Big data analysis of endovascular treatment of intracranial aneurysms: a bibliometric analysis of the top 100 most cited articles

Background  The impact of a literature report on a particular subject can be measured by its number of citations. Objective  The purpose of this study was to evaluate the characteristics of the literature reports in the field of endovascular treatment of intracranial aneurysms (IAs) by analyzing the top 100 most cited articles. It should be noted that the focus of this study is to describe the bibliometric characteristics. Methods  This bibliometric analysis dedicated only to endovascular treatment of IAs in our study. We searched the top 100 most cited articles in the field of endovascular treatment of IAs using the search tool of the Web of Science (WOS). We evaluated the characteristics of these high-impact publications, including publication year, category, journal, author's country, etc. Results  The top 100 most cited articles were cited 281.3 times, on average. The United States has published the most articles every year compared with other countries. These highly cited articles are mostly published in the Journal of Neurosurgery. Eighty-six of the top 100 most cited articles were clinical studies. Conclusion  The bibliometric analysis provides insight over the development and the growing trend in endovascular treatment of IAs. This study can help researchers better understand the global overview of this field, and it also provides leads about promising areas of future research and potential collaborations.


INTRODUCTION
Endovascular technology has been used to embolize intracranial aneurysms (IAs) since the Guglielmi detachable coil (GDC) was introduced for clinical use in 1990. 1 Currently, an increasing number of patients with ruptured or unruptured IAs are being treated with endovascular therapy. The endovascular treatment methods for IAs include simple coil embolization, stent-assisted embolization, and placement of Flow Diversion Device. According to the international multi-center randomized controlled study (International Subarachnoid Aneurysm Trial, ISAT), endovascular treatment was better than neurosurgical clipping and reduced the mortality and disability rate of IAs patients. Moreover, the complication rate of endovascular treatment was lower than that of craniotomy. But the rebleeding rate was higher than craniotomy. 2,3 To our knowledge, endovascular therapy is more suitable for patients with advanced age, weak physique, or severe organic diseases who cannot tolerate craniotomy, as well as for patients with posterior circulation, wide neck, or huge IAs.
Many researchers have focused on research reports on the endovascular treatment of IAs. We have learned that bibliometric analysis is an analytical method that provides comprehensive knowledge about a particular area of study and identifies current research hotspots or research directions. We aim to provide a new perspective through bibliometric analysis to understand the overall research status of endovascular treatment of IAs.
The impact of a research report can be evaluated by the number of citations. An overview of the research area can be obtained through bibliometric analysis of the most cited literature. There have been many reports of bibliometric analysis in many fields. However, the bibliometric analysis dedicated to endovascular treatment for IAs has not been reported. Therefore, the purpose of this study is to understand the development in the field of endovascular treatment of IAs and to use bibliometric methods to analyze the characteristics of the 100 most cited articles in the field.

METHODS
This study was a bibliometric analysis, so ethical approval was not required.

Search strategy
Web of Science (WOS) is an online database platform. It can provide information on the annual/total number of citations, authors, publication year, source journals, article types, citation indexes, etc. We searched the literature on endovascular treatment of IAs from the 1950s to the present day on WOS (►Figure 1).
In this study, the following secondary IAs were excluded: traumatic, infectious, and aneurysms secondary to radiotherapy or surgery. The articles were ranked based on the number of citations. The top 100 most cited articles were selected for analysis, and the full texts of these 100 articles were downloaded for analysis.
understand the global overview of this field, and it also provides leads about promising areas of future research and potential collaborations.

Information collection and analysis
We analyzed the top 100 most cited articles, and the following information of each article was obtained (►Figures 2-5, The extraction of the above-mentioned information was completed by two reviewers (neurointerventional physicians). If there was a dispute, the task was handed over to the third reviewer (senior neurointerventional physician), who made the final decision.

The overall situation
A total of 7,504 articles were retrieved. The top 100 most cited articles that met the inclusion criteria for analysis were selected. The details of the top 100 most cited articles are shown in ►Supplementary Table S1. The top 100 most cited articles were cited 281.3 times on average (range, 135-2254).

The annual citations number
As shown in ►Figure 2, the annual number of citations of these articles increased in the beginning and then decreased over time. These articles were cited with the most in 2012.
Time of publication, publication area distribution, annual number in some countries, and cooperation between countries

Journals publishing the top 100 most cited articles
The journals that have published the most number of articles are shown in ►Table 1. Among them, the Journal of Neurosurgery has published the most articles (24), with a total of 150 citations. It was followed by the Journal of Stroke, which published 20 articles, with a total of 69 citations.

High-yield countries/individuals
The institutions with more output ( 5 articles) are shown in ►Table 3. The University of California system has the most output, with a total of 15 articles published. Studies from the University of California system have been cited 50

Article category
Among the top 100 most cited articles, most (86) of them were clinical studies, only 8 were review studies, 3 were basic studies, and 2 were commentary articles.

DISCUSSION
The rupture of IAs can cause subarachnoid hemorrhage leading to disastrous consequences in patients. 4 With the advancement of interventional therapy technology, the endovascular treatment of IAs has become an important treatment method. 5 The purpose of this study was to review the most highly cited articles in the field of endovascular treatment of IAs, and to explore the characteristics of research studies in this field. To the best of our knowledge, the bibliometric analysis of intracranial aneurysmal subarachnoid hemorrhage has been reported. 6 However, the bibliometric analysis dedicated to the endovascular treatment of IAs has not been reported yet. The bibliometric analysis in this study is a contrived in-depth summary based on previous work. We reviewed the 100 most cited reports in the field of endovascular treatment of IAs as the basis for understanding this type of treatment. Next, we will discuss the results of the bibliometric analysis. It should be noted that the focus of this study is to describe the bibliometric characteristics.

The characteristics of the citation number per year and the publication time of the top 100 most cited articles
The number of annual citations gradually increased from 1986 to 2013 (►Figure 2). The top 100 most cited articles were mainly published between 1997 and 2013. This was also a period with rapid development of endovascular treatment of IAs. During this period, the technology of interventional materials developed rapidly. Practitioners in this field also communicated with each other more conveniently with the development of the internet and social media. These  reasons may have led to higher production of the top 100 most-cited articles during that period. After 2013, the number decreased gradually. This was consistent with the general literature being cited. These reports attracted more and more physicians' interest in the early stage as the technique became more popular. Gradually, the endovascular treatment for IAs became well known to many physicians and less attention was paid to this field. In addition, with the emergence of new treatment equipment and technologies, people's attention to traditional endovascular treatment technologies gradually decreased.      may be due to the fact that readers of comprehensive journals lack sufficient interest in reports on intravascular therapy of IAs compared with the readers of professional journals.

Main contributing countries and the cooperation network between these countries
As shown in ►Table 2, the United States published the highest number of papers among the top 100 ones, and that number was significantly higher than those of other countries. Developing countries have published fewer articles of the top 100 most cited articles. As shown in ►Figure 5, the United States was the hub of the collaboration network, which is similar to other bibliometric analysis results. The United States is the largest economy in the world and provides economic support to medical research worldwide. There are also many scientific and technological innovations in the United States that may accelerate the production of highly cited documents in this field. Other countries also seek to cooperate with the United States to promote their own development in this field.
It should be noted that although the United States has contributed the most in number, this does not mean that it has made the greatest contribution to this field. For example, the International Subarachnoid Aneurysm Trial (ISAT) is a multi-center study, and its research branch did not include the United States.

Productive institutions and individuals
As shown in ►Table 3, the University of California system has the largest academic output. As the first author, Fiorella et al. have published the four most cited articles. Most of these highly accomplished individuals were affiliated with the United States and European institutions. There are fewer institutions and individuals from developing countries. This difference may be due to the higher investment in scientific research in western developed countries, which results in strong innovation capabilities and a good academic atmosphere in these countries compared with developing countries.

Analysis of research type
Among the top 100 most cited reports, clinical studies accounted for 86%, followed by review reports (8%), and basic research (3%). Some clinical research reports have provided high-quality data for clinical decision-making. For example, the International Unruptured Intracranial Aneurysm (ISUIA) study and the ISAT, are examples of multi-center and multicountry cooperation and provided an important reference for the establishment of intravascular treatment norms for IAs. The ISUIA showed that if the diameter of the aneurysm exceeds 7 mm, the risk of rupture is increased. 3,7 We noted that there are few basic research reports. So, it is necessary to strengthen the cooperation in basic research. For instance, we should cooperate to explore the mechanism of hemodynamic changes after endovascular treatment of IAs. A deep understanding of pathogenesis may be beneficial to increase the long-term occlusion rate.

Limitations of this study
In this study, we only analyzed literature reports in English. This may omit contributions made by non-English authors. Besides, we selected the top 100 most cited articles based on the number of citations, this may underestimate some important articles and overestimate those articles that appeared in the list. Furthermore, the results of bibliometric analysis will change with the update of the number of citations. Moreover, the number of citations used as a reference basis for the influence of the article may not be completely accurate. In the future, it may be more accurate if we can combine multiple indicators to comprehensively judge the influence of the article and then analyze the bibliometrics characteristics of the literature.
In conclusion, this study highlights the top 100 most cited reports in endovascular treatment of IAs. The bibliometric analysis provides insight into the development and growth trend in endovascular treatment of IAs. This study can help researchers to better understand the global overview of this disease and provide information about promising areas of research and potential collaborations.