Assessment of human exposure doses received by activation of medical linear accelerator components

Lee, D.-Y.; Kim, J.-H.; Park, E.-T.

doi:10.1088/1748-0221/12/08/p08022

Cited by 5 publications

(5 citation statements)

References 14 publications

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“…Based on the dose rate for the linac equipment using 15 MV energy at 20% to 50% of linac (5) in the results section, the dose rate after treatment was observed to be as high as 2.773 uSv/h. For linac (9), even after approximately 5 h, it was as high as 0.532 uSv/h. When handling radioactive waste, the annual allowable dose for workers is 20 mSv.…”

Section: Plos Onementioning

confidence: 95%

“…uSv/h for linac (5) and 2.773 uSv/h for linac (9). For linac (5), we measured the gamma dose rate after approximately 5 hours.…”

Section: Plos Onementioning

confidence: 99%

“…Studies on radiation occurring in various parts of the linac head are available. Lee et al and Juste B et al [9][10][11][12] conducted a study using the Monte Carlo method by considering only the main components, such as targets and filters. The effect of the radiation in the internal parts of the linac head on workers when dismantling or relocating equipment for disposal have not been considered.…”

Section: Introductionmentioning

confidence: 99%

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Assessment of radio-activation using spectroscopy in medical linear accelerators

Kwon,

Jang,

et al. 2024

PLoS ONE

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In radiotherapy, when photon energy exceeding 8 MV is utilized, photoneutrons can activate the components within the gantry of the linear accelerator (linac). At the end of the linac’s lifecycle, radiation workers are tasked with its dismantling and disposal, potentially exposing them to unintentional radiation. This study aims to identify and measure the radioisotopes generated by this activation through spectroscopy, and to evaluate the effective dose rate. We selected nine medical linacs, considering various factors such as manufacturer (Siemens, Varian, and Elekta), model, energy, period of operation, and workload. We identified the radionuclides in the linac head by employing an in situ high-purity germanium (HPGe) detector. Spectroscopy and dose-rate measurements were conducted post-shutdown. We also measured the dose rates at the beam-exit window following irradiation with 10 MV and 15 MV photon beams. As a result of the spectroscopy, we identified approximately 20 nuclides including those with half-lives of 100 days or longer, such as 54Mn, 60Co, 65Zn, 122Sb, and 198Au. The dose rate measurements after 10 MV irradiation decreased to the background level in 10 min. By contrast, on 15 MV irradiation, the dose rate was 628 nSv/h after 10 min and decreased to 268 nSv/h after 1.5 hours. It was confirmed that the difference in the level of radiation and the type of nuclide depends on the period of use, energy, and workload. However, the type of nuclide does not differ significantly between the linacs. It is necessary to propose appropriate guidelines for the safety of workers, and disposal/move-install should be planned while taking into consideration the equipment’s energy usage rate.

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Section: Plos Onementioning

confidence: 95%

“…uSv/h for linac (5) and 2.773 uSv/h for linac (9). For linac (5), we measured the gamma dose rate after approximately 5 hours.…”

Section: Plos Onementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Assessment of radio-activation using spectroscopy in medical linear accelerators

Kwon,

Jang,

et al. 2024

PLoS ONE

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“…Radioactive nuclides are generated when high-energy photon beams irradiate high-density materials owing to photonuclear reactions [19]. Although many studies have focused on the radioactivation of high-atomic number materials in the RT vault [20][21][22][23], to the best of our knowledge, no previous studies have demonstrated the TRA of the tissue expander.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Temporary Radioactivation for Tissue Expanders in Breast Radiation Therapy: Preliminary Study

Lee¹,

Oh²,

Yoo³

et al. 2023

J Radiat Prot Res

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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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“…With continuous irradiation, neutrons are generated through a photonuclear reaction (γ, n) inside the LINAC's head, and these then interact with the components inside the LINAC head, generates gamma rays [5][6][7]. The LINAC gradually becomes radioactive, exposing radiologists and patients receiving treatment to unintentional radiation [8]. Furthermore, the radiation exposure to workers in the process of dismantling a LINAC which is intended to be disposed after the end of its operation should be considered.…”

Section: Introductionmentioning

confidence: 99%

Measurements of Neutron Activation and Dose Rate Induced by High-Energy Medical Linear Accelerator

Kwon

Jang

Kim

et al. 2021

Progress in Medical Physics

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During the treatments of cancer patients with a linear accelerator (LINAC) using photon beams with energies ≥8 MV, the components inside the LINAC head get activated through the interaction of photonuclear reaction (γ, n) and neutron capture (n, γ). We used spectroscopy and measured the dose rate for the LINAC in operation after the treatment ended. Methods:We performed spectroscopy and dose rate measurements for three units of LINACs with a portable high-purity Germanium (HPGe) detector and a survey meter. The spectra were obtained after the beams were turned off. Spectroscopy was conducted for 3,600 seconds, and the dose rate was measured three times. We identified the radionuclides for each LINAC.Results: According to gamma spectroscopy results, most of the nuclides were short-lived radionuclides with half-lives of 100 days, except for 60 Co, 65 Zn, and 181 W nuclides. The dose rate for three LINACs obtained immediately in front of the crosshair was in the range of 0.113 to 0.129 µSv/h. The maximum and minimum dose rates measured on weekends were 0.097 µSv/h and 0.092 µSv/h, respectively. Compared with the differences in weekday data, there was no significant difference between the data measured on Saturday and Sunday.Conclusions: Most of the detected radionuclides had half-lives <100 days, and the dose rate decreased rapidly. For equipment that primarily used energies ≤10 MV, when the equipment was transferred after at least 10 minutes after shutting it down, it is expected that there will be little effect on the workers' exposure.

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Assessment of human exposure doses received by activation of medical linear accelerator components

Cited by 5 publications

References 14 publications

Assessment of radio-activation using spectroscopy in medical linear accelerators

Assessment of radio-activation using spectroscopy in medical linear accelerators

Assessment of Temporary Radioactivation for Tissue Expanders in Breast Radiation Therapy: Preliminary Study

Measurements of Neutron Activation and Dose Rate Induced by High-Energy Medical Linear Accelerator

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