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Erschienen in:
01.03.2016 | Original Research
Dosimetric comparison of volumetric modulated arc therapy and intensity-modulated radiation therapy for liver stereotactic ablative body radiotherapy
Erschienen in: Journal of Radiation Oncology | Ausgabe 1/2016
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Objectives
The objectives of this study were to compare the dosimetric differences between volumetric modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) techniques in treatment planning for liver stereotactic ablative body radiation (SABR) and, secondly, to identify when alternative VMAT arc configurations could provide dosimetric gains.
Methods
Ten consecutive patients previously treated with IMRT to a single liver lesion were selected and planned retrospectively using VMAT while employing the same dose objectives and dose constraints. Differences in dose conformality, normal liver sparing, and organs at risk (OARs) doses were compared between the IMRT and corresponding single circumferential arc (SCA) VMAT plan for each patient. Relative dosimetric differences were quantified for each of eight alternative VMAT arc configurations.
Results
The VMAT SCA plans were associated with a 4.8 and 8.1 % improvement of the 95 % conformity index (p = 0.02) and the 50 % gradient index (p = 0.05), respectively. A trend toward significance was found for normal liver sparing and the dose to the adjacent OAR with SCA vs. IMRT. The optimal VMAT arc arrangement was a single ipsilateral 180 degree arc in patients having small (<2–3 cm) lesions away from OARs (excluding the liver), a combination of coplanar arc and non-coplanar partial arc for patients with lesions adjacent to two or more critical OARs and an SCA which was sufficient for the remaining patients.
Conclusion
VMAT planning for liver SABR provided measurably higher levels of dose conformality compared with IMRT. An ipsilateral partial arc, single circumferential arc, or circumferential arc with added non-coplanar partial arc proved to be the most promising arc configuration in the majority of patients.