# Dose Estimation by Geant4-Based Simulations for Cone-Beam CT Applications: A Systematic Review
## 2 Methodology
### Data Extraction and Analysis  
Three examiners performed the eligibility and quality assessment of relevant studies. To construct a query suitable for WOS, PubMed, and Scopus, we extracted the following important information: author, journal, year of publication, citations, country or region, source, keywords, and CBCT applications. We also searched the reference lists of the studies encountered. We examined key elements of their titles, abstracts, and keywords analyzing the obtained results. If this information did not give enough evidence about the eligibility, the full text was screened. Furthermore, the whole text was also screened if one of the authors detected that one of the inclusion criteria was not accomplished. We also individually extracted the simulation toolkit (source Geant4, GATE, GAMOS), as well as the specific application (breast imaging, proton therapy, IGRT, etc.) from each study. In case of the author's disagreement over the study selection or data extraction, the issue was solved by consensus discussion among the reviewers. The selected articles were ranked based on the total citations received from the three databases.  
The screening of the results from the literature search, based on title and abstract reading, revealed that 41 papers were potentially eligible for full-text reading. After examination of the full texts, papers that did not meet the inclusion criteria were excluded. The principal reasons for exclusion were: studies did not focus on humans (1 article); not CBCT applications (1 article); dose was not evaluated by MC simulations (2 articles); dose was not estimated by Geant4 codes (1 article). Each stage of the search and the eligibility screening processes with the number of papers identified, included, and excluded is illustrated in Figure 1.  
\begin{table}
\begin{tabular}{c l} \hline \hline
**Indexing Terms** & **Items (n)** \\ \hline Scopus & 324.712 \\ \hline
#1 & Geant4 OR GATE OR GAMOS & 23.097 \\
#2 & Cone Beam Computed Tomography OR CBCT & 2.46 \\
#3 & Radiation Dosage OR Dose* OR Dosimetry OR Radiation protection & 7.584 \\
#4 & \#1 AND \#2 AND \#3 & 36 \\ \hline PubMed & 23.473 \\ \hline
#01 & Geant4 OR GATE OR GAMOS & 14.283 \\
#02 & Cone beam computed tomography & 9.704 \\
#03 & Cone beam computed tomography [MeSH] & 959.263 \\
#04 & Dose* & 109.722 \\
#05 & Radiation Dosage & 62.177 \\
#06 & Radiation dosage [MeSH] & 30.678 \\
#07 & Radiation protection & 12.216 \\
#08 & Radiation protection [MeSH] & 14.283 \\
#09 & \#2 OR \#3 OR & 1.02 \\
#10 & \#4 OR \#5 OR \#6 OR \#7 OR \#8 OR \#9 & 1.140 \\
#11 & \#9 AND \#10 AND \#1 & 24 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Cont.  
To answer the proposed research question, we performed a bibliometric analysis based on Bibliometric R-package for scientometric factors and bibliosihiny [89]. For visualization, the author's name, corresponding author's country, the total number of publications, author's keywords, and keywords plus were generated. For keywords, the co-occurrence of keyword and keyword plus and abstract phrases were evaluated. VOSviewer (version 1.6.16) was also used to perform a cluster analysis and construct a knowledge map of the topics.