Influence of beam efficiency through the patient‐specific collimator on secondary neutron dose equivalent in double scattering and uniform scanning modes of proton therapy

Hecksel, Draik; Anferov, V. A.; Fitzek, Markus M.; Shahnazi, Kambiz

doi:10.1118/1.3431575

Cited by 26 publications

(29 citation statements)

References 28 publications

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“…This is because the collimators are located close to the patient, and many primary particles stop at this location in the beam line (Brenner et al, 2009;Yonai et al, 2009;Hecksel et al, 2010).…”

Section: Out-of-field Volumementioning

confidence: 99%

“…(ii) Beam parameters (105) The influences of beam parameters have been investigated by several groups (Polf and Newhauser, 2005;Mesoloras et al, 2006;Zheng et al, 2007;Yonai et al, 2008;Athar and Paganetti, 2009;Shin et al, 2009;Hecksel et al, 2010). The following parameters are considered to have the main effects on the neutron dose to patients in ion beam radiotherapy using the broad beam method.…”

Section: Out-of-field Volumementioning

confidence: 99%

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Cellular mechanisms underlying failed beta cell regeneration in offspring of protein-restricted pregnant mice

Cox

Beamish

Carter

et al. 2013

Exp Biol Med (Maywood)

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Low birth weight and poor foetal growth following low protein (LP) exposure are associated with altered islet development and glucose intolerance in adulthood. Additionally, LP-fed offspring fail to regenerate their β-cells following depletion with streptozotocin (STZ) in contrast to control-fed offspring that restore β-cell mass. Our objective was to identify signalling pathways and cellular functions that may be critically altered in LP offspring rendering them susceptible to developing long-term glucose intolerance and decreased β-cell plasticity. Pregnant Balb/c mice were fed a control (C; 20% protein) or an isocaloric LP (8% protein) diet throughout gestation and C diet thereafter. Female offspring were injected intraperitoneally with 35 mg/kg STZ or vehicle on days 1 to 5 for each dietary treatment. At 30 days of age, total RNA was extracted from pancreatic tissue for microarray analysis using the Affymetrix GeneChip Mouse Genome 430 2.0. Gene and protein expression were quantified from isolated islets. Finally, β-cell proliferation was determined in vitro following REG1α treatment. The microarray data and GO enrichment analysis indicated that foetal protein restriction alters the early expression of genes necessary for many cell functions, such as oxidative phosphorylation and free radical scavenging. Expression of Reg1 was upregulated following STZ, whereas protein content was decreased in LP + STZ islets. Furthermore, REG1α failed to stimulate β-cell proliferation in vitro in LP + STZ islets. Therefore, early nutritional insults may programme the Reg1 pathway resulting in a limited ability to increase β-cell mass during metabolic stress. In conclusion, this study implicates the Reg1 pathway in β-cell regeneration and describes altered programming of gene expression in LP offspring, which underlies later development of cell dysfunction and glucose intolerance in adulthood.

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Section: Out-of-field Volumementioning

confidence: 99%

Section: Out-of-field Volumementioning

confidence: 99%

Cellular mechanisms underlying failed beta cell regeneration in offspring of protein-restricted pregnant mice

Cox

Beamish

Carter

et al. 2013

Exp Biol Med (Maywood)

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“…The efficiency of most proton therapy treatment heads is quite low (typically only between 3 and 30% depending on the field size). The neutron dose depends on the ratio of field size to aperture opening and neutron doses from treatment head neutrons typically increase with decreasing field size (Mesoloras et al 2006; Zacharatou Jarlskog et al 2008; Hecksel et al 2010). It has been shown that for a small target volume, the contribution of neutrons from the treatment head can reach ~99 % of the total neutron contribution, while for a large target volume it can go down to ~60 % (Zacharatou Jarlskog et al 2008).…”

Section: Studies To Estimate the Risk For Second Cancersmentioning

confidence: 99%

Assessment of the Risk for Developing a Second Malignancy From Scattered and Secondary Radiation In Radiation Therapy

Paganetti¹

2012

Health Physics

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With the average age of radiation therapy patients decreasing and the advent of more complex treatment options comes the concern that the incidences of radiation-induced cancer might increase in the future. The carcinogenic effects of radiation are not well understood for the entire dose range experienced in radiation therapy. Longer epidemiological studies are needed to improve current risk models and reduce uncertainties of current risk model parameters. On the other hand, risk estimations are needed today to judge the risks vs. benefits of modern radiation therapy techniques. This paper describes the current state-of-the-art in risk modeling for radiation-induced malignancies in radiation therapy, distinguishing between two volumes. First, the organs within the main radiation field receiving low or intermediate doses (typically between 0.1 and 50 Gy). Second, the organs far away from the treatment volume receiving low doses mainly due to scattered and secondary radiation (typically below 0.1 Gy). The dosimetry as well as the risk model formalisms are outlined. Furthermore, example calculations and results are presented for intensity-modulated photon therapy vs. proton therapy.

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“…1,[9][10][11][12][13][14] There are a few reports of neutron doseequivalent measurements made in proton therapy centers with either the wide-energy neutron detection instrument (WENDI) or smart WENDI (SWENDI), a type of Rem-meter that is sensitive over an energy range adequate for measuring neutrons from proton therapy. [14][15][16][17] Like standard Remmeters, however, these detectors provide only a single doseequivalent value and do not provide the neutron spectrum. There are also several reports of measurements with detectors such as track etch detectors 14,18 or thermoluminescent detectors 19 that have limited or no response to neutrons with energies greater than 10 MeV.…”

Section: Introductionmentioning

confidence: 99%

Secondary neutron spectrum from 250‐MeV passively scattered proton therapy: Measurement with an extended‐range Bonner sphere system

Howell

Burgett

2014

Medical Physics

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Purpose: Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. Methods: The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. Results: The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies ≥20 MeV. Conclusions: The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire energy range being measured, i.e., thermal to 250 MeV. The authors used the neutron fluence spectrum to demonstrate experimentally the contribution of neutrons with different energies to the total dose equivalent and in particular the contribution of high-energy neutrons (≥20 MeV). These are valuable reference data that can be directly compared with Monte Carlo and experimental data in the literature. © 2014 Author(s)

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Influence of beam efficiency through the patient‐specific collimator on secondary neutron dose equivalent in double scattering and uniform scanning modes of proton therapy

Cited by 26 publications

References 28 publications

Cellular mechanisms underlying failed beta cell regeneration in offspring of protein-restricted pregnant mice

Cellular mechanisms underlying failed beta cell regeneration in offspring of protein-restricted pregnant mice

Assessment of the Risk for Developing a Second Malignancy From Scattered and Secondary Radiation In Radiation Therapy

Secondary neutron spectrum from 250‐MeV passively scattered proton therapy: Measurement with an extended‐range Bonner sphere system

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