Abstract
Background
The number of citations that an article has received can be used to evaluate its impact on a particular research area.
Purpose
The aim of this study was to identify and characterize the 100 top-cited articles focused on magnetic resonance (MR).
Material and Methods
We determined the 100 top-cited articles on MR via the Scopus database, using the search term. The following information was recorded for each article: year of publication; journal title; impact factor of journal; number of citations; number of annual citations; authorship; department; institution; country; type of article; topic; MR protocol; and disease.
Results
The number of citations for the 100 top-cited articles was in the range of 898–5679 (median = 1342.5) and the number of annual citations was in the range of 19.7–372.4 (median = 60.9). The 100 top-cited articles were published in 46 journals, led by Magnetic Resonance in Medicine (n = 13). The majority of articles were published in 1990–1999 (n = 53), originated in the United States (n = 69), were original articles (n = 81), and dealt with the clinical application of MR (n = 57). The Department of Radiology, Massachusetts General Hospital (n = 5) was the leading institution. The majority of articles did not use any specific protocol (n = 51) and was not associated with any specific disease (n = 56).
Conclusion
Our study presents a detailed list and analysis of the 100 top-cited articles on MR, which provides an insight into historical development in this field.
Introduction
Magnetic resonance (MR) was developed by Paul Lauterbur in September 1971 (1). In 2003, Paul Lauterbur and Peter Mansfield were awarded the Nobel Prize in Physiology or Medicine for their “discoveries concerning magnetic resonance imaging” (2).
In the early 1980s, there were only 12 MR machines but recently, there are approximately 36,000 MR machines worldwide (1). MR is non-invasive and does not involve radiation, making it widely used in medical field for diagnosis of various diseases.
A citation is the acknowledgment that a previous article has been referenced by another article. The number of citations an article receives after its publication is widely used to evaluate the impact of an article on the scientific community (3,4). Therefore, reviewing the top-cited articles (so-called “citation classics”) can provide interesting information about scientific progress and research trends in a specific field of discipline (5). Although a number of studies have reported the top-cited articles in various clinical disciplines, such as general surgery (6), anesthesiology (7), obstetrics and gynecology (8), orthopedics (9), rehabilitation (10), respiratory system (11), and radiology (12), there have been only two studies (13,14) of citation classics on a specific imaging technique in biomedical field.
The purpose of this study was to identify and characterize the 100 top-cited articles focused on MR.
Material and Methods
Institutional review board approval was not taken as our study was a bibliometric analysis that did not involve human subjects.
Two reviewers (SJY and KJL) independently conducted article identification and extraction of information from articles. In cases of disagreement, a third reviewer (DYY) was included in the discussion until consensus was achieved.
Identification of the 100 top-cited articles
A search was conducted through the Scopus Library database (Elsevier, Amsterdam, The Netherlands), including the keyword “MR” OR “MRI” OR “Magnetic Resonance” in the title word. This search, performed on 4 April 2017, returned articles published from 1950 up to and including the date of the search. These articles were then ranked in descending order based on citation number and reviewed to determine if they were relevant to MR.
The title and abstract (and full text if required) of each article were reviewed to ensure that it was a MR article. A MR article was defined as any study that mainly focuses on MR technique/technology, interpretation of MR images, and utilization of MR in medical field including experimental and animal studies.
Analysis of articles
The 100 top-cited articles were reviewed and the following information was extracted according to their specific characteristics: (i) year of publication; (ii) journal title; (iii) impact factor (IF) of journal (based on the 2016 science edition of the Journal Citation Reports (Thomson Reuters, New York, NY, USA)); (iv) number of citations; (v) number of annual citations (calculated by total number of citations over the number of years and months since publication); (vi) authorship; (vii) department; (viii) institution; (ix) country; (x) type of article (original article [reports that investigated clearly stated objectives or hypotheses, and contained specifically articulated methods and results sections], review, guideline/consensus statement, or meta-analysis); (xi) topic; (xii) MR protocol used; and (xiii) disease.
For the purpose of our study, the department, institution, and country of origin were defined by the affiliation provided for the first author. If the first author is affiliated to more than one institution or group name, the corresponding author’s affiliation was used for the origin of the article.
Results
The 100 top-cited articles on MR and the corresponding number of citations are presented in Supporting Table S1. Of these 100 articles, 30 articles were overlapped with previous citation classics in neuroimaging (15) (n = 26) and in cardiovascular MR (14) (n = 4). The number of citations of the 100 top-cited articles was in the range of 898–5679 (mean = 1687.1 ± 930.7; median = 1342.5). The number of annual citations was in the range of 19.7–372.4 (mean = 88.6 ± 67.1; median = 60.9). When comparing the ranking of the number of annual citations to the overall amount, the change in position ranged from −67 + 73 with a mean absolute rank change of 18.4 ± 17.5. The top-ranking article was published in 2002 by Tzourio-Mazoyer et al. (16), describing the tool of automated anatomical labeling of activations in SPM using a macroscopic anatomical parcellation of the MNI MR single-subject brain. The following article was “Advances in functional and structural MR image analysis and implementation as FSL” by Smith et al., published in 2004 (17). These articles also had the highest number of annual citations.
The 100 top-cited articles were published in 46 journals, led by Magnetic Resonance in Medicine (n = 13) and followed by Proceedings of the National Academy of Sciences of the United States of America (n = 7) (Table 1). Articles were published from 1948 to 2012, with the period with the greatest number of top-cited articles being 1990–1999 (n = 53), followed by 2000–2012 (n = 28) (Table 2). There were 10 authors who published four citation classics in the list. These included Basser PJ, Belliveau JW, Brady TJ, Dale AM, Judd RM, Kim RJ, Kwong KK, Ogawa S, Rosen BR, and Smith SM (Table 3). The most common institution of authors was Massachusetts General Hospital, Department of Radiology (n = 5), followed by AT&T Bell Laboratories (n = 4), and Biophysics Research Institute, Medical College of Wisconsin (n = 3) (Table 4). The majority of the articles originated in the United States (n = 69), distantly followed by United Kingdom (n = 14), Canada (n = 4), and France and Switzerland (n = 3 each) (Table 5). Type of article was most frequently original article (n = 81), 40 of which were clinical observational studies, 35 were basic research, and six were experimental/animal studies (Table 6). The main topic of articles composed of clinical application (n = 57) and basic science (n = 43). The most common topic was predominantly neuroimaging (n = 43) (Table 7). The majority of articles did not use any specific protocol (n =51) (Table 8) and was not associated with any specific disease (n = 56) (Table 9).
Journals in which two or more of the 100 top-cited MR articles were published.
*Based on the Journal Citation Reports for the year 2016.
NA, not applicable.
Distribution of the 100 top-cited MR articles by publication date.
Authors who contributed three or more of the 100 top-cited MR articles.
Institutions which contributed two or more of the 100 top-cited MR articles*.
*For the purpose of our research, institution of origin was defined by the address provided for the first author. If the first author has affiliation to more than one institution or group name, the corresponding author’s affiliation was used for the origin of the article.
Countries of origin of the 100 top-cited MR articles.*
*For the purpose of our research, country of origin was defined by the address provided for the first author. If the first author has affiliation to more than one institution or group name, the corresponding author’s affiliation was used for the origin of the article.
Types of the 100 top-cited MR articles.
Topics covered in the 100 top-cited MR articles.
Protocols used in the 100 top-cited MR articles.
Disease entities covered in the 100 top-cited MR articles.
Discussion
The overall number of citations of an article could be influenced by its publication year because citations accumulate over time; older articles have had more time to be cited than recent articles (18). In our study, we analyzed not only the number of citations, but also the number of annual citations of articles because this metric can be used to evaluate the current impact of an article, regardless of the duration since publication (19,20). Our results showed significant shifts in rank between the total number of citations and the number of citations per year for the 100 top-cited articles. Articles with a high total citation count but low number of annual citations are more likely historically important and may not reflect the current impact. In contrast, articles with both high total citation count and number of annual citations still retain relevance for current researchers.
The analysis of journals showed that the 100 top-cited articles were published in 46 different journals, such as radiology, neuroscience/clinical neurology, biochemical/chemical research, cardiovascular, computer science, oncology, orthopedics, pharmacology, physics, psychiatry, and multidisciplinary journals. This broad distribution of journals in our list might reflect that MR research has been related to various medical disciplines and research topics.
We found that the 81% of the top-cited articles were published from 1990 to 2012. This result is consistent with the previous results for general radiology (12,19) and respiratory system (11) but in contrast to those of other medical specialties, which revealed that a majority of highly cited articles were published before 1990. This difference reflects the relatively recent evolutions and rapid developments in the field of MR, rather than the increase in published articles and development of bibliometric studies.
We identified the majority (n = 69) of the 100 top-cited articles originated from the United States, reflecting the strong influence of the United States on medical research. The United States is one of the most productive countries for research in general, which can be attributed to the large size of the scientific community and the abundant financial resources (21). In addition, the international scientific community speaks English and most scientific journals publish articles written in the English language only. Thus, American researchers take advantage of writing in their native language, i.e. better and in a more appealing way than non-USA researchers.
With regard to the type of articles, our results showed that original articles accounted for 81% of all MR citation classics. This result might be attributable to a preference for citing the primary literature rather than review articles.
We found one interesting observation that 43% of main topics covered in the top-cited MR articles were those that presented basic science (e.g. contrast material/enhancement, diffusion/perfusion, MR spectroscopy). In addition, 51% of articles did not use any specific MR protocol and 56% was not associated with any specific disease. These findings are likely to reflect the relative importance of basic science on the progress of MR as a whole.
In our study, the majority (n = 43) of the 100 top-cited articles focused on neuroimaging. Among them, four articles were included in the top 10 total citation articles and seven articles were included in the top 10 annual citation articles. These findings are not surprising considering MR is the most frequently used imaging technique and investigative tool of choice in neuroimaging.
There are several inherent limitations like other citation classic studies. First, the number of citations can be influenced by not only the quality of the article, but also many other factors such as obliteration by incorporation (i.e. the phenomenon that information from highly influential articles has been incorporated into common knowledge such that they are not explicitly cited), omission bias (i.e. tendency to not cite competitors or sources contradictory to one’s own results), self-citation, referencing high-IF core journals in the field of study, attitude toward citing review articles over original research, and national or language preferences (22). Second, the reliability of the citation analysis using search terms is highly dependent on the accuracy and comprehensiveness of the keywords. We used search terms “MR” or “MRI” or “magnetic resonance” to identify the 100 top-cited articles. Consequently, some important and influential articles might be missed from a representative list of classic articles because of using other words in title of their articles. Third, there are several citation databases such as Scopus, Web of Science (Thomson Reuters), and Google Scholar (Google Inc, Mountain View, CA, USA). Thus, it is possible that the citation count from these databases differs (23). In our study, we sought to use the Scopus database, which has been shown to be commonly used and robust method for clinical medicine.
In conclusion, we identified and bibliometrically analyzed the 100 top-cited articles focused on MR. Our 100 top-cited articles list provides an insight into historical developments and allows for the recognition of important advances in MR.
Supplemental Material
Supplemental material for The 100 top-cited articles focused on magnetic resonance: a bibliometric analysis
Supplemental material for The 100 top-cited articles focused on magnetic resonance: a bibliometric analysis by Soo Jeong Yoon, Dae Young Yoon, Kyoung Ja Lim, Ji Yoon Moon, Su Jin Hong, Sora Baek and Eun Joo Yun in Acta Radiologica
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
References
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