Absolute Calibration of the Elekta Unity MR Linac Using the UK Code of Practice for High-Energy Photon Dosimetry

Budgell, Geoff J; Gohil, Pooja; Agnew, J. P.; Berresford, J.; Billas, Ilias; Duane, S

doi:10.1007/978-981-10-9023-3_82

Cited by 2 publications

(2 citation statements)

References 2 publications

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“…MR-guided radiotherapy could improve the accuracy of SRS and SBRT treatments because of better soft tissue contrast with MR for the sites that have been treated with these techniques. Several investigators have worked on the dosimetry methods, dosimetry accuracy, and proper dosimeter in the presence of a magnetic field [18][19][20][21]. So far few studies were focused on the the effect of magnetic fields on dosimetric properties of small fields.…”

Section: Introductionmentioning

confidence: 99%

The effect of magnetic field on Linac based Stereotactic Radiosurgery dosimetric parameters

Nedaie¹,

Gholami²,

Longo³

et al. 2020

Biomed. Phys. Eng. Express

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Objective: MR-linac machines are being developed for image-guided radiation therapy but the magnetic field of such machines could affect dose distributions. The purpose of this work was to evaluate the effect of a magnetic field on linac beam dosimetric parameters including penumbra for circular cones used in radiosurgery. Methods: Monte Carlo simulation was conducted for a linac machine with circular cones at 6 MV beam. A homogenous magnetic field of 1.5 T was applied transversely and parallel to the radiation beam. Percentage depth dose (PDD) and beam profiles in a water phantom with and without the magnetic field were calculated. Results: The results have shown that when the magnetic field is applied transversely, the PDDs in the water phantom differ in the buildup region and distant part of PDD curves. The beam profiles at three different depths are all significantly different from those without the magnetic field. The penumbra is greater when a magnetic field has been applied. Conclusion: Linear accelerator-based SRT and SRS use small circular cones. The beam penumbra for these cones can change in the presence of a magnetic field. The perturbation of dose distribution has been also observed in a patient plan due to the presence of a magnetic field. The results of this study show that dose distributions in the presence of a magnetic field must be considered for MR-guided radiotherapy treatments.

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Section: Introductionmentioning

confidence: 99%

The effect of magnetic field on Linac based Stereotactic Radiosurgery dosimetric parameters

Nedaie¹,

Gholami²,

Longo³

et al. 2020

Biomed. Phys. Eng. Express

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“…Although the definition of specifies an SSD of 100 cm, the value of is essentially independent of SDD provided that the field size 10 cm 10 cm is maintained [ 65 ], which is relevant as both currently commercially available MRI-linac systems have SSDs differing from 100 cm.…”

Section: Reference Dosimetrymentioning

confidence: 99%

ACPSEM position paper: dosimetry for magnetic resonance imaging linear accelerators

et al. 2023

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Consistency and clear guidelines on dosimetry are essential for accurate and precise dosimetry, to ensure the best patient outcomes and to allow direct dose comparison across different centres. Magnetic Resonance Imaging Linac (MRI-linac) systems have recently been introduced to Australasian clinics. This report provides recommendations on reference dosimetry measurements for MRI-linacs on behalf of the Australiasian College of Physical Scientists and Engineers in Medicine (ACPSEM) MRI-linac working group. There are two configurations considered for MRI-linacs, perpendicular and parallel, referring to the relative direction of the magnetic field and radiation beam, with different impacts on dose deposition in a medium. These recommendations focus on ion chambers which are most commonly used in the clinic for reference dosimetry. Water phantoms must be MR safe or conditional and practical limitations on phantom set-up must be considered. Solid phantoms are not advised for reference dosimetry. For reference dosimetry, IAEA TRS-398 recommendations cannot be followed completely due to physical differences between conventional linac and MRI-linac systems. Manufacturers’ advice on reference conditions should be followed. Beam quality specification of TPR20,10 is recommended. The configuration of the central axis of the ion chamber relative to the magnetic field and radiation beam impacts the chamber response and must be considered carefully. Recommended corrections to delivered dose are $${k}_{{Q}_{msr}{Q}_{0}}^{{f}_{msr}{f}_{ref}}$$ k Q msr Q 0 f msr f ref , a correction for beam quality and $${k}_{\overrightarrow{B},{Q}_{msr}}^{{f}_{msr}}$$ k B → , Q msr f msr , for the impact of the magnetic field on dosimeter response in the magnetic field. Literature based values for $${k}_{\overrightarrow{B},{Q}_{msr}}^{{f}_{msr}}$$ k B → , Q msr f msr are given. It is important to note that this is a developing field and these recommendations should be used together with a review of current literature.

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Absolute Calibration of the Elekta Unity MR Linac Using the UK Code of Practice for High-Energy Photon Dosimetry

Cited by 2 publications

References 2 publications

The effect of magnetic field on Linac based Stereotactic Radiosurgery dosimetric parameters

The effect of magnetic field on Linac based Stereotactic Radiosurgery dosimetric parameters

ACPSEM position paper: dosimetry for magnetic resonance imaging linear accelerators

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