Ionizing radiation damage and repair from 3D-genomic perspective.

Ionizing radiation (IR)-induced DNA damage and repair are complex and occur at hierarchical chromatin structures; radiobiology needs to be studied from a 3D-genomic perspective. Differences in IR damage and repair throughout the 3D genome may help to explain differences in radiosensitivity.

Defined Sensing Mechanisms and Signaling Pathways Contribute to the Global Inflammatory Gene Expression Output Elicited by Ionizing Radiation.

Environmental insults are often detected by multiple sensors that activate diverse signaling pathways and transcriptional regulators, leading to a tailored transcriptional output. To understand how a tailored response is coordinated, we examined the inflammatory response elicited in mouse macrophages by ionizing radiation (IR). RNA-sequencing studies revealed that most radiation-induced genes were strongly dependent on only one of a small number of sensors and signaling pathways, notably the DNA damage-induced kinase ATM, which regulated many IR-response genes, including interferon response genes, via an atypical IRF1-dependent, STING-independent mechanism. Moreover, small, defined sets of genes activated by p53 and NRF2 accounted for the selective response to radiation in comparison to a microbial inducer of inflammation. Our findings reveal that genes comprising an environmental response are activated by defined sensing mechanisms with a high degree of selectivity, and they identify distinct components of the radiation response that might be susceptible to therapeutic perturbation.

Tumor hypoxia and radiotherapy: A major driver of resistance even for novel radiotherapy modalities.

Hypoxia in solid tumors is an important predictor of poor clinical outcome to radiotherapy. Both physicochemical and biological processes contribute to a reduced sensitivity of hypoxic tumor cells to ionizing radiation and hypoxia-related treatment resistances. A conventional low-dose fractionated radiotherapy regimen exploits iterative reoxygenation in between the individual fractions, nevertheless tumor hypoxia still remains a major hurdle for successful treatment outcome. The technological advances achieved in image guidance and highly conformal dose delivery make it nowadays possible to prescribe larger doses to the tumor as part of single high-dose or hypofractionated radiotherapy, while keeping an acceptable level of normal tissue complication in the co-irradiated organs at risk. However, we insufficiently understand the impact of tumor hypoxia to single high-doses of RT and hypofractionated RT. So-called FLASH radiotherapy, which delivers ionizing radiation at ultrahigh dose rates (> 40 Gy/sec), has recently emerged as an important breakthrough in the radiotherapy field to reduce normal tissue toxicity compared to irradiation at conventional dose rates (few Gy/min). Not surprisingly, oxygen consumption and tumor hypoxia also seem to play an intriguing role for FLASH radiotherapy. Here we will discuss the role of tumor hypoxia for radiotherapy in general and in the context of novel radiotherapy treatment approaches.

In-depth mapping of DNA-PKcs signaling uncovers noncanonical features of its kinase specificity.

DNA-PKcs is a DNA damage sensor kinase with established roles in DNA double-strand break repair via nonhomologous end joining. Recent studies have revealed additional roles of DNA-PKcs in the regulation of transcription, translation, and DNA replication. However, the substrates through which DNA-PKcs regulates these processes remain largely undefined. Here, we utilized quantitative phosphoproteomics to generate a high coverage map of DNA-PKcs signaling in response to ionizing radiation and mapped its interplay with the ATM kinase. Beyond the detection of the canonical S/T-Q phosphorylation motif, we uncovered a noncanonical mode of DNA-PKcs signaling targeting S/T-ψ-D/E motifs. Sequence and structural analyses of the DNA-PKcs substrate recognition pocket revealed unique features compared to closely related phosphatidylinositol 3-kinase-related kinases that may explain its broader substrate preference. These findings expand the repertoire of DNA-PKcs and ATM substrates while establishing a novel preferential phosphorylation motif for DNA-PKcs.

RNF8- and Ube2S-Dependent Ubiquitin Lysine 11-Linkage Modification in Response to DNA Damage.

Ubiquitin modification of proteins plays pivotal roles in the cellular response to DNA damage. Given the complexity of ubiquitin conjugation due to the formation of poly-conjugates of different linkages, functional roles of linkage-specific ubiquitin modification at DNA damage sites are largely unclear. We identify that Lys11-linkage ubiquitin modification occurs at DNA damage sites in an ATM-dependent manner, and ubiquitin-modifying enzymes, including Ube2S E2-conjugating enzyme and RNF8 E3 ligase, are responsible for the assembly of Lys11-linkage conjugates on damaged chromatin, including histone H2A/H2AX. We show that RNF8- and Ube2S-dependent Lys11-linkage ubiquitin conjugation plays an important role in regulating DNA damage-induced transcriptional silencing, distinct from the role of Lys63-linkage ubiquitin in the recruitment of DNA damage repair proteins 53BP1 and BRCA1. Thus, our study highlights the importance of linkage-specific ubiquitination at DNA damage sites, and it reveals that Lys11-linkage ubiquitin modification plays a crucial role in the DNA damage response.

Formation of clustered DNA damage in vivo upon irradiation with ionizing radiation: Visualization and analysis with atomic force microscopy.

SignificanceDNA damage causes loss of or alterations in genetic information, resulting in cell death or mutations. Ionizing radiations produce local, multiple DNA damage sites called clustered DNA damage. In this study, a complete protocol was established to analyze the damage complexity of clustered DNA damage, wherein damage-containing genomic DNA fragments were selectively concentrated via pulldown, and clustered DNA damage was visualized by atomic force microscopy. It was found that X-rays and Fe ion beams caused clustered DNA damage. Fe ion beams also produced clustered DNA damage with high complexity. Fe ion beam-induced complex DNA double-strand breaks (DSBs) containing one or more base lesion(s) near the DSB end were refractory to repair, implying their lethal effects.

Scintillation Properties of CsPbBr3 Nanocrystals Prepared by Ligand-Assisted Reprecipitation and Dual Effect of Polyacrylate Encapsulation toward Scalable Ultrafast Radiation Detectors.

Lead halide perovskite nanocrystals (LHP-NCs) embedded in polymeric hosts are gaining attention as scalable and low-cost scintillation detectors for technologically relevant applications. Despite rapid progress, little is currently known about the scintillation properties and stability of LHP-NCs prepared by the ligand assisted reprecipitation (LARP) method, which allows mass scalability at room temperature unmatched by any other type of nanostructure, and the implications of incorporating LHP-NCs into polyacrylate hosts are still largely debated. Here, we show that LARP-synthesized CsPbBr3 NCs are comparable to particles from hot-injection routes and unravel the dual effect of polyacrylate incorporation, where the partial degradation of LHP-NCs luminescence is counterbalanced by the passivation of electron-poor defects by the host acrylic groups. Experiments on NCs with tailored surface defects show that the balance between such antithetical effects of polymer embedding is determined by the surface defect density of the NCs and provide guidelines for further material optimization.

Astragalus polysaccharide promotes the regeneration of intestinal stem cells through HIF-1 signalling pathway.

Ionizing radiation (IR)-induced intestinal injury is usually accompanied by high lethality. Intestinal stem cells (ISCs) are critical and responsible for the regeneration of the damaged intestine. Astragalus polysaccharide (APS), one of the main active ingredients of Astragalus membranaceus (AM), has a variety of biological functions. This study was aimed to investigate the potential effects of APS on IR-induced intestine injury via promoting the regeneration of ISCs. We have established models of IR-induced intestinal injury and our results showed that APS played great radioprotective effects on the intestine. APS improved the survival rate of irradiated mice, reversed the radiation damage of intestinal tissue, increased the survival rate of intestinal crypts, the number of ISCs and the expression of intestinal tight junction-related proteins after IR. Moreover, APS promoted the cell viability while inhibited the apoptosis of MODE-K. Through organoid experiments, we found that APS promoted the regeneration of ISCs. Remarkably, the results of network pharmacology, RNA sequencing and RT-PCR assays showed that APS significantly upregulated the HIF-1 signalling pathway, and HIF-1 inhibitor destroyed the radioprotection of APS. Our findings suggested that APS promotes the regeneration of ISCs through HIF-1 signalling pathway, and it may be an effective radioprotective agent for IR-induced intestinal injury.

Primary cilium participates in radiation-induced bystander effects through TGF-ß1 signaling.

Many studies have indicated that tumor growth factor-beta (TGF-ß) signaling mediates radiation-induced bystander effects (RIBEs). The primary cilium (PC) coordinates several signaling pathways including TGF-ß signaling to regulate diverse cellular processes. But whether the PC participates in TGF-ß induced RIBEs remains unclear. The cellular levels of TGF-ß1 were detected by western blot analysis and the secretion of TGF-ß1 was measured by ELISA kit. The ciliogenesis was altered by CytoD treatment, STIL siRNA transfection, IFT88 siRNA transfection, or KIF3a siRNA transfection, separately, and was detected by western blot analysis and immunofluorescence staining. G0 /G1 phase cells were arrested by serum starvation and S phase cells were induced by double thymidine block. The TGF-ß1 signaling was interfered by LY2109761, a TGF-ß receptor 1 (TßR1) inhibitor, or TGF-ß1 neutral antibody. The DNA damages were induced by TGF-ß1 or radiated conditional medium (RCM) from irradiated cells and were reflected by p21 expression, 53BP1 foci, and γH2AX foci. Compared with unirradiated control, both A549 and Beas-2B cells expressed and secreted more TGF-ß1 after carbon ion beam or X-ray irradiation. RCM collected from irradiated cells or TGF-ß1 treatment caused an increase of DNA damage in cocultured unirradiated Beas-2B cells while blockage of TGF-ß signaling by TßR1 inhibitor or TGF-ß1 neutral antibody alleviates this phenomenon. IFT88 siRNA or KIF3a siRNA impaired PC formation resulted in an aggravated DNA damage in bystander cells, while elevated PC formation by CytoD or STIL siRNA resulted in a decrease of DNA damage. Furthermore, TGF-ß1 induced more DNA damages in S phases cells which showed lower PC formation rate and less DNA damages in G0 /G1 phase cells which showed higher PC formation rate. This study demonstrates the particular role of primary cilia during RCM induced DNA damages through TGF-ß1 signaling restriction and thereby provides a functional link between primary cilia and RIBEs.

KCa channel targeting impairs DNA repair and invasiveness of patient-derived glioblastoma stem cells in culture and orthotopic mouse xenografts which only in part is predictable by KCa expression levels.

Prognosis of glioblastoma patients is still poor despite multimodal therapy. The highly brain-infiltrating growth in concert with a pronounced therapy resistance particularly of mesenchymal glioblastoma stem-like cells (GSCs) has been proposed to contribute to therapy failure. Recently, we have shown that a mesenchymal-to-proneural mRNA signature of patient derived GSC-enriched (pGSC) cultures associates with in vitro radioresistance and gel invasion. Importantly, this pGSC mRNA signature is prognostic for patients' tumor recurrence pattern and overall survival. Two mesenchymal markers of the mRNA signature encode for IKCa and BKCa Ca2+-activated K+ channels. Therefore, we analyzed here the effect of IKCa- and BKCa-targeting concomitant to (fractionated) irradiation on radioresistance and glioblastoma spreading in pGSC cultures and in pGSC-derived orthotopic xenograft glioma mouse models. To this end, in vitro gel invasion, clonogenic survival, in vitro and in vivo residual DNA double strand breaks (DSBs), tumor growth, and brain invasion were assessed in the dependence on tumor irradiation and K+ channel targeting. As a result, the IKCa- and BKCa-blocker TRAM-34 and paxilline, respectively, increased number of residual DSBs and (numerically) decreased clonogenic survival in some but not in all IKCa- and BKCa-expressing pGSC cultures, respectively. In addition, BKCa- but not IKCa-blockade slowed-down gel invasion in vitro. Moreover, systemic administration of TRAM-34 or paxilline concomitant to fractionated tumor irradiation increased in the xenograft model(s) residual number of DSBs and attenuated glioblastoma brain invasion and (numerically) tumor growth. We conclude, that KCa-blockade concomitant to fractionated radiotherapy might be a promising new strategy in glioblastoma therapy.

Site-specific cancer mortality after low level exposure to ionizing radiation: Findings from an update of the International Nuclear Workers Study (INWORKS).

A major update to the International Nuclear Workers Study was undertaken that allows us to report updated estimates of associations between radiation and site-specific solid cancer mortality. A cohort of 309,932 nuclear workers employed in France, the United Kingdom, and United States were monitored for external radiation exposure and associations with cancer mortality were quantified as the excess relative rate (ERR) per gray (Gy) using a maximum likelihood and a Markov chain Monte Carlo method (to stabilize estimates via a hierarchical regression). The analysis included 28,089 deaths due to solid cancer, the most common being lung, prostate, and colon cancer. Using maximum likelihood, positive estimates of ERR per Gy were obtained for stomach, colon, rectum, pancreas, peritoneum, larynx, lung, pleura/mesothelioma, bone and connective tissue, skin, prostate, testis, bladder, kidney, thyroid, and residual cancers; negative estimates of ERR per Gy were found cancers of oral cavity and pharynx, esophagus, and ovary. A hierarchical model stabilized site-specific estimates of association, including for lung (ERR per Gy=0.65; 95% credible interval [CrI]: 0.24, 1.07), prostate (ERR per Gy=0.44; 95% CrI: -0.06, 0.91), and colon cancer (ERR per Gy=0.53; 95% CrI: -0.07, 1.11). The results contribute evidence regarding associations between low dose radiation and cancer.

Experimental evolution of extremophile resistance to ionizing radiation.

A growing number of known species possess a remarkable characteristic - extreme resistance to the effects of ionizing radiation (IR). This review examines our current understanding of how organisms can adapt to and survive exposure to IR, one of the most toxic stressors known. The study of natural extremophiles such as Deinococcus radiodurans has revealed much. However, the evolution of Deinococcus was not driven by IR. Another approach, pioneered by Evelyn Witkin in 1946, is to utilize experimental evolution. Contributions to the IR-resistance phenotype affect multiple aspects of cell physiology, including DNA repair, removal of reactive oxygen species, the structure and packaging of DNA and the cell itself, and repair of iron-sulfur centers. Based on progress to date, we overview the diversity of mechanisms that can contribute to biological IR resistance arising as a result of either natural or experimental evolution.

Quantitative morphological analysis of Deinococcus radiodurans elucidates complex dose-dependent nucleoid condensation during recovery from ionizing radiation.

The extremophile Deinococcus radiodurans maintains a highly organized and condensed nucleoid as its default state, possibly contributing to its high tolerance to ionizing radiation (IR). Previous studies of the D. radiodurans nucleoid were limited by reliance on manual image annotation and qualitative metrics. Here, we introduce a high-throughput approach to quantify the geometric properties of cells and nucleoids using confocal microscopy, digital reconstructions of cells, and computational modeling. We utilize this novel approach to investigate the dynamic process of nucleoid condensation in response to IR stress. Our quantitative analysis reveals that at the population level, exposure to IR induced nucleoid compaction and decreased the size of D. radiodurans cells. Morphological analysis and clustering identified six distinct sub-populations across all tested experimental conditions. Results indicate that exposure to IR induced fractional redistributions of cells across sub-populations to exhibit morphologies associated with greater nucleoid condensation and decreased the abundance of sub-populations associated with cell division. Nucleoid-associated proteins (NAPs) may link nucleoid compaction and stress tolerance, but their roles in regulating compaction in D. radiodurans are unknown. Imaging of genomic mutants of known and suspected NAPs that contribute to nucleoid condensation found that deletion of nucleic acid-binding proteins, not previously described as NAPs, can remodel the nucleoid by driving condensation or decondensation in the absence of stress and that IR increased the abundance of these morphological states. Thus, our integrated analysis introduces a new methodology for studying environmental influences on bacterial nucleoids and provides an opportunity to further investigate potential regulators of nucleoid condensation.IMPORTANCEDeinococcus radiodurans, an extremophile known for its stress tolerance, constitutively maintains a highly condensed nucleoid. Qualitative studies have described nucleoid behavior under a variety of conditions. However, a lack of quantitative data regarding nucleoid organization and dynamics has limited our understanding of the regulatory mechanisms controlling nucleoid organization in D. radiodurans. Here, we introduce a quantitative approach that enables high-throughput quantitative measurements of subcellular spatial characteristics in bacterial cells. Applying this to wild-type or single-protein-deficient populations of D. radiodurans subjected to ionizing radiation, we identified significant stress-responsive changes in cell shape, nucleoid organization, and morphology. These findings highlight this methodology's adaptability and capacity for quantitatively analyzing the cellular response to stressors for screening cellular proteins involved in bacterial nucleoid organization.

Carbon Dots based Tissue Equivalent Dosimeter as an Ionizing Radiation Sensor.

This work explores the potential of carbon dots as a fluorescent probe in the determination of heavy ions and as an electrochemical biosensor. It also discusses how carbon dots can be introduced into the Fricke solution to potentially serve as an ionizing radiation sensor. The study presents a novel tissue equivalent dosimeter carbon dots-based as an ionizing radiation sensor. The methodology for the synthesis of Nitrogen-doped Carbon Dots N-CDs and the characterization of the material are described. The results show that the N-CDs have a high sensitivity to ionizing radiation and can be used as a dosimeter for radiation detection. The study also discusses the limitations and challenges of using carbon dots as a dosimeter for ionizing radiation. Overall, this study provides valuable insights into the potential applications of carbon dots in different fields and highlights the importance of further research in this area.

Low-dose ionizing radiation promotes motor recovery and brain rewiring by resolving inflammatory response after brain injury and stroke.

Traumatic brain injury (TBI) and stroke share a common pathophysiology that worsens over time due to secondary tissue injury caused by sustained inflammatory response. However, studies on pharmacological interventions targeting the complex secondary injury cascade have failed to show efficacy. Here, we demonstrated that low-dose ionizing radiation (LDIR) reduced lesion size and reversed motor deficits after TBI and photothrombotic stroke. Magnetic resonance imaging demonstrated significant reduction of infarct volume in LDIR-treated mice after stroke. Systems-level transcriptomic analysis showed that genes upregulated in LDIR-treated stoke mice were enriched in pathways associated with inflammatory and immune response involving microglia. LDIR induced upregulation of anti-inflammatory- and phagocytosis-related genes, and downregulation of key pro-inflammatory cytokine production. These findings were validated by live-cell assays, in which microglia exhibited higher chemotactic and phagocytic capacities after LDIR. We observed substantial microglial clustering at the injury site, glial scar clearance and reversal of motor deficits after stroke. Cortical microglia/macrophages depletion completely abolished the beneficial effect of LDIR on motor function recovery in stroke mice. LDIR promoted axonal projections (brain rewiring) in motor cortex and recovery of brain activity detected by electroencephalography recordings months after stroke. LDIR treatment delayed by 8 h post-injury still maintained full therapeutic effects on motor recovery, indicating that LDIR is a promising therapeutic strategy for TBI and stroke.

Megakaryocytic IGF1 coordinates activation and ferroptosis to safeguard hematopoietic stem cell regeneration after radiation injury.

BACKGROUND: Hematopoietic stem cell (HSC) regeneration underlies hematopoietic recovery from myelosuppression, which is a life-threatening side effect of cytotoxicity. HSC niche is profoundly disrupted after myelosuppressive injury, while if and how the niche is reshaped and regulates HSC regeneration are poorly understood. METHODS: A mouse model of radiation injury-induced myelosuppression was built by exposing mice to a sublethal dose of ionizing radiation. The dynamic changes in the number, distribution and functionality of HSCs and megakaryocytes were determined by flow cytometry, immunofluorescence, colony assay and bone marrow transplantation, in combination with transcriptomic analysis. The communication between HSCs and megakaryocytes was determined using a coculture system and adoptive transfer. The signaling mechanism was investigated both in vivo and in vitro, and was consolidated using megakaryocyte-specific knockout mice and transgenic mice. RESULTS: Megakaryocytes become a predominant component of HSC niche and localize closer to HSCs after radiation injury. Meanwhile, transient insulin-like growth factor 1 (IGF1) hypersecretion is predominantly provoked in megakaryocytes after radiation injury, whereas HSCs regenerate paralleling megakaryocytic IGF1 hypersecretion. Mechanistically, HSCs are particularly susceptible to megakaryocytic IGF1 hypersecretion, and mTOR downstream of IGF1 signaling not only promotes activation including proliferation and mitochondrial oxidative metabolism of HSCs, but also inhibits ferritinophagy to restrict HSC ferroptosis. Consequently, the delicate coordination between proliferation, mitochondrial oxidative metabolism and ferroptosis ensures functional HSC expansion after radiation injury. Importantly, punctual IGF1 administration simultaneously promotes HSC regeneration and hematopoietic recovery after radiation injury, representing a superior therapeutic approach for myelosuppression. CONCLUSIONS: Our study identifies megakaryocytes as a last line of defense against myelosuppressive injury and megakaryocytic IGF1 as a novel niche signal safeguarding HSC regeneration.

Indole-3-carboxaldehyde ameliorates ionizing radiation-induced hematopoietic injury by enhancing hematopoietic stem and progenitor cell quiescence.

Indole-3-carboxaldehyde (I3A), one of tryptophan metabolites derived from gut microbiota, extends the lifespan of mice after high-dose ionizing radiation exposure. Persistent myelosuppression is the most common and fatal complication for victims of nuclear accidents and patients undergoing radiotherapy, with few therapeutic options available. However, whether and how I3A protects ionizing radiation-induced hematopoietic toxicity remain unknown. In this study, we demonstrated that I3A treatment effectively ameliorated radiation-induced hematopoietic injury through accelerating peripheral blood cells recovery, promoting bone marrow cellularity restoration and enhancing functional HSPC regeneration. Additionally, I3A also suppressed intracellular reactive oxygen species production and inhibited apoptosis in irradiated HSPCs. Mechanistically, I3A treatment significantly increased HSPC quiescence, thus conferring HSPCs with resistance against radiation injury. Finally, I3A treatment could improve survival of lethally irradiated mice. Taken together, our data suggest that I3A acts as a gut microbiota-derived paracrine factor that regulates HSPC regeneration and may serve as a promising therapeutic agent for ionizing radiation-induced myelosuppression.

Recurrent medical imaging exposures for the care of patients: one way forward.

Medical imaging is both valuable and essential in the care of patients. Much of this imaging depends on ionizing radiation with attendant responsibilities for judicious use when performing an examination. This responsibility applies in settings of both individual as well as multiple (recurrent) imaging with associated repeated radiation exposures. In addressing the roles and responsibilities of the medical communities in the paradigm of recurrent imaging, both the International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) have issued position statements, each affirmed by other organizations. The apparent difference in focus and approach has resulted in a lack of clarity and continued debate. Aiming towards a coherent approach in dealing with radiation exposure in recurrent imaging, the IAEA convened a panel of experts, the purpose of which was to identify common ground and reconcile divergent perspectives. The effort has led to clarifying recommendations for radiation exposure aspects of recurrent imaging, including the relevance of patient agency and the provider-patient covenant in clinical decision-making. CLINICAL RELEVANCE STATEMENT: An increasing awareness, generating some lack of clarity and divergence in perspectives, with patients receiving relatively high radiation doses (e.g., ≥ 100 mSv) from recurrent imaging warrants a multi-stakeholder accord for the benefit of patients, providers, and the imaging community. KEY POINTS: • Recurrent medical imaging can result in an accumulation of exposures which exceeds 100 milli Sieverts. • Professional organizations have different perspectives on roles and responsibilities for recurrent imaging. • An expert panel reconciles differing perspectives for addressing radiation exposure from recurrent medical imaging.

The potential longevity-promoting hypoxic-hypercapnic environment as a measure for radioprotection.

Many biological mechanisms of aging well converge with radiation's biological effects. We used scientific insights from the field of aging to establish a novel hypoxic-hypercapnic environment (HHE) concept for radioprotection. According to this concept, HHE which possesses an anti-aging and longevity-promoting potential, should also act as a radiomitigator and radioprotector. As such, it might contribute greatly to the safety and wellbeing of individuals exposed to high levels of radiation, whether in planned events (e.g. astronauts) or in unplanned events (e.g. first responders in nuclear accidents).

Radiation exposure during sacral neuromodulation lead placement: Multi-institutional descriptive study.

OBJECTIVES: Fluoroscopy has significantly improved lead placement and decreased surgical time for implantable sacral neuromodulation (SNM). There is a paucity of data regarding radiation and safety of fluoroscopy during SNM procedures. Our study aims to characterize fluoroscopy time and dose used during SNM surgery across multiple institutions and assess for predictors of increased fluoroscopy time and radiation dose. METHODS: Electronic medical records were queried for SNM procedures (Stage 1 and full implant) from 2016 to 2021 at four academic institutions. Demographic, clinical, and intraoperative data were collected, including fluoroscopy time and radiation dose in milligray (mGy). The data were entered into a centralized REDCap database. Univariate and multivariate analysis were performed to assess for predictive factors using STATA/BE 17.0. RESULTS: A total of 664 procedures were performed across four institutions. Of these, 363 (54.6%) procedures had complete fluoroscopy details recorded. Mean surgical time was 58.8 min. Of all procedures, 79.6% were performed by Female Pelvic Medicine and Reconstructive Surgery specialists. There was significant variability in fluoroscopy time and dose based on surgical specialty and institution. Most surgeons (76.4%) were considered "low volume" implanters. In a multivariate analysis, bilateral finder needle testing, surgical indication, surgeon volume, and institution significantly predicted increased fluoroscopy time and radiation dose (p < 0.05). CONCLUSIONS: There is significant variability in fluoroscopy time and radiation dose utilized during SNM procedures, with differences across institutions, surgeons, and subspecialties. Increased radiation exposure can have harmful impacts on the surgical team and patient. These findings demonstrate the need for standardized fluoroscopy use during SNM procedures.