학술논문
Is it beneficial to use apertures in proton radiosurgery with a scanning beam? A dosimetric comparison in neurinoma and meningioma patients
Document Type
Report
Author
Source
Journal of Applied Clinical Medical Physics. February 2022, Vol. 23 Issue 2
Subject
Language
English
Abstract
INTRODUCTION Proton radiosurgery was pioneered in the 1960s at the Harvard Cyclotron Laboratory,[sup.1] and over the course of years has evolved with respect to both immobilization and imaging systems. Moreover, [...]
: Purpose: To assess the dosimetric advantages of apertures in intracranial single fraction proton radiosurgery. Materials and methods: Six neuroma and 10 meningioma patients were investigated. For each patient, six plans were computed, with two spot spacing and three aperture settings (no apertures, 5 and 8 mm margin between aperture and clinical target volume [CTV]). All plans were optimized on the CTV with the same beam arrangement and the same single‐field robust optimization (2 mm setup errors, 3.5% range uncertainties). Robustness analysis was performed with 0.5 and 1.0 mm systematic setup errors and 3.5% range uncertainties. CTV coverage in the perturbed scenarios and healthy brain tissue sparing in the surrounding of the CTV were compared. Results: Meningiomas were larger and at a shallow depth than neuromas. In neuromas, spot spacing did not affect OAR doses or the robustness of CTV coverage and the apertures reduced brain dose without any significant impact on CTV robustness. In meningiomas, smaller spot spacing produced a reduction in brain V5Gy and improved robustness of CTV coverage; in addition, an 8 mm margin aperture reduced low and medium brain tissue doses without affecting robustness in the 0.5 mm perturbed scenario. A 5 mm margin aperture caused a reduction of plan robustness. Conclusion: The optimal use of apertures is a trade‐off between sparing of low and medium dose to the healthy brain and robustness of target coverage, also depending on size and depth of the lesion.
: Purpose: To assess the dosimetric advantages of apertures in intracranial single fraction proton radiosurgery. Materials and methods: Six neuroma and 10 meningioma patients were investigated. For each patient, six plans were computed, with two spot spacing and three aperture settings (no apertures, 5 and 8 mm margin between aperture and clinical target volume [CTV]). All plans were optimized on the CTV with the same beam arrangement and the same single‐field robust optimization (2 mm setup errors, 3.5% range uncertainties). Robustness analysis was performed with 0.5 and 1.0 mm systematic setup errors and 3.5% range uncertainties. CTV coverage in the perturbed scenarios and healthy brain tissue sparing in the surrounding of the CTV were compared. Results: Meningiomas were larger and at a shallow depth than neuromas. In neuromas, spot spacing did not affect OAR doses or the robustness of CTV coverage and the apertures reduced brain dose without any significant impact on CTV robustness. In meningiomas, smaller spot spacing produced a reduction in brain V5Gy and improved robustness of CTV coverage; in addition, an 8 mm margin aperture reduced low and medium brain tissue doses without affecting robustness in the 0.5 mm perturbed scenario. A 5 mm margin aperture caused a reduction of plan robustness. Conclusion: The optimal use of apertures is a trade‐off between sparing of low and medium dose to the healthy brain and robustness of target coverage, also depending on size and depth of the lesion.