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KMID : 0364920230480020100
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Journal of Radiation Protection and Research
2023 Volume.48 No. 2 p.100 ~ p.106
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Assessment of Temporary Radioactivation for Tissue Expanders in Breast Radiation Therapy: Preliminary Study
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Lee Hwa-Jung
Oh Do-Hoon
Yoo Lee
Chun Min-Soo
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Abstract
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Background : As breast tissue expanders consist of metallic materials in the needle guard and ferromagnetic injection port, irradiation can produce radioactivation.
Materials and Methods : A CPX4 (Mentor Worldwide LLD) breast tissue expander was exposed using the Versa HD (Elekta) linear accelerator. Two photon energies of 6 and 10 MV-flattening filter free (FFF) beams with 5,000 monitor units (MU) were irradiated to identify the types of radiation. Furthermore, 300 MU with 10 MV-FFF beam was exposed to the CPX4 breast tissue expander by varying the machine dose rates (MDRs) 600, 1,200, and 2,200 MU/min. To assess the instantaneous dose rates (IDRs) solely from the CPX4, a tissue expander was placed outside the treatment room after beam irradiation, and a portable radioisotope identification device was used to identify the types of radiation and measure IDR.
Results and Discussion : After 5,000 MU delivery to the CPX4 breast tissue expander, the energy spectrum whose peak energy of 511 keV was found with 10 MV-FFF, while there was no resultant one with 6 MV-FFF. The time of each measurement was 1 minute, and the mean IDRs from the 10 MV-FFF were 0.407, 0.231, and 0.180 μSv/hr for the three successive measurements. Following 10 MV-FFF beam irradiation with 300 MU indicated around the background level from the first measurement regardless of MDRs.
Conclusion : As each institute room entry time protocol varies according to the working hours and occupational doses, we suggest an addition of 1 minute from the institutes’ own room entry time protocol in patients with CPX4 tissue expander and the case of radiotherapy vaults equipped with a maximum energy of 10 MV photon beams.
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KEYWORD
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Breast Radiation Therapy, Breast Tissue Expander, Ferromagnetic Material, Radioactivation
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