Highlights
- •A new range optimization procedure was developed for adaptive proton therapy.
- •The new method accounts for tumor dose coverage and dose sparing in OARs.
- •The new method was applied to an abdominal metastasis.
- •Unless the new method is used, dose exposure in OARs may be increased.
- •The new method achieves better tumor coverage and dose sparing in OARs.
Abstract
Purpose
The purpose of this study was to design and develop a new range optimization for target
and organs at risk (OARs) in dynamic adaptive proton beam therapy (PBT).
Methods
The new range optimization for target and OARs (RO-TO) was optimized to maintain target
dose coverage but not to increase the dose exposure of OARs, while the other procedure,
range optimization for target (RO-T), only focused on target dose coverage. A retrospective
analysis of a patient who received PBT for abdominal lymph node metastases was performed
to show the effectiveness of our new approach. The original plan (OP), which had a
total dose of 60 Gy (relative biological effectiveness; RBE), was generated using
six treatment fields. Bone-based registration (BR) and tumor-based registration (TR)
were performed on each pretreatment daily CT image dataset acquired once every four
fractions, to align the isocenter.
Results
Both range adaptive approaches achieved better coverage (D95%) and homogeneity (D5%−D95%) than BR and TR only. However, RO-T showed the greatest increases in D2cc and Dmean values of the small intestine and stomach and exceeded the limitations of dose exposure
for those OARs. RO-TO showed comparable or superior dose sparing compared with the
OP for all OARs.
Conclusions
Our results suggest that BR and TR alone may reduce target dose coverage, and that
RO-T may increase the dose exposure to the OARs. RO-TO may achieve the planned dose
delivery to the target and OARs more efficiently than the OP. The technique requires
testing on a large clinical dataset.
Keywords
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Article info
Publication history
Accepted:
November 15,
2018
Received in revised form:
September 26,
2018
Received:
May 28,
2018
Identification
Copyright
© 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
