Highlight
- •Impact of magnetic fields on the response of a nanoDot OSLD was investigated.
- •Response RQ,B varied depending on the magnetic field strength.
- •Variation of RQ,B reduced as the photon beam energy increased.
- •Top and bottom air- gaps affected the dose deposition due to the electron return effect (ERE).
Abstract
Purpose
We investigated the impact of transverse magnetic fields on the dose response of a
nanoDot optically stimulated luminescence dosimetry (OSLD) in megavoltage photon beams.
Methods
The nanoDot OSLD response was calculated via Monte Carlo (MC) simulations. The responses
RQ and RQ,B without and with the transverse magnetic fields of 0.35–3 T were analyzed as a function
of depth at a 10 cm × 10 cm field for 4–18 MV photons in a solid water phantom. All
responses were determined based on comparisons with the response under the reference
conditions (depth of 10 cm and a 10 cm × 10 cm field) for 6 MV without the magnetic
field. In addition, the influence of air-gaps on the nanoDot response in the magnetic
field was estimated according to Burlin’s general cavity theory.
Results
The RQ as a function of depth for 4–18 MV ranged from 1.013 to 0.993, excepting the buildup
region. The RQ,B increased from 2.8% to 1.5% at 1.5 T and decreased from 3.0% to 1.1% at 3 T in comparison
with RQ as the photon energy increased. The depth dependence of RQ,B was less than 1%, excepting the buildup region. The top air-gap and the bottom air-
gap were responsible for the response reduction and the response increase, respectively.
Conclusions
The response RQ,B varied depending on the magnetic field intensity, and the variation of RQ,B reduced as the photon beam energy increased. The air-gaps affected the dose deposition
in the magnetic fields.
Keywords
To read this article in full you will need to make a payment
Purchase one-time access:
Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online accessOne-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:
Subscribe to Physica Medica: European Journal of Medical PhysicsAlready a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
References
- MRI/linac integration.Radiother Oncol. 2008; 86: 25-29https://doi.org/10.1016/j.radonc.2007.10.034
- MRI-linear accelerator radiotherapy systems.Clin Oncol. 2018; 30: 686-691https://doi.org/10.1016/j.clon.2018.08.003
- Dosimetry for the MRI accelerator: The impact of a magnetic field on the response of a Farmer NE2571 ionization chamber.Phys Med Biol. 2009; 54: 2993-3002https://doi.org/10.1088/0031-9155/54/10/002
- Radiation dosimetry in magnetic fields with Farmer-type ionization chambers: determination of magnetic field correction factors for different magnetic field strengths and field orientations.Phys Med Biol. 2017; 62: 6708-6728https://doi.org/10.1088/1361-6560/aa7ae4
- Reference dosimetry in magnetic fields: formalism and ionization chamber correction factors.Med Phys. 2016; 43: 4915-4927https://doi.org/10.1118/1.4959785
- Relative dosimetry with an MR-linac: Response of ion chambers, diamond, and diode detectors for off-axis, depth dose, and output factor measurements: Response.Med Phys. 2018; 45: 884-897https://doi.org/10.1002/mp.12699
- Dose response of selected solid state detectors in applied homogeneous transverse and longitudinal magnetic fields.Med Phys. 2014; 41https://doi.org/10.1118/1.4893276
- Influence of a transverse magnetic field on the response of different detectors in a high energy photon beam near the surface.Med Phys. 2019; 29: 22-30https://doi.org/10.1016/j.zemedi.2018.07.001
- Dosimetry in clinical static magnetic fields using plastic scintillation detectors.Radiat Meas. 2013; 56: 357-360https://doi.org/10.1016/j.radmeas.2013.03.012
- Investigation of magnetic field effects on the dose – Response of 3D dosimeters for magnetic resonance – image guided radiation therapy applications.Radiother Oncol. 2017; 125: 426-432https://doi.org/10.1016/j.radonc.2017.08.027
- Feasibility of dosimetry with optically stimulated luminescence detectors in magnetic fields.Radiat Meas. 2017; 106: 346-351https://doi.org/10.1016/j.radmeas.2017.03.018
- Response of a nanoDot OSLD system in megavoltage photon beams.Phys Med. 2019; 64: 74-80https://doi.org/10.1016/j.ejmp.2019.06.014
- Commissioning of optically stimulated luminescence dosimeters for use in radiotherapy.Radiat Meas. 2013; 51: 31-39https://doi.org/10.1016/j.radmeas.2013.01.012
- Angular dependence of dose sensitivity of nanoDot optically stimulated luminescent dosimeters in different radiation geometries.Med Phys. 2015; 42: 5633-5641https://doi.org/10.1118/1.4929558
- The energy dependence and dose response of a commercial optically stimulated luminescent detector for kilovoltage photon, megavoltage photon, and electron, proton, and carbon beams: Energy dependence of optically stimulated luminescent detector.Med Phys. 2009; 36: 1690-1699https://doi.org/10.1118/1.3097283
- Changes in optically stimulated luminescent dosimeter (OSLD) dosimetric characteristics with accumulated dose.Med Phys. 2010; 37: 132-140https://doi.org/10.1118/1.3267489
- On the use of optically stimulated luminescent dosimeter for surface dose measurement during radiotherapy.PLoS One. 2015; 10: 1-15https://doi.org/10.1371/journal.pone. 0128544
- In vivo measurements for high dose rate brachytherapy with optically stimulated luminescent dosimeters.Med Phys. 2013; 40071730https://doi.org/10.1118/1.4811143
- Multi-institutional evaluation of end-to-end protocol for IMRT/VMAT treatment chains utilizing conventional linacs.Med Dosim. 2019; 44: 61-66https://doi.org/10.1016/j.meddos.2018.02.002
- TLD and OSLD dosimetry systems for remote audits of radiotherapy external beam calibration.Radiat Meas. 2017; 106: 412-415https://doi.org/10.1016/j.radmeas.2017.01.005
- Remote auditing of radiotherapy facilities using optically stimulated luminescence dosimeters.Med Phys. 2014; 41032102https://doi.org/10.1118/1.4865786
- Long term OSLD reader stability in the ACDS level one audit.Australas Phys Eng Sci Med. 2015; 38: 151-156https://doi.org/10.1007/s13246-014-0320-7
- Accurate condensed history Monte Carlo simulation of electron transport. I. EGSnrc, the new EGS4 version.Med Phys. 2000; 27: 485-498https://doi.org/10.1118/1.598917
Kawrakow I, Mainegra-Hing E, Rogers DWO, Tessier F, Walters BRB. The EGSnrc code system: Monte Carlo simulation of electron and photon transport. National Research Council of Canada Report 2013;PIRS-701.
- EGSnrc C++ class library: EGSnrc C++ user code, egs_chamber.Nat Res Council of Canada Report. 2009; : PIRS-898
- Kawrakow I. Efficiency improvements for ion chamber calculations in high energy photon beams.Med Phys. 2008; 35: 1328-1336https://doi.org/10.1118/1.2874554
- Fano cavity test for electron Monte Carlo transport algorithms in magnetic fields: comparison between EGSnrc, PENELOPE, MCNP6 and Geant4.Phys Med Biol. 2018; 63195013https://doi.org/10.1088/1361-6560/aadf29
- BEAM: a Monte Carlo code to simulate radiotherapy treatment units.Med Phys. 1995; 22: 503-524https://doi.org/10.1118/1.597552
Rogers DW, Walters BR, Kawrakow I. BEAMnrc Users Manual. National Research Council of Canada Report 2013;PIRS-509 (A) revL.
Berger MJ, Hubbell JH. XCOM: Photon cross sections on a personal computer Report NBSIR87-3597 National Institute of Standards Technology, Gaithersburg, MD 20899; 1987/1999.
- A general theory of cavity ionisation.Br J Radiol. 1966; 39: 727-734https://doi.org/10.1259/0007-1285-39-466-727
- A theory of cavity ionization.Radiat Res. 1995; 3: 239-254
- The response of a radiophotoluminescent glass dosimeter in megavoltage photon and electron beams.Med Phys. 2014; 41122102https://doi.org/10.1118/1.4901639
Rogers DWO, Kawrakow I, Seuntjens JP, Walters BRB, Mainegra-Hing E. NRC User Code for EGSnrc. National Research Council of Canada Report 2011;PIRS-702 (revC).
- Stopping-power and mass energy absorption coefficient ratios for solid water.Med Phys. 1986; 13: 403-404https://doi.org/10.1118/1.595884
Seltzer SM, Hubbell J H. Tables and graphs of photon mass attenuation coefficients and mass energy-absorption coefficients for photon energies 1 keV to 20 MeV for elements Z=1 to 92, The X-ray Attenuation and Absorption for Materials of Dosimetric Interest Database, NIST 1996.
Article info
Publication history
Published online: February 04, 2020
Accepted:
January 26,
2020
Received in revised form:
January 24,
2020
Received:
July 1,
2019
Identification
Copyright
© 2020 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
