Dose and Gamma-Ray Spectra From Neutron-Induced Radioactivity in Medical Linear Accelerators Following High-Energy Total Body Irradiation

Keehan, Stephanie; Taylor, M. L.; Smith, R. L.; Dunn, Leon; Kron, Tomas; Franich, Rick

doi:10.1093/rpd/ncv480

Cited by 10 publications

(8 citation statements)

References 9 publications

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“…Activation product as a results (n,γ ) neutron capture interaction disintegrate by emitting γ-rays , β+ and β− particles with half-lives that range from 2 min to more than 5 years [7,11,12]. Thus, deemed as the major source of occupational radiation exposure for technologist and physicist who repeatedly enter the treatment room after radiotherapy treatment for patient management or quality assurance measurements [13,14].…”

Section: Resultsmentioning

confidence: 99%

The Spectral Measurement of Scattered Radiation From a Clinical Linear Accelerator Using a CZT Detector

2020

ALST

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The study of the induced radioactivity following radiotherapy with high energy X-rays from medical linear accelerator. Patient equivalent phantom made of Polymethyl methacrylate (PMMA) of 30x30x27 cm size irradiated with 15 MV X-rays from Versa HD medical linear accelerator form Elekta. Induced radioactive and ambient dose rates were measured at 0.25, 0.5 and 1 m from beam center using GR1® spectrometry with Cadmium Zinc Telluride (CZT) detectors having energy resolution less than 2%. Spectrum analysis was performed using MultiSpect software. The measured spectrum showed 511 keV annihilation photons possibly as a result of positron emitter of which most likely candidates are 62 Cu(T1/2: 9.7 min), 64 Cu (T1/2: 12.7 h) and 57 Ni (T1/2: 35.6 h) and a peak at ≈ 1780 keV that could be attributed 28 Al and 214 Bi radioisotope. Ambient photon dose rates post radiotherapy treatment ranged 660 µGyh-1 at o.5 m to 41 µGyh-1 at 1 m. These values agree well with the results presented in the literature.

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Section: Resultsmentioning

confidence: 99%

The Spectral Measurement of Scattered Radiation From a Clinical Linear Accelerator Using a CZT Detector

2020

ALST

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“…The isotopes produced are identified with gamma spectroscopy and the resulting doses are determined from ion chamber and TLD measurements. The work in this chapter has also been published in peer reviewed journals; please see Keehan et al (2015) and (Keehan et al 2017).…”

Section: Indirect Risks Posed By Neutron Productionmentioning

confidence: 99%

Risks posed by neutron contamination in high energy radiotherapy

Keehan¹

2017

Australas Phys Eng Sci Med

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This thesis also presents a summary of neutron dose equivalent values from peer reviewed publications and compares the effects of a number of parameters on the neutron dose. Comparison between studies is made difficult by a lack of detail on the magnitude of energy corrections used in published papers.The indirect risk from secondary activations is considerably lower, however may be reduced by employing the existing collimation devices within linacs as shielding. A small amount of activation in hip prostheses does occur, but does not result in a significant dose to surrounding tissue.

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“…Using γ spectroscopy and dose decay curve measurements on various linacs, many induced radioisotopes have been identified, including 24 Na, 28 Al, 38 Cl, 56 Mn, 57 Co, 57 Ni, 62 Cu, 122,124 Sb, 187 W, and 196 Au. 14,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Based on the properties of the radioisotopes, several models were established to describe the induced activity and discuss the occupational dose [20][21][22] that ranged from 0.1 mSv/y to 5.9 mSv/y [21][22][23][24][25][26][27][36][37][38][39] and 17 mSv/y under extreme conditions. 21 However, establishing a universal model to predict the dose is difficult because it depends sensitively on many factors, such as the different treatment installations (linac, bunker, console room, etc.…”

Section: Introductionmentioning

confidence: 99%

“…Many studies have been dedicated to the investigation of induced activity in various aspects 14–40 . In general, as beam energy increases, the induced activity tends to increase greatly 17–20 .…”

Section: Introductionmentioning

confidence: 99%

“…γ spectroscopy and dosimetry measurements are necessary to analyze the induced activity. Using γ spectroscopy and dose decay curve measurements on various linacs, many induced radioisotopes have been identified, including 24 Na, 28 Al, 38 Cl, 56 Mn, 57 Co, 57 Ni, 62 Cu, 122,124 Sb, 187 W, and 196 Au 14,17–36 . Based on the properties of the radioisotopes, several models were established to describe the induced activity and discuss the occupational dose 20–22 that ranged from 0.1 mSv/y to 5.9 mSv/y 21–27,36–39 and 17 mSv/y under extreme conditions 21 .…”

Section: Introductionmentioning

confidence: 99%

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Technical Note: Induced radioactivity in stereotactic body radiation therapy with a flattening‐filter‐free 10 MV beam model

et al. 2021

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The induced radioactivity in stereotactic body radiation therapy with a flattening-filter-free 10 MV beam model (10 FFF SBRT) was investigated for the risk to therapists. Methods: This study was performed on a Varian TrueBeam linac. The induced radioisotopes were identified by γ spectroscopy. The dose rate from the induced activity was measured for 12 treatment cycles in 4 h continuously. The impacts of the characteristic factors of 10 FFF SBRT on the dose rate were investigated, including monitor units (MU), beam rate, field size, and flattening filter. The dose rate was compared between the SBRT plans and conventional fractionation plans. A mathematical model was used to analyze the results and estimate the annual dose to therapists. Results: (a) The induced radioisotopes included 24 Na, 28 Al, 38 Cl, 56 Mn, 66 Cu, 187 W, and 196 Au. (b) In 4 h, the total dose contribution ratios were more than 70% for 28 Al, about 20% for 56 Mn, and 10% for all other long-lived radioisotopes, combining doses at the isocenter and end of the treatment couch. (c) The dose rate showed a nonlinear growth with increasing MU and beam rate. The variation of the dose rate was complicated with the jaw field and not sensitive to the MLC field. The removal of the flattening filter reduced the dose rate by about 40%. The dose level of SBRT was two to three times that of conventional fractionation. (d) The estimated annual dose to therapists was up to 0.20 mSv/y. Conclusions: The induced radioactivity in 10 FFF SBRT was higher compared with that in 10 MV conventional fractionation. More MU and higher beam rate were the primary factors that caused the increase. The therapists should wait longer after beam-off to reduce the occupational dose. In addition, aluminum and manganese should be less used in the treatment room.

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Dose and Gamma-Ray Spectra From Neutron-Induced Radioactivity in Medical Linear Accelerators Following High-Energy Total Body Irradiation

Cited by 10 publications

References 9 publications

The Spectral Measurement of Scattered Radiation From a Clinical Linear Accelerator Using a CZT Detector

The Spectral Measurement of Scattered Radiation From a Clinical Linear Accelerator Using a CZT Detector

Risks posed by neutron contamination in high energy radiotherapy

Technical Note: Induced radioactivity in stereotactic body radiation therapy with a flattening‐filter‐free 10 MV beam model

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