First National Diagnostic Reference Levels Established for Cardiovascular Interventional Procedures Based on a Korean Hospital Survey

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Please see the attached file.

Comments for author File: Comments.pdf

Author Response

 Dear Editor and Reviewers,

Thank you for your careful review, valuable comments, and suggestions. We have revised the manuscript according to your comments and have provided point-by-point responses below.

Introduction

The introduction describes that the NRDs for angiography in Korea were updated in 2012 and 2019 but does not explain in sufficient detail why those updates did not cover interventional cardiology. It would be useful to specify this gap more explicitly to reinforce the justification and title of the study: The First National Diagnostic Reference Levels for Cardiovascular Interventional Procedures...."

Response

• National DRLs for angiographic and interventional procedures were updated in 2012 and 2019 but were largely confined to the radiology domain; national DRLs specific to coronary angiography (CAG) and interventional cardiology procedures have not yet been formally reported [14]. The KDCA updated the national DRLs for neurointerventional and abdominal interventional radiology in 2012 and 2019, respectively. Despite these updates in other vascular fields, to our knowledge, the cardiovascular sector is yet to undergo a national DRL survey conducted by the KDCA.

Study Design and Sample Representativeness

Of the 114 certified centres that are members of the Korean Society of Interventional Cardiology, only 20 participated (17.5%), selected on the basis of expressed willingness. This self-selection mechanism introduces a systematic bias towards institutions with a greater culture of radiation protection and more modern equipment. The authors do not analyse whether the participating centres are representative of the national distribution in terms of volume of procedures, type of hospital (university vs. community), or level of equipment. Authors should include a characterization of participating centres with respect to the total population of eligible centres (type of hospital, annual volume of procedures, age of equipment) and explicitly discuss the potential impact of this bias on the external validity of the proposed NRDs. On the other hand, the geographical distribution is markedly unbalanced: 18 of the 20 centers are located in the Gyeonggi/Gangwon and Gyeongsang regions; only 2 in Jeolla, and there is no representation from the Seoul metropolitan region. Authors should justify this distribution or explicitly recognize it as a limitation affecting the national generalization of the values obtained. 

Response

• I have added the following suggestions: “The study’s limitations are as follows. First, the predominant use of cardiovascular angiography equipment from a single manufacturer in domestic hospitals restricted the ability to conduct a comprehensive comparative evaluation across different brands. Furthermore, as the data were collected only from institutions that voluntarily participated during periods of ongoing challenges in the healthcare sector, the results may not perfectly represent the circumstances of all medical institutions.
• Seoul is located in the Gyeonggi region. The total numbers of certification bodies in the Jeolla and Gyeongsang regions were 10 and 32, respectively. Therefore, 20% and 30% of the regional institutions participated. Accordingly, the following modifications were made.
• Dose data were obtained from 20 angiographic systems: eight, 10, and two were located in Seoul, Gyeonggi and Gangwon, Gyeongsang, and Jeolla regions, respectively.

Sample Size by Procedure Category

The study analyses a total of 1,980 procedures distributed in 7 categories. However, the manuscript does not describe the number of procedures per category, which prevents assessing the statistical robustness of the 75th percentile in each subgroup. Less common clinical categories such as coronary spasm or CTO are likely to have (n) considerably lower than the ICRP recommendations (minimum between 20-30 procedures per facility and category). Tables 3 and 4 should include the sample size (n) for each procedure category. It is also necessary to calculate and report the confidence intervals of the 75th percentile for each category to know the dispersion of the data

Response

• For better visual clarity, Tables 3 and 4 were transformed into graphs with the addition of sample size (n) and standard deviation (SD). We also included p-values and 75th percentile dispersion to illustrate the distribution and statistical significance of the data more effectively. “The results of the one-sample t-test indicated that both KAP and FT were significantly different from the test value (0) across all procedures (p < .001). For CAG, the mean KAP was 14.92 (75% confidence interval [CI] [14.39, 15.46]) and the mean FT was 395.84 (75% CI [379.97, 411.72]). In CAG+PCI, KAP and FT were 48.78 (75% CI [47.15, 50.41]) and 938.28 (75% CI [912.23, 964.33]), respectively.
• For CAG+PTCA, mean values were 42.89 (75% CI [38.89, 46.89]) for KAP and 1091.80 (75% CI [897.94, 1285.67]) for FT. In CAG+SPASM, the mean KAP was 18.68 (75% CI [17.75, 19.61]) and FT was 298.52 (75% CI [275.05, 322.00]). AMI showed a mean KAP of 56.38 (75% CI [53.10, 59.66]) and FT of 874.69 (75% CI [825.04, 924.34]).

CTO procedures recorded the highest mean values with KAP at 78.95 (75% CI [71.15, 86.75]) and FT at 2099.02 (75% CI [1912.14, 2285.90]). Finally, for PCI, the mean KAP was 34.13 (75% CI [29.72, 38.54]) and FT was 1192.61 (75% CI [1055.44, 1329.79]).”

Heterogeneity in Data Capture

The data collection system operates in two different modes: real-time RDSR transmission (14 sites) and manual batch upload with subsequent mapping ("6 sites"). This hybrid approach introduces a source of uncontrolled systematic variability. In batch upload mode, manual mapping of procedure codes after the exam is completed is susceptible to classification errors. Authors should assess whether there are statistically significant differences in KAP values and fluoroscopy duration between the two groups of centers (real-time transmission vs. batch upload). If there are differences, their implications for the validity of the obtained NRDs should be discussed.

Response

• Regarding the data collection process, data in bulk upload mode were provided by each medical institution via Excel files containing examination categories and results, which were then uploaded according to their respective categories. This systematic approach was employed to minimize potential errors during manual mapping. Although the statistical differences between DICOM RDSR and manual methods were not analyzed in the current study, we acknowledge this as a limitation. We plan to conduct follow-up studies to investigate these differences and report our findings in future studies.

“Potential statistical variations arising from the data collection process, specifically between automated DICOM RDSR extraction and manual data entry, were excluded from the analysis.”

Dosimetric magnitudes reported The study uses only the product kerma-area (KAP) and the duration of fluoroscopy as reference magnitudes. The European and Spanish reference studies cited in the manuscript itself also report the accumulated kerma at the interventional reference point and the number of cinema frames, parameters directly related to the risk of cutaneous deterministic effects (radiodermatitis) and operator performance, respectively. This absence is especially relevant for the assessment of tissue injury risk in complex procedures such as CTO. If the RDSR systems of the participating teams generate this data and number of cinema images, these should be included in the analysis. Otherwise, authors should explicitly justify their absence and discuss the implications for radiodermatitis risk management.

Response

• I have added the following to the Discussion section: “The procedural categories in this study were designed to reflect real-world clinical settings, specifically to provide distinct DRLs for complex cases such as CTO versus standard PCI and PTCA. Complex interventions often require extended fluoroscopy and increased imaging, which significantly increases the risk of high radiation doses to the patient’s skin. Consequently, implementing the category-specific DRLs proposed in this study is crucial for mitigating radiation-related risks, including deterministic and stochastic radiation hazards, thereby ensuring patient safety.”

Comparison with the 2019 Korean Preliminary Study

One of the most striking findings of the manuscript is the drastic reduction in the NRD for PCI

compared to the 2019 Korean multicenter study: from 171.26 Gy·cm² to 49.94-53.89 Gy·cm², which is a reduction of 68%. This difference is of an unusual magnitude even considering technological improvements, and which the authors vaguely attribute to the "proactive adoption of advanced technologies", without a more rigorous causal analysis".

The authors should analyze in greater depth the causes of this divergence, considering at least: (a) methodological differences between the two studies (selection of centers, mode of data

collection, classification of procedures); (b) possible differences in the casemix of included procedures; (c) documentable technological changes in the equipment fleet between 2019 and 2024. Without this analysis, there is a risk that part of the observed reduction will be artifactual and will not reflect a real improvement in clinical practice.

Response

• I have added the following to the Discussion section: “In the 2019 study by Kim et al., the PTCA category indiscriminately included procedures for complex lesions such as CTO and multivessel disease, accounting for the substantial difference from the results of the present study. Furthermore, this discrepancy is likely attributable to the fact that Kim et al.'s data were collected between 2016 and 2017, a transitional period during which analog and digital imaging systems coexisted.
• Since then, medical institutions in Korea have adopted new and advanced equipment. Additionally, following a radiation dose reduction campaign initiated by the Korean Society of Interventional Cardiology, numerous institutions have shown heightened awareness of radiation exposure and have subsequently optimized their clinical protocols. We believe that these factors collectively contributed to the improved outcomes observed in this study.”

Absence of Adjustment for Patient Characteristics The proposed NRDs are not adjusted for patient body size or weight, even though patient thickness is one of the main determinants of radiation dose in fluoroscopic procedures. The ICRP Publication 135 recommends documenting the distribution of anthropometric characteristics of the sample and, when feasible, stratifying or adjusting for this variable. Authors should report the basic anthropometric characteristics (weight, height, or BMI) of patients included in each category. If this data are not available in the RDSR system, it should be recognized as an important limitation and its impact on the applicability of NRDs to centers with different patient profiles should be discussed.

Response

• We have added the following information to the Materials and Methods section: “In the data collection process, standard Korean body sizes were considered by targeting adults aged ≥20 years with body weights ranging from 55.2 kg to 89.1 kg. This specific weight range represented the 25th and 95th percentiles of the national standard body weight data.”

 

Dominance of a Manufacturer in the Equipment Park 80% of the angiographic systems analyzed correspond to Philips Healthcare (16 out of 20). Since automatic dose control algorithms (DAP, pulsed fluoroscopy, kVp reduction) vary significantly between manufacturers, the proposed NRDs may be biased towards the dosimetric performance characteristics of this manufacturer. Authors should report KAP values and fluoroscopy duration stratified by manufacturer to assess the degree of influence of this variable on the suggested NRDs.

Response

• I have added the following to the Limitations section: “First, the predominant use of cardiovascular angiography equipment from a single manufacturer in domestic hospitals restricted the ability to conduct a comprehensive comparative evaluation across different brands.”

Presentation of Results

Tables 3 and 4 present the 25th, 50th, and 75th percentile values along with the mean. The mean is a measure of central tendency sensitive to extreme values and is not the recommended magnitude for the definition of DRR; their inclusion can generate confusion. It is recommended that authors clarify the role of the mean in the context of the manuscript, or consider replacing it with the standard deviation or interquartile range to express dispersion.

Figure 2 shows the mean values of kVp and mA for each procedure, but it is not analyzed whether there are statistically significant differences between procedures nor are these technical parameters related to the KAP values obtained. This analysis would add value for the interpretation of the dosimetric differences observed between categories.

Response

• Thank you for your detailed and insightful comments. We have replaced Tables 3 and 4 with graphical representations to enhance readability. Because the primary focus of this study was to establish Diagnostic Reference Levels, analyzing the correlation between technical parameters and KAP values was outside the scope of this study. We plan to address this issue in our future

Discussion

The discussion mentions that Korean NRDs are lower than those of the UK, Germany, and the US, but does not cite the specific sources of these countries' NRDs for that claim. Only the USA (2012) appears in Table 5 with specific values; data from the United Kingdom and Germany are not documented in the manuscript. Authors are requested to cite the relevant national reference sources or withdraw the comparison with those countries if they cannot be substantiated with data.

Response

• We have modified this as follows: “In particular, their analysis revealed that Korean DRLs were generally lower than those in the European countries and the USA and that adoption of advanced technologies is widespread in leading medical institutions.”

 

The discussion does not address the impact of vascular access (radial vs. femoral) on dosimetric values. Radial access, more prevalent in Korea than in other countries, is associated with longer fluoroscopy time but comparable to shorter KAP, and could partially explain the observed pattern (low KAP with relatively prolonged fluoroscopy in CAG).

Response

• Thank you for your detailed and insightful comments. As the primary focus of this study was to establish Diagnostic Reference Levels (DRLs), we did not address variations based on vascular access routes (e.g., radial vs. femoral). The important points you have raised will be addressed in future research."

Conclusions

The conclusions are concise and proportionate to the findings. However, they must be qualified in relation to the limitations of sample representativeness identified in this report. To claim that "the first official national NRDs" have been established requires acknowledging that geographical coverage and non-probabilistic selection of centers limit their applicability to the entire national territory until future studies validate these values with more representative samples.

Response

• We have modified this as follows: “Furthermore, as the data were collected only from institutions that voluntarily participated during periods of ongoing challenges in the healthcare sector, the results may not perfectly represent the circumstances of all medical institutions.”

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study involves a large-scale survey on radiation exposure during cardiovascular interventional procedures. The experimental design is robust, and the results have been analyzed with high clinical and statistical rigor. The manuscript effectively conveys the authors' intended message and provides valuable insights into the field. 

As this study focuses on extensive data collection and multi-institutional cooperation, its primary value lies in the synthesis and presentation of these findings rather than in complex scientific modeling. This study presents a comprehensive large-scale survey on radiation exposure during cardiovascular interventional procedures, which is a critical topic for both patient safety and occupational health.

The experimental design is robust, particularly in its multi-institutional approach, which ensures that the findings reflect a realistic clinical landscape rather than a single-center bias. The results have been analyzed with high clinical and statistical rigor, and the establishment of these diagnostic reference levels (DRLs) provides a necessary benchmark for radiation dose optimization (ALARA principle) in the field.

While the manuscript effectively conveys the authors' intended message, providing further clarity on the data distribution would enhance its impact. Specifically, representing the extensive data in Tables 3 and 4 through box plots would help readers more intuitively grasp the variability and potential outliers across different complex procedures. With these minor enhancements in data visualization, this study will serve as a highly valuable resource for relevant professionals and those looking to optimize radiation safety in clinical practice.

 

Author Response

 Thank you for your detailed review. Tables 3 and 4 have been replaced with graphs.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript presents a multicenter study establishing the first national diagnostic reference levels (DRLs) for coronary angiography and interventional cardiology procedures in Korea. The topic is relevant, however some improvements are needed before the manuscript can be considered for publication.

-The statistical analysis is mainly descriptive, do you have analysis about variability between centers and predictors of higher dose?

-Minor issues include language inconsistencies and some redundancy (fluroscopy duration change to fluoroscopy time, Korea with capital letter, DRLs is to DRLs are....).

 

Comments on the Quality of English Language

This manuscript presents a multicenter study establishing the first national diagnostic reference levels (DRLs) for coronary angiography and interventional cardiology procedures in Korea. The topic is relevant, however some improvements are needed before the manuscript can be considered for publication.

-The statistical analysis is mainly descriptive, do you have analysis about variability between centers and predictors of higher dose?

-Minor issues include language inconsistencies and some redundancy (fluroscopy duration change to fluoroscopy time, Korea with capital letter, DRLs is to DRLs are....).

Author Response

Response to review 3

To the editor and participating reviewers of this manuscript.

Thank you for reviewing this manuscript and giving us an additional opportunity to clarify our intent.

Following the editor and reviewer's comments we have revised the manuscript accordingly.

This manuscript presents a multicenter study establishing the first national diagnostic reference levels (DRLs) for coronary angiography and interventional cardiology procedures in Korea. The topic is relevant, however some improvements are needed before the manuscript can be considered for publication.

-The statistical analysis is mainly descriptive, do you have analysis about variability between centers and predictors of higher dose?

Response

-> We determined DRLs based on descriptive statistics, with procedural variability reflected in interquartile ranges. To ensure data quality and reduce inconsistencies, we specifically engaged centers certified for quality by the Korean Society of Interventional Cardiology. Although the current analysis is descriptive, we expect to incorporate a center-by-center analysis in the next DRL update to provide a more detailed assessment of variability.

Thank you for your insightful comment. In the current study, we were unable to analyze the factors contributing to higher doses due to procedural complexity. We will consider your valuable suggestions and incorporate them into our future investigations.

-Minor issues include language inconsistencies and some redundancy (fluroscopy duration change to fluoroscopy time, Korea with capital letter, DRLs is to DRLs are....).

Response

-> We have corrected these linguistic errors.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

This study establishes national diagnostic reference levels  for interventional cardiology procedures in South Korea. The research is very relevant and good for public health. It provides updated, modern data to help hospitals control radiation doses and improve patient safety. Using DICOM RDSR to collect data automatically is a modern and reliable approach. It adds great value to the subject area.

Overall, it is a valuable paper with strong methods. I recommend acceptance with minor revisions after addressing the following question:

1. The authors call this the "first national DRLs" for South Korea, but the paper also mentions older Korean multi-center studies. Please clearly explain why this new study is different. Is it because it is an official national project, uses automatic data collection, or covers more procedures? Making this clear will show the study's true value.

Author Response

Response to review 4

To the editor and participating reviewers of this manuscript,

Thank you for reviewing this manuscript and giving us an additional opportunity to clarify our intent.

Following the comments of the editor and reviewers, we have revised the manuscript accordingly.

This study established national diagnostic reference levels for interventional cardiology procedures in South Korea. The research is very relevant and good for public health. It provides updated, modern data to help hospitals control radiation doses and improve patient safety. Using DICOM RDSR to collect data automatically is a modern and reliable approach. It adds great value to the subject area.

Overall, it is a valuable paper with strong methods. I recommend acceptance with minor revisions after addressing the following question:

1. The authors call this the "first national DRLs" for South Korea, but the paper also mentions older Korean multicenter studies. Please clearly explain why this new study is different. Is it because it is an official national project, uses automatic data collection, or covers more procedures? Making this clear will show the study's true value.

Response

We have added the following sentence to the Introduction section:

“The KDCA updated the national DRLs for neurointerventional and abdominal interventional radiology in 2012 and 2019, respectively. Despite these updates in other vascular fields, to our knowledge, the cardiovascular sector is yet to undergo a national DRL survey conducted by the KDCA. “

-> We have added the following sentence to the Conclusion:

“This study demonstrates the potential of an automated dose monitoring system based on DICOM RDSR in the cardiovascular field. By improving the system's accessibility, we have paved the way for more diverse medical institutions to join the DRL initiatives. This progress is expected to serve as a cornerstone for regular updating and management of national DRLs in interventional cardiology.“

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have satisfactorily answered all the questions asked. In my opinion, the text has improved significantly and deserves prompt publication.

Author Response

First of all, we would like to express our sincere gratitude to the reviewers for their insightful and constructive comments on our manuscript. Their feedback has been immensely helpful in improving the quality and clarity of our work

Reviewer 3 Report

Comments and Suggestions for Authors

The authors stated that they are unable to further deepen the statistical analysis as suggested and that they will address this in a future study.Nevertheless, the text is full of typographical and grammatical errors. A detailed revision by a native English-speaking expert is required to improve the clarity and readability of the manuscript.

Comments on the Quality of English Language

The authors stated that they are unable to further deepen the statistical analysis as suggested and that they will address this in a future study.Nevertheless, the text is full of typographical and grammatical errors. A detailed revision by a native English-speaking expert is required to improve the clarity and readability of the manuscript.

Author Response

Thank you for your detailed review. I have re-proofread and revised the text, and re-checked the references.