Highlights
- •Proton therapy is an emerging modality for CSI in pediatric patients.
- •Whole brain irradiation is delivered by opposed lateral beams.
- •Lateral-beam size is limited by the shoulders, increasing the number of isocenters.
- •An advanced junction approach allowed to fully exploit the maximal field size.
- •This approach can reduce the number of isocenters and thus the treatment time.
Abstract
Purpose
To present an advanced junction concept in craniospinal irradiation (CSI) by proton
pencil beam scanning (PBS).
Materials and methods
In PBS CSI, whole brain irradiation (WBI) is commonly delivered by opposed lateral-beams,
whereas spine irradiation is delivered by posterior entrances. Since lateral-beams
would cross a large portion of the patient at the shoulder level, the junction between
WBI and spine irradiation cannot extend below that level, thus the size of the lateral-beams
needs to be limited and the number of required isocenters can increase. To overcome
such limitation, a pseudo-junction was introduced below the posterior fossa, to turn in this region the WBI beam arrangement
to a single posterior beam pointed at the same isocenter, that was matched to the
posterior spinal beam more caudally, below shoulder level, in the true-junction. After assessing robustness of the technique to range and setup uncertainties, twenty-three
treated patients were reviewed to estimate the percentage that might benefit of being
treated by two instead of three isocenters.
Results
Target coverage at the junction levels resulted robust, with D95% > 95% on pseudo-junction and D95% > 90% on the true-junction. By the advanced junction concept, 91% of patients might by treated with only two
isocenters, whereas, by the conventional method, 83% of patients required three isocenters.
Conclusion
With the presented junction concept the number of isocenters can be reduced, with
a consequent relevant reduction of treatment time, which is particularly valuable
in the management of pediatric patients under anesthesia.
Keywords
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Article info
Publication history
Published online: April 09, 2019
Accepted:
April 6,
2019
Received in revised form:
April 3,
2019
Received:
December 21,
2018
Identification
Copyright
© 2019 Published by Elsevier Ltd on behalf of Associazione Italiana di Fisica Medica.
