Radiation-induced Signal Research Articles

ESR response of soda–lime glasses irradiated with gamma radiation in the 0.5–20.0 Gy range

ABSTRACTESR readout improvement of gamma-irradiated soda–lime glasses is presented by considering the dose-dependent differences in temperature behaviour of the radiation-induced signal and background signal, and effective difference in g-values of those two signals. Our experimental results demonstrate that the dose-dependent temperature behaviour can improve the ESR signal response for 30–80% in the dose range below 20 Gy by detection at 200 K compared to the room temperature signal readout. The application of improvement can be expected in the low-level dose range where the radiation-induced signal is comparable with an inhomogeneous background signal.

(Invited) Thin Film Transistor Response to Terahertz Radiation

Increasing sophistication, improved performance, and application of new material systems ranging from wide band gap oxides to van der Waals materials make testing Thin Film Transistor (TFT devices and circuits a growing challenge. We recently developed a new testing technique using the sub-terahertz (sub-THz) and THz radiation for testing electronic components, including transistors, Microwave Monolithic Integrated Circuits (MMIC) and Very Large Scale Integrated (VLSI) circuits. The THz radiation impinging on the transistors couples via contacts or interconnects and excites overdamped waves of the electron density – plasma waves - that are rectified by the transistor nonlinearities. This rectification results in the induced DC signal between the transistor contacts. The impinging THz modulation is modulated at a low frequency and a lock-in amplifier amplifies the resulting slowly modulated DC response. The resolution of this technique is better than the device feature size and scanning the beam allows to record the response images. The transistor response is sensitive to the applied bias voltage. The comparison of the responses between good and defective devices or circuits allows for developing the defect signatures. To analyze the application of this technique to TFTs, we introduce and analyze the TFT current dispersion length that determines the penetration of the radiation induced signals into the device channel and calculate the responsivity as a function of frequency for different TFT feature sizes using TFT Unified Charge Control Model. We also analyze the effect of the contact resistances and fringing parasitic capacitances on the response. Our results demonstrate the applicability of this new testing technique for the TFT testing.

Developments in Biodosimetry Methods for Triage With a Focus on X-band Electron Paramagnetic Resonance In Vivo Fingernail Dosimetry.

Instrumentation and application methodologies for rapidly and accurately estimating individual ionizing radiation dose are needed for on-site triage in a radiological/nuclear event. One such methodology is an in vivo X-band, electron paramagnetic resonance, physically based dosimetry method to directly measure the radiation-induced signal in fingernails. The primary components under development are key instrument features, such as resonators with unique geometries that allow for large sampling volumes but limit radiation-induced signal measurements to the nail plate, and methodological approaches for addressing interfering signals in the nail and for calibrating dose from radiation-induced signal measurements. One resonator development highlighted here is a surface resonator array designed to reduce signal detection losses due to the soft tissues underlying the nail plate. Several surface resonator array geometries, along with ergonomic features to stabilize fingernail placement, have been tested in tissue-equivalent nail models and in vivo nail measurements of healthy volunteers using simulated radiation-induced signals in their fingernails. These studies demonstrated radiation-induced signal detection sensitivities and quantitation limits approaching the clinically relevant range of ≤ 10 Gy. Studies of the capabilities of the current instrument suggest that a reduction in the variability in radiation-induced signal measurements can be obtained with refinements to the surface resonator array and ergonomic features of the human interface to the instrument. Additional studies are required before the quantitative limits of the assay can be determined for triage decisions in a field application of dosimetry. These include expanded in vivo nail studies and associated ex vivo nail studies to provide informed approaches to accommodate for a potential interfering native signal in the nails when calculating the radiation-induced signal from the nail plate spectral measurements and to provide a method for calibrating dose estimates from the radiation-induced signal measurements based on quantifying experiments in patients undergoing total-body irradiation or total-skin electron therapy.

EPR dosimetry in nail samples irradiated in vivo during total body irradiation procedures

Electron paramagnetic resonance (EPR) measurements of human's nails is a newly proposed method of retrospective biodosimetry based on quantitative ex vivo determination of EPR signals originating from free radicals induced in nails by ionizing radiation. In the presented study the nails were irradiated in vivo under controlled exposure conditions during total body irradiation (TBI) procedures with doses in nails about 15 Gy delivered through 3 days in 2 fractions per day. The authors applied two methods of reconstruction of the doses: one based on individualized calibration of the radiation-induced EPR signal (RIS) and the second one based on determination of the dose of maximum response (DMR) of so-called RIS5 EPR signal. The first method yielded doses from −3.5 Gy to 22.1 Gy for seven TBI patients. In all but one patient the reconstructed doses were considerably lower than the actual doses calculated by treatment plan, probably due to decay of the dosimetric EPR signal caused by contact of the nails with water during the patients' personal hygiene activities. The second method, based on the RIS5 signal, did not allow for reconstruction of the TBI doses mostly due to lack of the dose saturation features characteristic to RIS5. Further studies on the RIS5 method suggested, that its applicability can be related to the samples' geometry, i.e. the ratio of the total length (l) of cut edges to the mass (m) of the nail clippings: the dose saturation effect, characteristic for RIS5 radicals, was not observed for samples of relatively high l/m ratio. In addition, the study showed only limited resistance of the RIS5 radicals to water – water treatments longer than 10 min resulted in a decrease in the RIS intensity up to complete decay of the RIS for 60 min exposures of the irradiated clippings to water. Therefore it is concluded, that both methods are of limited reliability – only the method of direct calibration can provide, under conditions of minimized contact of nails with water before and after cutting, an indication of the radiation exposure in the examined dose range.

Study of new practical ESR dosimeter based on carbonated hydroxyapatite and its dosimetric properties.

The development of new dosimeters with good dosimetric properties is important for quality control in radiation applications. A new practical electron spin resonance (ESR) dosimeter based on carbonated hydroxyapatite that simulated the composition and structure of tooth enamel was specially synthesized. The synthesized material was investigated by transmission electron microscope, X-ray diffraction, fourier transform infrared spectroscopy and X-ray photo electron spectroscopy to confirm to the main composition of carbonated hydroxyapatite with CO32- successfully doped into the crystal lattice through optimizing the synthesis process of C/P molar ratio, pH value dynamical adjustment, annealing temperature and time. The dosimetric properties were systematically investigated by ESR spectroscopy. The results indicated that the radiation induced signal had a good dose response within a relatively wide dose range. The dose response was linear in the dose range of 0–400 Gy with a correlation coefficient of 0.9999 and had dose accumulative effect in the experimental dose range of 0–100 Gy. In a wider dose range up to 30 kGy, the dose response also presented linear feature in double-logarithmic coordinate system with a correlation coefficient of 0.9970. The dose detection limit was about 0.34Gy with a given probability of 95% confidence level depending upon a rigid calculation algorithm. The signal was extremely stable in the observation time of 360 days with a variation coefficient of 3.8%. The radiation sensitivity of the material showed no remarkable variation against photon energy from 662 KeV to 1.25 MeV and dose rate from 0.86 Gy/min to 12.17 Gy/min. The material showed more sensitive in lower photon energy range below 662 keV, which hint additional calibration may need when using in special photon energy condition. The preliminary results suggested that this newly developed dosimeter was potential to become a practical dosimeter that would expand the application fields of ESR dosimetry.

High-energy radiographic imaging performance of LYSO

A comprehensive comparison of the dominant sources of radiation-induced blur for radiographic imaging system performance is made. End-point energies of 6, 10, 15, and 20 MeV bremsstrahlung photon radiation produced at the Los Alamos National Laboratory Microtron facility were used to examine the performance of large-panel cerium-doped lutetium yttrium silicon oxide (LYSO:Ce) scintillators 3, 5 and 10 mm thick. The system resolution was measured and compared between the various end-point energies and scintillator thicknesses. Contrary to expectations, it is found that there was only a minor dependence of system resolution on scintillator thickness or beam end-point energy. This indicates that increased scintillator thickness does not have a dramatic effect on system performance. The data are then compared to Geant4 simulations to assess contributions to the system performance through the examination of modulation transfer functions. It was determined that the low-frequency response of the system is dominated by the radiation-induced signal, while the higher-frequency response of the system is dominated by the optical imaging of the scintillation emission.

Effect of the tooth surface water on the accuracy of dose reconstructions in the X-band in vivo EPR dosimetry

The X-band in vivo EPR tooth dosimetry is promising as a tool for the initial triage after a large-scale radiation accident. The dielectric losses caused by water on the tooth surface (WTS) are one of the major sources of inaccuracies in this method. The effect was studied by theoretical simulation calculations and experiments with water films of various thicknesses on teeth. The results demonstrate the possibility of sufficiently accurate measurements of the radiation-induced signal of the tooth enamel provided that the thickness of the water film on the tooth is below 60 µm. The sensitivity of the cavity decreases with increasing thickness of the water layer. The interference of WTS can be diminished by normalization of the radiation-induced signal to the signal of a reference sample permanently present in the cavity.

Identification of X-ray irradiated walnuts by ESR spectroscopy

Samples of non-irradiated walnuts exhibit a single line with a g value of 2.0045 ± 0.0006. The irradiation process gives rise to “cellulose-like” Electron Spin Resonance (ESR) spectrum two lines symmetrical to the central line, at a distance of ca. 3 mT. Irradiation increases the central line and produces two satellite peaks (lines) with an amplitude growing with dose. The stability of the radiation-induced ESR signal at room temperature was studied from a quantitative point of view. The fading study and dose evaluation were pursued for a period of two years analyzing irradiated walnuts samples.The reported curves, describing the fading at different doses, differ only by a multiplicative factor and the attenuation factor (the ratio between the amplitude measured and the amplitude evaluated after irradiation) depends only on the time elapsed following treatment.

THE DEGREE OF INFLUENCE RADIATION FROM MOBILE PHONES ON THE QUALITY OF EPR SPECTRA

The results of the investigation of the effect of mobile phone radiation on the formation of electron paramagnetic resonance (EPR) spectra and electromagnetic noise on the example of measurements of dental enamel samples for the low dose range are presented. To this end, spectra of irradiated dental samples were obtained. The spectra of ten samples irradiated in nominal doses of 0, 100, 200, 300 and 500 mGy in pairs were registered at different times with and without a mobile phone. The mobile phone was located near the resonator of the EPR spectrometer. Specially software was used to extract the radiation-induced signal (RIS) from the full EPR spectrum and determine its intensity. As mentioned above to study the effect of the mobile phone signal on the EPR signal in this study, the radiation signal (RIS) (standard deviation (SD)) will be estimated by the background signal and the residual amount. These parameters were obtained for single measurements and, on average, for four repeated measurements.

From radiation osteitis to osteoradionecrosis: incidence and MR morphology of radiation-induced sacral pathologies following pelvic radiotherapy.

To investigate the incidence rate, time-to-onset and recovery, MRI morphology and occurrence of insufficiency fractures in radiation-induced changes in the sacrum following pelvic radiotherapy. 410 patients with pelvic malignancies treated with radiotherapy were reviewed. Follow-up was 1-124 months (mean 22 months). Serial MRI (average four studies/patient) were analysed using a new semi-quantitative score (Radiation-Induced Sacral Changes=RISC). A size category (I/II/III), a type category for MR signal morphologies (a/b/c) and sacral insufficiency fractures (+/-) were applied. Seventy-two patients (17.6 %) were found to have new pathological signal changes. Radiation osteitis was documented in 83.3 % (60/72, RISC stage a + b), and definite osteonecrosis (stage c) in 12 patients (16.7 %, 12/72). Thirty-one patients (43.1 %) had sacral insufficiency fractures. Initial bone marrow signal changes were found 1-35 months (median 4 months) after radiotherapy. The maximum manifestation of radiation-induced signal changes occurred after 1-35 months (mean 11 months). Fifty-six cases (77.8 %) showed a significant signal recovery within 16.5 months. Radiation-induced bone marrow changes appear with a high incidence at the sacrum with an early onset and frequent recovery. The majority presented a pattern of radiation osteitis, whereas osteoradionecrosis was proportionately rare. • Radiation-induced sacral bone marrow changes appear frequently (17.6 %) following pelvic radiotherapy. • Insufficiency fractures are common late effects (43 %). • Radiation osteitis develops early (4 mo), withrecovery between 16.5 and 39.5 months. • Definite radiological osteoradionecrosis is proportionately rare (3 %). • A 3-stage classification system simplifies and standardizes the morphological disease staging.

Retrospective dosimetry using fingernail electron paramagnetic resonance response

Abstract Human fingernails were used to estimate the radiation dose via electron paramagnetic resonance measurements of radiation-induced radicals. The limiting factors in this research were mechanically induced electron paramagnetic resonance signals due to the mechanical stress during the preparation of the samples. Therefore, different treatment methods of fingernails were used to reduce the mechanically induced signals. The results demonstrate that the mechanically induced and radiation-induced signals have apparently different microwave power saturation behaviors. In addition, the mechanically induced signal shows a fading evolution over time and reaches a constant value. Chemical treatment using the different reagents showed that the minimum mechanically induced signal was obtained using the dithiothreitol reagent. The dose–response curves of the samples treated with dithiothreitol for 30 minutes demonstrated a greater linearity than those of samples treated for 5 minutes. Therefore, to find an unknown absorbed dose in a fingernail sample using a calibration curve, we recommend adopting the mentioned chemical treatment procedure to reduce the uncertainty.

Total Ionizing Dose Radiation-Induced Dark Current Random Telegraph Signal in Pinned Photodiode CMOS Image Sensors

In this paper, several studies on total ionizing dose effects on pinned photodiode CMOS images sensors are presented. More precisely, the evolution of a parasitic signal called random telegraph signal (RTS) is analyzed through several photodiode designs. It is shown that the population of pixels exhibiting this fluctuation depends on the design variants. This population also increases in a different way with the dose: the effects are not the same considering a low or high X-rays irradiation. Moreover, a statistical analysis is realized in order to better characterize the defects responsible for RTS. It turns out that an electric-field enhancement signature can appear in some specific cases.

Camel molar tooth enamel response to gamma rays using EPR spectroscopy.

Tooth enamel samples from molar teeth of camel were prepared using a combined procedure of mechanical and chemical tooth treatment. Based on electron paramagnetic resonance (EPR) spectroscopy, the dose response of tooth enamel samples was examined and compared to that of human enamel. The EPR dose response of the tooth enamel samples was obtained through irradiation to gamma doses from 1Gy up to 100kGy. It was found that the radiation-induced EPR signal increased linearly with gamma dose for all studied tooth enamel samples, up to about 15kGy. At higher doses, the dose response curve leveled off. The results revealed that the location of the native signal of camel tooth enamel was similar to that of enamel from human molars at 2.00644, but different from that of enamel from cows and goats. In addition, the peak-to-peak width (ΔH pp) for human and camel molar teeth was similar. It was also found that the response of camel enamel to gamma radiation was 36% lower than that of human enamel. In conclusion, the results indicate the suitability of camel teeth for retrospective gamma dosimetry.

In Vivo Electron Paramagnetic Resonance Tooth Dosimetry: Dependence of Radiation-Induced Signal Amplitude on the Enamel Thickness and Surface Area of Ex Vivo Human Teeth.

In vivo L-band electron paramagnetic resonance tooth dosimetry is a newly developed and very promising method for retrospective biodosimetry in individuals who may have been exposed to significant levels of ionizing radiation. The present study aimed to determine the relationships among enamel thickness, enamel area, and measured electron paramagnetic resonance signal amplitude with a view to improve the quantitative accuracy of the dosimetry technique. Ten isolated incisors were irradiated using well-characterized doses, and their radiation-induced electron paramagnetic resonance signals were measured. Following the measurements, the enamel thickness and area of each tooth were measured using micro-focus computed tomography. Linear regression showed that the enamel area at each measurement position significantly affected the radiation-induced electron paramagnetic resonance signal amplitude (p < 0.001). Simulation data agreed well with this result. These results indicate that it is essential to properly consider enamel thickness and area when interpreting electron paramagnetic resonance tooth dosimetry measurements to optimize the accuracy of dose estimation.

Developments for emergency dosimetry using components of mobile phones

Several modifications are proposed for emergency dosimetry with different components of mobile phones. Two dosimetric techniques have been exploited, namely optically stimulated luminescence (OSL) from surface mount resistors (SMRs) and integrated circuits (ICs), and electron paramagnetic resonance (EPR) from samples of protective glass (PG). For OSL with SMRs, it was found that fading of the corresponding radiation-induced signal (RIS) is variable among the resistors of different brands and depends also on the value of the administered dose. In the case of ICs, the effect of sample sensitization with an increase in the accumulated dose was compensated by preheating the samples to some selected temperature. An approach based on the matrix spectra deconvolution of EPR spectra was proposed and tested for EPR dosimetry using smartphone protective glasses.

Stability of X-band EPR signals from fingernails under vacuum storage

EPR signals of different origin have been tested in human finger- and toe-nails with an X-band EPR technique for different conditions of nail storage. Three different signals were identified, namely a singlet at g = 2.005, a doublet at g = 2.004 with a splitting constant A = 1.8mT, and an anisotropic signal at g1 = 2.057, g2 = 2.029 and g3 = 2.003 (positions of local extrema). All EPR spectra from nails, whether irradiated or mechanically stressed, can be described as a superposition of these three signals. The singlet is responsible for the background signal (BG), is the main component of radiation-induced signals (RIS) for low doses (100Gy or lower) and also contributes to mechanically-induced signals (MIS). This signal is quite stable under vacuum storage, but can be reduced almost to zero by soaking in water. The behavior of this signal under ambient conditions depends on many factors, such as absorbed dose, air humidity, and ambient illumination intensity at the place of storage. The doublet arises after exposure of nails to high (few hundreds Gy and higher) doses or after mechanical stress of samples. Depending on how this signal was obtained, it may have bulk or surface locations with quite different stability properties. The surface-located doublet (generated on the nail edges during cutting or clipping) is quite unstable and decays over about two hours for samples stored at ambient conditions and within several seconds for samples immersed in water. The volume-distributed doublet decays within a few minutes in water, several hours at ambient conditions and several days in vacuum. The anisotropic signal may also be generated by both ionizing radiation and mechanical stress; this signal is quite stable in vacuum and decays over several days at ambient conditions or a few tens of minutes in water. The reference lines for the above-described three EPR signals were obtained and a procedure of spectra deconvolution was developed and tested on samples exposed to both ionizing radiation and mechanical stress.

The sensitivity variation of the radiation induced signal in deciduous teeth to be used in ESR tooth enamel dosimetry

The sensitivities to dose of the radiation induced signal observed in tooth enamel were examined by electron spin resonance (ESR) for individual deciduous and permanent teeth. The sensitivities in deciduous teeth are in agreement with those in permanent teeth within the statistical error while the variation is larger in deciduous teeth than in permanent teeth. While the intensities of the interfering background signal are also similar, the average value of the line widths of the background signal are larger but statistically indistinguishable due to larger variations in deciduous teeth than in permanent teeth. The position of the background signal (g factor) in deciduous teeth is slightly different from that in permanent teeth. With these similarities and differences, the ESR dosimetry with deciduous teeth will be useful as with permanent teeth using the same experimental procedures. The obtained dose will have larger statistical error in deciduous teeth than in permanent teeth when the calibration line method is applied, as the variation in sensitivity of deciduous teeth is larger.

Characterizing responses to gamma radiation by a highly clonogenic fish brain endothelial cell line

PurposeThe clonogenic property and radiobiological responses of a fish brain endothelial cell line, eelB, derived from the American eel were studied. MethodsClonogenic assays were performed to determine the plating efficiency of the eelB cells and to evaluate the clonogenic survival fractions after direct irradiation to low-dose low-LET gamma radiation or receiving irradiated cell conditioned medium in the bystander effect experiments. ResulteelB had the second highest plating efficiency ever reported to date for fish cell lines. Large eelB macroscopic colonies could be formed in a short period of time and were easy to identify and count. Unlike with other fish clonogenic cell lines, which had a relatively slow proliferation profile, clonogenic assays with the eelB cells could be completed as early as 12 days in culture. After direct irradiation with gamma rays at low doses ranging from 0.1Gy to 5Gy, the dose-clonogenic survival curve of the eelB cell line showed a linear trend and did not develop a shoulder region. A classical radio-adaptive response was not induced with the clonogenic survival endpoint when the priming dose (0.1 or 0.5Gy) was delivered 6h before the challenge dose (3 or 5Gy). However, a radio-adaptive response was observed in progeny cells that survived 5Gy and developed lethal mutations. eelB appeared to lack the ability to produce damaging radiation-induced bystander signals on both eelB and HaCaT recipient cells. ConclusioneelB cell line could be a very useful cell model in the study of radiation impacts on the aquatic health.

Extracellular Vesicles Mediate Radiation-Induced Systemic Bystander Signals in the Bone Marrow and Spleen.

Radiation-induced bystander effects refer to the induction of biological changes in cells not directly hit by radiation implying that the number of cells affected by radiation is larger than the actual number of irradiated cells. Recent in vitro studies suggest the role of extracellular vesicles (EVs) in mediating radiation-induced bystander signals, but in vivo investigations are still lacking. Here, we report an in vivo study investigating the role of EVs in mediating radiation effects. C57BL/6 mice were total-body irradiated with X-rays (0.1, 0.25, 2 Gy), and 24 h later, EVs were isolated from the bone marrow (BM) and were intravenously injected into unirradiated (so-called bystander) animals. EV-induced systemic effects were compared to radiation effects in the directly irradiated animals. Similar to direct radiation, EVs from irradiated mice induced complex DNA damage in EV-recipient animals, manifested in an increased level of chromosomal aberrations and the activation of the DNA damage response. However, while DNA damage after direct irradiation increased with the dose, EV-induced effects peaked at lower doses. A significantly reduced hematopoietic stem cell pool in the BM as well as CD4+ and CD8+ lymphocyte pool in the spleen was detected in mice injected with EVs isolated from animals irradiated with 2 Gy. These EV-induced alterations were comparable to changes present in the directly irradiated mice. The pool of TLR4-expressing dendritic cells was different in the directly irradiated mice, where it increased after 2 Gy and in the EV-recipient animals, where it strongly decreased in a dose-independent manner. A panel of eight differentially expressed microRNAs (miRNA) was identified in the EVs originating from both low- and high-dose-irradiated mice, with a predicted involvement in pathways related to DNA damage repair, hematopoietic, and immune system regulation, suggesting a direct involvement of these pathways in mediating radiation-induced systemic effects. In conclusion, we proved the role of EVs in transmitting certain radiation effects, identified miRNAs carried by EVs potentially responsible for these effects, and showed that the pattern of changes was often different in the directly irradiated and EV-recipient bystander mice, suggesting different mechanisms.

Exosomes are released by bystander cells exposed to radiation-induced biophoton signals: Reconciling the mechanisms mediating the bystander effect.

ObjectiveThe objective of our study was to explore a possible molecular mechanism by which ultraviolet (UV) biophotons could elicit bystander responses in reporter cells and resolve the problem of seemingly mutually exclusive mechanisms of a physical UV signal & a soluble factor-mediated bystander signal.MethodsThe human colon carcinoma cell line, HCT116 p53 +/+, was directly irradiated with 0.5 Gy tritium beta particles to induce ultraviolet biophoton emission. Bystander cells were not directly irradiated but were exposed to the emitted UV biophotons. Medium was subsequently harvested from UV-exposed bystander cells. The exosomes extracted from this medium were incubated with reporter cell populations. These reporter cells were then assayed for clonogenic survival and mitochondrial membrane potential with and without prior treatment of the exosomes with RNase.ResultsClonogenic cell survival was significantly reduced in reporter cells incubated with exosomes extracted from cells exposed to secondarily-emitted UV. These exosomes also induced significant mitochondrial membrane depolarization in receiving reporter cells. Conversely, exosomes extracted from non-UV-exposed cells did not produce bystander effects in reporter cells. The treatment of exosomes with RNase prior to their incubation with reporter cells effectively abolished bystander effects in reporter cells and this suggests a role for RNA in mediating the bystander response elicited by UV biophotons and their produced exosomes.ConclusionThis study supports a role for exosomes released from UV biophoton-exposed bystander cells in eliciting bystander responses and also indicates a reconciliation between the UV-mediated bystander effect and the bystander effect which has been suggested in the literature to be mediated by soluble factors.