Imaging Sci Dent.  2018 Mar;48(1):21-30. 10.5624/isd.2018.48.1.21.

Estimation of the effective dose of dental cone-beam computed tomography using personal computer-based Monte Carlo software

• Kim EK
• Han WJ
• Choi JW
• Battulga B

• KMID: 2406979
• DOI: http://doi.org/10.5624/isd.2018.48.1.21

Abstract

PURPOSE
To calculate the effective doses of cone-beam computed tomography (CBCT) using personal computer-based Monte Carlo (PCXMC) software (Radiation and Nuclear Safety Authority, Helsinki, Finland) and to compare the calculated effective doses with those measured using thermoluminescent dosimeters (TLDs) and an anthropomorphic phantom.
MATERIALS AND METHODS
An Alphard VEGA CBCT scanner (Asahi Roentgen Ind. Co., Kyoto, Japan) with multiple fields of view (FOVs) was used for this study. The effective doses of the scout and main projections of CBCT using 1 large and 2 medium FOVs with a height >10 cm were calculated using PCXMC and PCXMCRotation software and then were compared with the doses obtained using TLD-100 LiF and an anthropomorphic adult human male phantom. Furthermore, it was described how to determine the reference points on the Y- and Z-axes in PCXMC, the important dose-determining factors in this software.
RESULTS
The effective doses at CBCT for 1 large (20.0 cm×17.9 cm) and 2 medium FOVs (15.4 cm×15.4 cm and 10.2 cm×10.2 cm) calculated by the PCXMC software were 181, 300, and 158 µSv, respectively. These values were comparable (16%-18% smaller) to those obtained through TLD measurements in each mode.
CONCLUSION
The use of PCXMC software could be an alternative to the TLD measurement method for effective dose estimation in CBCT with large and medium FOVs.

Keyword

Cone-Beam Computed Tomography; Radiation Dosage; Radiation Protection

MeSH Terms

Adult
Cone-Beam Computed Tomography*
Humans
Male
Methods
Radiation Dosage
Radiation Protection

Figure

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  Fig. 1 Coronal image of 3-dimensionally reconstructed cone-beam computed tomography (C mode) of the phantom with superimposed PCXMC Z coordinates. The Zref of the rotation center was set to approximately 86.2 cm.

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  Fig. 2 Coronal image of 3-dimensionally reconstructed cone-beam computed tomography (P mode) of the phantom with superimposed PCXMC Z coordinates. The Zref of the rotation center was set to approximately 85.0 cm.

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  Fig. 3 Coronal image of 3-dimensionally reconstructed cone-beam computed tomography (I mode) of the phantom with superimposed PCXMC Z coordinates. The Zref of the rotation center was set to approximately 84.5 cm.

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  Fig. 4 Lateral image of 3-dimensionally reconstructed cone-beam computed tomography (C mode) of the phantom. The width of this image is 20.0 cm and the length from the left margin to most mid-anterior point of the cervical vertebrae is 13.0 cm. Thus, the length from center to most mid-anterior point of cervical vertebrae is 3.0 cm. Meanwhile, the Y-axis value of the most mid-anterior point of cervical vertebrae inferior to the mandible was approximately −1.0. Thus, the Yref value of the rotation center was determined to be approximately −4.0 cm.

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  Fig. 5 Lateral image of 3-dimensionally reconstructed cone-beam computed tomography (P mode) of the phantom. The width of this image is 15.4 cm and the length from the left margin to most mid-anterior point of the cervical vertebrae is 10.5 cm. Thus, the length from center to most mid-anterior point of cervical vertebrae is 2.8 cm and the Yref value of the rotation center was determined to be approximately −3.8 cm.

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  Fig. 6 Lateral image of 3-dimensionally reconstructed cone-beam computed tomography (I mode) of the phantom. The width of this image is 10.2 cm and the length from the left margin to most mid-anterior point of the cervical vertebrae is 9.9 cm. Thus, the length from center to most mid-anterior point of cervical vertebrae is 4.8 cm and the Yref value of the rotation center was determined to be approximately −5.8 cm.

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  Fig. 7 Bar graphs show the absorbed organ doses in various organs and tissues calculated by PCXMC software and measured using TLD technology (Upper: C mode, Middle: P mode for maxilla, Lower: I mode for maxilla). C: cephalometric, P: panoramic, I: implant, TLD: thermoluminescent dosimetry.

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