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. 2022 Apr 25;12(1):6712.
doi: 10.1038/s41598-022-10498-0.

Compact bunker shielding assessment for 1.5 T MR-Linac

Jiwon Sung  1 , Yeonho Choi  2 , Jun Won Kim  1 , Ik Jae Lee  1 , Ho Lee  3
Affiliations

Compact bunker shielding assessment for 1.5 T MR-Linac

Jiwon Sung et al. Sci Rep. .

Abstract

This study evaluated the effect of the 1.5 T magnetic field of the magnetic resonance-guided linear accelerator (MR-Linac) on the radiation leakage doses penetrating the bunker radiation shielding wall. The evaluated 1.5 T MR-Linac Unity system has a bunker of the minimum recommended size. Unlike a conventional Linac, both primary beam transmission and secondary beam leakage were considered independently in the design and defined at the machine boundary away from the isocenter. Moreover, additional shielding was designed considering the numerous ducts between the treatment room and other rooms. The Linac shielding was evaluated by measuring the leakage doses at several locations. The intrinsic vibration and magnetic field were inspected at the proposed isocenter of the system. For verification, leakage doses were measured before and after applying the magnetic field. The intrinsic vibration and magnetic field readings were below the permitted limit. The leakage dose (0.05-12.2 µSv/week) also complied with internationally stipulated limits. The special shielding achieved a five-fold reduction in leakage dose. Applying the magnetic field increased the leakage dose by 0.12 to 4.56 µSv/week in several measurement points, although these values fall within experimental uncertainty. Thus, the effect of the magnetic field on the leakage dose could not be ascertained.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Magnitude of vibration according to (a) measurement time and (b) frequency.
Figure 2
Figure 2
AC magnetic field measurement over 20 min.
Figure 3
Figure 3
DC magnetic field measurement for 30 min.
Figure 4
Figure 4
Comparison (a) before and (b) after the special shielding design to reduce leakage dose around the ducts.
Figure 5
Figure 5
Unity structure.
Figure 6
Figure 6
Unity area layout including (a) measurement locations (red dots) and (b) distances between isocenter and shielding walls.
Figure 7
Figure 7
Location of vibration and magnetic field examination (red point).
See this image and copyright information in PMC

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