Impact of prescription isodose level and collimator selection on dose homogeneity and plan quality in robotic radiosurgery.

Autor: Hellerbach A; Faculty of Medicine and University Hospital Cologne, Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany. alexandra.hellerbach@uk-koeln.de., Eichner M; Faculty of Medicine and University Hospital Cologne, Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany., Rueß D; Faculty of Medicine and University Hospital Cologne, Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany., Luyken K; Faculty of Medicine and University Hospital Cologne, Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany., Hoevels M; Faculty of Medicine and University Hospital Cologne, Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany., Judge M; Faculty of Medicine and University Hospital Cologne, Institute of Radiation Oncology, University of Cologne, Cologne, Germany., Baues C; Faculty of Medicine and University Hospital Cologne, Institute of Radiation Oncology, University of Cologne, Cologne, Germany., Ruge M; Faculty of Medicine and University Hospital Cologne, Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany., Kocher M; Faculty of Medicine and University Hospital Cologne, Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany., Treuer H; Faculty of Medicine and University Hospital Cologne, Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Kerpener Straße 62, 50937, Cologne, Germany.
Jazyk: angličtina
Zdroj: Strahlentherapie und Onkologie : Organ der Deutschen Rontgengesellschaft ... [et al] [Strahlenther Onkol] 2022 May; Vol. 198 (5), pp. 484-496. Date of Electronic Publication: 2021 Dec 09.
DOI: 10.1007/s00066-021-01872-4
Abstrakt: Purpose: In stereotactic radiosurgery (SRS), prescription isodoses and resulting dose homogeneities vary widely across different platforms and clinical entities. Our goal was to investigate the physical limitations of generating dose distributions with an intended level of homogeneity in robotic SRS.
Methods: Treatment plans for non-isocentric irradiation of 4 spherical phantom targets (volume 0.27-7.70 ml) and 4 clinical targets (volume 0.50-5.70 ml) were calculated using Sequential (phantom) or VOLO TM (clinical) optimizers (Accuray, Sunnyvale, CA, USA). Dose conformity, volume of 12 Gy isodose (V12Gy) as a measure for dose gradient, and treatment time were recorded for different prescribed isodose levels (PILs) and collimator settings. In addition, isocentric irradiation of phantom targets was examined, with dose homogeneity modified by using different collimator sizes.
Results: Dose conformity was generally high (nCI ≤ 1.25) and varied little with PIL. For all targets and collimator sets, V12Gy was highest for PIL ≥ 80% and lowest for PIL ≤ 65%. The impact of PIL on V12Gy was highest for isocentric irradiation and lowest for clinical targets (VOLO TM optimization). The variability of V12Gy as a function of collimator selection was significantly higher than that of PIL. V12Gy and treatment time were negatively correlated. Plans utilizing a single collimator with a diameter in the range of 70-80% of the target diameter were fastest, but showed the strongest dependence on PIL.
Conclusion: Inhomogeneous dose distributions with PIL ≤ 70% can be used to minimize dose to normal tissue. PIL ≥ 90% is associated with a marked and significant increase in off-target dose exposure. Careful selection of collimators during planning is even more important.
(© 2021. The Author(s).)
Databáze: MEDLINE
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