Threshold Radiation Dose Research Articles

Assessing Radiation Effects on Chemo-Treated BT20 and 4T1 Breast Cancer, and Neuroblastoma Cell Lines: A Study of Single and Multiple-Cell Ionization via Infrared Laser Trapping

Background: Our study aimed to assess the radiation sensitivity of BT20, a human breast tumor cell line, using the laser-trapping technique and compare it with N2a and 4T1 cells. Additionally, we investigated the impact of the antitumor compound 2-Dodecyl-6-methoxycyclohexa-2,5-diene-1,4-dione (DMDD) on radiation sensitivity. Methods and Materials: We employed laser trapping to calculate both the threshold ionization energy (TIE) and threshold radiation dose (TRD) for BT20, N2a, and 4T1 cells. We assessed the effect of DMDD on BT20 cells’ radiosensitivity and conducted comparisons across these cell lines. Results: Our findings reveal that DMDD significantly enhances the radiosensitivity of BT20 breast carcinoma cells. Moreover, we observed distinct trends in TIE and TRD across the three cell lines, with differences attributed to variations in cell size and composition. When multiple cell ionizations were considered, a notable reduction in TRD was observed, implicating factors such as the chain effect of ionizing radiation and the influence of DMDD. The study found that TIE increased with the number of cells in the trap while TRD consistently decreased across all three cell lines, suggesting comparable radiation sensitivity, and oligostilbene treatment further reduced TRD, presenting the potential for enhancing therapeutic ratios in cancer treatment. Conclusion: The antitumor compound DMDD enhances the radiosensitivity of BT20 breast carcinoma cells, highlighting its potential in cancer treatment. Furthermore, our study underscores the impact of cell size and multiple-cell ionizations on TRD. Leveraging laser trapping techniques, biocompatible nanoparticles, and advanced optical tweezers opens promising avenues for personalized and effective cancer therapy approaches.

Involvement of retinoic acid‑inducible gene‑I in radiation‑induced senescence of human umbilical vein endothelial cells.

In 2012, the threshold radiation dose (0.5 Gy) for cardiovascular and cerebrovascular diseases was revised, and this threshold dose may be exceeded during procedures involving radiation such as interventional radiology. Therefore, in addition to regulating radiation dose, it is necessary to develop strategies to prevent and mitigate the development of cardiovascular disease. Cellular senescence is irreversible arrest of cell proliferation. Although cellular senescence is one of the mechanisms for suppressing cancer, it also has adverse effects. For example, senescence of vascular endothelial cells is involved in development of vascular disorders. However, the mechanisms underlying induction of cellular senescence are not fully understood. Therefore, the present study explored the factors involved in the radiation-induced senescence in human umbilical vein endothelial cells (HUVECs). The present study reanalyzed the gene expression data of senescent normal human endothelial cells and fibroblast after irradiation (NCBI Gene Expression Omnibus accession no. GSE130727) and microarray data of HUVECs 24 h after irradiation (NCBI Gene Expression Omnibus accession no. GSE76484). Numerous genes related to viral infection and inflammation were upregulated in radiation-induced senescent cells. In addition, the gene group involved in the retinoic acid-inducible gene-I (RIG-I)-like receptor (RLR) signaling pathway, which plays an important role to induce anti-viral response, was altered in irradiated HUVECs. Therefore, to investigate the involvement of RIG-I and melanoma differentiation-associated gene 5 (MDA5), which are RLRs, in radiation-induced senescence of HUVECs, the protein expression of RIG-I and MDA5 and the activity of senescence-associated β-galactosidase (SA-β-gal), a representative senescence marker, were analyzed. Of note, knockdown of RIG-I in HUVECs significantly decreased radiation-increased proportion of cells with high SA-β-gal activity (i.e., senescent cells), whereas this phenomenon was not observed in MDA5-knockdown cells. Taken together, the present results suggested that RIG-I, but not MDA5, was associated with radiation-induced senescence in HUVECs.

Level of Knowledge about the Effects of Radiation on Pregnant Women among Medical Imaging Techniques Program Students

For this purpose, this study will examine the level of knowledge about the effects of radiation on pregnant women among the students of Medical Imaging Techniques at the Vocational School of Health Services of Çanakkale Onsekiz Mart University in the province of Çanakkale and compare the level of knowledge about the effects of radiation on pregnant women between the 1st grade students who have just started school and the 2nd grade students who are more experienced both theoretically and practically compared to the 1st grade students. The knowledge level of the students who do practice/internship/skill training in diagnostic radiology units of hospitals from Çanakkale Onsekiz Mart University Vocational School of Health Services, which provides Medical Imaging and Radiology education in Çanakkale, will be determined by applying a 24-question survey. When the answers given to the question "Do you know the time period when the fetus is most sensitive to radiation?" were analyzed, it was reported that 67.8% of the 2nd grade students knew it compared to 50.8% of the 1st grade students (p=0.04). When the answers to the question "Do you know the threshold radiation doses for pregnancy termination?" were analyzed; 52.5% of the 1st grade students did not know the threshold radiation dose for pregnancy termination, whereas only 40.7% of the 2nd grade students did not (p=0.02). Although 2nd year Medical Imaging Techniques students have more knowledge about the pregnancy-related effects of radiation than 1st year students in terms of both theory and practice, there is still room for improvement.

Influence of neutron and gamma irradiation on the electrocaloric properties of Mn-doped 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 ceramics

The influence of neutron and gamma irradiation on the low- and high-field dielectric and electrocaloric (EC) properties of Mn-doped 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (PMN–10PT) ceramic is studied. Upon exposure to neutron fluences of up to 1017 cm−2 and gamma-ray doses of up to 1200 kGy the Mn-doped PMN–10PT exhibits a lower saturated polarization, increased internal bias field and reduced EC temperature change. In comparison, the respective properties of the undoped PMN–10PT remain almost unchanged upon exposure to neutrons and gamma rays. In Mn-doped PMN–10PT, the acceptor-oxygen vacancy defect complexes, introduced via doping, contribute to the lowering of the threshold radiation dose that the material survives without noticeable changes in properties. Radiation-induced degradation of the EC response of Mn-doped PMN–10PT can be partially healed by annealing at 450 °C. The study provides guidance for designing EC ceramic materials for solid-state cooling applications in environments of high ionizing radiation, such as the medical field or space technologies.

The use of single-timepoint images to link administered radioiodine activity (MBq) to a prescribed lesion radiation-absorbed dose (cGy): a regression-based prediction interval tool for the management of well-differentiated thyroid cancer patients

PurposeTo introduce a biomarker-based dosimetry method for the rational selection of a treatment activity for patients undergoing radioactive iodine 131I therapy (RAI) for metastatic differentiated thyroid cancer (mDTC) based on single-timepoint imaging of individual lesion uptake by 124I PET.MethodsPatients referred for RAI therapy of mDTC were enrolled in institutionally approved protocols. A total of 208 mDTC lesions (in 21 patients) with SUVmax > 1 underwent quantitative PET scans at 24, 48, 72, and 120 h post-administration of 222 MBq of theranostic NaI-124I to determine the individual lesion radiation-absorbed dose. Using a general estimating equation, a prediction curve for biomarker development was generated in the form of a best-fit regression line and 95% prediction interval, correlating individual predicted lesion radiation dose metrics, with candidate biomarkers (“predictors”) such as SUVmax and activity in microcurie per gram, from a single imaging timepoint.ResultsIn the 169 lesions (in 15 patients) that received 131I therapy, individual lesion cGy varied over 3 logs with a median of 22,000 cGy, confirming wide heterogeneity of lesion radiation dose. Initial findings from the prediction curve on all 208 lesions confirmed that a 48-h SUVmax was the best predictor of lesion radiation dose and permitted calculation of the 131I activity required to achieve a lesional threshold radiation dose (2000 cGy) within defined confidence intervals.ConclusionsBased on MIRD lesion-absorbed dose estimates and regression statistics, we report on the feasibility of a new single-timepoint 124I-PET-based dosimetry biomarker for RAI in patients with mDTC. The approach provides clinicians with a tool to select personalized (precision) therapeutic administration of radioactivity (MBq) to achieve a desired target lesion-absorbed dose (cGy) for selected index lesions based on a single 48-h measurement 124I-PET image, provided the selected activity does not exceed the maximum tolerated activity (MTA) of < 2 Gy to blood, as is standard of care at Memorial Sloan Kettering Cancer Center.Trial registrationNCT04462471, Registered July 8, 2020.NCT03647358, Registered Aug 27, 2018.

The radiation response measurement of a single and multiple cell ionization of neuroblastoma cells by infrared laser trap.

Neuroblastoma (NB) is a common type of cancer found mostly in infants and arising from the immature neural crest cells of the sympathetic nervous system. Using laser trapping (LT) technique, the present work contributes to advancing radiotherapy (RT), a leading treatment method for cancer. A single, 2-cells, 3-cells, 4-cells, and 5-cells were trapped using the high-intensity gradient infrared laser at 1064nm and allowed to become ionized. In this work, a systematic study of Threshold Ionization Energy (TIE) and Threshold Radiation Dose (TRD) versus mass for both single and multi-cell ionization using laser trapping (LT) techniques on NB is presented. The results show that TIE increased as the mass of cells increased, meanwhile TRD decreased with the increase of cell mass. We observed an inverse correlation between TRD and cell mass. We demonstrate how to compute the maximum radiation dosage for cell death using the LT technique. Results show a possible blueprint for computing the TRD in vivo. The use of multiple cell ionization to determine radiation dosage along with better data accuracy concerning the tumor size and density will have profound implications for radiation dosimetry. The diminution in TRD becomes more significant in multiple cell ionization as we see in TRD vs the number of cells entering the trap. This is due to the chain effect generated by radiation and the absorption by water molecules at 1064nm. This result provides us with better insight into the optimization of the therapeutic ratio.

Quantitative characteristics of radiation-induced lung damage in oncological patients during radiotherapy based on RCT data

Objective. Comparison of the magnitude of the change in the density of lung tissue and the volume of these changes after radiation therapy over time based on the data obtained using the new method of quantitative analysis developed by us and with the usual visual assessment of the CT data.Materials and methods. We used the data of dynamic observation of 90 patients who underwent RT for the tumors of thoracic localization during the period from 2014 to 2021 at the Federal Institution “Russian Scientific Center of Roentgenoradiology”. These patients had CT examinations performed before and after RT. Control CT studies were performed 1–237 days after RT (mean control interval 96 ± 64.3 days). A total of 238 CT studies of these patients were analyzed, with an average number of RCT studies per patient of 2.6. Among the selected patients, there were 36 (40%) men and 54 (60%) women aged 23 to 86 years (the average age was 51.9 ± 15.6 years).Results. Radiation damage in the lungs using the method of quantitative analysis of CT data is detected starting from the value of ΔHU = 20 and volume from 3.2% for the early period (15–35 days) after the end of treatment. Starting from 15–25 to 50 days after the end of RT, quantitative analysis reveals primary changes in the lung tissue, incl. and undetectable visually (from 20 to 80 HU), and to suggest further dynamics of these changes depending on the characteristics of the performed RT. From 50 to 80 days – reveals the real volume of radiation pulmonitis by taking into account the changes invisible during visual analysis in the lung tissue irradiated at a dose of 20 Gy to 30 Gy. From 80 to 120 days – allows you to assess the presence and dynamics of changes in the lung tissue with the threshold radiation dose in the lung tissue 30–35 Gy. From 120 onwards, quantitative analysis of CT data, as well as visual assessment, reveals damage in areas of the lungs with the dose of more than 30–35 Gy, which is caused by post-radiation pneumofibrosis. On the basis of the obtained quantitative data on radiation lung damage, the mathematical regularities of the development of this process were calculated, taking into account the time and dose factors.Conclusions. Quantitative assessment of changes in lung density according to CT data in dynamics, carried out using the technique developed by us, is a radiomic indicator of their radiation damage during therapeutic irradiation in cancer patients, which, in combination with the presented mathematical model, can be used for diagnostic purposes to quantify the severity and predicting the dynamics of radiation damage to the lungs in general, as well as identifying individual radiosensitivity.The results obtained can be presented not only in the form of graphs, but also in the form of color maps with preservation of anatomical landmarks, which is convenient for use in clinical practice to support medical decision-making on patient management.

Radiation-Induced Angiosarcoma of the Breast: A Systematic Review and Meta-Analysis

INTRODUCTION: The purpose of this study is to summarize the totality of evidence on Radiation Induced Angiosarcoma (RIAS) of the breast through a meta-analysis and systematic literature review to assess overall survival (OS), recurrence, mortality, and prognostic factors. METHODS: A systematic review and meta-analysis was performed in accordance with PRISMA guidelines. Patient demographics, index cancer, and RIAS characteristics, recurrence, and mortality data were collected. Univariate and multivariate statistical analysis were performed. Kaplan-Meier analysis was used to plot survival probabilities and log-rank statistics to determine radiation cutoff dose. RESULTS: Full-text review identified 201 studies that reported patient-specific data for 531 individual patients. The median age of RIAS diagnosis was 70. The median latency period, from index breast cancer to RIAS diagnosis, was 6.7 years. A recurrence rate of 48.13% was identified. Index breast cancer tumor size was significantly larger in patients who died vs survived (3 cm vs 2 cm, p = 0.028). A threshold radiation dose of 59 Gray was associated with decreased survival probability, p = 0.047 (Figure 1). The latency period was significantly longer for patients who received chemotherapy for their index breast cancer (90.6 vs 72.0 months, p = 0.024). Use of reirradiation as treatment for RIAS did not confer a significant mortality benefit or decrease recurrence. The 5-year overall survival was 55%.Figure 1CONCLUSION: RIAS of the breast is a highly morbid disease. Tumor size, index radiation dose, and chemotherapy use are prognostic factors of RIAS recurrence and mortality. Further research into effective treatment modalities is necessary.

Radiation pneumonitis in patients with non-small-cell lung cancer receiving chemoradiotherapy and an immune checkpoint inhibitor: a retrospective study

BackgroundImmunotherapy has been administered to many patients with non-small-cell lung cancer (NSCLC). However, only few studies have examined toxicity in patients receiving an immune checkpoint inhibitor (ICI) after concurrent chemoradiotherapy (CCRT). Therefore, we performed a retrospective study to determine factors that predict radiation pneumonitis (RP) in these patients.MethodsWe evaluated the size of the planning target volume, mean lung dose (MLD), and the lung volume receiving more than a threshold radiation dose (VD) in 106 patients. The primary endpoint was RP ≥ grade 2, and toxicity was evaluated.ResultsAfter CCRT, 51/106 patients were treated with ICI. The median follow-up period was 11.5 months (range, 3.0–28.2), and RP ≥ grade 2 occurred in 47 (44.3%) patients: 27 and 20 in the ICI and non-ICI groups, respectively. Among the clinical factors, only the use of ICI was associated with RP (p = 0.043). Four dosimetric variables (MLD, V20, V30, and V40) had prognostic significance in univariate analysis for occurrence of pneumonitis (hazard ratio, p-value; MLD: 2.3, 0.009; V20: 2.9, 0.007; V30: 2.3, 0.004; V40: 2.5, 0.001). Only V20 was a significant risk factor in the non-ICI group, and MLD, V30, and V40 were significant risk factors in the ICI group. The survival and local control rates were superior in the ICI group than in the non-ICI group, but no significance was observed.ConclusionsPatients receiving ICI after definitive CCRT were more likely to develop RP, which may be related to the lung volume receiving high-dose radiation. Therefore, several factors should be carefully considered for patients with NSCLC.

Primary Hypothyroidism in Childhood Cancer Survivors Treated With Radiation Therapy: A PENTEC Comprehensive Review

From the Pediatric Normal Tissue Effects in the Clinic (PENTEC) initiative, a systematic review and meta-analysis of publications reporting on radiation dose-volume effects for risk of primary hypothyroidism after radiation therapy for pediatric malignancies was performed. All studies included childhood cancer survivors, diagnosed at age <21 years, whose radiation therapy fields exposed the thyroid gland and who were followed for primary hypothyroidism. Children who received pituitary-hypothalamic or total-body irradiation were excluded. PubMed and the Cochrane Library were searched for studies published from 1970 to 2017. Data on age at treatment, patient sex, radiation dose to neck or thyroid gland, specific endpoints for hypothyroidism that were used in the studies, and reported risks of hypothyroidism were collected. Radiation dose-volume effects were modeled using logistic dose response. Relative excess risk of hypothyroidism as a function of age at treatment and sex was assessed by meta-analysis of reported relative risks (RR) and odds ratios. Fifteen publications (of 1709 identified) were included for systematic review. Eight studies reported data amenable for dose-response analysis. At mean thyroid doses of 10, 20, and 30 Gy, predicted rates of uncompensated (clinical) hypothyroidism were 4%, 7%, and 13%, respectively. Predicted rates of compensated (subclinical) hypothyroidism were 12%, 25%, and 44% after thyroid doses of 10, 20, and 30 Gy, respectively. Female sex (RR = 1.7, P < .0001) and age >15 years at radiation therapy (RR = 1.3, P = .005) were associated with higher risks of hypothyroidism. After a mean thyroid dose of 20 Gy, predicted risks of hypothyroidism were 13% for males <14 years of age, increasing to 29% for females >15 years of age. A radiation dose response for risk of hypothyroidism is evident; a threshold radiation dose associated with no risk is not observed. Thyroid dose exposure should be minimized when feasible. Data on hypothyroidism after radiation therapy should be better reported to facilitate pooled analyses.

Dose-volumetric Predictors for Thyroid Dysfunction after 3D Conformal Radiotherapy: An Observational, Prospective Study

Aim: This study was conducted to assess the dose-volumetric threshold of radiation induced hypothyroidism (RIHT) in patients receiving radiotherapy (RT) to the neck.&#x0D; Study Design: This is a prospective cohort observational study.&#x0D; Place and Duration of the Study: The study was conducted at Mansoura University Hospital, Mansoura, Egypt, between April 2016 until March 2019.&#x0D; Methods: We have completed 2 years of follow up to 50 patients with different malignancies who were treated by radiotherapy to the neck. Baseline assessment of the thyroid clinically and radiologically was done prior to the start of radiotherapy. Periodic testing of the cohort through the follow up period was done by clinical examination, measurement of TSH, fT4 and thyroid ultrasonography.&#x0D; Results: the incidence of RIHT was 26%. No statistical significance for the clinical risk factors. The dose-volumetric risk factors were studied and showed positive results. A mean dose of 5185 cGy was found a significant risk factor. Also, V40 ≥ 89%, V45 ≥ 63.5%, V50 ≥ 22.5% were found to be the cutoff predictors for the threshold radiation dose to induce hypothyroidism. Also decreasing the size of the gland by ≥0.7 cm3, fT4 value by ≥ 3.5 pmol/L and TSH by ≥ 0.75 uIU/L after one year from the end of EBRT is the cutoff value for prediction of occurrence of RIHT within the 2nd year of follow up.&#x0D; Conclusion: RIHT is a considerable late adverse effect for patients receiving RT to the neck. Mean dose, V40, V45 and V50 were found significantly related to RIHT. Mean dose of ≥ 5185 cGy, V40 ≥ 89%, V45 ≥ 63.5%, V50≥ 22.5% were proven to be the dose-volumetric threshold.

Chemo-treated 4T1 breast cancer cells radiation response measured by single and multiple cell ionization using infrared laser trap

We present a study that uses a laser trapping technique for measurement of radiation sensitivity of untreated and chemo-treated cancer cells. We used a human mammary tumor cell line (4T1) treated by an antitumor compound, 2-Dodecyl-6-methoxycyclohexa-2, 5-diene-1,4-dione (DMDD), which was extracted from the root of Averrhoa carambola L. The untreated control group, and both 2-hour and 24-hour treated groups of 4T1 cells were used in this study. The absorbed threshold ionization energy (TIE) and the threshold radiation dose (TRD) were determined using a high-power infrared laser (at 1064 nm) trap by single and multiple cells trapping and ionization. The results were analyzed using descriptive and t-statistics. The relation of the TIE and TRD to the mass of the individual cells were also analyzed for different hours of treatment in comparison with the control group. Both TIE and TRD decrease with increasing treatment periods. However, the TRD decreases with mass regardless of the treatment. Analyses of the TRD for single vs multiple cells ionizations within each group have also consistently showed this same behavior regardless of the treatment. The underlying factors for these observed relations are explained in terms of radiation, hyperthermia, and chemo effects.

Depth resolved defect characterization of energetic ion irradiated ZnO by positron annihilation techniques and photoluminescence

Depth resolved positron annihilation spectroscopy (PAS) has been employed to characterize the 1.2 MeV Ar and 800 keV O ion beam induced defects in ZnO. The first extraordinary result was the observation of defects in ion beam irradiated ZnO beyond the maximum penetration depth of the respective ions. The positron annihilation results revealed the formation of vacancy clusters consisting of both VZn and VO in ZnO which are saturated at a threshold radiation dose (defined as nuclear energy loss, Sn × fluence). From the photoluminescence (PL) spectra it has been observed that the PL intensity at the band edge degraded with the increase of open volume defects in ZnO. The evolution of the 2.4 eV PL, which is linked with the oxygen vacancies, is more significant due to Ar irradiation than the oxygen irradiation.

Hepatotoxic Dose Thresholds by Positron-Emission Tomography After Yttrium-90 Radioembolization of Liver Tumors: A Prospective Single-Arm Observational Study.

To define a threshold radiation dose to non-tumoral liver from 90Y radioembolization that results in hepatic toxicity using pair-production PET. This prospective single-arm study enrolled 35 patients undergoing radioembolization. A total of 34 patients (27 with HCC and 7 with liver metastases) were included in the final analysis. Of 27 patients with underlying cirrhosis, 22 and 5 patients were Child-Pugh A and B, respectively. Glass and resin microspheres were used in 32 (94%) and 2 (6%) patients, respectively. Lobar and segmental treatment was done in 26 (76%) and 8 (24%) patients, respectively. Volumetric analysis was performed on post-radioembolization time-of-flight PET imaging to determine non-tumoral parenchymal dose. Hepatic toxicity was evaluated up to 120days post-treatment, with CTCAE grade ≤ 1 compared to grade ≥ 2. The median dose delivered to the non-tumoral liver in the treated lobe was 49Gy (range 0-133). A total of 15 patients had grade ≤ 1 hepatic toxicity, and 19 patients had grade ≥ 2 toxicity. Patients with a grade ≥ 2 change in composite toxicity (70.7 vs. 43.8Gy), bilirubin (74.1 vs. 43.3Gy), albumin (84.2 vs. 43.8Gy), and AST (94.5 vs. 47.1Gy) have significantly higher non-tumoral parenchymal doses than those with grade ≤ 1. Liver parenchymal dose and Child-Pugh status predicted grade ≥ 2 toxicity, observed above a dose threshold of 54Gy. Increasing delivered 90Y dose to non-tumoral liver measured by internal pair-production PET correlates with post-treatment hepatic toxicity. The likelihood of toxicity exceeds 50% at a dose threshold of 54Gy. ClinicalTrials.gov identifier: NCT02848638.

4:12 PM Abstract No. 129 Intrahepatic flow redistribution prior to segmental Yttrium-90 radioembolization for challenging tumor vasculature

Hepatic tumors with complex vascular supply, inaccessible feeding vessels, and/or poor tumor perfusion are prone to transarterial treatment failure. This concern is compounded in the setting of Yttrium-90 (Y90) radioembolization (RE), which is often non-embolic, flow-dependent, and relies on high threshold radiation dose for response. We describe our experience with intrahepatic flow redistribution using bland or coil embolization prior to RE of tumors with challenging vascular supply. Between 4/2014-7/2017, 19 patients (14 male, median age 62) with focal hepatocellular carcinoma underwent embolization for the purpose of intrahepatic flow redistribution during RE mapping or treatment. Hepatic redistribution (HR) was performed by embolization of vessels supplying normal hepatic parenchyma in cases when flow was not preferential to target tumor. Tumor-specific redistribution (TR) was performed by embolization of accessory feeding vessel(s) supplying the lesion, but not amenable to subselective RE. Lesion characteristics, vascular supply, treatment approach, angiography, and adverse events (AEs) were reviewed. Dosimetry coverage based on mTc-MAA and Y90 SPECT-CT was evaluated against pretreatment CT or MRI. Radiographic response was assessed by mRECIST. 13 cases of HR and 6 cases of TR were identified. Embolization was performed at the segmental (n = 4) or subsegmental level (n = 14), and at the gastroduodenal artery (n = 1). Fourteen right and 5 left-sided HCCs were treated (mean size 3.7 ± 2.1 cm). Embolic material included: calibrated microspheres (n = 12, range 40-500 μm), detachable microcoils (n = 7), and Gelfoam (n = 1). There were no procedure-related AEs. Post-treatment SPECT-CT dosimetry coverage was concordant with target lesions in all cases. Mean follow-up was 7.2 ± 6.7 months. Tumor-specific response was 68% complete response, 11% partial response, 5% stable disease, and 16% progressive disease by mRECIST. No major adverse events or grade 3/4 hepatotoxicity occurred up to 30 days. Intrahepatic flow redistribution prior to RE is safe with 79% objective response in the setting of complex vascular supply or poor relative tumor perfusion.

UV Effects on the Tensile and Creep Behaviour of HDPE

The tensile and creep behaviour of a high-density polyethylene grade used to manufacture pipes were evaluated as a function of the time of exposure to UV radiation. The effect of the creep stress level was also analysed. A threshold radiation dose was determined, above which UV radiation causes loss of the macroscopic mechanical behaviour for this particular HDPE grade. Below the threshold value, macromolecular modifications were also taking place, but the deleterious effect of UV radiation was masked by the development of a more rigid structure. Scanning electron microscopy, melt flow index and thermogravimetric analysis were used to support the results of the mechanical analysis.

Single cell ionization by a laser trap: a preliminary study in measuring radiation dose and charge in BT20 breast carcinoma cells.

In this work, a preliminary study in the application of a laser trap for ionization of living carcinoma cells is presented. The study was conducted using BT20 breast carcinoma cells cultured and harvested in our laboratory. Each cell, for a total of 50 cells, was trapped and ionized by a high intensity infrared laser at 1064 nm. The threshold radiation dose and the resultant charge from the ionization for each cell were determined. With the laser trap serving as a radiation source, the cell underwent dielectric breakdown of the membrane. When this process occurs, the cell becomes highly charged and its dielectric susceptibility changes. The charge creates an increasing electrostatic force while the changing dielectric susceptibility diminishes the strength of the trapping force. Consequently, at some instant of time the cell gets ejected from the trap. The time inside the trap while the cell is being ionized, the intensity of the radiation, and the post ionization trajectory of the cell were used to determine the threshold radiation dose and the charge for each cell. The measurement of the charge vs ionization radiation dose at single cell level could be useful in the accuracy of radiotherapy as the individual charges can collectively create a strong enough electrical interaction to cause dielectric breakdown in other cells in a tumor.

125P Comparison efficacy of preoperative chemotherapy and surgery with surgery alone in patients with stage IIIA non-small-cell lung cancer

pneumonitis (RP) among patients with lung cancer. However, such relationships between the dosimetric factors and RP incidences weremostly discussed in a definitive treatment setting. Here, we retrospectively evaluated the possible predictive DVH parameters for acute severe RP in lung cancer patients treated with post-operation radiation therapy (PORT). Methods: Eighty-five lung cancer patients treated with PORT was evaluated. Radiotherapy was delivered at 2 Gy per fraction to a total of 50–66Gy. Acute RP was graded according to Common Terminology Criteria for Adverse Events, version 3.0. The percent lung volume receiving more than a threshold radiation dose (Vdose), and the mean lung dose (MLD) were analyzed for their association with risk of RP. This retrospective study was carried out with the approval of the Ethics Committee of West China Hospital, Sichuan University. Results: Twenty-eight patients (32.9%) developed acute grade 2 RP, twenty-two patients (25.9%) developed acute grade 3 or worse RP, and one patient died of grade 5 RP. By multivariate analysis, the V5 of the ipsilateral lung (V5−Ip) and the V20 of the total lung (V20−Total) were significantly associated with G3 or higher acute RP (p = 0.023 and p =0.029, respectively). By receiver operating characteristics curve analysis (ROC), the areas under curve were 0.659 (p = 0.027) and 0.666 (p = 0.021) for V5−Ip and V20−Total, respectively. The optimal V5−Ip threshold to predict acute severe RP was 71.2%, with sensitivity/specificity of 68.2%/61.9%. The optimal V20−Total threshold was 21.4%, and its sensitivity and specificity were 63.6% and 71.4% respectively. Conclusions: V5−Ip and V20−Total were the predictive factors of acute severe RP among lung cancer patients treated with PORT. And it should be considered in the evaluation of treatment planning and require further investigation. Legal entity responsible for the study: West China Hospital Funding: West China Hospital Disclosure: All authors have declared no conflicts of interest.

Application of p-Channel Power VDMOSFET as a High Radiation Doses Sensor

This paper presents a comparative study of RADFETs and commercial p-channel power VDMOSFETs sensitivity to gamma-ray irradiation. Sensitivity was characterized by the threshold voltage shift determined from extrapolated linear region of transfer characteristics in saturation as a function of radiation dose. Sensitivity was followed in the dose range from 100 Gy to 500 Gy without and with $ + 10~\hbox{V}$ gate bias. Linear dependence between threshold voltage shift and radiation dose was established for components for which the gate bias during irradiation was $ + 10~\hbox{V}$ . Sensitivity of p-channel power VDMOSFETs is larger than the RADFETs, and it is a consequence of a larger concentration of fixed traps generated by gamma-ray irradiation. The mechanisms responsible for the threshold voltage shift during irradiation have been discussed as well. The fading of these components was also monitored at room temperature up to 24 hours and it was shown that it is larger in p-channel power VDMOSFETs then in RADFETs.

Cardiac Resynchronization Therapy Delivered Via a Multipolar Left Ventricular Lead is Associated with Reduced Mortality and Elimination of Phrenic Nerve Stimulation: Long-Term Follow-Up from a Multicenter Registry.

Lower Mortality and Eliminated PNS Associated with Quadripolar LeadsIntroductionCardiac resynchronization therapy (CRT) using quadripolar left ventricular (LV) leads provides more pacing vectors compared to bipolar leads. This may avoid phrenic nerve stimulation (PNS) and allow optimal lead placement to maximize biventricular pacing. However, a long‐term improvement in patient outcome has yet to be demonstrated.MethodsA total of 721 consecutive patients with conventional CRTD criteria implanted with quadripolar (n = 357) or bipolar (n = 364) LV leads were enrolled into a registry at 3 UK centers. Lead performance and mortality was analyzed over a 5‐year period.ResultsPatients receiving a quadripolar lead were of similar age and sex to those receiving a bipolar lead, although a lower proportion had ischemic heart disease (62.6% vs. 54.1%, P = 0.02). Both groups had similar rates of procedural success, although lead threshold, impedance, and procedural radiation dose were significantly lower in those receiving a quadripolar lead. PNS was more common in those with quadripolar leads (16.0% vs. 11.6%, P = 0.08), but was eliminated by switching pacing vector in all cases compared with 60% in the bipolar group (P < 0.001). Furthermore, LV lead displacement (1.7% vs. 4.6%, P = 0.03) and repositioning (2.0% vs. 5.2%, P = 0.03) occurred significantly less often in those with a quadripolar lead. All‐cause mortality was also significantly lower in the quadripolar compared to bipolar lead group in univariate and multivariate analysis (13.2% vs. 22.5%, P < 0.001).ConclusionsIn a large, multicenter experience, the use of quadripolar LV leads for CRT was associated with elimination of PNS and lower overall mortality. This has important implications for LV pacing lead choice.