Highlights
- •AAA overestimates PTV and OAR dose-volume parameters compared to AXB Dm in H&N VMAT.
- •No systematic trend is observed in the differences between AAA and AXB Dw.
- •All dose-volume parameters are significantly higher for AXB Dw versus AXB Dm.
- •The largest differences are found –for the cochleas and the mandible.
- •Inter-patient variability of differences is greater when switching from AAA to AXB Dw than to AXB Dm.
Abstract
Purpose
To assess the dosimetric impact of switching from the Analytical Anisotropic Algorithm
(AAA) to Acuros XB (AXB) for both dose-to-medium (Dm) and dose-to-water (Dw) in VMAT
for H&N patients. To study whether it should be linked to a change in the dose prescriptions
to the PTVs and in the constraints to the OARs.
Methods
110H&N patients treated with VMAT were included. Calculations were performed with
AAA and AXB. PTV54, PTV60, PTV70, spinal cord, brainstem, brain, larynx, oral cavity,
cochleas, parotid glands and mandible were delineated. Clinically-relevant dose-volume
parameters were compared. Paired t-tests were used to analyze the differences in mean
values. The Pitman-Morgan dispersion test was computed to evaluate inter-patient variability
of these differences.
Results
AAA overestimated all dose-volume parameters compared to AXB Dm (0.2 Gy to 2.4 Gy).
No systematic trend was observed in the differences between AAA and AXB Dw (-5.3 Gy
to 0.6 Gy). Dose-volume parameters were significantly higher for AXB Dw compared to
AXB Dm (0.1 Gy to 6.6 Gy). In all cases, the largest absolute differences (4%–14%)
were found for maximum absorbed doses to the cochleas and the mandible. The number
of parameters with significant inter-patient variability was greater when switching
from AAA to AXB Dw than from AAA to AXB Dm.
Conclusions
There are important differences between AXB and AAA in VMAT planning for H&N cancer.
The systematic differences and their inter-patient variability identified may help
to facilitate decision-making about the dose prescriptions to the PTVs and the constraints
to the OAR.
Keywords
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Article info
Publication history
Accepted:
October 30,
2018
Received in revised form:
October 19,
2018
Received:
June 10,
2018
Identification
Copyright
© 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
