Radiation-induced Lung Damage Research Articles

Apigenin's Influence on Inflammatory and Epigenetic Responses in Rat Lungs After Radiotherapy.

The lung is a moderately radio-sensitive organ. When cells are damaged due to accidental radiation exposure or treatment, they release molecules that lead to the recruitment of immune cells, accumulating inflammatory cytokines at the site of damage. Apigenin (Api) is a natural flavonoid known for its anti-inflammatory properties. In this study, we investigated the radioprotective properties of Api in the lung. Thirty-six Wistar rats were randomly assigned to nine groups: control, radiation (Rad), CMC+Rad, Api10+Rad, and Api20+Rad. Api was administered with an intraperitoneal injection for 7 days, after which the rats were irradiated with 6 Gy whole-body X-ray. At 6 and 72 hours post-irradiation, the rats were euthanized, and their lung tissue was extracted. Radiation led to increased alveolar wall thickness and the infiltration of macrophages and lymphocytes. Furthermore, the expression levels of inflammatory factors such as a nuclear factor of kappa light polypeptide gene enhancer in B-cells (NF-ĸB), Glycogen synthase kinase-3 beta (GSK-3β), transforming growth factor-beta1 (TGF-β1), and epigenetic factors including DNA methyltransferase 3a (DNMT3a) and Histone deacetylase 2 (HDAC2) were elevated in the lung tissue following radiation. Meanwhile, the expression level of IκB-α decreased. However, administration of Api (at both 10&20 mg/kg) reversed the adverse effects of radiation. Api administration mitigated radiation-induced lung damage by reversing inflammatory and epigenetic changes.

Expression of Tenascin-C Is Upregulated in the Early Stages of Radiation Pneumonitis/Fibrosis in a Novel Mouse Model.

The lung is a major dose-limiting organ for radiation therapy (RT) for cancer in the thoracic region, and the clarification of radiation-induced lung damage (RILD) is important. However, there have been few reports containing a detailed comparison of radiographic images with the pathological findings of radiation pneumonitis (RP)/radiation fibrosis (RF). We recently reported the upregulated expression of tenascin-C (TNC), an inflammation-associated extracellular matrix molecule, in surgically resected lung tissue, and elevated serum levels were elevated in a RILD patient. Therefore, we have developed a novel mouse model of partial lung irradiation and studied it with special attention paid to the computed tomography (CT) images and immunohistological findings. The right lungs of mice (BALB/c) were irradiated locally at 30 Gy/1fr, and the following two groups were created. In Group 1, sequential CT was performed to confirm the time-dependent changes in RILD. In Group 2, the CT images and histopathological findings of the lung were compared. RP findings were detected histologically at 16 weeks after irradiation; they were also observed on the CT images from 20 weeks. The immunostaining of TNC was observed before the appearance of RP on the CT images. The findings suggest that TNC could be an inflammatory marker preceding lung fibrosis.

Evidence of Alveolar Macrophage Metabolic Shift Following Stereotactic Body Radiation Therapy -Induced Lung Fibrosis in Mice

Radiation-induced pneumopathy is the main dose-limiting factor in cases of chest radiation therapy. Macrophage infiltration is frequently observed in irradiated lung tissues and may participate in lung damage development. Radiation-induced lung fibrosis can be reproduced in rodent models using whole thorax irradiation but suffers from limits concerning the role played by unexposed lung volumes in damage development. Here, we used an accurate stereotactic body radiation therapy preclinical model irradiating 4% of the mouse lung. Tissue damage development and macrophage populations were followed by histology, flow cytometry, and single-cell RNA sequencing. Wild-type and CCR2 KO mice, in which monocyte recruitment is abrogated, were exposed to single doses of radiation, inducing progressive (60 Gy) or rapid (80 Gy) lung fibrosis. Numerous clusters of macrophages were observed around the injured area, during progressive as well as rapid fibrosis. The results indicate that probably CCR2-independent recruitment and/or in situ proliferation may be responsible for macrophage invasion. Alveolar macrophages experience a metabolic shift from fatty acid metabolism to cholesterol biosynthesis, directing them through a possible profibrotic phenotype. Depicted data revealed that the origin and phenotype of macrophages present in the injured area may differ from what has been previously described in preclinical models exposing large lung volumes, representing a potentially interesting trail in the deciphering of radiation-induced lung damage processes. Our study brings new possible clues to the understanding of macrophage implications in radiation-induced lung damage, representing an interesting area for exploration in future studies.

Two-Part Mixed Effects Mixture Model for Zero-Inflated Longitudinal Compositional Data

Compositional data (CD) is mostly analyzed using ratios of components and log-ratio transformations to apply known multivariable statistical methods. Therefore, CD where some components equal zero represents a problem. Furthermore, when the data is measured longitudinally, and appear to come from different sub-populations, the analysis becomes highly complex. Our objective is to build a statistical model addressing structural zeros in longitudinal CD and apply it to the analysis of radiation-induced lung damage (RILD) over time. We propose a two-part mixed-effects model extended to the case where the non-zero components of the vector might come from a two-component mixture population. Maximum likelihood estimates for fixed effects and variance components were calculated by an approximate Fisher scoring procedure base on sixth-order Laplace approximation. The expectation-maximization (EM) algorithm estimates the mixture model’s probability. This model was used to analyze the radiation therapy effect on tissue change in one patient with non-small cell lung cancer (NSCLC), utilizing five CT scans over 24 months. Instead of using voxel-level data, voxels were grouped into larger subvolumes called patches. Each patch’s data is a CD vector showing proportions of dense, hazy, or normal tissue. Proposed method performed reasonably for estimation of the fixed effects, and their variability. However, the model produced biased estimates of the nuisance parameters in the model.

The radioprotectant nano-genistein enhances radiotherapy efficacy of lung tumors in mice.

Radiotherapy for non-small cell lung cancer (NSCLC) can be dose-limiting due to treatment-related toxicities. Genistein has been shown to be a robust radioprotective agent in preclinical models. A novel genistein oral nanosuspension formulation (nano-genistein) has demonstrated efficacy in mitigating radiation-induced lung damage in preclinical animal models. However, while those studies have confirmed that nano-genistein can protect normal lung tissue from radiation-induced toxicities, no studies have assessed the effect of nano-genistein on lung tumors. Here, we evaluated the impact of nano-genistein on the efficacy of radiation treatment of lung tumors in a mouse xenograft model. Two separate studies were conducted utilizing human A549 cells implanted either dorsally within the upper torso or in the flank. Daily oral administration of nano-genistein (200 or 400 mg/kg/day) occurred prior to and after exposure to a single dose of thoracic or abdominal 12.5 Gy radiation. Tumor growth was monitored twice weekly, nano-genistein treatment continued for up to 20 weeks and histopathology of tissues was completed post euthanasia. Continuous nano-genistein dosing was safe across all study groups in both studies. Animals receiving nano-genistein better maintained body weight following irradiation compared to corresponding vehicle treated animals. Animals that received nano-genistein also had reduced tumor growth and improved normal lung histopathology compared to those receiving vehicle suggesting that nano-genistein does not protect tumors from radiotherapy but is radioprotective of the lungs. There were no treatment-related histopathological findings noted in the skin adjacent to the tumor, esophagus, or uterus. These results, including the safety following extended dosing, support the continued evaluation of nano-genistein as an adjunctive treatment for patients with NSCLC undergoing radiotherapy and serve as the basis of a phase 1b/2a multicenter clinical trial.

Exhaled breath condensate identifies metabolic dysregulation in patients with radiation-induced lung injury.

Radiation-induced lung injury (RILI) is a consequence of therapeutic thoracic irradiation (TR) for many cancers, and there are no FDA-approved curative strategies. Studies report that 80% of patients who undergo TR will have CT-detectable interstitial lung abnormalities, and strategies to limit the risk of RILI may make radiotherapy less effective at treating cancer. Our lab and others have reported that lung tissue from patients with idiopathic pulmonary fibrosis (IPF) exhibits metabolic defects including increased glycolysis and lactate production. In this pilot study, we hypothesized that patients with radiation-induced lung damage will exhibit distinct changes in lung metabolism that may be associated with the incidence of fibrosis. Using liquid chromatography/tandem mass spectrometry to identify metabolic compounds, we analyzed exhaled breath condensate (EBC) in subjects with CT-confirmed lung lesions after TR for lung cancer, compared with healthy subjects, smokers, and cancer patients who had not yet received TR. The lung metabolomic profile of the irradiated group was significantly different from the three nonirradiated control groups, highlighted by increased levels of lactate. Pathway enrichment analysis revealed that EBC from the case patients exhibited concurrent alterations in lipid, amino acid, and carbohydrate energy metabolism associated with the energy-producing tricarboxylic acid (TCA) cycle. Radiation-induced glycolysis and diversion of lactate to the extracellular space suggests that pyruvate, a precursor metabolite, converts to lactate rather than acetyl-CoA, which contributes to the TCA cycle. This TCA cycle deficiency may be compensated by these alternate energy sources to meet the metabolic demands of chronic wound repair. Using an "omics" approach to probe lung disease in a noninvasive manner could inform future mechanistic investigations and the development of novel therapeutic targets.NEW & NOTEWORTHY We report that exhaled breath condensate (EBC) identifies cellular metabolic dysregulation in patients with radiation-induced lung injury. In this pilot study, untargeted metabolomics revealed a striking metabolic signature in EBC from patients with radiation-induced lung fibrosis compared to patients with lung cancer, at-risk smokers, and healthy volunteers. Patients with radiation-induced fibrosis exhibit specific changes in tricarboxylic acid (TCA) cycle energy metabolism that may be required to support the increased energy demands of fibroproliferation.

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.

Diagnostic Value of 18F-NOTA-FAPI PET/CT in a Rat Model of Radiation-Induced Lung Damage.

In this study, we explore the diagnostic value of a novel PET/CT imaging tracer that specifically targets fibroblast activation protein (FAP), 18F-NOTA-FAPI, in a radiation induced lung damage (RILD) rat model. High focal radiation (40, 60, or 90 Gy) was administered to a 5-mm diameter area of the right lung in Wistar rats for evaluation of RILD induction. Lung tissues exposed to 90 Gy radiation were scanned with 18F-NOTA-FAPI PET/CT and with 18F-FDG. Dynamic 18F-NOTA-FAPI PET/CT scanning was performed on day 42 post-irradiation. After in vivo scanning, lung cryosections were prepared for autoradiography, hematoxylin and eosin (HE) and immunohistochemical (IHC) staining. An animal model of RILD was established and validated by histopathological analysis. On 18F-NOTA-FAPI PET/CT, RILD was first observed on days 42, 35 and 7 in the 40, 60 and 90 Gy groups, respectively. After treatment with 90 Gy, 18F-NOTA-FAPI uptake in an area of RILD emerged on day 7 (0.65 ± 0.05%ID/ml) and reappeared on day 28 (0.81 ± 0.09%ID/ml), remaining stable for 4–6 weeks. Autoradiography and HE staining IHC staining revealed that 18F-NOTA-FAPI accumulated mainly in the center of the irradiated area. IHC staining confirmed the presence of FAP+ macrophages in the RILD area, while FAP+ fibroblasts were observed in the peripheral area of irradiated lung tissue. 18F-NOTA-FAPI represents a promising radiotracer for in vivo imaging of RILD in a dose- and time-dependent manner. Noninvasive imaging of FAP may potentially aiding in the clinical management of radiotherapy patients.

Amifostine analog, DRDE-30, alleviates radiation induced lung damage by attenuating inflammation and fibrosis

BackgroundRadiotherapy of thoracic neoplasms and accidental radiation exposure often results in pneumonitis and fibrosis of lungs. Here, we investigated the potential of amifostine analogs: DRDE-07, DRDE-30, and DRDE-35, in alleviating radiation-induced lung damage. MethodsC57BL/6 mice were exposed to 13.5 Gy thoracic irradiation, 30 min after intraperitoneal administration of the analogs, and assessed for modulation of the pathological response at 12 and 24 weeks. Key findingsDRDE-07, DRDE-30 and DRDE-35 increased the survival of irradiated mice from 20% to 30%, 80% and 70% respectively. Reduced parenchymal opacity (X-ray CT) in the lungs of DRDE-30 pre-treated mice corroborated well with the significant decrease in Ashcroft score (p < 0.01). Two-fold increase in SOD and catalase activities (p < 0.05), coupled with a 50% increase in GSH content and a 60% decrease in MDA content (p < 0.05) suggested restoration of the antioxidant defence system. A 20% to 40% decrease in radiation-induced apoptotic and mitotic death in the lung tissue (micronuclei: p < 0.01), resulted in attenuated lung and vascular permeability (FITC-Dextran leakage) by 50% (p < 0.01), and a commensurate reduction (~50%) in leukocyte infiltration in the injured tissue (p < 0.05). DRDE-30 abrogated the activation of pro-inflammatory NF-κB and p38/MAPK signaling cascades, suppressing the release of pro-inflammatory cytokines (IL-1β: p < 0.05; TNF-α: p < 0.05; IL-6: p < 0.05) and up-regulation of CAMs on the endothelial cell surface. Reduction in hydroxyproline content (p < 0.01) and collagen suggested inhibition of lung fibrosis which was associated with attenuation of TGF-β/Smad pathway-mediated-EMT. ConclusionDRDE-30 could be a potential prophylactic agent against radiation-induced lung injury.

Quantitative Analysis of Radiation-Associated Parenchymal Lung Change.

Simple SummaryRadiotherapy is commonly used to treat inoperable locally advanced lung cancer. Despite the use of sophisticated modern planning and imaging techniques to target the tumour and minimise dose to normal lung tissue, patients can suffer from acute and chronic respiratory problems after treatment. Currently, our understanding of the impact that radiotherapy has on patients’ lungs is inadequate. We have, therefore, proposed a novel classification of the damage to the lung tissue, as seen on CT scans after a course of radiotherapy to a lung tumour. We have used deep learning algorithms to allow large numbers of CT scans to be labelled at the level of the individual voxel according to the degree of damage. The dose delivered to the tumour and the change in lung function of the patient after treatment both correlated well to the degree of radiological change measured. Our novel, automated classification combined with a dedicated image registration method has demonstrated an important clinical application that could be used to improve radiotherapy delivery in the future by allowing us to precisely track the changes seen after radiation treatment.We present a novel classification system of the parenchymal features of radiation-induced lung damage (RILD). We developed a deep learning network to automate the delineation of five classes of parenchymal textures. We quantify the volumetric change in classes after radiotherapy in order to allow detailed, quantitative descriptions of the evolution of lung parenchyma up to 24 months after RT, and correlate these with radiotherapy dose and respiratory outcomes. Diagnostic CTs were available pre-RT, and at 3, 6, 12 and 24 months post-RT, for 46 subjects enrolled in a clinical trial of chemoradiotherapy for non-small cell lung cancer. All 230 CT scans were segmented using our network. The five parenchymal classes showed distinct temporal patterns. Moderate correlation was seen between change in tissue class volume and clinical and dosimetric parameters, e.g., the Pearson correlation coefficient was ≤0.49 between V30 and change in Class 2, and was 0.39 between change in Class 1 and decline in FVC. The effect of the local dose on tissue class revealed a strong dose-dependent relationship. Respiratory function measured by spirometry and MRC dyspnoea scores after radiotherapy correlated with the measured radiological RILD. We demonstrate the potential of using our approach to analyse and understand the morphological and functional evolution of RILD in greater detail than previously possible.

In-vivo X-ray dark-field computed tomography for the detection of radiation-induced lung damage in mice.

Radiotherapy of thoracic tumours can lead to side effects in the lung, which may benefit from early diagnosis. We investigated the potential of X-ray dark-field computed tomography by a proof-of-principle murine study in a clinically relevant radiotherapeutic setting aiming at the detection of radiation-induced lung damage. Six mice were irradiated with 20Gy to the entire right lung. Together with five unirradiated control mice, they were imaged using computed tomography with absorption and dark-field contrast before and 16weeks post irradiation. Mean pixel values for the right and left lung were calculated for both contrasts, and the right-to-left-ratio R of these means was compared. Radiologists also assessed the tomograms acquired 16weeks post irradiation. Sensitivity, specificity, inter- and intra-reader accuracy were evaluated. In absorption contrast the group-average of R showed no increase in the control group and increased by 7% (p=0.005) in the irradiated group. In dark-field contrast, it increased by 2% in the control group and by 14% (p=0.005) in the irradiated group. Specificity was 100% for both contrasts but sensitivity was almost four times higher using dark-field tomography. Two cases were missed by absorption tomography but were detected by dark-field tomography. The applicability of X-ray dark-field computed tomography for the detection of radiation-induced lung damage was demonstrated in a pre-clinical mouse model. The presented results illustrate the differences between dark-field and absorption contrast and show that dark-field tomography could be advantageous in future clinical settings.

A multichannel feature-based approach for longitudinal lung CT registration in the presence of radiation induced lung damage

Quantifying parenchymal tissue changes in the lungs is imperative in furthering the study of radiation induced lung damage (RILD). Registering lung images from different time-points is a key step of this process. Traditional intensity-based registration approaches fail this task due to the considerable anatomical changes that occur between timepoints. This work proposes a novel method to successfully register longitudinal pre- and post-radiotherapy (RT) lung computed tomography (CT) scans that exhibit large changes due to RILD, by extracting consistent anatomical features from CT (lung boundaries, main airways, vessels) and using these features to optimise the registrations. Pre-RT and 12 month post-RT CT pairs from fifteen lung cancer patients were used for this study, all with varying degrees of RILD, ranging from mild parenchymal change to extensive consolidation and collapse. For each CT, signed distance transforms from segmentations of the lungs and main airways were generated, and the Frangi vesselness map was calculated. These were concatenated into multi-channel images and diffeomorphic multichannel registration was performed for each image pair using NiftyReg. Traditional intensity-based registrations were also performed for comparison purposes. For the evaluation, the pre- and post-registration landmark distance was calculated for all patients, using an average of 44 manually identified landmark pairs per patient. The mean (standard deviation) distance for all datasets decreased from 15.95 (8.09) mm pre-registration to 4.56 (5.70) mm post-registration, compared to 7.90 (8.97) mm for the intensity-based registrations. Qualitative improvements in image alignment were observed for all patient datasets. For four representative subjects, registrations were performed for three additional follow-up timepoints up to 48 months post-RT and similar accuracy was achieved. We have demonstrated that our novel multichannel registration method can successfully align longitudinal scans from RILD patients in the presence of large anatomical changes such as consolidation and atelectasis, outperforming the traditional registration approach both quantitatively and through thorough visual inspection.

HSCs transdifferentiate primarily to pneumonocytes in radiation-induced lung damage repair.

Accumulative radiation exposure leads to hematopoietic or tissue aging. Whether hematopoietic stem cells (HSCs) are involved in lung damage repair in response to radiation remains controversial. The aim of this study is to identify if HSC can transdifferentiate to pneumonocytes for radiation-induced damage repair. To this end, HSCs from male RosamT/mG mice were isolated by fluorescence-activated cell sorting (FACS) and transplanted into lethally irradiated female CD45.1 mice. 4 months after transplantation, transplanted HSC was shown to repair the radiation-induced tissue damage, and donor-derived tdTomato (phycoerythrin, PE) red fluorescence cells and Ddx3y representing Y chromosome were detected exclusively in female recipient lung epithelial and endothelial cells. Co-localization of donor-derived cells and recipient lung tissue cells were observed by laser confocal microscopy and image flow cytometry. Furthermore, the results showed HSC transplantation replenished radiation-induced lung HSC depletion and the PE positive repaired lung epithelial cells were identified as donor HSC origin. The above data suggest that donor HSC may migrate to the injured lung of the recipient and some of them can be transdifferentiated to pneumonocytes to repair the injury caused by radiation.

Radiation-induced lung damage in patients treated with stereotactic body radiotherapy after EGFR-TKIs: is there any difference from stereotactic body radiotherapy alone?

To quantitatively evaluate lung damage after treatment of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) and stereotactic body radiotherapy (SBRT) in patients with nonsmall cell lung cancer (NSCLC), and compare that of SBRT only treatment. Eligible patients from an IRB-approved prospective clinical trial had one month of EGFRTKIs treatment followed by SBRT (TKI + SBRT) and with 3-month follow-up high resolution CT. NSCLC patients treated with SBRT alone during the same time period without EGFR-TKIs or other systemic therapies were identified as controls. The lung damage was assessed clinically by pneumonitis and quantitatively using by CT intensity (Hounsfield unit, HU) changes. The mean HU values were extracted for regions of the lungs receiving the same dose range at 10 Gy intervals to generate dose-response curves (DRC). The relationship of HU changes and radiation dose was modeled using a Probit model. Four out of 20 (25%) TKI + SBRT patients and none of 19 (0%) SBRT alone patients had developed grade 2 and above pneumonitis (P=0.053), respectively. Sixty percent of TKI + SBRT patients and 30% SBRT alone patients had HU changes of the normal lung density >200 HU, respectively. There were significant differences in the DRC and in lung HU changes between the two groups (all P<0.05). The physical dose for a 50% complication risk (TD50) of CT lung damage was 52 Gy (CI: 46-59) in TKI + SBRT group versus 72 Gy (CI: 58-107) in SBRT alone group (P<0.01). Compared to patients treated with SBRT alone, patients treated with EGFR-TKIs followed by SBRT were more incline to develop radiation pneumonitis, and resulted in greater lung CT intensity changes and steeper dose-CT lung damage response relationship at 3 months post treatment. Future study with larger number of patients and longer follow-up period is warranted to validate this finding.

Protective Effects of Hydrogen against Irradiation.

Radiation-induced lung injury is characterized by an acute pneumonia phase followed by a fibrotic phase. At the time of irradiation, a rapid, short-lived burst of reactive oxygen species (ROS) such as hydroxyl radicals (•OH) occurs, but chronic radiation-induced lung injury may occur due to excess ROS such as H2O2, O2•-, ONOO-, and •OH. Molecular hydrogen (H2) is an efficient antioxidant that quickly diffuses cell membranes, reduces ROS such as •OH and ONOO-, and suppresses damage caused by oxidative stress in various organs. In 2011, through the evaluation of electron-spin resonance and fluorescent indicator signals, we had reported that H2 can eliminate •OH and can protect against oxidative stress-related apoptotic damage induced by irradiation of cultured lung epithelial cells. We had explored for the first time the radioprotective effects of H2 treatment on acute and chronic radiation-induced lung damage in mice by inhaled H2 gas (for acute) and imbibed H2-enriched water (for chronic). Thus, we had proposed that H2 be considered a potential radioprotective agent. Recent publications have shown that H2 directly neutralizes highly reactive oxidants and indirectly reduces oxidative stress by regulating the expression of various genes. By regulating gene expression, H2 functions as an anti-inflammatory and anti-apoptotic molecule and promotes energy metabolism. The increased evidence obtained from cultured cells or animal experiments reveal a putative place for H2 treatment and its radioprotective effect clinically. This review focuses on major scientific advances in the treatment of H2 as a new class of radioprotective agents.

In Silico Ventilation Within the Dose-Volume is Predictive of Lung Function Post-radiation Therapy in Patients with Lung Cancer

Lung cancer is a leading cause of death worldwide. Radiation therapy (RT) is one method to treat this disease. A common side effect of RT for lung cancer is radiation-induced lung damage (RILD) which leads to loss of lung function. RILD often compounds pre-existing smoking-related regional lung function impairment. It is difficult to predict patient outcomes due to large variability in individual response to RT. In this study, the capability of image-based modelling of regional ventilation in lung cancer patients to predict lung function post-RT was investigated. Twenty-five patient-based models were created using CT images to define the airway geometry, size and location of tumour, and distribution of emphysema. Simulated ventilation within the 20 Gy isodose volume showed a statistically significant negative correlation with the change in forced expiratory volume in 1 s 12-months post-RT (p = 0.001, R = − 0.61). Patients with higher simulated ventilation within the 20 Gy isodose volume had a greater loss in lung function post-RT and vice versa. This relationship was only evident with the combined impact of tumour and emphysema, with the location of the emphysema relative to the dose-volume being important. Our results suggest that model-based ventilation measures can be used in the prediction of patient lung function post-RT.

Monte Carlo 90Y PET/CT dosimetry of unexpected focal radiation-induced lung damage after hepatic radioembolisation

Transarterial radioembolization (TARE) with 90Y-loaded microspheres is an established therapeutic option for inoperable hepatic tumors. Increasing knowledge regarding TARE hepatic dose-response and dose-toxicity correlation is available but few studies have investigated dose-toxicity correlation in extra-hepatic tissues. We investigated absorbed dose levels for the appearance of focal lung damage in a case of off-target deposition of 90Y microspheres and compared them with the corresponding thresholds recommended to avoiding radiation induced lung injury following TARE. A 64-year-old male patient received 1.6 GBq of 90Y-labelled glass microspheres for an inoperable left lobe hepatocellular carcinoma. A focal off-target accumulation of radiolabeled microspheres was detected in the left lung upper lobe at the post-treatment 90Y-PET/CT, corresponding to a radiation-induced inflammatory lung lesion at the 3-months 18F-FDG PET/CT follow-up. 90Y-PET/CT data were used as input for Monte-Carlo based absorbed dose estimations. Dose-volume-histograms were computed to characterize the heterogeneity of absorbed dose distribution. The dose level associated with the appearance of lung tissue damage was estimated as the median absorbed dose measured at the edge of the inflammatory nodule. To account for respiratory movements and possible inaccuracy of image co-registration, three different methods were evaluated to define the irradiated off-target volume. Monte Carlo-derived absorbed dose distribution showed a highly heterogeneous absorbed dose pattern at the site of incidental microsphere deposition (volume = 2.13 ml) with a maximum dose of 630 Gy. Absorbed dose levels ranging from 119 Gy to 133 Gy, were estimated at the edge of the inflammatory nodule, depending on the procedure used to define the target volume. This report describes an original Monte Carlo based patient-specific dosimetry methodology for the study of the radiation-induced damage in a focal lung lesion after TARE. In our patient, radiation-induced focal lung damage occurred at significantly higher absorbed doses than those considered for single administration or cumulative lung dose delivered during TARE.

Early detection of radiation-induced lung damage with X-ray dark-field radiography in mice

ObjectiveAssessing the advantage of x-ray dark-field contrast over x-ray transmission contrast in radiography for the detection of developing radiation-induced lung damage in mice.MethodsTwo groups of female C57BL/6 mice (irradiated and control) were imaged obtaining both contrasts monthly for 28 weeks post irradiation. Six mice received 20 Gy of irradiation to the entire right lung sparing the left lung. The control group of six mice was not irradiated. A total of 88 radiographs of both contrasts were evaluated for both groups based on average values for two regions of interest, covering (irradiated) right lung and healthy left lung. The ratio of these average values, R, was distinguished between healthy and damaged lungs for both contrasts. The time-point when deviations of R from healthy lung exceeded 3σ was determined and compared among contrasts. The Wilcoxon-Mann-Whitney test was used to test against the null hypothesis that there is no difference between both groups. A selection of 32 radiographs was assessed by radiologists. Sensitivity and specificity were determined in order to compare the diagnostic potential of both contrasts. Inter-reader and intra-reader accuracy were rated with Cohen’s kappa.ResultsRadiation-induced morphological changes of lung tissue caused deviations from the control group that were measured on average 10 weeks earlier with x-ray dark-field contrast than with x-ray transmission contrast. Sensitivity, specificity, and accuracy doubled using dark-field radiography.ConclusionX-ray dark-field radiography detects morphological changes of lung tissue associated with radiation-induced damage earlier than transmission radiography in a pre-clinical mouse model.Key Points• Significant deviations from healthy lung due to irradiation were measured after 16 weeks with x-ray dark-field radiography (p = 0.004).• Significant deviations occur on average 10 weeks earlier for x-ray dark-field radiography in comparison to x-ray transmission radiography.• Sensitivity and specificity doubled when using x-ray dark-field radiography instead of x-ray transmission radiography.

PD-0417: The evolution of radiation-induced lung damage following dose-escalated chemo-radiotherapy

PD-0417: The evolution of radiation-induced lung damage following dose-escalated chemo-radiotherapy

Automated Pulmonary Fibrosis Segmentation Using a 3D Multi-Scale Convolutional Encoder-Decoder Approach in Thoracic CT for the Rhesus Macaque with Radiation-Induced Lung Damage

To develop an automated pulmonary fibrosis (PF) segmentation methodology using a 3D multi-scale convolutional encoder-decoder approach following the robust atlas-based active volume model in thoracic CT for Rhesus Macaques with radiation-induced lung damage. 152 thoracic computed tomography scans of Rhesus Macaques with radiation-induced lung damage were collected. The 3D input data are randomly augmented with the Gaussian blurring when applying the 3D multi-scale convolutional encoder-decoder (3D MSCED) segmentation method.PF in each scan was manually segmented in which 70% scans were used as training data, 20% scans were used as validation data, and 10% scans were used as testing data. The performance of the method is assessed based on a10-fold cross validation method. The workflow of the proposed method has two parts. First, the compromised lung volume with acute radiation-induced PF was segmented using a robust atlas-based active volume model. Next, a 3D multi-scale convolutional encoder-decoder segmentation method was developed which merged the higher spatial information from low-level features with the high-level object knowledge encoded in upper network layers. It included a bottom-up feed-forward convolutional neural network and a top-down learning mask refinement process. The quantitative results of our segmentation method achieved mean Dice score of (0.769, 0.853), mean accuracy of (0.996, 0.999), and mean relative error of (0.302, 0.512) with 95% confidence interval. The qualitative and quantitative comparisons show that our proposed method can achieve better segmentation accuracy with less variance in testing data. This method was extensively validated in NHP datasets. The results demonstrated that the approach is more robust relative to PF than other methods. It is a general framework which can easily be applied to segmentation other lung lesions.