Highlights
- •The effect of magnetic field on two QED™ detector was investigated for clinical use.
- •Angular dependence, response on depth, and output factor were evaluated.
- •Black QED on surface requires the correction for directions and magnetic-field.
- •Blue QED does not require correction for clinical use.
Abstract
Purpose
To evaluate the effect of a low magnetic field (B-field, 0.35 T) on QED™ for clinical
use.
Methods
Black and Blue QED were irradiated using tri-Co-60 magnetic resonance image-guided
radiation therapy systems with and without the B-field. For both detectors, angular
dependence of the beam orientation was evaluated by rotating the gantry and detector
in parallel and perpendicular directions to the B-field. Angular dependence between the directions of both QED and B-field was also measured. Response on the depth and
output factor of both detectors was investigated for parallel and perpendicular setups, respectively.
Results
When Black QED was placed on a surface, detector response decreased by 1.8% and 4.5%
for parallel and perpendicular setups, respectively, owing to the B-field. The angular dependence of the beam orientation
was not affected by B-field for both detectors. There was a significant angular dependence
between Black QED and B-field direction and for the Black QED when the gantry was
rotated. Owing to the B-field, the detector response at 90° decreased by 2.4%, response
of Black QED on the depth was changed only on the surface, and output factor of Black
QED was changed only on the surface. The response of Blue QED was not affected by
the B-field for all examined situations.
Conclusions
Using Black QED on a surface in the same position as that in the calibration requires
some correction to the B-field. Blue QED does not require correction as it is not
affected by the B-field.
Keywords
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Article info
Publication history
Published online: April 04, 2019
Accepted:
April 1,
2019
Received in revised form:
March 18,
2019
Received:
September 13,
2018
Identification
Copyright
© 2019 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
