Effects of low-dose ionizing radiation on genomic instability in interventional radiology workers.

Interventional radiologists are chronically exposed to low-dose ionizing radiation (IR), which may represent a health risk. The aim of the present study was to evaluate genomic instability by analyzing chromosomal aberrations, micronuclei, and 53BP1 DNA repair foci in peripheral blood lymphocytes of radiologists. Based on the IAEA guidelines on biodosimetry using dicentrics, the average protracted whole-body dose in radiologists were estimated. Since preleukemic fusion genes (PFG) are the primary events leading to leukemia, we also studied their presence by RT-qPCR and FISH. No significant difference in 53BP1 foci and incidence of PFG (MLL-AF4, MLL-AF9, AML1-ETO, BCR-ABL p190) was found in cells of interventional radiologists in comparison to controls. However, our results showed an increased frequency of micronuclei and various types of chromosomal aberrations including dicentrics in interventional radiologists. The average protracted whole body estimated dose was defined at 452.63 mGy. We also found a significantly higher amplification of the MLL gene segment and increased RNA expression in cells of interventional radiologists in comparison to controls. In conclusion, our results showed that long-term low-dose IR induces genomic instability in interventional radiologists.

Chromosome damage in regions with different levels of air pollution.

Air pollution is an important environmental factor influencing human health. In this study, we compared chromosome damage in city policemen from three cities in the Czech Republic: industrial Ostrava characterized by high levels of benzo[a]pyrene, Prague with heavy traffic emitting nitrogen oxides, and relatively clean Ceske Budejovice located in an area with predominantly agricultural activity. Chromosomal aberrations in lymphocytes were evaluated by fluorescence in situ hybridization with painting probes for chromosomes 1, 2, 3, and 4 in spring and autumn. An increase in the frequency of unstable chromosome aberrations, that is, dicentric chromosomes and acentric fragments, was observed in spring samples from Ostrava (p = .014 and p = .044, respectively) and Prague (p = .002 and p = .006, respectively) in comparison with Ceske Budejovice. The difference was significant only for samples taken after the winter period, when the concentration of pollutants in the air increases due to poor dispersion conditions. An increased frequency of dicentric chromosomes was observed in spring compared to autumn in both Ostrava and Prague (p = .017 and p = .023, respectively), but not in Ceske Budejovice. More breakpoints were observed on chromosome 1 than on the other chromosomes examined (p < .001). The number of breakpoints in the heterochromatin region 1p11-q12 was lower than in other parts of chromosome 1 (p < .001), suggesting a protective function of heterochromatin against damage. Our study showed, that air pollution increased the frequency of unstable chromosome aberrations, especially dicentric chromosomes. However, we did not show an effect on stable chromosome rearrangements.

Embolization of Ruptured Infratentorial Pial AVM in Pregnancy.

A primigravida 22-year-old woman, at a gestation of 23 weeks, experienced bleeding from a pial arteriovenous malformation (AVM) located in the right cerebellum. After interdisciplinary consensus and with the informed consent of the patient and her family, AVM embolization was performed. Complete occlusion of the AVM was achieved by embolization with PHIL (precipitating hydrophobic injectable liquid). The calculated dose in the uterus was less than 1 µSv, which represents a negligible risk of harmful effects on the fetus. She delivered a baby at 37 weeks of gestation by cesarean section without complications. No congenital disorders were diagnosed by standard screening methods until the age of the newborn was two years. The angiography protocol must be optimized to minimize the radiation dose. Adequate shielding protection of the uterus is important. Premature termination of pregnancy is not necessary. Multidisciplinary care of neurologists, neurosurgeons, interventional radiologists, anesthesiologists, neonatologists, and obstetricians is necessary.

Radiation dose and image quality of CT coronary angiography in patients with high heart rate or irregular heart rhythm using a 16-cm wide detector CT scanner.

Aim of the study was to evaluate the effect of high and irregular heart rate on the image quality and on the radiation exposure using a 256-row, 16-cm wide detector computed tomography (CT) system. Between March and December 2019, 349 patients undergoing CT coronary angiography (CTCA) were prospectively enrolled. Patients were divided into 2 study groups; Group 1 included patients with a regular heart rate of ≤70 bpm, while Group 2 included patients with an irregular heart rhythm or heart rate of >70 bpm. In all patients, image quality score and radiation dose were analyzed and recorded. In Group 1, there were a total of 195 patients, while in Group 2, there were 154 patients. Of the 349 patients, 299 of them had a regular heart rhythm (85.7%) and 50 (14.3%) had an irregular heart rhythm. Mean heart rate during scanning was 59 ± 7 bpm in Group 1 and 80 ± 12 bpm in Group 2. Mean effective dose of CTCA in Group 1 (1.2 ± 0.8 mSv) was lower than in Group 2 (1.9 ± 1.2 mSv, P < .001). Mean image quality (Likert score) of Group 1 was significantly higher than in Group 2 (4.1 vs 3.4, P < .001). CT scanner with 16-cm wide detector enables low-radiation exposure during CTCA even at high heart rate or irregular heart rhythm. Good CTCA image quality and low dose are related to low heart rate.

DIAGNOSTIC REFERENCE LEVELS IN SCREENING MAMMOGRAPHY CENTERS IN SLOVAKIA.

Optimization in mammography remains the most important tool in practice. In the optimization process, we look for a balanced relationship between image quality and patient dose. For mammographic examinations, the diagnostic reference levels (DRLs) are expressed as the average glandular dose (AGD) based on the thickness of the compressed breast. The aim of this study was to analyse DRL compliance in diagnostic mammography at 16 mammography screening centres using an automated system for tracking patient doses during the period between January 2020 and December 2020 and to subsequently propose new DRLs for the screening mammography centres in Slovakia. The new DRLs were ~20% lower than the existing national DRLs in diagnostic mammography in Slovakia and significantly lower than the achievable AGD levels published in the fourth edition of the European Guidelines for Quality Assurance in Breast Cancer Screening and Diagnosis.

Response of Escherichia coli minimal ter operon to UVC and auto-aggregation: pilot study.

AIM: The study of minimal ter operon as a determinant of tellurium resistance (TeR) is important for the purpose of confirming the relationship of these genes to the pathogenicity of microorganisms. The ter operon is widespread among bacterial species and pathogens, implicated also in phage inhibition, oxidative stress and colicin resistance. So far, there is no experimental evidence for the role of the Escherichia coli (E. coli) minimal ter operon in ultraviolet C (UVC) resistance, biofilm formation and auto-aggregation. To identify connection with UVC resistance of the minimal ter operon, matched pairs of Ter-positive and -negative E. coli cells were stressed and differences in survival and whole genome sequence analysis were performed. This study was aimed also to identify differences in phenotype of cells induced by environmental stress. METHODS: In the current study, a minimal ter operon(terBCDEΔF) originating from the uropathogenic strain E. coli KL53 was used. Clonogenic assay was the method of choice to determine cell reproductive death after treatment with UVC irradiation at certain time intervals. Bacterial suspensions were irradiated with 254 nm UVC-light (germicidal lamp in biological safety cabinet) in vitro. UVC irradiance output was 2.5 mW/cm2 (calculated at the UVC device aperture) and plate-lamp distance of 60 cm. DNA damage analysis was performed using shotgun sequencing on Illumina MiSeq platform. Biofilm formation was measured by a crystal violet retention assay. Auto-aggregation assay was performed according to the Ghane, Babaeekhou & Ketabi (2020). RESULTS: A large fraction of Ter-positive E. coli cells survived treatment with 120-s UVC light (300 mJ/cm2) compared to matched Ter-negative cells; ∼5-fold higher resistance of Ter-positive cells to UVC dose (p = 0.0007). Moreover, UVC surviving Ter-positive cells showed smaller mutation rate as Ter-negative cells. The study demonstrated that a 1200-s exposure to UVC (3,000 mJ/cm2) was sufficient for 100% inhibition of growth for all the Ter-positive and -negative E. coli cells. The Ter-positive strain exhibited of 26% higher auto-aggregation activities and was able to inhibit biofilm formation over than Ter- negative strain (**** P < 0.0001). CONCLUSION: Our study shows that Ter-positive cells display lower sensitivity to UVC radiation, corresponding to a presence in minimal ter operon. In addition, our study suggests that also auto-aggregation ability is related to minimal ter operon. The role of the minimal ter operon (terBCDEΔF) in resistance behavior of E. coli under environmental stress is evident.

Neurointerventionalist and Patient Radiation Doses in Endovascular Treatment of Acute Ischemic Stroke.

PURPOSE: To evaluate the patient and the neurointerventionalist radiation dose levels during endovascular treatment of acute ischemic stroke, and to analyze factors affecting doses. MATERIALS AND METHODS: From October 2017 to January 2019, we prospectively collected patient radiation data and neurointerventionalist data from real-time dosimetry from all consecutive thrombectomies. Multivariate analysis was performed to analyze patient total dose area product (DAP) and neurointerventionalist dose variability in terms of clinical characteristics and the technical parameters of thrombectomies. Local dose reference levels (RL) were derived as the 75th percentile of the patient dose distributions. RESULTS: A total of 179 patients were treated during the study period and included in this study. Local dose RL for thrombectomy was derived for total DAP to 34 Gy cm2, cumulative air kerma of 242 mGy and fluoroscopy time of 12 min. The mean neurointerventionalist dose for thrombectomy was 7.7 ± 7.4 µSv. Height (P = 0.018), weight (P = 0.004), body mass index (P = 0.015), puncture to recanalisation (P < 0.001), fluoro time (P < 0.001), number of passes (P < 0.001), thrombolysis in cerebral infarction 2b/3 recanalisation (P = 0.034) and aspiration thrombectomy (P < 0.001) were independent factors affecting patient total DAP, whereas baseline National Institutes of Health Stroke Scale (P = 0.043), puncture to recanalisation (P = 0.003), fluoroscopy time (P = 0.009) and number of passes (P = 0.009) were factors affecting the neurointerventionalist dose. CONCLUSION: New reference patient doses lower than those in previously published studies were defined. However, the operator's doses were higher than those in the only available study reporting on operator's dose during cerebral interventions.

Patients undergoing recurrent CT scans: assessing the magnitude.

OBJECTIVES: To assess percent of patients undergoing multiple CT exams that leads to cumulative effective dose (CED) of ≥ 100 mSv and determine their age distribution. METHODS: Data was retrieved retrospectively from established radiation dose monitoring systems by setting the threshold value of 100 mSv at four institutions covering 324 hospitals. The number of patients with CED ≥ 100 mSv only from recurrent CT exams during a feasible time period between 1 and 5 years was identified. Age and gender distribution of these patients were assessed to identify the magnitude of patients in the relatively lower age group of ≤ 50 years. RESULTS: Of the 2.5 million (2,504,585) patients who underwent 4.8 million (4,819,661) CT exams during the period of between 1 and 5 years, a total of 33,407 (1.33%) patients received a CED of ≥ 100 mSv with an overall median CED of 130.3 mSv and maximum of 1185 mSv. Although the vast majority (72-86%) of patients are > 50 years of age, nearly 20% (13.4 to 28%) are ≤ 50 years. The minimum time to accrue 100 mSv was a single day at all four institutions, an unreported finding to date. CONCLUSIONS: We are in an unprecedented era, where patients undergoing multiple CT exams and receiving CED ≥ 100 mSv are not uncommon. While underscoring the need for imaging appropriateness, the consideration of the number and percent of patients with high exposures and related clinical necessities creates an urgent need for the industry to develop CT scanners and protocols with sub-mSv radiation dose, a goal that has been lingering. KEY POINTS: • We are in an era where patients undergoing multiple CT exams during a short span of 1 to 5 years are not uncommon and a sizable fraction among them are below 50 years of age. • This leads to cumulative radiation dose to individual patients at which radiation effects are of real concern. • There is an urgent need for the industry to develop CT scanners with sub-mSv radiation dose, a goal that has been lingering.

RISK EVALUATION IN THE LOW-DOSE RANGE CT FOR RADIATION-EXPOSED CHILDREN, BASED ON DNA DAMAGE.

One of the most common usages of radiation in current medical diagnosis is computed tomography (CT) using X-rays. The potential health risk of CT scans has been discussed in various studies to determine whether low-dose radiation from CT could enhance the chromosome aberration yields in pediatric patients and increase their risk of carcinogenesis. For this reason, it is of great interest to study the effects of low-dose radiation. The induction of DNA damage by a CT scan examination has been demonstrated in several reports by the γ-H2AX assay, the micronuclei assay and dicentrics measurements. However, the results of most studies showed limitations. On the other hand, epidemiological studies give contradictory results for post-natal radiation exposure in the low-dose range, so it is still difficult to draw conclusions about the effects of CT examinations and risk of carcinogenesis. This article provides an overview of previously published data and summarizes the current state of knowledge.

IAEA survey of dental cone beam computed tomography practice and related patient exposure in nine Central and Eastern European countries.

OBJECTIVES: Cone beam CT (CBCT) in dentistry and maxillofacial surgery is a widely used imaging method for the assessment of various maxillofacial and dental pathological conditions. The objective of this study was to summarize the results of a multinational retrospective-prospective study that focused on patient exposure in this modality. METHODS: The study included 27 CBCT units and 325 adult and paediatric patients, in total. Data on patients, clinical indications, technical parameters of exposure, patient dose indicator, or, alternatively, dose to phantom were collected. The dose indicator used was air kerma-area product, PKA. RESULTS: In most scanners operators are offered with a variety of options regarding technical parameters, especially the field of view size. The median and the third quartile value of PKA for adult patients in 14 different facilities were 820 mGy cm² and 1000 mGy cm² (interquartile range = 1058 mGy cm²), and 653 mGy cm² and 740 mGy cm² (interquartile range = 1179 mGy cm²) for children, as reported by four different institutions. Phantom dose data were reported from 15 institutions, and median PKA ranged from 125 mGy cm² to 1951 mGy cm². Median PKA values varied by more than a 10-fold between institutions, mainly due to differences in imaging protocol used, in particular field of view and tube current-exposure time product. CONCLUSIONS: The results emphasize the need for a cautious approach to using dental CBCT. Imaging only when the clinical indications are clear, accompanied with the appropriate radiographic techniques and the optimum imaging protocol, will help reduce radiation dose to patients.