Impact of Procedural-Imaging Configurations on Radiation Dose During Endovascular Flow Diverter Treatment for Intracranial Aneurysms: A Comparison Between Hybrid Operating Room and Neuroangiography Suite

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript can be accepted after the authors correct the following comments:

 

Major comments:

 

1. There is a major discrepancy between the abstract and the results/table regarding total DAP in the neuroangiography suite. The abstract reports 299.1 vs. 196.3 Gy·cm², whereas the Results section and Table 2 report 299.1 vs. 96.3 Gy·cm². This should be corrected throughout the manuscript.

 

 

2. The manuscript concludes that the higher total radiation dose in the HOR is due to the “essential use” or “reliance” on rotational angiography. However, the number of 3D rotational angiography acquisitions did not significantly differ between the HOR and NIS groups. The observed difference appears to be driven primarily by the substantially higher dose per 3D acquisition in the HOR environment, rather than by more frequent use of 3D imaging. This interpretation should be revised in the Abstract, Discussion, and Conclusion.

 

3. The study is more accurately comparing two procedural-imaging configurations rather than isolating the effect of “environment” alone. The title, abstract, and discussion should reflect this limitation more precisely.?

 

4. The regression models would benefit from confidence intervals, model fit statistics, and clearer interpretation of coefficients after log transformation.

 

5. In particular, the explanation that higher radiation in posterior circulation and fusiform aneurysms is mainly due to skull-base attenuation and automatic brightness control is plausible, but it was not directly tested in the present study and should be presented more cautiously.

 

6. The authors state that low-dose protocols may reduce exposure, but they should more explicitly connect this literature to the large dose difference observed between the two study environments and discuss whether the HOR protocol could reasonably be modified in that direction.

 

7. In conclusion. given the retrospective single-center design and small HOR sample, the findings are better framed as preliminary institutional benchmark data rather than definitive radiation reference levels.

 

 

Minor comments:

 

1. Replace “Median (5–10 mm)” with “Medium (5–10 mm)” in Table 1.
2. In Table 2, “Acquisition count, n (%)” appears incorrect and should likely be mean (SD).
3. Standardize terminology for the neuroangiography suite throughout the manuscript.
4. Improve Figure 2 readability, especially axis labels and embedded statistics.
5. Revise minor grammatical issues in the Data Availability and Conflict of Interest statements.

Author Response

Major comments:

1. There is a major discrepancy between the abstract and the results/table regarding total DAP in the neuroangiography suite. The abstract reports 299.1 vs. 196.3 Gy·cm², whereas the Results section and Table 2 report 299.1 vs. 96.3 Gy·cm². This should be corrected throughout the manuscript.

Response:  We sincerely apologize for this error in the Abstract. The correct mean total DAP value for the neuroangiography suite (NIS) group is indeed 96.3 Gy.cm², as accurately presented in the Results section and Table 2. We have thoroughly reviewed the entire manuscript and corrected "196.3" to "96.3" in the Abstract to ensure consistency across all sections. Thank you for catching this oversight.

Updated Text (abstract):  "...While the HOR significantly reduced fluoroscopy time (19.3 vs. 26.1 min, P=0.002), it was associated with a higher total DAP compared to the NIS (299.1 vs. 96.3 Gy·cm², P<0.001)

2. The manuscript concludes that the higher total radiation dose in the HOR is due to the “essential use” or “reliance” on rotational angiography. However, the number of 3D rotational angiography acquisitions did not significantly differ between the HOR and NIS groups. The observed difference appears to be driven primarily by the substantially higher dose per 3D acquisition in the HOR environment, rather than by more frequent use of 3D imaging. This interpretation should be revised in the Abstract, Discussion, and Conclusion.

Response: We completely agree with the reviewer’s astute observation. A closer re-examination of our data (Table 2) confirms that the mean number of 3D-RA acquisitions was nearly identical between the HOR and NIS groups (3.0 vs. 2.8, P = 0.38), indicating that the increased cumulative radiation was not driven by a higher frequency or "over-reliance" on 3D imaging in the HOR. Rather, as the reviewer correctly pointed out, the discrepancy stems from a significantly higher radiation dose delivered per individual 3D acquisition within the HOR system architecture.

We have thoroughly revised our interpretation throughout the Abstract, Results, Discussion, and Conclusion sections. The narrative has been shifted away from "procedural reliance on 3D imaging" toward "environment- and system-specific dosimetric differences per acquisition," focusing on technological factors inherent to the HOR.

Updated Text

(abstract):

“…This increase was primarily driven by a substantially higher radiation dose delivered per 3D-RA acquisition in the HOR environment, rather than an increased frequency of 3D imaging. Multivariate analysis confirmed that the surgical-imaging configuration was the dominant factor influencing total radiation exposure, rather than aneurysm complexity or patient characteristics….”

(discussion):

“…Notably, number of 3D-RA acquisitions did not significantly differ between the two groups (3.0 vs. 2.8, P = 0.38). This implies that the cumulative dose discrepancy is primarily driven by a system-inherent factor: a remarkably higher radiation dose per single 3D-RA scan in the HOR system. Several technical and geometric factors may explain this elevated dose per 3D acquisition in the HOR. First, the HOR utilized a single-plane system optimized for combined open-surgical and endovascular workflows, which often involves different automatic brightness control (ABC) baseline algorithms and pulse configurations compared to a dedicated biplane NIS. Second, to clear the surgical table and anesthesia equipment, the gantry geometry and source-to-image distance (SID) in an HOR might be automatically maximized during a rotational cone-beam CT sweep, forcing the X-ray tube to output higher mAs/kVp to maintain image quality through the automatic exposure control. These configuration differences result in a steeper dose delivery per rotation, even when the absolute number of scans remains unchanged….”

(conclusions):
“…We found that despite lower fluoroscopy times, the single-plane HOR incurred higher total radiation doses, driven primarily by a higher system-specific radiation dose output per 3D rotational angiography acquisition…)

 

3. The study is more accurately comparing two procedural-imaging configurations rather than isolating the effect of “environment” alone. The title, abstract, and discussion should reflect this limitation more precisely.?

Response:  We entirely agree with this valuable conceptual refinement. The observed dosimetric variances are indeed a function of the distinct procedural-imaging configurations rather than the physical environment alone.

To reflect this more precisely, we have revised the manuscript as follows:

1、Title: Updated to emphasize "imaging configurations" instead of just the "surgical environment."

2、Abstract & Introduction: Rephrased text to frame the comparison around imaging architectures.

3、Discussion: Added an explicit paragraph addressing this as a structural characteristic and inherent limitation, clarifying that our data reflects the synergistic effect of system geometry, detector type, and room workflow.

Updated Text

(title)

Impact of Procedural-Imaging Configurations on Radiation Dose during Endovascular Flow Diverter Treatment for Intracranial Aneurysms: A Comparison Between Hybrid Operating Room and Neuroangiography Suite

(abstract)

“…This study evaluated the impact of distinct procedural-imaging configurations on patient radiation exposure…”

(discussion)

“…Finally, it is important to clarify that this study compared two holistic procedural-imaging configurations rather than isolating the effect of the physical surgical environment alone. Consequently, the observed dosimetric discrepancies represent the combined impact of system geometry, hardware-specific baseline outputs, and environmental workflows. Future prospective studies utilizing identical imaging systems across different surgical spaces are required to completely isolate the environmental factor….”

 

4. The regression models would benefit from confidence intervals, model fit statistics, and clearer interpretation of coefficients after log transformation.

 

Response:

We thank the reviewer for this excellent methodological recommendation. We have significantly strengthened our statistical reporting in Table 3 by restructuring it to present both univariate and multivariate linear regression models side-by-side, explicitly including 95% Confidence Intervals (CIs) and overall model fit statistics (Model R²).

 Correspondingly, we have updated the Statistical Analysis section to clarify that logarithmic transformation was performed on dependent variables to ensure statistical assumptions were met, and that all clinical, morphological, and device-specific variables (including age, size, type, location, and PED vs. non-PED) were simultaneously controlled within the final multivariate framework. The Results section has also been updated to present these adjusted findings concisely.

Updated Text

(material and method)
“…Univariate and multivariate linear regression analyses were performed to identify independent predictors of radiation dose metrics and fluoroscopy time. Logarithmic transformation was applied to all dependent variables to correct for skewed distributions and ensure normality of residuals. To rigorously control for confounding, the final multivariate models simultaneously incorporated important clinical, morphological, and procedural variables (including age, aneurysm size, type, location, device type [pipeline embolization device vs. non-pipeline embolization device], and imaging configurations). Overall model fit and explanatory power were evaluated using the coefficient of determination (Model R2), and 95% confidence intervals (CIs) were reported for all estimates….)

(result)
“…To identify independent predictors of radiation dose and procedural efficiency, univariate and multivariate linear regression analyses were performed (Table 3). Within the final multivariate framework, the imaging configuration emerged as the single dominant independent predictor; performing procedures in the HOR was independently associated with a higher total DAP and 2D DAP, but shorter fluoroscopy times (all P < 0.05). In contrast, patient characteristics, morphological factors (including age, aneurysm size, type, and location), and device type (pipeline embolization device vs. non-pipeline embolization device) did not significantly influence cumulative radiation exposure. The final multivariate models demonstrated strong explanatory power for total DAP (Model R2 = 0.5795, P < 0.0001)….”

(Table 3) 

5. In particular, the explanation that higher radiation in posterior circulation and fusiform aneurysms is mainly due to skull-base attenuation and automatic brightness control is plausible, but it was not directly tested in the present study and should be presented more cautiously.

Response: > We completely agree with the reviewer’s excellent point. While the physical mechanism of automatic brightness control (ABC) and skull-base bone attenuation is highly plausible, we acknowledge that these parameters were not directly tested in our current retrospective clinical data.

Accordingly, we have revised the corresponding paragraph in the Discussion section to soften our tone. We have removed causal statements and reframed this section as a cautious, literature-supported hypothesis regarding potential anatomical and systems-level contributors to the observed dosimetric trends.

Updated Text

(discussion)

“…Instead, these subtle dosimetric trends may be partially explained by regional anatomical characteristics rather than increased procedural difficulty, given that fluoroscopy times for these cases remained notably shorter. Speculatively, the higher radiopacity of skull-base structures—such as the clivus and petrous bone—is hypothesized to cause greater X-ray attenuation during posterior circulation imaging. This could potentially prompt the system’s automatic brightness control (ABC) algorithm to baseline at a higher tube voltage or current to preserve image quality. Although the lack of intraoperative tube-parameter logging limits our ability to directly test this mechanism, such system-driven adjustments in anatomically dense regions represent a plausible contributing factor. Advanced filtration or customized low-dose baselines may help mitigate these potential anatomical variances, though further investigation in larger cohorts is needed to confirm these technical mechanisms….”

6. The authors state that low-dose protocols may reduce exposure, but they should more explicitly connect this literature to the large dose difference observed between the two study environments and discuss whether the HOR protocol could reasonably be modified in that direction.

Response:  We deeply appreciate the reviewer’s prompt for a more realistic and actionable discussion on protocol modification. We have expanded the Discussion to disclose a critical institutional and operational variance that directly explains the 3-fold dose discrepancy and dictates the feasibility of future modifications.

In our institution, the biplane NIS is a dedicated neuroradiology suite. During its initial installation, our radiological team underwent a user-specific optimization process, tailoring the baseline imaging curves to the lowest acceptable radiation threshold for neuro-interventional workloads. Conversely, the HOR is a shared, multidisciplinary facility utilized by various surgical subspecialties (e.g., cardiovascular, thoracic, neurosurgical specialists). To accommodate the diverse imaging habits and visualization requirements of different surgical teams without disrupting individual workflows, the HOR system was left at its pre-configured factory default standard-dose settings.

While modifying the HOR protocols toward lower-dose settings is conceptually feasible and highly recommended, the shared nature of the suite presents a pragmatic barrier, as any systemic alteration must maintain consensus across multiple surgical disciplines. We have integrated this essential real-world constraint into the revised Discussion, providing a more balanced and impactful perspective on radiation governance in hybrid environments.

Updated Text

(discussion)

Our study demonstrated that the biplane NIS achieved notably lower radiation doses, which can be directly elucidated by the distinct operational governance and protocol optimization between the two environments. In our institution, the biplane NIS functions as a dedicated neuroradiology-specific suite. During its initial installation, our radiological team actively optimized the system parameters to the lowest radiation thresholds acceptable to the primary operators. Literature confirms that such tailored refinements—including reducing pulse rates and enhancing spectral filtration—can lower cumulative exposure by 20%–43% [12, 18, 19] . In contrast, the robotic HOR operates as a shared, multidisciplinary facility utilized by multiple surgical disciplines. To accommodate the heterogeneous visualization habits of various surgical teams without disrupting cross-departmental workflows, the HOR system predominantly relies on standard factory-default settings. Consequently, while modifying the HOR imaging protocols toward a low-dose direction is technically straightforward via system recalibration, its implementation in real-world practice faces pragmatic institutional constraints. Collaborative, multi-specialty radiation governance is required to modify shared HOR baselines safely, ensuring that dose-reduction strategies do not compromise the stringent visualization demands across different surgical portfolios [20, 8]. 

7. In conclusion. given the retrospective single-center design and small HOR sample, the findings are better framed as preliminary institutional benchmark data rather than definitive radiation reference levels.

 

Response:  We entirely agree with this judicious assessment. Given the inherent constraints of our single-center retrospective design and the modest size of the HOR cohort, we have softened our wording across the Abstract, Discussion, and Conclusion sections.

We have removed claims regarding the establishment of definitive diagnostic reference levels (DRLs) and have re-framed our findings more appropriately as preliminary institutional benchmark data. These metrics are now presented as a foundational local baseline intended to guide internal quality improvement and spark broader multi-center investigations.

 

(abstract)

These findings serve as preliminary institutional benchmark data, underscoring the need for adaptive radiation management and configuration-specific protocols to optimize patient safety across diverse surgical-imaging suites.

 

(discussion)

“…This disparity underscores the critical role of imaging configurations. However, given our single-center retrospective design and the modest HOR cohort size, these findings should not be interpreted as definitive reference levels. Instead, they provide valuable preliminary institutional benchmark data that can serve as a localized reference for dose monitoring and guide future multi-center registry studies aimed at defining standardized benchmarks….”

“…This study systematically evaluated radiation exposure associated with FD procedures in different clinical environments, offering critical preliminary institutional benchmark data regarding the transition to robotic hybrid suites….”

 

Minor comments:

1. Replace “Median (5–10 mm)” with “Medium (5–10 mm)” in Table 1.

Response: We thank the reviewer for catching this typographical error. We have corrected "Median" to "Medium" in Table 1 to accurately reflect the aneurysm size categories.

 

2. In Table 2, “Acquisition count, n (%)” appears incorrect and should likely be mean (SD).

Response: > We agree with the reviewer's observation. This label was a formatting oversight. We have corrected the label in Table 2 from “Acquisition count, n (%)” to “Acquisition count, mean (SD)” to accurately reflect the continuous numerical data presented in those rows.

 

3. Standardize terminology for the neuroangiography suite throughout the manuscript.

Response:  We thank the reviewer for this formatting correction. We have standardized the terminology for the conventional angiography environment to "neuroangiography suite" (abbreviated as "NIS") throughout the entire manuscript (including the title, abstract, text, and table labels) to ensure absolute consistency and clarity.

4. Improve Figure 2 readability, especially axis labels and embedded statistics.

 

Response: > We highly appreciate the reviewer's practical suggestions regarding the visual clarity of our figures. We have completely revised and reconstructed Figure 2 to drastically maximize its readability.

(Figure 2, new)

5. Revise minor grammatical issues in the Data Availability and Conflict of Interest statements.

 

Response: > We thank the reviewer for this meticulous grammatical check. We have corrected the minor linguistic errors in both statements to comply with standard academic phrasing. Specifically, the missing copula verb "are" has been inserted into the Data Availability statement, and the headings have been converted to their standard singular forms.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

This manuscript investigates the impact of different surgical environments on radiation exposure during flow diverter treatment for intracranial aneurysms, comparing a hybrid operating room with a conventional biplane neuroangiography suite. The topic is clinically relevant and the study provides useful preliminary data regarding radiation management in modern neurointerventional settings. However, several important methodological and interpretative issues need to be addressed before the manuscript can be reconsidered for publication. Attached find the revisions that must be done before reconsidering the paper for publication.

1. The manuscript would benefit from a clearer explanation of why HOR imaging protocols were not optimized to low-dose settings comparable to the NIS.
   This point is central to the interpretation of the higher DAP observed in the HOR group.
2. Please clarify the apparent discrepancy in the Results section regarding total DAP values.
   The Abstract reports a mean NIS DAP of 196.3 Gy·cm², while Table 2 reports 96.3 Gy·cm².
3. The authors should better explain the rationale for the significantly higher use of the Surpass Evolve device in the HOR cohort.
   This imbalance may represent a confounding factor influencing radiation exposure and procedural workflow.
4. The statistical analysis would be strengthened by including device type in the multivariate regression models.
   Different flow diverters may require different deployment strategies and imaging needs.
5. The Discussion section is overly repetitive regarding the contribution of rotational angiography to total radiation exposure.
   Several paragraphs reiterate the same concept and could be condensed for improved readability.
6. The manuscript lacks detailed information about image quality assessment between the two environments.
   Higher radiation doses should ideally be correlated with objective or subjective improvements in procedural visualization.
7. Please specify whether procedural complexity differed between groups beyond aneurysm morphology and size.
   Factors such as vessel tortuosity or difficult navigation may have influenced fluoroscopy and 3D imaging usage.
8. The authors should discuss whether operator learning curve or temporal bias may have influenced the results.
   Since procedures span 2020–2024, changes in experience and workflow optimization may affect radiation metrics.
9. The study would benefit from a more detailed comparison with recent literature on radiation optimization in neurointervention.
   In particular, please consider citing “The T-Top Technique for Tandem Lesions: A Single-Center Retrospective Study.” J. Clin. Med. 2025, 14, 2945. https://doi.org/10.3390/jcm14092945.
10. The limitations section should more explicitly acknowledge the absence of operator radiation exposure measurements.
    This is particularly relevant when comparing hybrid operating rooms with conventional neuroangiography suites.
11. Figure 2 could be improved by adding clearer labels and reporting median or percentile markers within the histogram.
    This would facilitate interpretation of dose distribution differences between environments.
12. The manuscript would benefit from minor English language revision to improve conciseness and reduce redundancy.
    Several sentences in the Discussion are excessively long and could be simplified for clarity.

Comments on the Quality of English Language

Minor grammar editing is needed

Author Response

1. The manuscript would benefit from a clearer explanation of why HOR imaging protocols were not optimized to low-dose settings comparable to the NIS.
   This point is central to the interpretation of the higher DAP observed in the HOR group.

Response:

 We thank the reviewer for this crucial and insightful comment. We entirely agree that elucidating the operational and institutional reasons behind the unoptimized HOR protocols is central to interpreting the dosimetric discrepancies. 

 

As suggested, we have revised the Discussion section to explicitly address the distinct operational governance, system customization history, and pragmatic institutional constraints that prevent immediate low-dose calibration in our shared HOR. Specifically, while our biplane NIS functions as a dedicated neuro-specific suite that has been actively optimized over time by our radiological team, the HOR operates as a shared, multidisciplinary facility utilized by multiple surgical disciplines. Maintaining standard factory-default settings in the HOR is currently required to facilitate cross-departmental workflows without compromising the heterogeneous visualization needs of different surgical teams.

 

Updated Text

(discussion)

“Our study demonstrated that the biplane NIS achieved notably lower radiation doses, which can be directly elucidated by the distinct operational governance and protocol optimization between the two environments. In our institution, the biplane NIS functions as a dedicated neuroradiology-specific suite. During its initial installation, our radiological team actively optimized the system parameters to the lowest radiation thresholds acceptable to the primary operators. Literature confirms that such tailored refinements—including reducing pulse rates and enhancing spectral filtration—can lower cumulative exposure by 20%–43% [12, 18, 19] . In contrast, the robotic HOR operates as a shared, multidisciplinary facility utilized by multiple surgical disciplines. To accommodate the heterogeneous visualization habits of various surgical teams without disrupting cross-departmental workflows, the HOR system predominantly relies on standard factory-default settings. Consequently, while modifying the HOR imaging protocols toward a low-dose direction is technically straightforward via system recalibration, its implementation in real-world practice faces pragmatic institutional constraints. Collaborative, multi-specialty radiation governance is required to modify shared HOR baselines safely, ensuring that dose-reduction strategies do not compromise the stringent visualization demands across different surgical portfolios [20, 8].  “

 

2. Please clarify the apparent discrepancy in the Results section regarding total DAP values.
   The Abstract reports a mean NIS DAP of 196.3 Gy·cm², while Table 2 reports 96.3 Gy·cm².

Response: We sincerely apologize for this typographical error in the Abstract. As noted by the reviewer, the correct mean total DAP value for the neuroangiography suite (NIS) group is 96.3 Gy.cm², which was accurately presented in the Results section and Table 2.  We have thoroughly reviewed the entire manuscript and corrected "196.3" to "96.3" in the Abstract to ensure strict consistency across all sections. Thank you for catching this oversight. 

 

Updated Text (abstract):  "...While the HOR significantly reduced fluoroscopy time (19.3 vs. 26.1 min, P=0.002), it was associated with a higher total DAP compared to the NIS (299.1 vs. 96.3 Gy·cm², P<0.001)

 

3. The authors should better explain the rationale for the significantly higher use of the Surpass Evolve device in the HOR cohort.
   This imbalance may represent a confounding factor influencing radiation exposure and procedural workflow.

Response: We thank the reviewer for pointing out this baseline imbalance, which is an important operational detail. From a clinical and logistical standpoint, the higher utilization of the Surpass Evolve device in the HOR cohort was not driven by aneurysm complexity or procedural difficulty. Rather, it was a reflection of institutional differences in device stock management between the two suites during the study period, where the HOR maintained a more comprehensive consignment inventory for this specific device. In terms of technical deployment, there was no meaningful difference in procedural difficulty or navigation workflow between the devices. However, to rigorously address the reviewer's concern regarding potential confounding, we updated our statistical analysis by incorporating device type as a covariate (categorized as Pipeline Embolization Device [PED] vs. non-PED, given that PED constituted the majority of the remaining cases) into both the univariate and multivariate linear regression models (Table 3).  As shown in the updated Table 3, the regression analysis demonstrated that device type was not an independent predictor for total DAP (P = 0.1586), fluoroscopy time (P = 0.7482), or 2D-DSA DAP (P = 0.2375). Conversely, the procedural-imaging configuration (Hybrid OR vs. NIS) remained the dominant and highly significant independent factor across all models (all P < 0.01).  These findings have been integrated into the revised Materials and Methods , Results , and Table 3  to ensure transparency and statistical rigor.

 

Updated Text

(material and method)
“…Univariate and multivariate linear regression analyses were performed to identify independent predictors of radiation dose metrics and fluoroscopy time. Logarithmic transformation was applied to all dependent variables to correct for skewed distributions and ensure normality of residuals. To rigorously control for confounding, the final multivariate models simultaneously incorporated important clinical, morphological, and procedural variables (including age, aneurysm size, type, location, device type [pipeline embolization device vs. non-pipeline embolization device], and imaging configurations). Overall model fit and explanatory power were evaluated using the coefficient of determination (Model R2), and 95% confidence intervals (CIs) were reported for all estimates….)

(result)
“…To identify independent predictors of radiation dose and procedural efficiency, univariate and multivariate linear regression analyses were performed (Table 3). Within the final multivariate framework, the imaging configuration emerged as the single dominant independent predictor; performing procedures in the HOR was independently associated with a higher total DAP and 2D DAP, but shorter fluoroscopy times (all P < 0.05). In contrast, patient characteristics, morphological factors (including age, aneurysm size, type, and location), and device type (pipeline embolization device vs. non-pipeline embolization device) did not significantly influence cumulative radiation exposure. The final multivariate models demonstrated strong explanatory power for total DAP (Model R2 = 0.5795, P < 0.0001)….”

(Table 3)

Abbreviations: β, regression coefficient; SE, standard error; CI, confidence interval; DAP, dose area product; NIS, neuroangiography suite; Hybrid OR, hybrid operating room; PED, Pipeline Embolization Device.

 

4. The statistical analysis would be strengthened by including device type in the multivariate regression models.
   Different flow diverters may require different deployment strategies and imaging needs.

Response: We completely agree with the reviewer’s excellent methodological recommendation. As detailed in our response to Question 3, we have updated our linear regression analyses (Table 3) by incorporating device type (Pipeline Embolization Device [PED] vs. non-PED) as a covariate in both the univariate and multivariate frameworks.  Consistent with the reviewer's note regarding potential variations in imaging needs, this adjustment ensures our findings are fully controlled for any device-specific confounding. The updated statistical results are now transparently presented in Table 3 and described in the Results section.

Updated Text

(material and method)
“…Univariate and multivariate linear regression analyses were performed to identify independent predictors of radiation dose metrics and fluoroscopy time. Logarithmic transformation was applied to all dependent variables to correct for skewed distributions and ensure normality of residuals. To rigorously control for confounding, the final multivariate models simultaneously incorporated important clinical, morphological, and procedural variables (including age, aneurysm size, type, location, device type [pipeline embolization device vs. non-pipeline embolization device], and imaging configurations). Overall model fit and explanatory power were evaluated using the coefficient of determination (Model R2), and 95% confidence intervals (CIs) were reported for all estimates….)

(result)
“…To identify independent predictors of radiation dose and procedural efficiency, univariate and multivariate linear regression analyses were performed (Table 3). Within the final multivariate framework, the imaging configuration emerged as the single dominant independent predictor; performing procedures in the HOR was independently associated with a higher total DAP and 2D DAP, but shorter fluoroscopy times (all P < 0.05). In contrast, patient characteristics, morphological factors (including age, aneurysm size, type, and location), and device type (pipeline embolization device vs. non-pipeline embolization device) did not significantly influence cumulative radiation exposure. The final multivariate models demonstrated strong explanatory power for total DAP (Model R2 = 0.5795, P < 0.0001)….”

(Table 3)

Abbreviations: β, regression coefficient; SE, standard error; CI, confidence interval; DAP, dose area product; NIS, neuroangiography suite; Hybrid OR, hybrid operating room; PED, Pipeline Embolization Device.

5. The Discussion section is overly repetitive regarding the contribution of rotational angiography to total radiation exposure.
   Several paragraphs reiterate the same concept and could be condensed for improved readability.

Response: We entirely agree with the reviewer and the other reviewers' insightful comments regarding this section. In the previous version, our discussion on rotational angiography was indeed repetitive and over-emphasized "procedural reliance." In light of these comments, we have thoroughly rewritten this entire section to focus strictly on factual, system-inherent parameters rather than usage frequency. We deleted all redundant paragraphs discussing the "necessity of use" or "reliance" on 3D imaging, given that the statistical evidence shows no significant difference in the absolute number of 3D-RA acquisitions between the two environments (3.0 vs. 2.8, P = 0.38).  Instead, we consolidated the findings into a single, high-density paragraph that seamlessly transitions from our dosimetric observations (80.1% vs. 47.2% dose contribution) directly into the plausible technical and geometric explanations (such as automatic brightness control baseline differences and maximized source-to-image distance under automatic exposure control). We believe this drastic condensation significantly improves the readability, focus, and scholarly rigor of the manuscript.

 

Updated Text

(discussion)

“Rotational angiography was identified as a major contributor to radiation exposure in this study, accounting for 80.1% of the total radiation exposure in the HOR compared to 47.2% in the neuroangiography suite. This difference highlights the disproportionate impact of rotational angiography on overall exposure, particularly within HOR environments. Although fluoroscopy time was notably shorter in the HOR, this reduction did not compensate for the higher total radiation dose, which was predominantly driven by the increased average doses associated with rotational angiography. Notably, number of 3D-RA acquisitions did not significantly differ between the two groups (3.0 vs. 2.8, P = 0.38). This implies that the cumulative dose discrepancy is primarily driven by a system-inherent factor: a remarkably higher radiation dose per single 3D-RA scan in the HOR system. Several technical and geometric factors may explain this elevated dose per 3D acquisition in the HOR. First, the HOR utilized a single-plane system optimized for combined open-surgical and endovascular workflows, which often involves different automatic brightness control (ABC) baseline algorithms and pulse configurations compared to a dedicated biplane NIS. Second, to clear the surgical table and anesthesia equipment, the gantry geometry and source-to-image distance (SID) in an HOR might be automatically maximized during a rotational cone-beam CT sweep, forcing the X-ray tube to output higher mAs/kVp to maintain image quality through the automatic exposure control. These configuration differences result in a steeper dose delivery per rotation, even when the absolute number of scans remains unchanged.  Future research should continue to explore imaging strategies that maintain these rigorous safety standards while reducing the overall reliance on high-dose techniques, thereby enhancing both patient and operator safety in complex neurointerventional procedures.”

 

6. The manuscript lacks detailed information about image quality assessment between the two environments.
   Higher radiation doses should ideally be correlated with objective or subjective improvements in procedural visualization.

 

Response: We acknowledge the reviewer’s comment regarding the correlation between radiation dose and image quality. Because this study was retrospective in nature and relied on real-world clinical registries, standardized objective image quality assessments (such as signal-to-noise or contrast-to-noise ratios) or prospective subjective visual grading scales were not routinely recorded and thus could not be analyzed. We have explicitly acknowledged this as a study limitation.

However, to provide a clinically relevant context for the higher DAP observed in the HOR group, we would like to reiterate that the higher dose delivery was primarily driven by different institutional imaging configurations and operational governance between the two environments, rather than a clinical need for superior visualization in specific cases. While we cannot quantitatively correlate the dose with image quality, the high technical success rate and the absence of periprocedural neurological complications in both groups demonstrate that the visualization provided by both configurations was fully sufficient to achieve safe and successful endovascular navigation and device deployment. The higher baseline output in the HOR reflects a standardized factory default designed to safely satisfy diverse surgical disciplines, rather than an operator-driven adjustment for enhanced image quality.

Updated Text

(discussion)

“…Fourth, due to the retrospective nature of this study, objective or subjective image quality assessments were not performed. Consequently, we could not directly evaluate whether the higher radiation dose in the HOR translated into superior procedural visualization, though the technical success rate was identical between the two environments….”

 

7. Please specify whether procedural complexity differed between groups beyond aneurysm morphology and size.
   Factors such as vessel tortuosity or difficult navigation may have influenced fluoroscopy and 3D imaging usage.

 

Response: We thank the reviewer for highlighting the potential impact of anatomical complexity, such as vessel tortuosity and navigation difficulty, on radiation metrics. We agree that these unmeasured factors can theoretically influence fluoroscopy time and the utilization of 3D imaging.

 

While we did not routinely quantify or grade individual vessel tortuosity angles in our retrospective registry, we believe that our study design and clinical context effectively minimized the impact of extreme procedural complexity across both cohorts through the following measures:

 

First, as noted in our Limitations section, this study strictly focused on small-to-medium, uncomplicated aneurysms. By excluding giant, wide-necked, or highly irregular aneurysms that typically require advanced scaffolding or prolonged microcatheter manipulation, we minimized baseline procedural complexity. Second, the study period was intentionally selected to cover cases performed exclusively after the introduction of the newer-generation Pipeline Flex Embolization Device. This device significantly enhanced deployment and tracking compared to the early-generation Pipeline Classic, drastically reducing the technical challenges associated with difficult vascular anatomy. Third, our neurointerventional team has routinely performed flow diverter treatments since 2016. By the start of this study's cohort period (2020), the operators had already surpassed the steep learning curve, ensuring highly stable and consistent navigation techniques across both the HOR and NIS environments.

 

To maintain full transparency, we have explicitly addressed the lack of anatomical grading (such as vessel tortuosity) as an extended part of our study's limitations in the revised manuscript

 

Updated Text

(discussion)

“…Third, the focus on small-to-medium, uncomplicated aneurysms allowed for a controlled analysis but did not fully capture the complexities of routine clinical practice, where larger or more morphologically complex aneurysms may necessitate higher radiation doses. Additionally, specific anatomical variations, such as extreme vessel tortuosity or challenging proximal catheter navigation, were not quantitatively graded or included in the regression models. However, because all procedures within the study period were performed exclusively using the lower-profile Pipeline Flex system or other modern devices, technical challenges related to device navigation were inherently minimized compared to early-generation devices…”

 

8. The authors should discuss whether operator learning curve or temporal bias may have influenced the results.
   Since procedures span 2020–2024, changes in experience and workflow optimization may affect radiation metrics.

 

Response: We thank the reviewer for raising this important point regarding potential temporal bias and the operator learning curve over the 4.5-year study period.

 

While evaluating the learning curve was not a primary objective of this study, we deliberately utilized a study design that minimized the impact of chronological changes in operator proficiency. Specifically, our institutional team had routinely performed flow diverter treatments since 2016, accumulating an institutional volume of over 150 successful cases between 2016 and 2020. Consequently, by the time the inclusion period for this study commenced in 2020, the operators had already surpassed the steep phase of the learning curve and reached a highly stable plateau of technical proficiency. This baseline expertise minimized technical and workflow variations across the 2020–2024 period.

 

Nonetheless, we agree that operator experience and institutional workflow optimization are critical factors that must be considered when attempting to externalize our findings. We have expanded our discussion on this point and explicitly integrated it into the revised Limitations to caution readers regarding the generalizability of our results to centers with different experience profiles.

 

Updated text

(discussion)

“…Second, the study was conducted at a single center with a consistent operator team. Although temporal bias or chronological variations in operator proficiency could potentially influence radiation and fluoroscopy metrics, our institutional team had already accumulated a high volume of experience prior to the study's inclusion period. Therefore, while individual learning curves were not explicitly modeled, technical proficiency remained stable throughout the study period, though caution should still be exercised when generalizing these single-center findings to institutions with differing operator experience profiles….”

 

9. The study would benefit from a more detailed comparison with recent literature on radiation optimization in neurointervention.
   In particular, please consider citing “The T-Top Technique for Tandem Lesions: A Single-Center Retrospective Study.” J. Clin. Med. 2025, 14, 2945. https://doi.org/10.3390/jcm14092945.

 

Response: We sincerely thank the reviewer for recommending this recent literature. We agree that contextualizing our single-center experience within the broader, evolving landscape of neurointerventional safety and workflow optimization enhances the discussion.

 

Although the referenced study by Romano et al. primarily focuses on ischemic tandem lesions and mechanical thrombectomy (EVT) techniques rather than electively treated unruptured aneurysms via flow diversion, it shares an important methodological foundation with our work regarding the crucial role of technical standardization and the ongoing pursuit of procedural safety in complex neurovascular interventions. As suggested, we have expanded our Discussion section to cite this recent work and integrate its conceptual emphasis on procedural and workflow optimization in dedicated neurointerventional settings

 

Updated text

(discussion)

“…Furthermore, the success of intricate neurointerventional procedures under tailored imaging configurations heavily relies on strict protocol compliance and streamlined team coordination, as highlighted by recent retrospective cohort studies addressing workflow optimization in neurovascular centers. [21]…”

 

10. The limitations section should more explicitly acknowledge the absence of operator radiation exposure measurements.
    This is particularly relevant when comparing hybrid operating rooms with conventional neuroangiography suites.

 

Response: We entirely agree with the reviewer’s excellent point. The occupational radiation exposure of the operator and surgical staff is a critical safety parameter, particularly when comparing an HOR with a conventional NIS, where scatter radiation profiles can differ due to distinct room configurations, gantry geometries, and spatial dynamics.

Because our retrospective registry was designed to track patient-specific quality and safety indicators, objective personal dosimetry data for the medical team were not systematically compiled for this analysis.

As suggested, we have explicitly acknowledged this as a new limitation in the revised manuscript   to ensure a balanced and comprehensive discussion on radiation safety in hybrid environments.

 

Updated text

(discussion)

"…Fifth, this study focused exclusively on patient radiation metrics (DAP and fluoroscopy time) and did not include measurements of operator or staff radiation exposure. In a hybrid operating room environment, occupational exposure from scatter radiation can vary significantly compared to conventional angiography suites due to differing room configurations, shielding setups, and single-plane gantry positioning. The lack of objective personal dosimeter data for the medical team represents a limitation that should be addressed in prospective future investigations…."

 

11. Figure 2 could be improved by adding clearer labels and reporting median or percentile markers within the histogram.
    This would facilitate interpretation of dose distribution differences between environments.

 

Response: We thank the reviewer for this excellent graphical suggestion. We agree that introducing central tendency and percentile markers significantly enhances the interpretability of the dose distribution histograms.

 

(Figure 2, new)

 

 

12. The manuscript would benefit from minor English language revision to improve conciseness and reduce redundancy.
    Several sentences in the Discussion are excessively long and could be simplified for clarity.

Response: We thank the reviewer for this constructive feedback. We agree that improving text conciseness and eliminating redundant long sentences enhance the overall readability of the manuscript.

 

In this revision, we have already undertaken a comprehensive internal language review, focusing heavily on the Discussion section. As highlighted in our response to Question 5, multiple overlapping paragraphs and excessively long sentences regarding the dosimetric pathways of rotational angiography have been streamlined and consolidated into a more direct, high-density narrative.

 

Furthermore, to ensure the highest linguistic standards and strict adherence to academic clarity, the final revised manuscript will be processed through professional English editing prior to final publication. We trust that these stylistic refinements successfully address the reviewer's concerns.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for correct all comments.

All the best

Reviewer 2 Report

Comments and Suggestions for Authors

The paper is ready for publication