Shielding measurements for a 230 MeV proton beam

Siebers, Jeffrey V.

doi:10.2172/6504628

Cited by 6 publications

(5 citation statements)

References 7 publications

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“…The calibration uncertainty is due to the determination of the alpha spectrum centroid and its lineal energy. This value was calculated elsewhere and is on the order of 3 % (24) . The W/e uncertainty, on the other hand, is due to the assumption of a uniform value for all particles created in the detector.…”

Section: Uncertaintiesmentioning

confidence: 87%

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Microdosimetric measurements for neutron-absorbed dose determination during proton therapy

Perez‐Andujar

DeLuca

Thornton³

et al. 2012

Radiation Protection Dosimetry

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This work presents microdosimetric measurements performed at the Midwest Proton Radiotherapy Institute in Bloomington, Indiana, USA. The measurements were done simulating clinical setups with a water phantom and for a variety of stopping targets. The water phantom was irradiated by a proton spread out Bragg peak (SOBP) and by a proton pencil beam. Stopping target measurements were performed only for the pencil beam. The targets used were made of polyethylene, brass and lead. The objective of this work was to determine the neutron-absorbed dose for a passive and active proton therapy delivery, and for the interactions of the proton beam with materials typically in the beam line of a proton therapy treatment nozzle. Neutron doses were found to be higher at 458 8 8 8 8 and 908 8 8 8 8 from the beam direction for the SOBP configuration by a factor of 1.1 and 1.3, respectively, compared with the pencil beam. Meanwhile, the pencil beam configuration produced neutron-absorbed doses 2.2 times higher at 08 8 8 8 8 than the SOBP. For stopping targets, lead was found to dominate the neutronabsorbed dose for most angles due to a large production of low-energy neutrons emitted isotropically.

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Section: Uncertaintiesmentioning

confidence: 87%

“…Finally, the factor, calculated using Equation (1), can also be used to convert the event size to units from keV mm 21 to Gy (Equation (2)) (24) . In any case, the total absorbed dose represented by the measured spectra is determined from:…”

mentioning

confidence: 99%

Microdosimetric measurements for neutron-absorbed dose determination during proton therapy

Perez‐Andujar

DeLuca

Thornton³

et al. 2012

Radiation Protection Dosimetry

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Section: Introductionmentioning

confidence: 99%

“…In some previous investigations, the calibration in terms of pulse amplitude is performed using only few points. Knowing the amplitude of the input pulse, a voltage divider is used so the pulse amplitude is reduced to a few values and a linear regression is then performed to correlate the channels to the respective pulse amplitude 13,14 …”

Section: Introductionmentioning

confidence: 99%

“…Knowing the amplitude of the input pulse, a voltage divider is used so the pulse amplitude is reduced to a few values and a linear regression is then performed to correlate the channels to the respective pulse amplitude. 13,14 Whether this assumption about the electronics linearity holds true, especially for low voltage input signals, has not been studied yet as well as their uncertainties assessment.…”

Section: Introductionmentioning

confidence: 99%

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On the measurement uncertainty of microdosimetric quantities using diamond and silicon microdosimeters in carbon‐ion beams

et al. 2022

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Purpose The purpose of this paper is to compare the response of two different types of solid‐state microdosimeters, that is, silicon and diamond, and their uncertainties. A study of the conversion of silicon microdosimetric spectra to the diamond equivalent for microdosimeters with different geometry of the sensitive volumes is performed, including the use of different stopping power databases. Method Diamond and silicon microdosimeters were irradiated under the same conditions, aligned at the same depth in a carbon‐ion beam at the MedAustron ion therapy center. In order to estimate the microdosimetric quantities, the readout electronic linearity was investigated with three different methods, that is, the first being a single linear regression, the second consisting of a double linear regression with a channel transition and last a multiple linear regression by splitting the data into odd and even groups. The uncertainty related to each of these methods was estimated as well. The edge calibration was performed using the intercept with the horizontal axis of the tangent through the inflection point of the Fermi function approximation multi‐channel analyzer spectrum. It was assumed that this point corresponds to the maximum energy difference of particle traversing the sensitive volume (SV) for which the residual range difference in the continuous slowing down approximation is equal to the thickness of the SV of the microdosimeter. Four material conversion methods were explored, the edge method, the density method, the maximum‐deposition energy method and the bin‐by‐bin transformation method. The uncertainties of the microdosimetric quantities resulting from the linearization, the edge calibration and the detectors thickness were also estimated. Results It was found that the double linear regression had the lowest uncertainty for both microdosimeters. The propagated standard (k = 1) uncertainties on the frequency‐mean lineal energy truey¯normalF${\bar{y}}_{\rm{F}}$ and the dose‐mean lineal energy truey¯normalD${\bar{y}}_{\rm{D}}$ values from the marker point, in the spectra, in the plateau were 0.1% and 0.2%, respectively, for the diamond microdosimeter, whilst for the silicon microdosimeter data converted to diamond, the uncertainty was estimated to be 0.1%. In the range corresponding to the 90% of the amplitude of the Bragg Peak at the distal part of the Bragg curve (R90) the uncertainty was found to be 0.1%. The uncertainty propagation from the stopping power tables was estimated to be between 5% and 7% depending on the method. The uncertainty on the truey¯normalF${\bar{y}}_{\rm{F}}$ and truey¯normalD${\bar{y}}_{\rm{D}}$ coming from the thickness of the detectors varied between 0.3% and 0.5%. Conclusion This article demonstrate that the linearity of the readout electronics affects the microdosimetric spectra with a difference in truey¯normalF${\bar{y}}_{\rm{F}}$ values between the different linearization methods of up to 17.5%. The combined uncertainty was dominated by the uncertainty of stopping power o...

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Shielding and activation study for proton medical accelerators

Knowles

Orthel

Hill

Proceedings of International Conference on Particle Accelerators

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Shielding measurements for a 230 MeV proton beam

Cited by 6 publications

References 7 publications

Microdosimetric measurements for neutron-absorbed dose determination during proton therapy

Microdosimetric measurements for neutron-absorbed dose determination during proton therapy

On the measurement uncertainty of microdosimetric quantities using diamond and silicon microdosimeters in carbon‐ion beams

Shielding and activation study for proton medical accelerators

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