The measurement of photoneutrons in the vicinity of a Siemens Primus linear accelerator

Lin, Jao-Perng; Chu, T. L.; Lin, Shih‐Yin; Liu, Mu-Tai

doi:10.1016/s0969-8043(01)00084-7

Cited by 59 publications

(43 citation statements)

References 3 publications

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“…Our Q value for the 18 MV photon beam measured on the Varian 21iX is in agreement with the 18 MV values for Varian linear accelerators found in the literature, 22 , 23 whereas our Q values for the electron beams are the first to be published. Neutron dose equivalent measurements have been made by Nath et al, (9) Lin et al, (10) and Biltekin et al (11) for high‐energy electron beams. Our results are in agreement with the relatively recent findings by Lin and colleagues, who found the neutron dose equivalent from a Siemens PRIMUS linear accelerator using a 15 MeV electron beam to be approximately 20 times less than dose equivalents from a 15 MV photon beam.…”

Section: Discussionmentioning

confidence: 99%

Out‐of‐field doses and neutron dose equivalents for electron beams from modern Varian and Elekta linear accelerators

Cárdenas

Nitsch

Kudchadker

et al. 2016

J Applied Clin Med Phys

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Out‐of‐field doses from radiotherapy can cause harmful side effects or eventually lead to secondary cancers. Scattered doses outside the applicator field, neutron source strength values, and neutron dose equivalents have not been broadly investigated for high‐energy electron beams. To better understand the extent of these exposures, we measured out‐of‐field dose characteristics of electron applicators for high‐energy electron beams on two Varian 21iXs, a Varian TrueBeam, and an Elekta Versa HD operating at various energy levels. Out‐of‐field dose profiles and percent depth‐dose curves were measured in a Wellhofer water phantom using a Farmer ion chamber. Neutron dose was assessed using a combination of moderator buckets and gold activation foils placed on the treatment couch at various locations in the patient plane on both the Varian 21iX and Elekta Versa HD linear accelerators. Our findings showed that out‐of‐field electron doses were highest for the highest electron energies. These doses typically decreased with increasing distance from the field edge but showed substantial increases over some distance ranges. The Elekta linear accelerator had higher electron out‐of‐field doses than the Varian units examined, and the Elekta dose profiles exhibited a second dose peak about 20 to 30 cm from central‐axis, which was found to be higher than typical out‐of‐field doses from photon beams. Electron doses decreased sharply with depth before becoming nearly constant; the dose was found to decrease to a depth of approximately E(MeV)/4 in cm. With respect to neutron dosimetry, Q values and neutron dose equivalents increased with electron beam energy. Neutron contamination from electron beams was found to be much lower than that from photon beams. Even though the neutron dose equivalent for electron beams represented a small portion of neutron doses observed under photon beams, neutron doses from electron beams may need to be considered for special cases.PACS number(s): 87.55.N‐, 87.55.ne, 87.56.bd, 87.56.jf

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Section: Discussionmentioning

confidence: 99%

Out‐of‐field doses and neutron dose equivalents for electron beams from modern Varian and Elekta linear accelerators

Cárdenas

Nitsch

Kudchadker

et al. 2016

J Applied Clin Med Phys

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“…However, they also found that neutron dose equivalent rate from conventional Saturn Linac was 42 times higher than the rate of Mobetron for the same geometry. Lin et al [22] also measured neutron dose for the energies of 15, 18 and 21 MeV as 100 ± 20.4, 262.7 ± 61.2 and 349.0 ± 29.6 mSv/Gy, respectively. They pointed out that neutron contamination for electron energies lower than 12 MeV was below the detection limits.…”

Section: Discussionmentioning

confidence: 99%

Investigating in-field and out-of-field neutron contamination in high-energy medical linear accelerators based on the treatment factors of field size, depth, beam modifiers, and beam type

2015

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“…As linac head constitute no shielding against neutrons, these particles are present all over the therapeutic room as it previously has been shown by several authors, e.g. [2,6,7,11] . Moreover, neutron flux can induce radioactivity itself.…”

Section: Introductionmentioning

confidence: 90%

“…Up to 30 MeV of photon beam generated by linacs, neutrons and protons are the main reaction products [2,5]. However, only neutrons are measured all over the accelerator room [6,7] due to much more limited range of charged particles [4,8].…”

Section: Introductionmentioning

confidence: 99%

Activation of Dosimeters Used in qa of Medical Linear Accelerators

Polaczek-Grelik

Nowacka

Raczkowski³

2017

EPJ Web Conf.

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This paper presents the first results of a project intended to investigate γ-radiation activity induced in dosimeters used in clinical practice during routine quality assurance of high-energy photon beams emitted by electron linear accelerators. Two aspects of the activation via photonuclear reactions (X,n) of therapeutic beam and subsequent capture of secondary neutrons (n,γ) are under considerations: the influence of activation on intrinsic background of the dosimeters and exposure of dosimetrists who operate this equipment. The activation of several types of ionization chambers as well as the silicon diodes was studied after long-time exposure (10 000 MUs) of the 15 MV photon beam (Elekta Synergy). Photon fluxes obtained from spectra of γ-rays registered by HPGe spectrometer were subsequently converted to equivalent doses using appropriate coefficients. The main contribution to the induced activity comes from the neutron capture process on Al, Mn and Cu, therefore it decays quite fast with the half-lives of the order of 15 minutes. Nevertheless, the activation of chlorine was also observed. The estimated equivalent doses to skin and eye lens were in the range 0.19 -0.62 μSv/min. However, no influence on intrinsic background signal of all studied dosimeters was observed. The preliminary results indicate that induced radioactivity of dosimeters is strongly influenced by therapeutic beam quality and neutron source strength of particular linac. This dependence will be studied deeper in order to quantify it more precisely.

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The measurement of photoneutrons in the vicinity of a Siemens Primus linear accelerator

Cited by 59 publications

References 3 publications

Out‐of‐field doses and neutron dose equivalents for electron beams from modern Varian and Elekta linear accelerators

Out‐of‐field doses and neutron dose equivalents for electron beams from modern Varian and Elekta linear accelerators

Investigating in-field and out-of-field neutron contamination in high-energy medical linear accelerators based on the treatment factors of field size, depth, beam modifiers, and beam type

Activation of Dosimeters Used in qa of Medical Linear Accelerators

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