Development and verification of the pulsed scanned proton beam at The Svedberg Laboratory in Uppsala

Tilly, Nina; Grusell, Erik; Kimstrand, Peter; Lorin, Stefan; Gajewski, Konrad; Pettersson, Mikael; Bäcklund, Andreas; Glimelius, Bengt

doi:10.1088/0031-9155/52/10/008

Cited by 13 publications

(9 citation statements)

References 13 publications

(19 reference statements)

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“…This can lead to a 2 mm difference in the measured range when two separate data sets, each with ±1 mm uncertainties are compared. Our uncertainty in range measurement is consistent with that specified by Tilly et al 19 …”

Section: B Measurements With the Computerized Water Tank Dosimetrysupporting

confidence: 92%

Quality assurance of proton beams using a multilayer ionization chamber system

et al. 2013

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Section: B Measurements With the Computerized Water Tank Dosimetrysupporting

confidence: 92%

Quality assurance of proton beams using a multilayer ionization chamber system

et al. 2013

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“…Although the concept of using energy selection systems and multilayer Faraday cups in charged particle beams is not new, 7 published details about the use of these devices and their calibration in clinical proton beams are sparse. [8][9][10] This article reports on the calibration of the MLFC, the effect of energy selection slit setting on the range modulation scheme, dose uniformity, and distal edge gradient under various conditions, and optimization of the energy slit settings at MPRI. Comparisons are also provided with measurements made for a system using beam delivery method 1.…”

Section: Introductionmentioning

confidence: 99%

Energy spectrum control for modulated proton beams

Hsi¹,

Moyers²,

Nichiporov

et al. 2009

Medical Physics

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In proton therapy delivered with range modulated beams, the energy spectrum of protons entering the delivery nozzle can affect the dose uniformity within the target region and the dose gradient around its periphery. For a cyclotron with a fixed extraction energy, a rangeshifter is used to change the energy but this produces increasing energy spreads for decreasing energies. This study investigated the magnitude of the effects of different energy spreads on dose uniformity and distal edge dose gradient and determined the limits for controlling the incident spectrum. A multilayer Faraday cup ͑MLFC͒ was calibrated against depth dose curves measured in water for nonmodulated beams with various incident spectra. Depth dose curves were measured in a water phantom and in a multilayer ionization chamber detector for modulated beams using different incident energy spreads. Some nozzle entrance energy spectra can produce unacceptable dose nonuniformities of up to Ϯ21% over the modulated region. For modulated beams and small beam ranges, the width of the distal penumbra can vary by a factor of 2.5. When the energy spread was controlled within the defined limits, the dose nonuniformity was less than Ϯ3%. To facilitate understanding of the results, the data were compared to the measured and Monte Carlo calculated data from a variable extraction energy synchrotron which has a narrow spectrum for all energies. Dose uniformity is only maintained within prescription limits when the energy spread is controlled. At low energies, a large spread can be beneficial for extending the energy range at which a single range modulator device can be used. An MLFC can be used as part of a feedback to provide specified energy spreads for different energies.

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“…However, the dosimetric advantages of proton beams may be negated to some extent by the generation of stray neutrons in proton therapy, which may affect the whole-body exposures and thereby increase patients' risk of developing secondary cancers. Stray neutron radiation from passively scattered nozzles is larger than that from active scanning nozzles (Kanai et al 1980, Pedroni et al 1995, Tilly et al 2007 because passive scattering nozzles have more material components in the beam path and, thus, more neutrons are produced. The additional stray radiation exposure is of particular concern for patients who have good prognoses with relatively long expected survival times because their lifetime risk of radiation-induced secondary cancers could be increased markedly (Lee et al 2005, Gibbs et al 2006, Miralbell et al 2002.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo simulations of neutron spectral fluence, radiation weighting factor and ambient dose equivalent for a passively scattered proton therapy unit

et al. 2007

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Stray neutron exposures pose a potential risk for the development of secondary cancer in patients receiving proton therapy. However, the behavior of the ambient dose equivalent is not fully understood, including dependences on neutron spectral fluence, radiation weighting factor and proton treatment beam characteristics. The objective of this work, therefore, was to estimate neutron exposures resulting from the use of a passively scattered proton treatment unit. In particular, we studied the characteristics of the neutron spectral fluence, radiation weighting factor and ambient dose equivalent with Monte Carlo simulations. The neutron spectral fluence contained two pronounced peaks, one a low-energy peak with a mode around 1 MeV and one a high-energy peak that ranged from about 10 MeV up to the proton energy. The mean radiation weighting factors varied only slightly, from 8.8 to 10.3, with proton energy and location for a closed-aperture configuration. For unmodulated proton beams stopped in a closed aperture, the ambient dose equivalent from neutrons per therapeutic absorbed dose (H*(10)/D) calculated free-in-air ranged from about 0.3 mSv/Gy for a small scattered field of 100 MeV proton energy to 19 mSv/Gy for a large scattered field of 250 MeV proton energy, revealing strong dependences on proton energy and field size. Comparisons of in-air calculations with in-phantom calculations indicated that the in-air method yielded a conservative estimation of stray neutron radiation exposure for a prostate cancer patient.

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Development and verification of the pulsed scanned proton beam at The Svedberg Laboratory in Uppsala

Cited by 13 publications

References 13 publications

Quality assurance of proton beams using a multilayer ionization chamber system

Quality assurance of proton beams using a multilayer ionization chamber system

Energy spectrum control for modulated proton beams

Monte Carlo simulations of neutron spectral fluence, radiation weighting factor and ambient dose equivalent for a passively scattered proton therapy unit

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