Impact of transverse magnetic fields on dose response of a nanoDot OSLD in megavoltage photon beams. (February 2020)

• Record Type: Journal Article
• Authors: Ito, Shotaro; Araki, Fujio; Hoshida, Kento; Ohno, Takeshi
• Is Part Of: Physica medica. Volume 70(2020)
• Page Start: 153
• Page End: 160
• Publication Date: 2020-02
• Subjects: Optically stimulated luminescence dosimeters -- MRI-guided radiation therapy -- Monte Carlo simulation -- Burlin's general cavity theory; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2020.01.022
• Languages: English
• ISSNs: 1120-1797

Abstract

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.