ESTRO 2024 - Abstract Book

S3484

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

References:

Milano, Grimm, Niemierko, et al., Single- and Multifraction Stereotactic Radiosurgery Dose/Volume Tolerances of the Brain. Int J Radiat Oncol Biol Phys. 110. 68-86. 2020

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Digital Poster

Impact of VOLO, VOLO ULTRA and RayStation on the treatment plan parameters for the Radixact system

Noelia Suárez Álvarez 1 , Rodrigo Astudillo Olalla 1 , Marina Gutierrez Ruiz 1 , Fernando Gómez Enríquez 1,2 , Guillermo Camacho de la Vega 1 , Jorge Alonso Muriedas 1 , Samuel Ruiz Arrebola 1 , Paula Delgado Tapia 1 , Juan Ignacio Raba Díez 1 , Andrés Vázquez Rodríguez 1 , Rosa Fabregat Borras 1 , Maria Teresa Pacheco Baldor 1 , Pedro José Prada Gómez 1 1 Hospital Universitario Marqués de Valdecilla, Radiation Oncology, Santander, Spain. 2 Complejo Asistencial de Zamora, Radiation Oncology, Zamora, Spain

Purpose/Objective:

The new VOLO ULTRA optimizer from Accuray aims to improve the optimization and dose calculation speed and to remove the overlap priority for the structures. It features an optimizer with a gradient-based algorithm, as opposed to the previous system (VOLO), which utilized a Non-Voxel Broad Beam (NVBB) calculation algorithm. The objective of this study was to evaluate the performance of these two systems in comparison to the RayStation TPS (RaySearch Lab), which is routinely employed in our department for creating patient plans for our Radixact machine.

Material/Methods:

We used 5 different targets contoured on the cylindrical Virtual Water phantom and 48 plans were optimized using three different systems: VOLO, VOLO ULTRA and RayStation. In each case, the plan parameters were fixed (pitch, field width, dynamic jaws, grid resolution) and a pre-defined set of constraints and priorities was used. The number of iterations was set to 60 (split in 3 rounds of 20 iterations) and the targets were prescribed to 60Gy in 30 fractions. The leaf open/close time cut-off parameter in VOLO ULTRA was kept to 20ms to equate the conditions between the three optimizers.

Beam modulation is linked to the modulation factor (MF). This parameter is chosen directly or indirectly depending on the system:

▪ In VOLO, the maximum MF available can be directly chosen in the TPS. ▪ In VOLO ULTRA, the modulation is indirectly controlled by manually choosing a maximum Beam On-Time or using the “accelerate treatment” option. ▪ The Delivery Time Factor (DTF) is a parameter that multiplies the delivery time required to irradiate the prescription dose to the target uniformly. According to Hagiyashi et al (2023), a DTF between 1.2 and 2