Highlights
- •Microbeam radiation therapy is an innovative radiotherapy technique.
- •Radiocromic film dosimetry at micrometric scale is fundamental.
- •Comparison between a microdensitometer and an optical microscope for film dosimetry.
- •Definition of film dosimetry protocol for microbeam dose analysis.
- •The microscope allows more precise, accurate and reliable dose evaluation.
Abstract
Purpose
Microbeam radiation therapy is a developing technique that promises superior tumour
control and better normal tissue tolerance using spatially fractionated X-ray beams
only tens of micrometres wide.
Radiochromic film dosimetry at micrometric scale was performed using a microdensitometer,
but this instrument presents limitations in accuracy and precision, therefore the
use of a microscope is suggested as alternative. The detailed procedures developed
to use the two devices are reported allowing a comparison.
Methods
Films were irradiated with single microbeams and with arrays of 50 µm wide microbeams
spaced by a 400 µm pitch, using a polychromatic beam with mean energy of 100 keV.
The film dose measurements were performed using two independent instruments: a microdensitometer
(MDM) and an optical microscope (OM).
Results
The mean values of the absolute dose measured with the two instruments differ by less
than 5% but the OM provides reproducibility with a standard deviation of 1.2% compared
to up to 7% for the MDM. The resolution of the OM was determined to be ~ 1 to 2 µm
in both planar directions able to resolve pencil beams irradiation, while the MDM
reaches at the best 20 µm resolution along scanning direction. The uncertainties related
to the data acquisition are 2.5–3% for the OM and 9–15% for the MDM.
Conclusion
The comparison between the two devices validates that the OM provides equivalent results
to the MDM with better precision, reproducibility and resolution. In addition, the
possibility to study dose distributions in two-dimensions over wider areas definitely
sanctions the OM as substitute of the MDM.
Keywords
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Article info
Publication history
Published online: August 23, 2019
Accepted:
August 14,
2019
Received in revised form:
August 13,
2019
Received:
April 22,
2019
Identification
Copyright
© 2019 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
