How radiosensitive are the developing embryo and fetus?

A Historical Survey of Key Epidemiological Studies of Ionizing Radiation Exposure

In this article we review the history of key epidemiological studies of populations exposed to ionizing radiation. We highlight historical and recent findings regarding radiation-associated risks for incidence and mortality of cancer and non-cancer outcomes with emphasis on study design and methods of exposure assessment and dose estimation along with brief consideration of sources of bias for a few of the more important studies. We examine the findings from the epidemiological studies of the Japanese atomic bomb survivors, persons exposed to radiation for diagnostic or therapeutic purposes, those exposed to environmental sources including Chornobyl and other reactor accidents, and occupationally exposed cohorts. We also summarize results of pooled studies. These summaries are necessarily brief, but we provide references to more detailed information. We discuss possible future directions of study, to include assessment of susceptible populations, and possible new populations, data sources, study designs and methods of analysis.

Comparing fetal phantoms with surrogate organs in female phantoms during CT exposure of pregnant patients

With the rising use of Computed Tomography (CT) in diagnostic radiology, there are concerns regarding radiation exposure to sensitive groups, including pregnant patients. Accurately determining the radiation dose to the fetus during CT scans is essential to balance diagnostic efficacy with patient safety. This study assessed the accuracy of using the female uterus as a surrogate for fetal radiation dose during CT imaging. The study used common CT protocols to encompass various scenarios, including primary beam, scatter, and partial exposure. The computational program NCICT was used to calculate radiation doses for an adult female and a fetus phantom. The study highlighted that using the uterus for dose estimation can result in consistent underestimations of the effective dose, particularly when the fetus lies within the primary radiation beam. These discrepancies may influence clinical decisions, affecting care strategies and perceptions of associated risks. In conclusion, while the female uterus can indicate fetal radiation dose if the fetus is outside the primary beam, it is unreliable when the fetus is within the primary beam. More reliable abdomen/pelvic organs were recommended.

Pencil Beam Scanning Proton Therapy for Pregnant Patients With Brain and Head and Neck Cancers

PURPOSE

When radiation therapy is medically necessary for pregnant patients, photon-based treatments (XRT) have traditionally been used, whereas proton radiation therapy (PRT) is avoided due to concerns about neutron dose. This retrospective study analyzes pregnant patients treated with XRT and models the equivalent dose that would have been delivered to the fetus with proton radiation compared with XRT. The purpose of this work is to provide a comprehensive analysis of pencil beam scanning proton therapy (PBS-PRT) for pregnant patients and to evaluate whether PBS-PRT should be the new standard of practice for treating pregnant patients with brain and head and neck cancers.

METHODS AND MATERIALS

PBS-PRT plans were made for seven pregnant patients who received XRT: four treated for brain tumors and three for head and neck tumors. Measurements were performed with the patient plans using an anthropomorphic phantom and Wendi-2 meter placed at the phantom's abdomen. Patient-specific measurements were used to determine the total fetal equivalent dose from PBS-PRT compared with XRT. Imaging dose was also evaluated with a Fluke 451 dose meter.

RESULTS

The average measured fetal equivalent dose, accounting for photons and neutrons, for the brain plans was 0.4 mSv for PBS-PRT and 7 mSv for XRT. For the head and neck plans, it was 6 mSv and 90 mSv for PBS-PRT and XRT, respectively. The PBS-PRT plans were preferred by the physicians for both tumor coverage and normal-tissue sparing. Daily imaging added between 0.05 and 1.5 mSv to the total dose.

CONCLUSIONS

This retrospective study showed that when treating brain or head and neck cancers in pregnant patients, fetal equivalent dose is reduced by approximately a factor of 10 with PBS-PRT compared with XRT without making any compromises in treatment planning objectives. These results support a change of practice to using PBS-PRT as the new standard for treating pregnant patients with brain or head and neck tumors compared with XRT.

Ethical and societal aspects of radiological protection for offspring and next generations

PURPOSE

Over the last decade or so, ethical and societal aspects of radiological protection have received increasing attention. This is also reflected in the publications of the International Commission on Radiological Protection (ICRP). The current paper aims at identifying relevant ethical and societal topics which should receive attention in the context of radiological protection for offspring and next generations.

MATERIALS AND METHODS

We present a non-comprehensive review of the subject, based on presentation made at an ICRP workshop in Budapest in 2022. We first discuss the ethical values promoted by ICRP, and the application of these values in cases of (potential) pre-conceptual and prenatal radiation exposures. We then consider experience gained after the Fukushima accident indicating particular societal concerns about the health effects of such exposures.

RESULTS AND CONCLUSIONS

Beneficence/non-maleficence, prudence, justice and dignity, the "core values" of the system of radiological protection have special roles to play when heritable and/or in utero effects are to be considered. Prudence, in particular, must be taken account of in view of the fact that solid scientific data in humans are largely lacking in this area, and it is necessary to rely on insights from animal experiments as well as theoretical considerations. As regards societal considerations, the perception of risk among (potentially) affected populations needs to be taken seriously. Accountability, transparency, and inclusivity, the "procedural values" promoted by ICRP for the practical implementation of the system of radiological protection play a central role in overcoming skepticism and creating trust. Stakeholder involvement should emphasize cooperation and dialogue, which allows for the joint evaluation of an exposure situation by experts and affected people.

Management of pregnant or potentially pregnant patients undergoing diagnostic and interventional radiology procedures: Investigation of clinical routine practice

It is well known that foetuses are highly sensitive to ionising radiation and special attention to justification and optimisation of radiological procedures involving a pregnant patient is required. A task to review, validate and compare different approaches to managing the pregnant patient and to estimating the associated foetal doses arising from a diagnostic or interventional radiology (DIR) procedure was designed in the framework of EURADOS working group 12. As a first step, a survey of radiation protection practice including dosimetry considerations among EURADOS members was performed using online questionnaire. Then, to evaluate the possible differences in the estimated foetal doses, a comparison of assessed dose values was made for three cases of pregnant patients that underwent different CT procedures. More than 120 professionals from 108 institutions and 17 countries that are involved in managing pregnant patients undergoing DIR procedures answered the questionnaire. Most of the respondents use national or hospital guidelines on the management of pregnant patients undergoing DIR procedures. However, the guidelines differ considerably among respondents. Comparison of foetal dose assessments performed by dosimetry experts showed the variety of methods used as well as large variability of estimated foetal doses in all three cases. Although European and International commission on radiation protection guidelines already exist, they are more than 20 years old and, in some aspects, they are obsolete. This paper shows that there is a need to revise and update these guidelines.

Low-dose radiation induces unstable gene expression in developing human iPSC-derived retinal ganglion organoids

The effects of low-dose radiation on undifferentiated cells carry important implications. However, the effects on developing retinal cells remain unclear. Here, we analyzed the gene expression characteristics of neuronal organoids containing immature human retinal cells under low-dose radiation and predicted their changes. Developing retinal cells generated from human induced pluripotent stem cells (iPSCs) were irradiated with either 30 or 180 mGy on days 4-5 of development for 24 h. Genome-wide gene expression was observed until day 35. A knowledge-based pathway analysis algorithm revealed fluctuations in Rho signaling and many other pathways. After a month, the levels of an essential transcription factor of eye development, the proportion of paired box 6 (PAX6)-positive cells, and the proportion of retinal ganglion cell (RGC)-specific transcription factor POU class 4 homeobox 2 (POU4F2)-positive cells increased with 30 mGy of irradiation. In contrast, they decreased after 180 mGy of irradiation. Activation of the "development of neurons" pathway after 180 mGy indicated the dedifferentiation and development of other neural cells. Fluctuating effects after low-dose radiation exposure suggest that developing retinal cells employ hormesis and dedifferentiation mechanisms in response to stress.

Avocado peel extract: The effect of radiation-induced on neuroanatomical and behavioral changes in rats

Avocado (Persea americana) contains a variety of physiological active substances such as polyphenol, which has excellent antioxidant properties. This study investigated the radioprotective effect of avocado peel extract on congenital malformations and on the behavior of Sprague-Dawley (SD) rats. Experimental animals were randomly classified into four groups: NC Group, normal control; PA Group, oral administration with avocado peel extract (200 mg/kg/day); IR Group, irradiation; and PA+IR Group, irradiation after orally administered with avocado peel extract. For irradiation, 2 Gy of 6 MV X-ray was used once for the whole body. After that, congenital malformations, histopathological evaluation of the brain, and behavioral evaluation were performed in the obtained offspring. Although the body weight of the offspring was decreased by radiation exposure, it was confirmed that the decrease in weight was smaller when treated with PA. As the congenital malformations, hydrocephalus, loss of eyes, and abnormal rat tail occurred, and the result for the PA+IR Group was significantly lower than that of IR Group. Histopathologically, the length of the cerebral cortex of the PA+IR Group was similar to that of the non-radiation group. It was confirmed that emotional and behavioral disorders such as anxiety and depression were improved in the open field test (OFT) and elevated plus maze (EPM) test. And proved that working memory and cognitive ability were enhanced in the novel object recognition (NOR) test and spontaneous alternation Y-maze (SAY) test. Therefore, it was concluded that avocado peel extract can reduce the incidence of congenital malformations and improve growth disorders, memory and cognitive abilities. In the future, based on these results, we will conduct research on the hippocampus and amygdala, which are major regions of the brain, and additional research on cell biology.

Development of a computational pregnant female phantom and calculation of fetal dose during a photon breast radiotherapy

BACKGROUND

The incidence of carcinoma during pregnancy is reported to be 1:1000-1:1500 pregnancies with the breast carcinoma being the most commonly diagnosed. Since the fetus is most sensitive to ionizing radiation during the first two trimesters, there are mixed clinical opinions and no uniform guidelines on the use of radiotherapy during pregnancy. Within this study the pregnant female phantom in the second trimester, that can be used for radiotherapy treatment planning (as DICOM data), Monte Carlo simulations (as voxelized geometry) and experimental dosimetry utilizing 3D printing of the molds (as .STL files), was developed.

MATERIALS AND METHODS

The developed phantom is based on MRI images of a female patient in her 18th week of pregnancy and CT images after childbirth. Phantom was developed in such a manner that a pregnant female was scanned "in vivo" using MRI during pregnancy and CT after childbirth. For the treatment of left breast carcinoma, 3D conformal radiotherapy was used. The voxelized geometry of the phantom was used for Monte Carlo (MC) simulations using Monte Carlo N-Particle transport code^TM 6.2 (MCNP).

CONCLUSIONS

The modeled photon breast radiotherapy plan, applied to the phantom, indicated that the fetus dose is 59 mGy for 50 Gy prescribed to the breast. The results clearly indicate that only 9.5% of the fetal dose is caused by photons that are generated in the accelerator head through scattering and leakage, but the dominant component is scattered radiation from the patient's body.

Age effects on radiation response: summary of a recent symposium and future perspectives

One of the principal uncertainties when estimating population risk of late effects from epidemiological data is that few radiation-exposed cohorts have been followed up to extinction. Therefore, the relative risk model has often been used to estimate radiation-associated risk and to extrapolate risk to the end of life. Epidemiological studies provide evidence that children are generally at higher risk of cancer induction than adults for a given radiation dose. However, the strength of evidence varies by cancer site and questions remain about site-specific age at exposure patterns. For solid cancers, there is a large body of evidence that excess relative risk (ERR) diminishes with increasing age at exposure. This pattern of risk is observed in the Life Span Study (LSS) as well as in other radiation-exposed populations for overall solid cancer incidence and mortality and for most site-specific solid cancers. However, there are some disparities by endpoint in the degree of variation of ERR with exposure age, with some sites (e.g., colon, lung) in the LSS incidence data showing no variation, or even increasing ERR with increasing age at exposure. The pattern of variation of excess absolute risk (EAR) with age at exposure is often similar, with EAR for solid cancers or solid cancer mortality decreasing with increasing age at exposure in the LSS. We shall review the human data from the Japanese LSS cohort, and a variety of other epidemiological data sets, including a review of types of medical diagnostic exposures, also some radiobiological animal data, all bearing on the issue of variations of radiation late-effects risk with age at exposure and with attained age. The paper includes a summary of several oral presentations given in a Symposium on "Age effects on radiation response" as part of the 67th Annual Meeting of the Radiation Research Society, held virtually on 3-6 October 2021.

Perinatal mortality after the Fukushima nuclear accident: An ecological study

OBJECTIVE

This study continues former studies on perinatal mortality in Japan after the Fukushima Daiichi nuclear power plant (FDNPP) accident in March 2011. An increased study region is chosen, and the study period is extended to 2019.

METHODS

Japanese monthly perinatal mortality data are provided on a prefecture level by the Japanese government. The study region consists of 12 prefectures around the FDNPP; the rest of Japan is used as the control region. A combined non-linear regression of perinatal mortality rates in the study- and control regions is conducted. The regression model allows for a common asymptotic lower limit of perinatal mortality, seasonal variations, and periodic peaks in 2012-2019 in the study region. To determine the dependency of the effect on distance from the FDNPP, the study region is divided into four core prefectures and eight prefectures surrounding the core prefectures.

RESULTS

Perinatal mortality rates in the study region show a significant 6.4% (95% CI: 1.8%, 13.4%) overall increase in 2012-2019 relative to the trend in preceding years with no attenuation during 2012-19. The increase translates to 590 (165, 1226) excess perinatal deaths (p = 0.016). It is characterized by annual peaks with maxima in April. A 13.6% increase is determined in the four core prefectures and a 4.3% increase in eight prefectures surrounding the core prefectures. Before 2012, there is a peak around April 2011 and a decline in October 2011; another significant peak is detected in November 2012. In the 4 core prefectures, large increases are found in the first quarter of 2018 (+70%) and in May 2019 (+130%).

CONCLUSION

This study finds periodic peaks in perinatal mortality in spring 2012-2019 in 12 prefectures of Japan surrounding the FDNPP. In light of massive increases in 2018 and 2019 in the four core prefectures, continued investigation of perinatal mortality in contaminated regions of Japan is recommended.

A hypothesis to derive the shape of the dose-response curve for teratogenic radiation effects

Reports of adverse pregnancy outcomes after in utero exposure to very low levels of ionizing radiation are inconsistent with a threshold dose of 100 mSv for teratogenic effects in humans. In the present study, it is hypothesized that the shape of the dose-response relationship for teratogenic effects is a cumulative lognormal distribution without threshold. This hypothesis relies on the assumption that both doses and radiosensitivities in human populations exposed to ionizing radiation are random variables, modeled by lognormal density functions. Here, radiosensitivity is defined as the dose limit up to which radiation damage can be repaired by the cellular repair systems, in short, the repair capacity. Monte Carlo simulation is used to generate N pairs of individual doses and repair capacities. Radiation damage occurs whenever the dose exceeds the related repair capacity. The rate of radiation damage is the number of damages, divided by the number N of pairs. Monte Carlo simulation is conducted for a sufficient number of ascending median doses. The shape of the dose-response relationship is determined by regression of damage rates on mean dose. Regression with a cumulative lognormal distribution function yields a perfect fit to the data. Acceptance of the hypothesis means that studies of adverse health effects following in-utero exposure to low doses of ionizing radiation should not be discarded primarily because they contradict the concept of a threshold dose for teratogenic effects.

BRAIN AND EYE AS POTENTIAL TARGETS FOR IONIZING RADIATION IMPACT: PART II - RADIATION CEREBRO/OPHTALMIC EFFECTS IN CHILDREN, PERSONS EXPOSED IN UTERO, ASTRONAUTS AND INTERVENTIONAL RADIOLOGISTS

BACKGROUND

Ionizing radiation (IR) can affect the brain and the visual organ even at low doses, while provoking cognitive, emotional, behavioral, and visual disorders. We proposed to consider the brain and the visual organ as potential targets for the influence of IR with the definition of cerebro-ophthalmic relationships as the «eye-brain axis».

OBJECTIVE

The present work is a narrative review of current experimental, epidemiological and clinical data on radiation cerebro-ophthalmic effects in children, individuals exposed in utero, astronauts and interventional radiologists.

MATERIALS AND METHODS

The review was performed according to PRISMA guidelines by searching the abstract and scientometric databases PubMed/MEDLINE, Scopus, Web of Science, Embase, PsycINFO, Google Scholar, published from 1998 to 2021, as well as the results of manual search of peer-reviewed publications.

RESULTS

Epidemiological data on the effects of low doses of IR on neurodevelopment are quite contradictory, while data on clinical, neuropsychological and neurophysiological on cognitive and cerebral disorders, especially in the left, dominant hemisphere of the brain, are nore consistent. Cataracts (congenital - after in utero irradiation) and retinal angiopathy are more common in prenatally-exposed people and children. Astronauts, who carry out longterm space missions outside the protection of the Earth's magnetosphere, will be exposed to galactic cosmic radiation (heavy ions, protons), which leads to cerebro-ophthalmic disorders, primarily cognitive and behavioral disorders and cataracts. Interventional radiologists are a special risk group for cerebro-ophthalmic pathology - cognitivedeficits, mainly due to dysfunction of the dominant and more radiosensitive left hemisphere of the brain, andcataracts, as well as early atherosclerosis and accelerated aging.

CONCLUSIONS

Results of current studies indicate the high radiosensitivity of the brain and eye in different contingents of irradiated persons. Further research is needed to clarify the nature of cerebro-ophthalmic disorders in different exposure scenarios, to determine the molecular biological mechanisms of these disorders, reliable dosimetric support and taking into account the influence of non-radiation risk factors.

Early Breast Cancers During Pregnancy Treated With Breast-Conserving Surgery in the First Trimester of Gestation: A Feasibility Study

Breast cancer is the most common malignancy occurring during gestation. In early-stage breast cancer during pregnancy (PrBC), breast-conserving surgery (BCS) with delayed RT is a rational alternative to mastectomy, for long considered the standard-of-care. Regrettably, no specific guidelines on the surgical management of these patients are available. In this study, we investigated the feasibility and safety of BCS during the first trimester of pregnancy in women with early-stage PrBC. All patients with a diagnosis of PrBC during the first trimester of pregnancy jointly managed in two PrBC-specialized Centers were included in this study. All patients underwent BCS followed by adjuvant radiotherapy to the ipsilateral breast after delivery. Histopathological features and biomarkers were first profiled on pre-surgical biopsies. The primary outcome was the isolated local recurrence (ILR). Among 168 PrBC patients, 67 (39.9%) were diagnosed during the first trimester of gestation. Of these, 30 patients (age range, 23-43 years; median=36 years; gestational age, 2-12 weeks; median=7 weeks; median follow-up time=6.5 years) met the inclusion criteria. The patients that were subjected to radical surgery (n=14) served as controls. None of the patients experienced perioperative surgical complications. No ILR were observed within three months (n=30), 1 year (n=27), and 5 years (n=18) after surgery. Among the study group, 4 (12.3%) patients experienced ILR or new carcinomas after 6-13 years, the same number (n=4) had metastatic dissemination after 3-7 years. These patients are still alive and disease-free after 14-17 years of follow-up. The rate of recurrences and metastasis in the controls were not significantly different. The findings provide evidence that BCS in the first trimester PrBC is feasible and reasonably safe for both the mother and the baby.

The truth will out: a reflection on the life and times of Alice Stewart

CONCLUSIONS

Dr Alice Stewart's research was pioneering, fundamental and challenging, and is now widely accepted.

Trichostatin A mitigates radiation induced teratogenesis in C57 Bl/6 mice

Radiation exposure in utero is known to lead to serious concerns to both the mother and children, including developmental anomalies in the children. In the recent past trichostatn A, an HDAC inhibitor and epigenetic modifier, has been shown to mitigate radiation induced anomalies in the male reproductive system of C57BL/6 mice. Therefore, the current study was undertaken to evaluate the mitigating effects of trichostatin A against radiation induced developmental anomalies in mice. Fetuses of in utero whole body gamma irradiated mice during active organogenesis period were examined for developmental anomalies on 8.5 and 18.5 day of gestation. In utero radiation exposure caused developmental anomalies like microcephaly, microphthalamia, gastroschisis and kinky tail besides prenatal mortality. Trichostatin A administration post irradiation was observed to reduce 50% of prenatal mortality at E18.5 by reducing congenital and developmental anomalies. Observation of such results could be corroborated with the HDAC inhibitory potential of trichostatin A knowing that developmental anomalies may have epigenetic origin. Trichostatin A therefore can be considered as a potential radiomitigator.

Mobile shielding evaluation on the fetal dose during a breast radiotherapy using Monte Carlo simulation

PURPOSE

Evaluation of the out-of-field dose is an important aspect in radiotherapy. Due to the fetus radiosensitivity, this evaluation becomes even more conclusive when the patient is pregnant. In this work, a linear accelerator Varian Clinac 2100c operating at 6 MV, a pregnant anthropomorphic phantom (Maria), and different shields added above the abdominal region of the phantom were used for the analysis based on MCNPX.

METHODS

The simulations were performed for the medial and lateral projections, using either an open field collimation (10×16cm²) or a multileaf collimator. The added shields (M1 and M2) were designed based on models proposed by Stovall et al. [1], intending to reduce the deposited dose on the fetus and related structures.

RESULTS

The presence of the shields showed to be effective in reducing the doses on the fetus, amniotic sac, and placenta, for example. A reduction of about 43% was found in the dose on the fetus when M2 was added, using the open field collimation, in comparison with the situation with no shield, being the lateral projection the main responsible for the dose. The use of MLC significatively reduced the doses in different structures, including on the fetus and amniotic sac, for example, in comparison to the open field situation. A slight increment on the dose in organs such as the eyes, thyroid and brain was found in both collimation systems, due to the presence of the shields. The contribution of the leakage radiation from the tube head of the linear accelerator was found to be in the order of µGy, being reduced by the presence of the M2 shield.

CONCLUSION

Using the shields showed to be an essential feature in order to reduce the dose not only on the fetus, but also in important structures responsible to its development.

Organ doses of the fetus from external environmental exposures

This article presents nuclide-specific organ dose rate coefficients for environmental external exposures due to soil contamination assumed as a planar source at a depth of 0.5 g cm-2 in the soil and submersion to contaminated air, for a pregnant female and its fetus at the 24th week of gestation. Furthermore, air kerma free-in-air coefficient rates are listed. The coefficients relate the organ equivalent dose rates (Sv s-1) to the activity concentration of environmental sources, in Bq m-2 or Bq m-3, allowing to time-integrate over a particular exposure period. The environmental radiation fields were simulated with the Monte Carlo radiation transport codes PHITS and YURI. Monoenergetic organ dose rate coefficients were calculated employing the Monte Carlo code EGSnrc simulating the photon transport in the voxel phantom of a pregnant female and fetus. Photons of initial energies of 0.015-10 MeV were considered including bremsstrahlung. By folding the monoenergetic dose coefficients with the nuclide decay data, nuclide-specific organ doses were obtained. The results of this work can be employed for estimating the doses from external exposures to pregnant women and their fetus, until more precise data are available which include coefficients obtained for phantoms at different stages of pregnancy.

Reduction in live births in Japan nine months after the Fukushima nuclear accident: An observational study

Background

After the Chernobyl accident on 26 April 1986, a drop in birth-rate was found in several European countries in the first quarter of 1987. The objective of the present study was to investigate whether a similar drop in live births occurred in Japan after the Fukushima nuclear accident.

Data and methods

A study region was defined consisting of Fukushima prefecture plus 10 nearby prefectures. The observed monthly numbers of live births (LB) in October 2011 through December 2012 were compared with the predicted numbers determined from the trend of live births in the remaining months from January 2006 through December 2018. The study region was divided into Fukushima plus three adjacent prefectures (Area A, assumed effective mean dose in the first year 1 mSv) and seven surrounding prefectures (Area B, 0.5 mSv). The rest of Japan (Area C) served as the comparison (control) region (0.1 mSv). A combined regression of live births (LB) in areas A, B, C was conducted with individual trend parameters but common parameters for monthly variations.

Results

In the study region as a whole (areas A and B combined) a highly significant 9.1% (95% CI: -12.2%, -6.0%) drop in LB was found in December 2011. Reduced numbers of live births were also observed in October-November 2011 (-3.3%, p = 0.006), i.e. in births exposed early in pregnancy. In the second quarter of 2012, i.e. in live births conceived more than 3 months after the Fukushima accident, the decrease was greater (-4.3%, p < 0.001) than in the first quarter (-1.6%, p = 0.11). i.e. in those conceived within the first three months after the accident while no significant decrease was detected in the third (-0.7%, p = 0.44) and fourth (-0.5%, p = 0.62) quarters. The effect in Dec 2011 was greater in Area A with -14.0 (-17.6, -10.3) % than in Area B with -7.8 (-11.1, -4.5) % and non-significant in Area C with -1.3 (-4.2, +1.6) %, p = 0.38. The combined regression of the data in areas A, B, and C found a highly significant association of the effect in December 2011 with radiation dose. Conclusion: It is suggested that the observed drop in LB in December 2011 may reflect early deaths of the conceptus from high radiation exposure following the triple meltdown at the Fukushima Daiichi nuclear power plant on March 12–15, 2011.

Comparison of estimated and calculated fetal radiation dose for a pregnant woman who underwent computed tomography and conventional X-ray examinations based on a phantom study

This study aimed to determine the mean fetal doses for patients who underwent computed tomography (CT) and/or conventional X-ray (CXR) examinations. In addition to developing an approach to estimate the fetal dose based on data registered in the picture archive and communication system (PACS), the radiation doses for pregnant women and their fetuses were estimated using the VirtualDoseCT and VirtualDoseIR softwares. To verify the data, the fetal dose was measured using thermoluminescent dosimeters (TLDs) implanted at different uterus sites of an anthropomorphic pregnant phantom. Calculated fetal dose values were estimated in relation to the dose-area product (DAP) and volume CT dose index (CTDI_vol). DAP and CTDI_vol were obtained from data registered in the PACS. The fetal doses varied between < 0.001 and 3.9 mGy and between 0.26 and 16.21 mGy for the CXR and CT examinations, respectively. These values were similar to those of previous studies on both imaging modalities. The conversion factors obtained to calculate fetal doses for CXR examinations were between 0.01 and 0.73 mGy/Gy cm², whereas they varied between 0.02 and 0.61 mGy/mGy for CT examinations. Overall, the fetal dose conversion factors based on DAP and CTDI_vol values can be used for fast fetal dose estimations in common CXR and CT examinations.

Ovarian Cancer and Pregnancy-A Current Problem in Perinatal Medicine: A Comprehensive Review

The frequency of concomitant adnexal tumors in pregnancy is reported to be at 0.15-5.7%, while ovarian cancer complicates 1 in 15,000 to 1 in 32,000 pregnancies, being the second most common gynecologic cancer diagnosed during pregnancy. The aim of this review is to discuss the problem of ovarian cancer complicating pregnancy and the current recommendations for diagnostics and treatment, with an emphasis on the risk to the fetus. A detailed analysis of the literature found in the PubMed and MEDLINE databases using the keywords "ovarian cancer", "ovarian malignancy", "adnexal masses", "ovarian tumor" and "pregnancy" was performed. There were no studies on a large series of pregnant women treated for ovarian malignancies and the management has not been well established. The diagnostics and therapeutic procedures need to be individualized with respect to the histopathology of the tumor, its progression, the gestational age at the time of diagnosis and the mother's decisions regarding pregnancy preservation. The multidisciplinary cooperation of specialists in perinatal medicine, gynecological oncology, chemotherapy, neonatology and psychology seems crucial in order to obtain the best possible maternal and neonatal outcomes.

Non-Human Primates Receiving High-Dose Total-Body Irradiation are at Risk of Developing Cerebrovascular Injury Years Postirradiation

Nuclear accidents and acts of terrorism have the potential to expose thousands of people to high-dose total-body iradiation (TBI). Those who survive the acute radiation syndrome are at risk of developing chronic, degenerative radiation-induced injuries [delayed effects of acute radiation (DEARE)] that may negatively affect quality of life. A growing body of literature suggests that the brain may be vulnerable to radiation injury at survivable doses, yet the long-term consequences of high-dose TBI on the adult brain are unclear. Herein we report the occurrence of lesions consistent with cerebrovascular injury, detected by susceptibility-weighted magnetic resonance imaging (MRI), in a cohort of non-human primate [(NHP); rhesus macaque, Macaca mulatta] long-term survivors of high-dose TBI (1.1-8.5 Gy). Animals were monitored longitudinally with brain MRI (approximately once every three years). Susceptibility-weighted images (SWI) were reviewed for hypointensities (cerebral microbleeds and/or focal necrosis). SWI hypointensities were noted in 13% of irradiated NHP; lesions were not observed in control animals. A prior history of exposure was correlated with an increased risk of developing a lesion detectable by MRI (P = 0.003). Twelve of 16 animals had at least one brain lesion present at the time of the first MRI evaluation; a subset of animals (n = 7) developed new lesions during the surveillance period (3.7-11.3 years postirradiation). Lesions occurred with a predilection for white matter and the gray-white matter junction. The majority of animals with lesions had one to three SWI hypointensities, but some animals had multifocal disease (n = 2). Histopathologic evaluation of deceased animals within the cohort (n = 3) revealed malformation of the cerebral vasculature and remodeling of the blood vessel walls. There was no association between comorbid diabetes mellitus or hypertension with SWI lesion status. These data suggest that long-term TBI survivors may be at risk of developing cerebrovascular injury years after irradiation.

Stage-Specific Effects of Ionizing Radiation during Early Development

Early embryonic cells are sensitive to genotoxic stressors such as ionizing radiation. However, sensitivity to these stressors varies depending on the embryonic stage. Recently, the sensitivity and response to ionizing radiation were found to differ during the preimplantation period. The cellular and molecular mechanisms underlying the change during this period are beginning to be elucidated. In this review, we focus on the changes in radio-sensitivity and responses to ionizing radiation during the early developmental stages of the preimplantation (before gastrulation) period in mammals, Xenopus, and fish. Furthermore, we discuss the underlying cellular and molecular mechanisms and the similarities and differences between species.

Incidence of spontaneous abortions and congenital anomalies in the vicinity of a uranium processing plant

OBJECTIVES

The exposure of embryos or foetuses to ionising radiation can cause serious detriments to health. Thus, an enhanced incidence of spontaneous abortions and congenital anomalies might be expected in the vicinity of a uranium processing plant. We analysed the situation in the vicinity of MAPE Mydlovary, a facility about 20 km from České Budějovice, South Bohemia, Czech Republic, which was in operation from 1963 to 1992.

METHODS

No relevant data are available for the period of operation of the uranium processing plant. Statistical data have only been collected since 1994. As sanitation work in the area was initiated at around that time and has yet to be completed, we considered a study of possible prenatal effects in the vicinity of MAPE Mydlovary to still be of interest. Data were provided by the Institute of Health Information and Statistics of the Czech Republic for the years 1994-2013.

RESULTS

We tested whether there are demonstrable, statistically significant differences between the microregions of the four closest villages (Mydlovary, Olešník, Zahájí, and Zliv), the District of České Budějovice, the South-Bohemian Region, and the Czech Republic.

CONCLUSIONS

No increase was found in the incidence of spontaneous abortions and congenital anomalies in the vicinity of this former uranium processing plant compared to the surrounding District of České Budějovice, the South Bohemian Region, or the Czech Republic as a whole.

Managing Heart Disease in Pregnancy

Cardiac disease is an important cause of mortality in pregnancy. It has the potential to remain undiagnosed and may present with cardiovascular decompensation during pregnancy, at the time of delivery, or immediately postpartum. It can have long-term implications to the life of the affected women and their families. This review summarises the current knowledge of the incidence, prevalence, and management of pregnancy-related cardiovascular disease in women presenting preconceptionally or during pregnancy.

Ionizing radiation for maternal medical indications

Ionizing radiation should be considered an avoidable exposure although all pregnant women receive some radiation from their environment. The potential effect of ionizing radiation on the fetus is determined by the dose and the timing of the exposure with growing interest in the potential risks of transgenerational effects of radiation as an epigenetic phenomenon. High dosage exposure is very unlikely in routine situations such as occupational, diagnostic, or therapeutic exposures. Individual diagnostic radiation procedures (fetal dosage <50 mGy), are not associated with any increase in lethality (miscarriage or stillbirth), genetic damage, teratogenicity, growth impairment, mental retardation, or sterility. More recent modeling has suggested that a 10 mGy fetal dose is associated with an excess risk of childhood cancer risk as low as 1 in 4545, well below historical estimates.When the mother's condition necessitates diagnostic radiation it is necessary to balance the risks of the procedure with the benefits to be gained. As almost all diagnostic imaging involves doses below the 50 mGy threshold, clinically indicated investigations should not be withheld because of concerns regarding fetal radiation exposure. Even radiotherapy directed away from the abdomen or pelvis may be considered during pregnancy, if the benefits outweigh the risks and no suitable alternative is available.

Diagnostic imaging in pregnancy: Making informed decisions

The use of diagnostic imaging involving ionising radiation may be necessary in pregnancy and requires an assessment of the most appropriate and safest imaging modality which will provide the necessary information balanced with the potential risks to the mother and fetus. In most cases, this will involve a potential fetal radiation dose well below 50 mGy. At these doses, there is no risk of lethality, genetic damage/epigenetic change, teratogenicity, growth impairment or sterility. Older epidemiological data indicating a potential increased cancer risk have been contradicted by newer data and better understanding of the biology of low dose radiation. The linear no-threshold rule has been challenged by many and more realistic estimates of oncogenicity risk along with the potential risks of contrast agents are summarised in this review. Imaging in the pregnant population is increasing in both the number of examinations performed and the number of patients being imaged, with the greatest increase being computed tomography scans. Counselling and obtaining informed consent for imaging that involves radiation requires the clinician to communicate with the woman and her family a realistic estimate of the potential radiation dose to herself and her fetus, to describe and quantitate the risks of this estimated dose, to outline the benefits of the imaging procedure and to respond to any questions or concerns. As almost all diagnostic imaging involves doses below the 50 mGy threshold, clinically indicated investigations should not be withheld during pregnancy. All allied staff must also be well informed to ensure the patient receives a consistent message about the risks and benefits of the proposed test.

Dosimetric Impact of a New Computational Voxel Phantom Series for the Japanese Atomic Bomb Survivors: Pregnant Females

An important cohort of the atomic bomb survivors are women who were pregnant when exposed to the photon and neutron fields at both Hiroshima and Nagasaki, as well as their children who were exposed in utero. Estimates of organ dose to the developing fetus allow for the development of dose-dependent and gestational age-dependent models of deterministic (e.g., organ malformation) and stochastic (e.g., leukemia) risk of in utero exposure. To date, both the 1986 and 2002 dosimetry systems at the Radiation Effects Research Foundation have utilized the uterine wall in the non-pregnant adult female as a dose surrogate for individual fetal organs and tissues. Here we present a new J45 (Japanese 1945) series of high-resolution phantoms of the adult pregnant female at 8-, 15-, 25- and 38-weeks post-conception. These models, which were derived from the University of Florida (UF) series of ICRP Publication 89 compliant reference phantoms, have been rescaled to approximate the pregnant mother using 1945 Japanese morphometry data. Fetal and maternal organ doses were estimated by computationally exposing the pregnant female phantom series to DS02 free-in-air photon and neutron fluences at three distances from the hypocenter at both Hiroshima and Nagasaki under frontal (AP) and isotropic (ISO) particle incidence. As for the fetal organ doses, our results indicate that the uterine wall of the non-pregnant female generally underestimates fetal organ dose within the pregnant female. The magnitude of these differences varies with both radiation type and irradiation geometry, with the smallest differences (5-7%) seen for ISO photon fields and the largest differences (20-30%) seen for AP neutron fields. Significant discrepancies were seen in fetal brain dose and its uterine wall surrogate, particularly for photon AP fields (ratio of uterine wall to brain dose varied from 0.9 to 1.3) and neutron AP fields (dose ratios from 0.75 to 2.0). As for the maternal organ doses, the use of organ doses in a non-pregnant female was shown, in general, to overestimate the corresponding organ doses in the pregnant female, with greater deviations seen at later stages of pregnancy (12-16% for AP photons and 44-53% for AP neutrons). The one exception was the uterine wall dose in pregnancy which was seen to be underestimated by that in the non-pregnant female phantom, particularly for ISO and AP neutron fields. These results demonstrate that the J45 pregnant female phantom series offers the opportunity for significant improvements in both fetal and maternal organ dose assessment within this unique cohort of the atomic bomb survivors.

Perinatal mortality after the Fukushima accident: a spatiotemporal analysis

OBJECTIVE

This study investigates the trend of perinatal mortality rates in Fukushima Prefecture and four neighboring prefectures (Miyagi, Gunma, Tochigi, and Ibaraki) after the disaster at the Fukushima Daiichi nuclear power plant in March 2011.

MATERIAL AND METHODS

Japanese monthly perinatal mortality data on a prefecture level are available on a website of the Japanese government. A combined regression of perinatal mortality rates from the study region and the rest of Japan (the control region) is conducted. The regression model allows for an asymptotic lower limit and a level change of perinatal mortality rates in 2012-2017 in the study region relative to the predicted trend.

RESULTS

In 2012-2017, perinatal mortality in the study region shows a significant 10.6% increase relative to the trend in preceding years (p = 0.006). The excess mortality translates to 195 (95% CI: 28, 462) excess perinatal deaths. The increase is three times greater in Fukushima Prefecture than in the four neighboring prefectures and the difference in excess rates is statistically significant (p = 0.010). Periodic peaks of perinatal mortality are found in 2012-2017 with maxima around April.

CONCLUSION

We find an increase in perinatal mortality in Fukushima and four neighboring prefectures after the Fukushima nuclear accident. The results agree with similar observations in Germany and Ukraine after the Chernobyl disaster. Due to its ecological design, the study cannot prove a causal link between radiation exposure and perinatal mortality. Continued observation of the trend of perinatal mortality in contaminated regions of Japan is recommended.

Cellular responses to ionizing radiation change quickly over time during early development in zebrafish

Animal cells constantly receive information about and respond to environmental factors, including ionizing radiation. Although it is crucial for a cell to repair radiation-induced DNA damage to ensure survival, cellular responses to radiation exposure during early embryonic development remain unclear. In this study, we analyzed the effects of ionizing radiation in zebrafish embryos and found that radiation-induced γH2AX foci formation and cell cycle arrest did not occur until the gastrula stage, despite the presence of major DNA repair-related gene transcripts, passed on as maternal factors. Interestingly, P21/WAF1 accumulation began ∼6 h post-fertilization, although p21 mRNA was upregulated by irradiation at 2 or 4 h post-fertilization. These results suggest that the cellular responses of zebrafish embryos at 2 or 4 h post-fertilization to radiation failed to overcome P21 protein accumulation and further signaling. Regulation of P21/WAF1 protein stabilization appears to be a key factor in the response to genotoxins during early embryogenesis.

Exploring the legacy and impact of historical IJRB articles and contributions to ICRP publications and Radiation Research articles through graphical reference mapping

The International Journal of Radiation Biology (IJRB) celebrates its 60th birthday this year. Ahead of this very special issue, we wanted to produce strong representations of the journal's publication history in order to celebrate the current status of the journal and to look forward to its future. This was accomplished using 'reference maps'. Reference data were used from 1959 onward from the highest-cited paper in IJRB, for each respective year, to create a figure displaying when those articles were cited in IJRB since their publication. This was done to show the relative impact of historical IJRB papers to future research. Common themes of research were also examined by decade. Additionally, to show the historical impact of the journal outside of its immediate area of research and its practical applications, information on IJRB articles cited by the International Commission on Radiological Protection (ICRP) was collected. It was in 1959 when IJRB published the first issue, and when ICRP also issued Publication 1. Among all Publications (1-139), 43 publications have thus far cited 320 IJRB papers and each of which have been cited 1-7 times. Most notably, Publications 90, 99, 118, and 131 cited more than 40 IJRB papers. Further research was done into references for IJRB's contemporary journal: Radiation Research. The most highly cited IJRB articles for each year together since its inception were cited 16,760 times since they were published and cited 1385 times in Radiation Research. Together, these three datasets and their representations show the diversity of historical IJRB publications, the impact of historical IJRB articles in both future research in the journal and outside of it, and articles which new prospective authors contributing to IJRB might find useful in their own research.

Effects of incomplete residential histories on studies of environmental exposure with application to childhood leukaemia and background radiation

When evaluating environmental exposures, residential exposures are often most relevant. In most countries, it is impossible to establish full residential histories. In recent publications, childhood leukaemia and background radiation have been studied with and without full residential histories. This paper investigates the consequences of lacking such full data. Data from a nationwide Finnish Case-Control study of Childhood Leukaemia and gamma rays were analysed. This included 1093 children diagnosed with leukaemia in Finland in 1990-2011. Each case was matched by gender and year of birth to three controls. Full residential histories were available. The dose estimates were based on outdoor background radiation measurements. The indoor dose rates were obtained with a dwelling type specific conversion coefficient and the individual time-weighted mean red bone marrow dose rates were calculated using age-specific indoor occupancy and the age and gender of the child. Radiation from Chernobyl fallout was included and a 2-year latency period assumed. The median separation between successive dwellings was 3.4 km and median difference in red bone marrow dose 2.9 nSv/h. The Pearson correlation between the indoor red bone marrow dose rates of successive dwellings was 0.62 (95% CI 0.60, 0.64). The odds ratio for a 10 nSv/h increase in dose rate with full residential histories was 1.01 (95% CI 0.97, 1.05). Similar odds ratios were calculated with dose rates based on only the first dwelling (1.02, 95% CI 0.99, 1.05) and only the last dwelling (1.00, 95% CI 0.98, 1.03) and for subjects who had lived only in a single dwelling (1.05, 95% CI 0.98, 1.10). Knowledge of full residential histories would always be the option of choice. However, due to the strong correlation between exposure estimates in successive dwellings and the uncertainty about the most relevant exposure period, estimation of overall exposure level from a single address is also informative. Error in dose estimation is likely to cause some degree of classical measurement error resulting in bias towards the null.

Diagnostic Criteria for Assessment by General Practitioners of Patients Injured in Radiation Incidents and Cases of Radiological Terrorism

The general practitioner is an important figure in the provision of medical care during radiation incidents and cases of radiological terrorism. Knowing the nature of the radiation injury is essential for correct diagnosis and treatment. Insufficient knowledge of most physicians, and of general practitioners in particular, on the clinical manifestation of radiation injuries is the reason such conditions remain unrecognized and improperly treated. We suggest some simple diagnostic criteria for assessment of the injured by general practitioners, based on the results of our own studies and on the recommendations of prominent international organizations. (Disaster Med Public Health Preparedness. 2018;12:507–512)

Gilbert W. Beebe Symposium on 30 Years after the Chernobyl Accident: Current and Future Studies on Radiation Health Effects

This commentary summarizes the presentations and discussions from the 2016 Gilbert W. Beebe symposium "30 years after the Chernobyl accident: Current and future studies on radiation health effects." The symposium was hosted by the National Academies of Sciences, Engineering, and Medicine (the National Academies). The symposium focused on the health consequences of the Chernobyl accident, looking retrospectively at what has been learned and prospectively at potential future discoveries using emerging 21st Century research methodologies.

Low-Dose Ionizing Radiation Exposure, Oxidative Stress and Epigenetic Programing of Health and Disease

Ionizing radiation exposure from medical diagnostic imaging has greatly increased over the last few decades. Approximately 80% of patients who undergo medical imaging are exposed to low-dose ionizing radiation (LDIR). Although there is widespread consensus regarding the harmful effects of high doses of radiation, the biological effects of low-linear energy transfer (LET) LDIR is not well understood. LDIR is known to promote oxidative stress, however, these levels may not be large enough to result in genomic mutations. There is emerging evidence that oxidative stress causes heritable modifications via epigenetic mechanisms (DNA methylation, histone modification, noncoding RNA regulation). These epigenetic modifications result in permanent cellular transformations without altering the underlying DNA nucleotide sequence. This review summarizes the major concepts in the field of epigenetics with a focus on the effects of low-LET LDIR (<100 mGy) and oxidative stress on epigenetic gene modification. In this review, we show evidence that suggests that LDIR-induced oxidative stress provides a mechanistic link between LDIR and epigenetic gene regulation. We also discuss the potential implication of LDIR exposure during pregnancy where intrauterine fetal development is highly susceptible to oxidative stress-induced epigenetic programing.

Risk of Hematologic Malignancies in the Offspring of Female Workers of the Mayak Nuclear Facility in the Southern Urals, Russian Federation

Long-term effects of in utero exposure to ionizing radiation remain poorly quantified in humans. In this study, the risk of hematologic malignancies was investigated in offspring of female workers of the Mayak Production Association, a large Russian nuclear facility. Excess relative risks (ERR) for exposure to gamma radiation and plutonium were estimated in a cohort of 8,466 offspring who were born between January 1, 1948 and December 31, 1988 and followed until 2009. An unstable linear ERR of 1.12 (95% CI 0.11-3.44) per 100 mGy gamma exposure in utero was estimated based on 32 incident hematologic malignancies in 277,002 person-years under risk. The ERR was increased in the dose category 20-79 mGy gamma exposure in utero (1.75, 95% CI 0.04; 5.63), while the other dose categories showed decreased or unstable estimates. Leukemia showed an ERR of 1.76 (95% CI 0.01-8.33) per 100 mGy based on 13 cases. There was no consistent association with plutonium exposure. While an increased risk of hematologic malignancies after gamma exposure in utero was suggested, the small numbers prevented more definitive conclusions.

Incidence and Mortality of Solid Cancers in People Exposed In Utero to Ionizing Radiation: Pooled Analyses of Two Cohorts from the Southern Urals, Russia

BACKGROUND

Previous studies have shown that acute external in utero exposure to ionizing radiation can increase cancer risk. It is not known whether chronic exposure at low dose rates, including due to radionuclide intake, influences the lifetime risk of solid cancers in the offspring. The objective of this study was to investigate solid cancer risk after in utero irradiation.

METHODS

Cancer incidence and mortality over a 60-year period (from January 1950 to December 2009) were analyzed in the Urals Prenatally Exposed Cohort (UPEC). The cohort comprised in utero exposed offspring of Mayak Production Association female workers and of female residents of Techa River villages. Some of the offspring also received postnatal exposure, either due to becoming radiation workers themselves or due to continuing to live in the contaminated areas of the Techa River. The mortality analyses comprised 16,821 subjects (601,372 person-years), and the incidence analyses comprised 15,813 subjects (554,411 person-years). Poisson regression was used to quantify the relative risk as a function of the in utero soft tissue dose (with cumulative doses up to 944.9 mGy, mean dose of 14.1 mGy in the pooled cohort) and the postnatal stomach dose for solid cancer incidence and mortality.

RESULTS

When a log-linear model was used, relative risk of cancer per 10 mGy of in utero dose was 0.99 (95% confidence interval (CI) = 0.96 to 1.01) based on incidence data and 0.98 (CI = 0.94 to 1.01) based on mortality data. Postnatal exposure to ionizing radiation was positively associated with the solid cancer risk in members of the UPEC, with a relative risk of 1.02 per 10mGy CI = 1.00 to 1.04).

CONCLUSIONS

No strong evidence was found that chronic low-dose-rate exposure of the embryo and fetus increased the risk of solid cancers in childhood or in adulthood. For both incidence and mortality, a tendency towards a decreased relative risk was noted with increasing doses to soft tissues of the fetus. Further follow-up will provide more precise radiation risk estimates of solid cancer as cohort members are approaching their 60s and cancer becomes more common.

Survivors and scientists: Hiroshima, Fukushima, and the Radiation Effects Research Foundation, 1975-2014

In this article, I reflect on the Radiation Effects Research Foundation and its ongoing studies of long-term radiation risk. Originally called the Atomic Bomb Casualty Commission (1947-1975), the Radiation Effects Research Foundation has carried out epidemiological research tracking the biomedical effects of radiation at Hiroshima and Nagasaki for almost 70 years. Radiation Effects Research Foundation scientists also played a key role in the assessment of populations exposed at Chernobyl and are now embarking on studies of workers at the Fukushima Daiichi Nuclear Power Plant. I examine the role of estimating dosimetry in post-disaster epidemiology, highlight how national identity and citizenship have mattered in radiation risk networks, and track how participants interpreted the relationships between nuclear weapons and nuclear energy. Industrial interests in Japan and the United States sought to draw a sharp line between the risks of nuclear war and the risks of nuclear power, but the work of the Radiation Effects Research Foundation (which became the basis of worker protection standards for the industry) and the activism of atomic bomb survivors have drawn these two nuclear domains together. This is so particularly in the wake of the Fukushima disaster, Japan's 'third atomic bombing'. The Radiation Effects Research Foundation is therefore a critical node in a complex global network of scientific institutions that adjudicate radiation risk and proclaim when it is present and when absent. Its history, I suggest, can illuminate some properties of modern disasters and the many sciences that engage with them.

Evaluation of staff, patient and foetal radiation doses due to endoscopic retrograde cholangiopancreatography (ERCP) procedures in a pregnant patient

The use of endoscopic retrograde cholangiopancreatography (ERCP) in pregnant patients is not rare. Most studies on the safety and efficacy of these procedures report short- and long-term pregnancy outcomes and but not foetal absorbed doses. This investigation reports on an ERCP procedure for a 40-y-old woman who was 32-34 weeks pregnant. Thermoluminescent dosemeters (TLD 100) were used to measure doses received by the patient and the staff. Additionally, Monte Carlo calculations were performed using a 3D computational phantom representing a 9-month pregnant patient to estimate the foetal absorbed dose. The results show that the spleen of the mother received the largest absorbed dose of 12.18 mGy since it was closer to the source than other internal organs. For the foetus and uterus, the lowest absorbed dose was found to be 0.01 mGy to the foetal brain, while the largest absorbed dose was estimated to be 0.13 mGy to the placenta.

Management of cancer in pregnancy

A multidisciplinary discussion is necessary to tackle a complex and infrequent medical problem such as cancer occurring during pregnancy. Pregnancy does not predispose to cancer, but cancers occurring in women of reproductive age are encountered during pregnancy. Ultrasonography and magnetic resonance imaging are the preferred staging examinations, but also a sentinel node staging procedure is possible during pregnancy. Standard cancer treatment is aimed for. Operations can safely be performed during pregnancy, but surgery of genital cancers can be challenging. The observation that chemotherapy administered during the second or third trimester of pregnancy, that is, after the period of organogenesis, has little effect on the long-term outcome of children adds to the therapeutic armamentarium during pregnancy. Cancer treatment during pregnancy adds in the continuation of the pregnancy and the prevention of prematurity.

Standardization and optimization of CT protocols to achieve low dose

The increase in radiation exposure due to CT scans has been of growing concern in recent years. CT scanners differ in their capabilities, and various indications require unique protocols, but there remains room for standardization and optimization. In this paper, the authors summarize approaches to reduce dose, as discussed in lectures constituting the first session of the 2013 UCSF Virtual Symposium on Radiation Safety and Computed Tomography. The experience of scanning at low dose in different body regions, for both diagnostic and interventional CT procedures, is addressed. An essential primary step is justifying the medical need for each scan. General guiding principles for reducing dose include tailoring a scan to a patient, minimizing scan length, use of tube current modulation and minimizing tube current, minimizing tube potential, iterative reconstruction, and periodic review of CT studies. Organized efforts for standardization have been spearheaded by professional societies such as the American Association of Physicists in Medicine. Finally, all team members should demonstrate an awareness of the importance of minimizing dose.

The UF Family of hybrid phantoms of the pregnant female for computational radiation dosimetry

Efforts to assess in utero radiation doses and related quantities to the developing fetus should account for the presence of the surrounding maternal tissues. Maternal tissues can provide varying levels of protection to the fetus by shielding externally-emitted radiation or, alternatively, can become sources of internally-emitted radiation following the biokinetic uptake of medically-administered radiopharmaceuticals or radionuclides located in the surrounding environment--as in the case of the European Union's SOLO project (Epidemiological Studies of Exposed Southern Urals Populations). The University of Florida had previously addressed limitations in available computational phantom representation of the developing fetus by constructing a series of hybrid computational fetal phantoms at eight different ages and three weight percentiles. Using CT image sets of pregnant patients contoured using 3D-DOCTOR(TM), the eight 50th percentile fetal phantoms from that study were systematically combined in Rhinoceros(TM) with the UF adult non-pregnant female to yield a series of reference pregnant female phantoms at fetal ages 8, 10, 15, 20, 25, 30, 35 and 38 weeks post-conception. Deformable, non-uniform rational B-spline surfaces were utilized to alter contoured maternal anatomy in order to (1) accurately position and orient each fetus and surrounding maternal tissues and (2) match target masses of maternal soft tissue organs to reference data reported in the literature.

Non-targeted effects of ionising radiation--implications for low dose risk

Non-DNA targeted effects of ionising radiation, which include genomic instability, and a variety of bystander effects including abscopal effects and bystander mediated adaptive response, have raised concerns about the magnitude of low-dose radiation risk. Genomic instability, bystander effects and adaptive responses are powered by fundamental, but not clearly understood systems that maintain tissue homeostasis. Despite excellent research in this field by various groups, there are still gaps in our understanding of the likely mechanisms associated with non-DNA targeted effects, particularly with respect to systemic (human health) consequences at low and intermediate doses of ionising radiation. Other outstanding questions include links between the different non-targeted responses and the variations in response observed between individuals and cell lines, possibly a function of genetic background. Furthermore, it is still not known what the initial target and early interactions in cells are that give rise to non-targeted responses in neighbouring or descendant cells. This paper provides a commentary on the current state of the field as a result of the non-targeted effects of ionising radiation (NOTE) Integrated Project funded by the European Union. Here we critically examine the evidence for non-targeted effects, discuss apparently contradictory results and consider implications for low-dose radiation health effects.

Cancer mortality following in utero exposure among offspring of female Mayak Worker Cohort members

Little is known about long-term cancer risks following in utero radiation exposure. We evaluated the association between in utero radiation exposure and risk of solid cancer and leukemia mortality among 8,000 offspring, born from 1948-1988, of female workers at the Mayak Nuclear Facility in Ozyorsk, Russia. Mother's cumulative gamma radiation uterine dose during pregnancy served as a surrogate for fetal dose. We used Poisson regression methods to estimate relative risks (RRs) and 95% confidence intervals (CIs) of solid cancer and leukemia mortality associated with in utero radiation exposure and to quantify excess relative risks (ERRs) as a function of dose. Using currently available dosimetry information, 3,226 (40%) offspring were exposed in utero (mean dose = 54.5 mGy). Based on 75 deaths from solid cancers (28 exposed) and 12 (6 exposed) deaths from leukemia, in utero exposure status was not significantly associated with solid cancer: RR = 0.94, 95% CI 0.58 to 1.49; ERR/Gy = -0.1 (95% CI < -0.1 to 4.1), or leukemia mortality; RR = 1.65, 95% CI 0.52 to 5.27; ERR/Gy = -0.8 (95% CI < -0.8 to 46.9). These initial results provide no evidence that low-dose gamma in utero radiation exposure increases solid cancer or leukemia mortality risk, but the data are not inconsistent with such an increase. As the offspring cohort is relatively young, subsequent analyses based on larger case numbers are expected to provide more precise estimates of adult cancer mortality risk following in utero exposure to ionizing radiation.

Imaging of pregnant and lactating patients: part 1, evidence-based review and recommendations

OBJECTIVE

The objectives of this article are to discuss the current evidence-based recommendations regarding radiation dose concerns, the use of iodinated and gadolinium-based contrast agents, and the comparative advantages of multimodality imaging (ultrasound, CT, and MRI) during pregnancy and lactation. We also discuss the use of imaging to evaluate pregnant trauma patients.

CONCLUSION

Maternal and fetal radiation exposure and dose are affected by gestational age, anatomic site, modality, and technique. The use of iodinated and gadolinium-based contrast agents during pregnancy and lactation has not been well studied in human subjects. Imaging should be used to evaluate pregnant trauma patients only when the benefits outweigh the risks.