thyroid gland) and apron (for shielding the torso) for flight attendants were produced. A lightweight fabric was produced that neither restricts the movement of the wearer nor causes them skin discomfort. The shielding performances of the tungsten composite and PET fiber fabrics containing BaSO4 were 0.018 mmPb and 0.03 mmPb, respectively, demonstrating low-dose shielding that may be useful for protecting aviation crew members from scattered rays. The characteristics of the developed fibers are comparable to those of materials used in clothing production; therefore, low-dose radiation-shielding clothing could be manufactured for use in aviation, medical, and other industries.

Longitudinal Improvements in Radiation Exposure in Cardiac Catheterization for Congenital Heart Disease

Background:

The C3PO-QI (Congenital Cardiac Catheterization Project on Outcomes – Quality Improvement), a multicenter registry launched in 2015, instituted quality improvement (QI) initiatives to reduce patient radiation exposure. Through regular collaboration, this initiative would allow for harmony among active participants, maximizing efforts and efficiency at achieving radiation best practices. This study sought to report these efforts with a detailed methodology for which institutions can target initiatives, reducing radiation exposure, and increasing patient safety.

Methods:

Data were collected prospectively by 8 C3PO-QI institutions between January 1, 2015 and December 31, 2017. Radiation exposure was measured in dose area product per body weight (dose area product/kg; µGy*m 2 /kg) and reported by expected radiation exposure categories (REC) and institution for 40 published unique procedure types. Targeted interventions addressing selected strategic domains for radiation reduction were implemented in the pediatric catheterization labs of the C3PO-QI institutions.

Results:

The study consisted of 15 257 unique cases. Median exposure (dose area product/kg) was decreased by 30% for all procedures. Dose area product/kg was reduced in all 3 REC, with the greatest improvement observed in REC I (REC I, −37%; REC II, −23%; REC III, −27%). Although the baseline radiation exposures and exact percent decrease varied across all C3PO-QI sites, each institution demonstrated improvements in radiation dose over time. These improvements occurred with the implementation of institution-specific QI interventions accelerated by participation in the C3PO-QI multicenter collaborative.

Conclusions:

Substantial radiation dose reductions can be achieved using targeted QI methodology and interventions. Participation in a multicenter QI collaborative may accelerate improvement across all centers due to enhanced engagement and shared learning between sites.

The supplemental value of mammographic screening over breast MRI alone in BRCA2 mutation carriers

Purpose

BRCA2 mutation carriers are offered annual breast screening with MRI and mammography. The aim of this study was to investigate the supplemental value of mammographic screening over MRI screening alone.

Methods

In this multicenter study, proven BRCA2 mutation carriers, who developed breast cancer during screening using both digital mammography and state-of-art breast MRI, were identified. Clinical data were reviewed to classify cases in screen-detected and interval cancers. Imaging was reviewed to assess the diagnostic value of mammography and MRI, using the Breast Imaging and Data System (BI-RADS) classification allocated at the time of diagnosis.

Results

From January 2003 till March 2019, 62 invasive breast cancers and 23 ductal carcinomas in situ were diagnosed in 83 BRCA2 mutation carriers under surveillance. Overall screening sensitivity was 95.2% (81/85). Four interval cancers occurred (4.7% (4/85)). MRI detected 73 of 85 breast cancers (sensitivity 85.8%) and 42 mammography (sensitivity 49.9%) (p < 0.001).

Eight mammography-only lesions occurred. In 1 of 17 women younger than 40 years, a 6-mm grade 3 DCIS, retrospectively visible on MRI, was detected with mammography only in a 38-year-old woman. The other 7 mammography-only breast cancers were diagnosed in women aged 50 years and older, increasing sensitivity in this subgroup from 79.5% (35/44) to 95.5% (42/44) (p ≤ 0.001).

Conclusions

In BRCA2 mutation carriers younger than 40 years, the benefit of mammographic screening over MRI was very small. In carriers of 50 years and older, mammographic screening contributed significantly. Hence, we propose to postpone mammographic screening in BRCA2 mutation carriers to at least age 40.

A Randomized Trial of Ultrasound- versus. Fluoroscopy-Guided Subclavian Vein Catheterization in Children with Hematologic Disease

OBJECTIVE

To compare the ultrasound- and fluoroscopy-guided subclavian vein catheterization in pediatric population with hematologic diseases.

METHODS

A randomized prospective study of subclavian vein catheterization in pediatric population with hematologic diseases was performed. After randomization, the patients were assigned to either ultrasound- or fluoroscopy-guided subclavian vein catheterization. The primary outcome was number of attempts at venous cannulation. Secondary outcomes included: catheterization success rate, fluoroscopy time, operation time, and surgical complications.

RESULTS

There were 170 children enrolled between February 2017 and July 2018. There was no difference between the two groups with regard to the demographic data. Success within 3 attempts was achieved in 82 cases (82/87, 92.0%) in the ultrasound (US) group vs. 65 cases (65/83, 78.3%) in the fluoroscopy group (P = 0.002). The average operation time was 10(7) min in US group vs. 10(6) min in fluoroscopy group (P = 0.722). There were 3 complications in the US group, while there were 6 complications in the fluoroscopy group (P = 0.321). There were 4 catheter-related thrombosis (CRTs) found in the US group during follow-up, however there was no CRT in the fluoroscopy group (P = 0.121).

CONCLUSIONS

Ultrasound-guided venous puncture is a more accurate method of subclavian vein catheterization. However, the catheter tip can be placed more precisely by fluoroscopy. Thus, combined ultrasound-and fluoroscopy-guided technology is more efficient in subclavian vein catheterization of children with hematologic disease.

Low-value clinical practices in injury care: A scoping review and expert consultation survey

BACKGROUND

Tests and treatments that are not supported by evidence and could expose patients to unnecessary harm, referred to here as low-value clinical practices, consume up to 30% of health care resources. Choosing Wisely and other organizations have published lists of clinical practices to be avoided. However, few apply to injury and most are based uniquely on expert consensus. We aimed to identify low-value clinical practices in acute injury care.

METHODS

We conducted a scoping review targeting articles, reviews and guidelines that identified low-value clinical practices specific to injury populations. Thirty-six experts rated clinical practices on a five-point Likert scale from clearly low value to clearly beneficial. Clinical practices reported as low value by at least one level I, II, or III study and considered clearly or potentially low-value by at least 75% of experts were retained as candidates for low-value injury care.

RESULTS

Of 50,695 citations, 815 studies were included and led to the identification of 150 clinical practices. Of these, 63 were considered candidates for low-value injury care; 33 in the emergency room, 9 in trauma surgery, 15 in the intensive care unit, and 5 in orthopedics. We also identified 87 "gray zone" practices, which did not meet our criteria for low-value care.

CONCLUSION

We identified 63 low-value clinical practices in acute injury care that are supported by empirical evidence and expert opinion. Conditional on future research, they represent potential targets for guidelines, overuse metrics and de-implementation interventions. We also identified 87 "gray zone" practices, which may be interesting targets for value-based decision-making. Our study represents an important step toward the deimplementation of low-value clinical practices in injury care.

LEVEL OF EVIDENCE

Systematic Review, Level IV.

Radiation Risk Categories in Cardiac Catheterization for Congenital Heart Disease: A Tool to Aid in the Evaluation of Radiation Outcomes

To stratify diverse procedure types into categories with similar radiation exposure in cardiac catheterization for congenital heart disease. Radiation exposures for a comprehensive list of specific procedure types and stratification of outcomes based on radiation risk are not currently available. Data between January 2014 and December 2015 were collected on all cases performed at sites participating in C3PO-QI (Congenital Cardiac Catheterization Outcomes Project-Quality Improvement Initiative) and 9 centers were included. Using expert consensus, 40 unique procedure types were defined by diagnostic characteristics or the intervention(s) performed, and dose area product (DAP) per kilogram of body weight (µGy × m²/kg) was summarized. Using empiric and consensus methods, three radiation risk categories were created. A total of 11,735 cases were included for analysis. Thirteen (n = 7918) procedure types with median DAP/kg < 100 were categorized in the low radiation exposure category (median DAP/kg 39). The medium exposure category (n = 1807) consisted of 16 procedure types with median DAP/kg values ranging 100 to < 200 (overall median DAP/kg 131). Finally, the high radiation exposure category (n = 1073) consisted of 11 procedure types with median DAP/kg ≥ 200 (overall median DAP/kg of 231). The radiation exposure risk categories created in this multi-center dataset are a critical step towards the development of a robust risk adjustment methodology for radiation exposure in catheterization for congenital heart disease.

Fluoroscopy-guided subclavian vein catheterization in 203 children with hematologic disease

Subclavian vein catheterization plays an important role in the treatment of children with hematologic disease. However, catheter placement is a difficult and high-risk procedure in children.Fluoroscopy-guided subclavian vein catheterization was used in 203 children (mean age, 6.99 years ± 3.722 years; range, 1-16 years) with hematologic disease. The number of vein punctures, catheterization success rate, fluoroscopy time, operation time, and surgical complications were recorded.There was a 100% success rate for fluoroscopy-guided subclavian vein catheterization. A total of 124 cases (61.1%) were successful on the first venipuncture attempt; 171 cases (84.2%) achieved success within 3 attempts. Twenty-five cases had 4 to 6 time venipunctures and the remaining 7 cases underwent ≥7 time venipunctures. All catheter tips were successfully placed at the junction of the superior vena cava and the right atrium. Fluoroscopy times ranged from 16 to 607 seconds (mean, 65.46 ± 85.864 seconds). Operation time ranged between 5 and 25 minutes (mean, 10.38 ± 4.036 minutes). Arterial punctured was happened during surgery in 2 cases. There were 2 cases of catheter-related infection, but no other complications. The mean follow-up time was 35 days; range 20 to 50 days.Fluoroscopy-guided subclavian vein catheterization in children is a safe procedure, with a high success rate, resulting in a reduced number of venipunctures, optimal catheter placement, and reduced complications.

Automatic spectral imaging protocol and iterative reconstruction for radiation dose reduction in typical hepatic hemangioma computed tomography with reduced iodine load: a preliminary study

OBJECTIVE

To evaluate the effect of automatic spectral imaging protocol selection (ASIS) and adaptive statistical iterative reconstruction (ASiR) technique in the reduction of radiation and contrast medium dose in typical hepatic hemangioma (HH) dual energy spectral CT (DEsCT).

METHODS

62 patients with suspected HH were randomly divided into two groups equally: Group A, conventional 120-kVp CT with standard iodine load; Group B, DEsCT with ASIS technique and reduced iodine load, two sets of monochromatic spectral images were reconstructed: 69 keV level with 30% ASiR (Group B₁) and 52 keV level with 50% ASiR (Group B₂). The radiation and total iodine dose, quantitative analysis (standard deviation value, contrast-to-noise and contrast enhancement ratio) and qualitative analysis were evaluated.

RESULTS

No difference was observed in the standard deviation values, subjective image noise, and the diagnostic acceptability score among the three groups (p > 0.05). Contrast to noise [Group B₂  vs A, B₁ in arterial phase (AP): 19.51 ± 6.29 vs 15.77 ± 5.93, 11.46 ± 2.84; Group B₂  vs A, B₁ in portal venous phase (PVP): 9.96 ± 2.18 vs 8.19 ± 3.04, 6.01 ± 1.82], contrast enhancement ratio (Group B₂  vs A, B₁ in AP: 6.88 ± 2.01 vs 5.47 ± 2.01, 4.15 ± 1.28; Group B₂  vs A, B₁ in PVP: 5.58 ± 1.02 vs 4.54 ± 1.13, 3.49 ± 0.83), and the lesion conspicuity score (Group B₂  vs A, B₁ in AP: 3.93 ± 0.26 vs 3.45 ± 0.51, 3.10 ± 0.49; Group B₂  vs A, B₁ in PVP: 3.90 ± 0.31 vs 3.48 ± 0.57, 3.14 ± 0.44) for Group B₂ were higher than those in Group A and B₁ (p < 0.05). Compared to Group A, the radiation dose and total iodine dose in Group B were reduced by 30 and 41%, respectively (radiation dose in Group B vs A: 5.53 ± 1.59 vs 7.91± 2.71 mSv; iodine dose in Group B vs A: 18.85 ± 2.88 vs 31.78±3.89 ml; p < 0.05).

CONCLUSION

DEsCT with ASIS and ASiR technique can reduce the radiation dose without image quality degradation as compared to the conventional 120-kVp CT. The monochromatic spectral images at 52 keV level with 50% ASiR allows the reduction in total iodine dose without deteriorating diagnostic performance. Advances in knowledge: ASIS combined with ASiR technique, by using monochromatic spectral images at 52 keV level, represents a feasible imaging protocol to reduce the radiation and total iodine dose in assessment of typical HH.

Computed Tomography Scans in Patients With Young Adult Hip Pain Carry a Lifetime Risk of Malignancy

PURPOSE

To calculate the lifetime risk of malignancy in young adult patients with hip pain using 5 different imaging and radiation dose protocols with or without pre- and postoperative computed tomography (CT).

METHODS

Radiographic and CT patient radiation doses were retrospectively reviewed. Imaging protocols for hip pain composed of radiographs with or without pre- and postoperative CT scans were modeled and radiation doses were estimated using the PCXMC computer code. Based on these radiation doses, lifetime attributable risks of cancer and mortality for a 10- through 60-year-old male and female were calculated as published by the committee on the Biological Effects of Ionizing Radiation (BEIR) in the BEIR VII report. Relative risks and number needed to harm (NNH) were calculated for each protocol.

RESULTS

Based on a review of our institutional database, 2 CT scan doses were used for this study: a high 5.06 mSv and a low 2.86 mSv. Effective doses of radiation ranged from 0.59 to 0.66 mSv for radiographs alone to 10.71 to 10.78 mSv for radiographs and CT both pre- and postoperatively at the higher dose. Lifetime attributable risk of cancer for radiographs alone was 0.006% and 0.011% for a 20-year-old male and female, respectively. Lifetime attributable risk of cancer for radiographs along with pre- and postoperative CT scans at higher dose was 0.105% and 0.177% for a 20-year-old male and female, respectively. Radiographs alone lead to an NNH of 16,667 for males and 9,090 for females, whereas the protocol with pre- and postoperative CT scans at the higher dose led to an NNH of 952 for males and 564 for females. The relative risk of this protocol compared to radiographs alone was 17.5 for males and 16.1 for females.

CONCLUSION

Protocols with CT scans of the hip/pelvis pose a small lifetime attributable risk (0.034%-0.177% for a 20-year-old) but a large relative risk (5-17 times) of cancer compared with radiographs alone in the imaging evaluation for hip pain that decreases with increasing age.

CLINICAL RELEVANCE

This study illustrates the need for clinicians to understand the imaging protocols used at their institution to understand the risks and benefits of using those protocols in their practice.

Assessment of female breast dose for thoracic cone-beam CT using MOSFET dosimeters

Objective: To assess the breast dose during a routine thoracic cone-beam CT (CBCT) check with the efforts to explore the possible dose reduction strategy.

Materials and Methods: Metal oxide semiconductor field-effect transistor (MOSFET) dosimeters were used to measure breast surface doses during a thorax kV CBCT scan in an anthropomorphic phantom. Breast doses for different scanning protocols and breast sizes were compared. Dose reduction was attempted by using partial arc CBCT scan with bowtie filter. The impact of this dose reduction strategy on image registration accuracy was investigated.

Results: The average breast surface doses were 20.02 mGy and 11.65 mGy for thoracic CBCT without filtration and with filtration, respectively. This indicates a dose reduction of 41.8% by use of bowtie filter. It was found 220° partial arc scanning significantly reduced the dose to contralateral breast (44.4% lower than ipsilateral breast), while the image registration accuracy was not compromised.

Conclusions: Breast dose reduction can be achieved by using ipsilateral 220° partial arc scan with bowtie filter. This strategy also provides sufficient image quality for thorax image registration in daily patient positioning verification.

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.

THE EFFECT OF RADIATION SHIELDS ON OPERATOR EXPOSURE DURING CONGENITAL CARDIAC CATHETERISATION

Cardiac catheterisation personnel are exposed to occupational radiation and its health risks. Little data exist regarding the efficacy of radiation-protective equipment from congenital catheterisation laboratories (CLs). The authors retrospectively reviewed data in which CL operators wore a radiation dosemeter during catheterizations on patients of >20 kg. A leaded under-table skirt was present in all cases. Three additional radiation-protective devices were utilised at operator discretion: a top extension to the under-table skirt, a ceiling-mounted shield and a disposable patient drape. Case details, operator position, fluoroscopy time, incident air KERMA in the patient plane (K, mGy) and dose-area product (DAP, µGy·m²) were recorded. A total of 136 catheterizations over 8 months were included. Median operator dose (OpD) was 12 µSv (range 0-930) and indexed to K and DAP to correct for patient factors and case times. Indexed OpD decreased significantly with each additional shield used (14.8 vs. 1.3 nSv µGy^-1 m^-2 and 124 vs. 14 nSv mGy^-1 with one and four shields, respectively, p < 0.001). This trend was not significant with operator at head-of-bed. Combinations that included the ceiling shield had the lowest indexed OpD. The patient drape did not further reduce OpD when all other shields were used (1.3 vs. 2.2 nSv µGy^-1 m^-2, p = 0.5; 14 vs. 17 nSv mGy^-1, p = 0.4) and was associated with higher patient exposure indexed to weight and fluoroscopy time (4.5 vs. 3.1 µGy m² kg-min^-1, p = 0.009; and 0.51 vs. 0.38 mGy kg-min^-1, p = 0.01). Supplemental radiation barriers can decrease operator-absorbed radiation. A ceiling-mounted shield may provide greatest benefit. The authors do not recommend routine use of disposable patient drapes.

Attitudes toward evidence-based clinical decision support tools to reduce exposure to ionizing radiation: The Canadian CT Head Rule

BACKGROUND AND PURPOSE

A large degree of variation in clinical practice exists among clinicians evaluating and treating individuals with minor head injuries. Noncontrast head computerized tomography (CT) scans are commonly used to assess for intracranial damage in patients presenting with head injury. This practice is not supported by the evidence and poses harm to patients by increasing exposure to ionizing radiation. This form of radiation exposure increases the risk of developing cancers over the course of the individual's life, and further strains the limited resources of the healthcare system.

PROJECT SUMMARY

This article describes the findings of an evidence-based practice project assessing the attitudes of clinicians toward an evidence-based clinical decision support tool (Canadian CT Head Rule [CCHR]). The CCHR has 100% sensitivity in detecting all clinically important brain injuries and any injury requiring neurosurgical intervention. This clinical decision support (CDS) tool is designed to help guide clinicians in the prudent use of head CT scans in people ages 16-64 that have sustained minor head injuries. The Evidence-Based Attitude Scale was also used to identify which domains were most influential on willingness to adopt into clinical practice.

CONCLUSIONS

The results revealed an 84% increase in clinician knowledge of the use of the CCHR. A majority (83%) of participants reported moderate likelihood of adoption of the CDS tool into clinical practice if they found the tool appealing, and it was required by a governing authority. The use of CDS tools can help healthcare providers mitigate the risk associated with caring for complex patients. CDS tools provide a systematic method to evaluate patients with minor head injuries while assuring consistency of care and quality outcomes. This practice of assuring consistency and good patient outcomes is foundational to the concept of standard of care, which serves to improve clinical practice.

Radiation dosage during pediatric diagnostic or interventional cardiac catheterizations using the "air gap technique" and an aggressive "as low as reasonably achievable" radiation reduction protocol in patients weighing <20 kg

Background:

Cardiac catheterizations expose both the patient and staff to the risks of ionizing radiation. Studies using the “air gap” technique (AGT) in various radiological procedures indicate that its use leads to reduction in radiation exposure but there are no data on its use for pediatric cardiac catheterization. The aim of this study was to retrospectively review the radiation exposure data for children weighing <20 kg during cardiac catheterizations using AGT and an “as low as reasonably achievable (ALARA)” radiation reduction protocol.

Patients and Methods:

All patients weighing <20 kg who underwent cardiac catheterization at the Children's Hospital at Montefiore (CHAM), New York, the United States from 05/2011 to 10/2013 were included. Transplant patients who underwent routine endomyocardial biopsy and those who had surgical procedures at the time of the catheterizations were excluded. The ALARA protocol was used in concert with AGT with the flat panel detector positioned 110 cm from the patient. Demographics, procedural data, and patient radiation exposure levels were collected and analyzed.

Results:

One-hundred and twenty-seven patients underwent 151 procedures within the study period. The median age was 1.2 years (range: 1 day to 7.9 years) and median weight was 8.8 kg (range: 1.9-19.7). Eighty-nine (59%) of the procedures were interventional. The median total fluoro time was 13 min [interquartile range (IQR) 7.3-21.8]. The median total air Kerma (K) product was 55.6 mGy (IQR 17.6-94.2) and dose area product (DAP) was 189 Gym2 (IQR 62.6-425.5).

Conclusion:

Use of a novel ALARA and AGT protocol for cardiac catheterizations in children markedly reduced radiation exposure to levels far below recently reported values.

Abbreviations: AGT: Air gap technique, ALARA: As low as reasonably achievable.

CT of the Abdomen with Reduced Tube Voltage in Adults: A Practical Approach

Recent innovations in computed tomographic (CT) hardware and software have allowed implementation of low tube voltage imaging into everyday CT scanning protocols in adults. CT at a low tube voltage setting has many benefits, including (a) radiation dose reduction, which is crucial in young patients and those with chronic medical conditions undergoing serial CT examinations for disease management; and (b) higher contrast enhancement. For the latter, increased attenuation of iodinated contrast material improves the evaluation of hypervascular lesions, vascular structures, intestinal mucosa in patients with bowel disease, and CT urographic images. Additionally, the higher contrast enhancement may provide diagnostic images in patients with renal dysfunction receiving a reduced contrast material load and in patients with suboptimal peripheral intravenous access who require a lower contrast material injection rate. One limitation is that noisier images affect image quality at a low tube voltage setting. The development of denoising algorithms such as iterative reconstruction has made it possible to perform CT at a low tube voltage setting without compromising diagnostic confidence. Other potential pitfalls of low tube voltage CT include (a) photon starvation artifact in larger patients, (b) accentuation of streak artifacts, and (c) alteration of the CT attenuation value, which may affect evaluation of lesions on the basis of conventional enhancement thresholds. CT of the abdomen with a low tube voltage setting is an excellent radiation reduction technique when properly applied to imaging of select patients in the appropriate clinical setting.

Measures of patient radiation exposure during endoscopic retrograde cholangiography: Beyond fluoroscopy time

AIM: To determine whether fluoroscope time is a good predictor of patient radiation exposure during endoscopic retrograde cholangiopancreatography.

METHODS: This is a prospective observational study of consecutive patients undergoing endoscopic retrograde cholangiopancreatography in a tertiary care setting. Data related to radiation exposure were collected. The following measures were obtained: Fluoroscopy time (FT), dose area product (DAP) and dose at reference point (DOSERP). Coefficients of determination were calculated to analyze the correlation between FT, DAP and DOSRP. Agreement between FT and DAP/DOSRP was assessed using Bland Altman plots.

RESULTS: Four hundred sixty-three data sets were obtained. Fluoroscopy time average was 7.3 min. Fluoroscopy related radiation accounted for 86% of the total DAP while acquisition films related radiation accounted for 14% of the DAP. For any given FT there are wide ranges of DAP and DOSERP and the variability in both increases as fluoroscopy time increases. The coefficient of determination (R²) on the non transformed data for DAP and DOSERP versus FT were respectively 0.416 and 0.554. While fluoroscopy use was the largest contributor to patient radiation exposure during endoscopic retrograde cholangiography (ERCP), there is a wide variability in DAP and DOSERP that is not accounted for by FT. DAP and DOSERP increase in variability as FT increases. This translates into poor accuracy of FT in predicting DAP and DOSERP at higher radiation doses.

CONCLUSION: DAP and DOSERP in addition to FT should be adopted as new ERCP quality measures to estimate patient radiation exposure.

Estimation of effective dose and lifetime attributable risk from multiple head CT scans in ventriculoperitoneal shunted children

PURPOSE

The purpose of this review is to determine the averaged effective dose and lifetime attributable risk factor from multiple head computed tomography (CT) dose data on children with ventriculoperitoneal shunts (VPS).

METHOD AND MATERIALS

A total of 422 paediatric head CT exams were found between October 2008 and January 2011 and retrospectively reviewed. The CT dose data was weighted with the latest IRCP 103 conversion factor to obtain the effective dose per study and the averaged effective dose was calculated. Estimates of the lifetime attributable risk were also calculated from the averaged effective dose using a conversion factor from the latest BEIR VII report.

RESULTS

Our study found the highest effective doses in neonates and the lowest effective doses were observed in the 10-18 years age group. We estimated a 0.007% potential increase risk in neonates and 0.001% potential increased risk in teenagers over the base risk.

CONCLUSION

Multiple head CTs in children equates to a slight potential increase risk in lifetime attributable risk over the baseline risk for cancer, slightly higher in neonates relative to teenagers. The potential risks versus clinical benefit must be assessed.

High and low doses of ionizing radiation induce different secretome profiles in a human skin model

It is postulated that secreted soluble factors are important contributors of bystander effect and adaptive responses observed in low dose ionizing radiation. Using multidimensional liquid chromatography-mass spectrometry based proteomics, we quantified the changes of skin tissue secretome – the proteins secreted from a full thickness, reconstituted 3-dimensional skin tissue model 48 hr after exposure to 3, 10 and 200 cGy of X-rays. Overall, 135 proteins showed statistical significant difference between the sham (0 cGy) and any of the irradiated groups (3, 10 or 200 cGy) on the basis of Dunnett adjusted t-test; among these, 97 proteins showed a trend of downregulation and 9 proteins showed a trend of upregulation with increasing radiation dose. In addition, there were 21 and 8 proteins observed to have irregular trends with the 10 cGy irradiated group either having the highest or the lowest level among all three radiated doses. Moreover, two proteins, carboxypeptidase E and ubiquitin carboxyl-terminal hydrolase isozyme L1 were sensitive to ionizing radiation, but relatively independent of radiation dose. Conversely, proteasome activator complex subunit 2 protein appeared to be sensitive to the dose of radiation, as rapid upregulation of this protein was observed when radiation doses were increased from 3, to 10 or 200 cGy. These results suggest that different mechanisms of action exist at the secretome level for low and high doses of ionizing radiation.

Should the justification of medical exposures take account of radiation risks from previous examinations?

With the growing availability of dose histories for patients, the question of whether previous diagnostic radiation exposures should affect decisions on future examinations is coming into sharper focus. This article discusses ways in which cumulative dose information may affect our thinking in justifying exposures. Based on a common tendency to see a connection between past and future events even where we know them to be independent-the gambler's fallacy-we may find ourselves treating past risks as if they contribute to the present risk. We take the example of two patients scheduled for CT scans, one with no previous diagnostic radiation exposures, the other with a history of previous CT scans, to show that the risks, and justification process, are equivalent in both cases. For the patient with a history of diagnostic exposures, there are only two possibilities: either harm has been caused or there has been no effect. If previous CT examinations have not caused harm, then, as past risks, they are irrelevant. The patient is in precisely the same position with regard to risk as a patient with no dose history. If harm has been caused, avoiding further diagnostic exposures does not change this outcome; again in this case, a justified radiation examination should proceed. We argue that bringing dose history into the decision process for justifying examinations is contrary to our understanding of risk for low-dose radiation and, rather than improving patient safety, would unnecessarily restrict access to radiation-based diagnostic examinations.

Analysis of limited-sequence head computed tomography for children with shunted hydrocephalus: potential to reduce diagnostic radiation exposure

OBJECT

Despite its diagnostic utility, head CT scanning imparts risks of radiation exposure. Children with shunt-treated hydrocephalus exhibit increased risks of radiation toxicity due to the higher vulnerability of developing, immature tissues and frequent scanning. Several methods have been used to achieve dose reduction, including modifications of CT scanner tube current and potential. This retrospective study explores the use of a newly defined limited sequence of axial head CT slices to evaluate children with shunted hydrocephalus and decrease radiation exposure from diagnostic CT scans.

METHODS

Consistent sequences of 7 axial slices were extracted from previously performed standard head CT scans in children with shunted hydrocephalus. Chronologically distinct limited sequences of each patient were blindly, retrospectively reviewed by 2 pediatric neuroradiologists and 1 pediatric neurosurgeon. Limited-sequence CT evaluation focused on the adequacy of portraying the ventricular system, changes in ventricular size, and visualization of the proximal catheter. Reviewers assessed all original full series head CT scans at least 4 months later for comparison. Adequacy and accuracy of the limited-sequence CT compared with the gold standard head CT was investigated using descriptive statistics. Effective dose (ED) estimates of the limited-sequence and standard head CT scans were compared using descriptive statistics and the Mann-Whitney test.

RESULTS

Two serial head CT scans from each of 50 patients (age range 0-17 years; mean age 5.5 years) were reviewed both in standard and limited-sequence forms. The limited-sequence CT adequately portrayed the ventricular system in all cases. The inaccuracy rate for assessing changes in ventricular size by majority assessment (2 of 3 reviewers evaluating inaccurately) was 3 (6%) of 50. In 1 case, the inaccurate assessment would not have altered clinical management, corresponding to a 2 (4%) of 50 clinically relevant inaccuracy rate. As compared with the gold standard complete head CT series, the limited-sequence CT exhibited high sensitivity (100%) and specificity (91%) for portraying changes in ventricular caliber. Additionally, the limited-sequence CT displayed the ventricular catheter in 91.7% of scans averaged across 3 observers. Among all scans reviewed, 97 pairs of standard head CT and complementary limited-sequence CT scans contained adequate dosing information to calculate the effective dose (ED). The ED50 of the limited-sequence CT (0.284 mSv) differed significantly from the ED50 of the standard head CT (4.27 mSv) (p < 0.0001). The limited-sequence CT reflected a median absolute reduction of 4.10 mSv and a mean percent reduction of 91.8% in ED compared with standard head CT.

CONCLUSIONS

Limited-sequence head CT scanning provided adequate and accurate diagnostic information in children with shunted hydrocephalus. Techniques including minimization of axial slice quantity and modification of CT scanner parameters can achieve significant dose reduction, maintaining a balance between diagnostic utility and patient safety.

Physicians' and midlevel providers' awareness of lifetime radiation-attributable cancer risk associated with commonly performed CT studies: relationship to practice behavior

OBJECTIVE

The purpose of this study is to investigate emergency department (ED) providers' knowledge of the lifetime cancer risk attributable to radiation from commonly performed CT scans and its association with the ordering providers' risk-benefit analysis before ordering the examination. This study further explores factors that may influence a provider's selection of a particular diagnostic imaging study in an ED setting.

MATERIALS AND METHODS

Sixty-seven ED providers at the University of Rochester Medical Center completed a multiple-choice questionnaire. The questions were derived to assess an individual provider's awareness of lifetime cancer risk attributable to radiation from a diagnostic CT scan of the abdomen or pelvis and the provider's behavior toward risk-benefit analysis before ordering the examination. The association between the questions and years since completion of clinical training was determined using the Spearman correlation test. Univariate logistic regression analysis was used for the same questions to predict the knowledge of lifetime cancer risk attributable to radiation.

RESULTS

Fewer than 30% of ED providers possessed accurate knowledge of lifetime cancer risk attributable to radiation (p = 0.025). Providers with greater clinical experience, although lacking in the knowledge of lifetime cancer risk attributable to radiation, were more likely to consider patients' radiation dose history and to conduct a risk-benefit analysis and were less likely to order a CT scan unnecessarily. Clinical experience was negatively correlated with perceived unnecessary use of CT scans (p = 0.01).

CONCLUSION

A large proportion of ED providers are unaware of the lifetime risk of carcinogenesis associated with commonly performed CT scans. Clinical experience, not knowledge of lifetime cancer risk attributable to radiation, is significantly associated with beneficial behavior toward the use of CT.

Genomic characterization of a three-dimensional skin model following exposure to ionizing radiation

This study aimed at characterizing the genomic response to low versus moderate doses of ionizing radiation (LDIR versus MDIR) in a three-dimensional (3D) skin model, which exhibits a closer tissue complexity to human skin than monolayer cell cultures. EpiDermFT skin plugs were exposed to 0, 0.1 and 1 Gy doses of X-rays and harvested at 5 min, 3, 8 and 24 h post-irradiation (post-IR). RNA was interrogated for global gene expression alteration. Our results show that MDIR modulated a larger number of genes over the course of 24 h compared to LDIR. However, immediately and throughout the first 3h post-IR, LDIR modulated a larger number of genes than MDIR, mostly associated with cell-cell signaling and survival promotion. Significant modulation of pathways was detected only at 3 h post-IR in MDIR with induction of genes promoting apoptosis. Collectively, the data show different dynamics in the response to LDIR versus MDIR, especially in cell-cycle distribution. LDIR-exposed tissues showed signs of attempted cell-cycle re-entry as early as 3 h post-IR, but were arrested beyond 8 h at the G1/S checkpoint. At 24 h, cells appeared to accumulate at the G2/M checkpoint. MDIR-exposed tissues did not exhibit a prolonged G1/S arrest but rather a prolonged G2/M arrest, which was sustained at least up to 24 h. By 24 h cells exhibited signs of recovery in both LDIR- and MDIR-exposed tissues. In summary, the most pronounced difference in the initial cellular response to LDIR versus MDIR is the promotion of protection and survival in LDIR versus the promotion of apoptosis in MDIR.

Cellular radiosensitivity: how much better do we understand it?

PURPOSE

Ionising radiation exposure gives rise to a variety of lesions in DNA that result in genetic instability and potentially tumourigenesis or cell death. Radiation extends its effects on DNA by direct interaction or by radiolysis of H(2)O that generates free radicals or aqueous electrons capable of interacting with and causing indirect damage to DNA. While the various lesions arising in DNA after radiation exposure can contribute to the mutagenising effects of this agent, the potentially most damaging lesion is the DNA double strand break (DSB) that contributes to genome instability and/or cell death. Thus in many cases failure to recognise and/or repair this lesion determines the radiosensitivity status of the cell. DNA repair mechanisms including homologous recombination (HR) and non-homologous end-joining (NHEJ) have evolved to protect cells against DNA DSB. Mutations in proteins that constitute these repair pathways are characterised by radiosensitivity and genome instability. Defects in a number of these proteins also give rise to genetic disorders that feature not only genetic instability but also immunodeficiency, cancer predisposition, neurodegeneration and other pathologies.

CONCLUSIONS

In the past 50 years our understanding of the cellular response to radiation damage has advanced enormously with insight being gained from a wide range of approaches extending from more basic early studies to the sophisticated approaches used today. In this review we discuss our current understanding of the impact of radiation on the cell and the organism gained from the array of past and present studies and attempt to provide an explanation for what it is that determines the response to radiation.

Health risk and biological effects of cardiac ionising imaging: from epidemiology to genes

Cardiac diagnostic or therapeutic testing is an essential tool for diagnosis and treatment of cardiovascular disease, but it also involves considerable exposure to ionizing radiation. Every exposure produces a corresponding increase in cancer risk, and risks are highest for radiation exposure during infancy and adolescence. Recent studies on chromosomal biomarkers corroborate the current radioprotection assumption showing that even modest radiation load due to cardiac catheter-based fluoroscopic procedures can damage the DNA of the cell. In this article, we review the biological and clinical risks of cardiac imaging employing ionizing radiation. We also discuss the perspectives offered by the use of molecular biomarkers in order to better assess the long-term development of health effects.