The development of image-guided small animal irradiators represents a significant improvement over standard irradiators by enabling preclinical studies to mimic radiotherapy in humans. The ability to deliver tightly collimated targeted beams, in conjunction with gantry or animal couch rotation, has the potential to maximize tumor dose while sparing normal tissues. However, the current commercial platforms do not incorporate respiratory gating, which is required for accurate and precise targeting in organs subject to respiration related motions that may be up to the order of 5 mm in mice. Therefore, a new treatment head assembly for the Xstrahl Small Animal Radiation Research Platform (SARRP) has been designed. This includes a fast X-ray shutter subsystem, a motorized beam hardening filter assembly, an integrated transmission ionization chamber to monitor beam delivery, a kinematically positioned removable beam collimator and a targeting laser exiting the center of the beam collimator. The X-ray shutter not only minimizes timing errors but also allows beam gating during imaging and treatment, with irradiation only taking place during the breathing cycle when tissue movement is minimal. The breathing related movement is monitored by measuring, using a synchronous detector/lock-in amplifier that processes diffuse reflectance light from a modulated light source. After thresholding of the resulting signal, delays are added around the inhalation/exhalation phases, enabling the “no movement” period to be isolated and to open the X-ray shutter. Irradiation can either be performed for a predetermined time of X-ray exposure, or through integration of a current from the transmission monitor ionization chamber (corrected locally for air density variations). The ability to successfully deliver respiratory-gated X-ray irradiations has been demonstrated by comparing movies obtained using planar X-ray imaging with and without respiratory gating, in addition to comparing dose profiles observed from a collimated beam on EBT3 radiochromic film mounted on the animal's chest. Altogether, the development of respiratory-gated irradiation facilitates improved dose delivery during animal movement and constitutes an important new tool for preclinical radiation studies. This approach is particularly well suited for irradiation of orthotopic tumors or other targets within the chest and abdomen where breathing related movement is significant.

Mitochondrial dysfunction plays an important role in gamma-radiation-induced mediating oxidative stress. Scavenging radiation-induced reactive oxygen species (ROS) can help mitochondria to maintain their physiological function. Rosmarinic acid is a polyphenol antioxidant that can scavenge radiation-induced ROS, but the structure prevents it from accumulating in mitochondria. In this study, we designed and synthesized a novel rosmarinic acid derivative (Mito-RA) that could use the mitochondrial membrane potential to enter the organelle and scavenge ROS. The DCFH-DA assay revealed that Mito-RA was more effective than rosmarinic acid at scavenging ROS. DNA double-strand breaks, chromosomal aberration, micronucleus and comet assays demonstrated the ability of Mito-RA to protect against radiation-induced oxidative stress in vitro. These findings demonstrate the potential of Mito-RA as an antioxidant, which can penetrate mitochondria, scavenge ROS and protect cells against radiation-induced oxidative damage.

Positive associations between external radiation dose and non-cancer mortality have been found in a number of published studies, primarily of populations exposed to high-dose, high-dose-rate ionizing radiation. The goal of this study was to determine whether external radiation dose was associated with non-cancer mortality in a large pooled cohort of nuclear workers exposed to low-dose radiation accumulated at low dose rates. The cohort comprised 308,297 workers from France, United Kingdom and United States. The average cumulative equivalent dose at a tissue depth of 10 mm [Hp(10)] was 25.2 mSv. In total, 22% of the cohort were deceased by the end of follow-up, with 46,029 deaths attributed to non-cancer outcomes, including 27,848 deaths attributed to circulatory diseases. Poisson regression was used to investigate the relationship between cumulative radiation dose and non-cancer mortality rates. A statistically significant association between radiation dose and all non-cancer causes of death was observed [excess relative risk per sievert (ERR/Sv) = 0.19; 90% CI: 0.07, 0.30]. This was largely driven by the association between radiation dose and mortality due to circulatory diseases (ERR/Sv = 0.22; 90% CI: 0.08, 0.37), with slightly smaller positive, but nonsignificant, point estimates for mortality due to nonmalignant respiratory disease (ERR/Sv = 0.13; 90% CI: –0.17, 0.47) and digestive disease (ERR/Sv = 0.11; 90% CI: –0.36, 0.69). The point estimate for the association between radiation dose and deaths due to external causes of death was nonsignificantly negative (ERR = –0.12; 90% CI: <–0.60, 0.45). Within circulatory disease subtypes, associations with dose were observed for mortality due to cerebrovascular disease (ERR/Sv = 0.50; 90% CI: 0.12, 0.94) and mortality due to ischemic heart disease (ERR/Sv = 0.18; 90% CI: 0.004, 0.36). The estimates of associations between radiation dose and non-cancer mortality are generally consistent with those observed in atomic bomb survivor studies. The findings of this study could be interpreted as providing further evidence that non-cancer disease risks may be increased by external radiation exposure, particularly for ischemic heart disease and cerebrovascular disease. However, heterogeneity in the estimated ERR/Sv was observed, which warrants further investigation. Further follow-up of these cohorts, with the inclusion of internal exposure information and other potential confounders associated with lifestyle factors, may prove informative, as will further work on elucidating the biological mechanisms that might cause these non-cancer effects at low doses.

A significant body of knowledge about radiobiology is based on studies of single dose cellular irradiation, despite the fact that conventional clinical applications using dose fractionation. In addition, cellular radiation response strongly depends on cell–cell and cell–extracellular matrix (ECM) interactions, which are poorly established in cancer cells grown under standard 2D cell culture conditions. In this study, we investigated the response of human colorectal carcinoma (CRC) DLD1 and HT29 cell lines, bearing distinct p53 mutations, to a single 2 or 10 Gy dose or fractionated 5 × 2 Gy doses of radiation using global transcriptomics analysis. To examine cellular response to radiation in a cell–ECM-interaction-dependent manner, CRC cells were grown under laminin-rich ECM 3D cell culture conditions. Microarray data analysis revealed that, overall, a total of 1,573 and 935 genes were differentially expressed (fold change >1.5; P < 0.05) in DLD1 and HT29 cells, respectively, at 4 h postirradiation. However, compared to a single dose of radiation, fractionated doses resulted in significantly different transcriptomic response in both CRC cell lines. Furthermore, pathway enrichment analysis indicated that p53 pathway and cell cycle/DNA damage repair or immune response functional categories were most significantly altered in DLD1 or HT29 cells, respectively, after fractionated irradiations. Novel observations of radiation-response-mediated activation of pro-survival pathways in CRC cells grown under lr-ECM 3D cell culture conditions using fractionated doses provide new directions for the development of more efficient radiotherapy strategies. Our results also indicated that cell line specific radiation response with or without activation of the conventional p53 pathway is ECM dependent, suggesting that the ECM is a key component in cellular radiation response.

Despite the longstanding role of radiation in cancer treatment and the presence of advanced, high-resolution imaging techniques, delineation of voxels at-risk for progression remains purely a geometric expansion of anatomic images, missing subclinical disease at risk for recurrence while treating potentially uninvolved tissue and increasing toxicity. This remains despite the modern ability to precisely shape radiation fields. A striking example of this is the treatment of glioblastoma, a highly infiltrative tumor that may benefit from accurate identification of subclinical disease. In this study, we hypothesize that parameters from physiologic and metabolic magnetic resonance imaging (MRI) at diagnosis could predict the likelihood of voxel progression at radiographic recurrence in glioblastoma by identifying voxel characteristics that indicate subclinical disease. Integrating dosimetry can reveal its effect on voxel outcome, enabling risk-adapted voxel dosing. As a system example, 24 patients with glioblastoma treated with radiotherapy, temozolomide and an anti-angiogenic agent were analyzed. Pretreatment median apparent diffusion coefficient (ADC), fractional anisotropy (FA), relative cerebral blood volume (rCBV), vessel leakage (percentage recovery), choline-to-NAA index (CNI) and dose of voxels in the T2 nonenhancing lesion (NEL), T1 post-contrast enhancing lesion (CEL) or normal-appearing volume (NAV) of brain, were calculated for voxels that progressed [NAV→NEL, CEL (N = 8,765)] and compared against those that remained stable [NAV→NAV (N = 98,665)]. Voxels that progressed (NAV→NEL) had significantly different (P < 0.01) ADC (860), FA (0.36) and CNI (0.67) versus stable voxels (804, 0.43 and 0.05, respectively), indicating increased cell turnover, edema and decreased directionality, consistent with subclinical disease. NAV→CEL voxels were more abnormal (1,014, 0.28, 2.67, respectively) and leakier (percentage recovery = 70). A predictive model identified areas of recurrence, demonstrating that elevated CNI potentiates abnormal diffusion, even far (>2 cm) from the tumor and dose escalation >45 Gy has diminishing benefits. Integrating advanced MRI with dosimetry can identify at voxels at risk for progression and may allow voxel-level risk-adapted dose escalation to subclinical disease while sparing normal tissue. When combined with modern planning software, this technique may enable risk-adapted radiotherapy in any disease site with multimodal imaging.

Health effects of in utero exposure to ionizing radiation, especially among adults, are still unclear. The aim of this study was to analyze cancer risk in a cohort of subjects exposed in utero due to releases of nuclear waste into the Techa River in the Southern Urals, taking into account additional postnatal exposure. Analysis for solid cancer was based on 242 cases among 10,482 cohort members, accumulating 381,948 person-years at risk, with follow-up from 1956–2009, while analysis for hematological malignancies was based on 26 cases among 11,070 persons, with 423,502 person-years at risk, with follow-up from 1953–2009. Mean doses accumulated in soft tissues and in red bone marrow during the prenatal period were 4 mGy and 30 mGy, respectively. Additional respective mean postnatal doses received by cohort members were 11 and 84 mGy. Poisson regression analysis was used to estimate the excess relative risk (ERR) of cancer incidence related to in utero and postnatal doses. No association was observed for in utero exposure with solid cancer risk [ERR per 10 mGy: −0.007; 95% confidence interval (CI): <−0.107; 0.148] or with hematological malignancy risk (ERR/10 mGy: −0.011; 95% CI: <–0.015; 0.099). However, ERR of solid cancer increased significantly with increasing postnatal dose (ERR/10 mGy: 0.11; 95% CI: 0.04; 0.22). The very wide confidence intervals in these ERR results are similar to those of studies performed on the LSS cohort and the offspring of the Mayak Female Worker Cohort, as well as case-control studies of effects after in utero medical exposure. There were limitations of this study, with decreased statistical power, due to the low prenatal doses received by most of the cohort members, the small number of cancer cases and the absence of cohort members over the age of 59 years (living cohort members had reached 49–59 years of age). Further aging of the cohort and extension of the follow-up period will enhance the statistical power of this study in the future. There is a shortage of cohort studies reporting on the effects of prenatal radiation exposure, as well as information on chronic exposure during the prenatal period. Therefore, further research of this unique cohort will be a useful addition to the published literature on this subject, and a valuable means of elucidating the long-term effects of low-dose radiation exposure in the fetus.

We have reported that circulating IL-18 can be used as a radiation biomarker in mice, minipigs and nonhuman primates (NHPs, Macaca mulatta). Here, we report the levels of IL-18 in individual NHP's urine before and at 6 h–7 days after 5.0, 6.5 and 8.5 Gy ⁶⁰Co total-body irradiation (TBI) using enzyme linked immunosorbent assay (ELISA). Six animals (3.5–5.5 kg, 3–4 years old) per radiation dose were investigated. Correlation values between urine IL-18 and blood cell counts and serum chemistry parameters including lactate dehydrogenase (LDH), lipase, and serum total protein (TP), as well as between urine IL-18 and 60-day survival, were analyzed. Our data, to the best of our knowledge, for the first time, demonstrate that concentrations of urine IL-18 from irradiated NHPs were increased in a radiation dose-dependent manner compared to pre-TBI levels in samples from these animal (N = 18, 11.02 ± 1.3 pg/ml). A 5.0 Gy low dose of radiation (∼LD_10/60) did not increase urine IL-18 levels. In contrast, high-dose TBI significantly increased urine IL-18 at day 1 to day 5 in a bell-shaped time course, reaching a peak of 5- to 10-fold of control levels on day 3 after 6.5 Gy (∼LD_50/60) and 8.5 Gy (∼LD_90/60), respectively. Statistical analysis using receiver operator characteristic (ROC) and MultiROC analysis indicated that white blood cell and platelet counts, serum LDH, lipase and TP, when combined with urine IL-18, provide discriminatory predictors of total-body radiation injury with a very high ROC area of 0.98. Urine IL-18 measurement, as an early prognostic indicator of survival, may facilitate rapid detection of lethal doses of radiation, based on the currently available data set.

The purpose of this study was to compare the biological effects of fractionated doses versus a single dose of high-LET carbon ions in bystander normal cells, and determine the effect on their progeny using the layered tissue co-culture system. Briefly, confluent human glioblastoma (T98G) cells received a single dose of 6 Gy or three daily doses of 2 Gy carbon ions, which were then seeded on top of an insert with bystander normal skin fibroblasts (NB1RGB) growing underneath. Cells were co-cultured for 6 h or allowed to grow for 20 population doublings, then harvested and assayed for different end points. A single dose of carbon ions resulted in less damage in bystander normal NB1RGB cells than the fractionated doses. In contrast, the progeny of bystander NB1RGB cells co-cultured with T98G cells exposed to fractionated doses showed less damage than progeny from bystander cells co-cultured with single dose glioblastoma cells. Furthermore, inhibition of gap junction communication demonstrated its involvement in the stressful effects in bystander cells and their progeny. These results indicate that dose fractionation reduced the late effect of carbon-ion exposure in the progeny of bystander cells compared to the effect in the initial bystander cells.

Exposure to ionizing radiation from nuclear devices, spaceflights or terrorist attacks represents a major threat to human health and public security. After a radiological incident, noninvasive biomarkers that can facilitate rapid assessment of exposure risk in the early stages are urgently needed for optimal medical treatment. Serum microRNAs (miRNAs) are ideal biomarkers because they are stable in response to environmental changes, they are common among different species and are easily collected. Here, we performed miRNA PCR arrays to analyze miRNA expression profiles at 24 h postirradiation. Blood samples were collected from animals that received 0.5–2 Gy total-body carbon-ion irradiation. A specific signature with 12 radiosensitive miRNAs was selected for further validation. After exposure to 0.1–2 Gy of carbon-ion, iron-ion or X-ray radiations, five miRNAs that showed a significant response to these radiation types were selected for further observation of dose- and time-dependent changes: miR-183-5p, miR-9-3p, miR-200b-5p, miR-342-3p and miR-574-5p. We developed a universal model using these five miRNAs to predict the degree of exposure to different radiation types with high sensitivity and specificity. In conclusion, we have identified a set of miRNAs that are quite sensitive to different radiation types in the early stages after exposure, demonstrating their potential use as effective indicators to predict the degree of exposure.

Monte Carlo track structure codes provide valuable information for understanding radiation effects down to the DNA level, where experimental measurements are most difficult or unavailable. It is well recognized that the performance of such codes, especially at low energies and/or subcellular level, critically depends on the reliability of the interaction cross sections that are used as input in the simulation. For biological media such as liquid water, one of the most challenging issues is the role of condensed-phase effects. For inelastic scattering, such effects can be conveniently accounted for through the complex dielectric response function of the media. However, for this function to be useful it must fulfill some important sum rules and have a simple analytic form for arbitrary energy- and momentum-transfer. The Emfietzoglou-Cucinotta-Nikjoo (ECN) model offers a practical, self-consistent and fully analytic parameterization of the dielectric function of liquid water based on the best available experimental data. An important feature of the ECN model is that it includes, in a phenomenological manner, exchange and correlation effects among the screening electrons, thus, going beyond the random-phase approximation implicit in earlier models. In this work, inelastic cross sections beyond the plane wave Born approximation are calculated for low-energy electrons (10 eV–10 keV) based on the ECN model, and used for Monte Carlo track structure simulations of physical quantities relevant to the microdosimetry of low-energy electrons in liquid water. Important new developments in the physics of inelastic scattering are discussed and their effect on electron track structure is investigated by a comparison against simulations (under otherwise identical conditions) using the Born approximation and a simpler form of the dielectric function based on the Oak Ridge National Laboratory model. The results reveal that both the dielectric function and the corrections to the Born approximation may have a sizeable effect on track structure calculations at the nanometer scale (DNA level), where the details of inelastic scattering and the role of low-energy electrons are most critical.