ESTRO 2023 - Abstract Book

S1411

Digital Posters

ESTRO 2023

bases, takes less than one minute. Figure 1 shows the array’s response parameters towards x- and y-shifts and spot size changes of the beam (top panels), as well as towards energy range changes of the beam (bottom panel) for one example beam line.

Figure 1: Top panels show the sensitivity of the QA parameter towards beam shifts in x- and y-directions, as well as to variations of the beam spot size, each measured at an energy of 226.7 MeV. The sensitivity towards energy range changes is characterized by the distal slopes, shown here as linear fits (bottom panel). Conclusion The prototype array offers a fast way to determine and track the spot position, spot size and energy range of the beam in daily QA measurements.

PO-1700 Size of mechanical isocenter of Varian accelerators – which accelerator is the best for SGRT

P. Kukolowicz 1 , M. Tarchalski 2 , D. Sa ł kowski 3

1 Maria Sklodowska-Curie National Research Institute of Oncology, Medical Physics Department, Warsaw, Poland; 2 Maria Sklodowska-Curie National Research Institute, Medical Physics Department, Warsaw, Poland; 3 Maria Sklodowska-Curie National Research Institute, Medical Physics Department , Medical Physics Department, Warsaw, Poland Purpose or Objective The safety and effectiveness of the stereotactic techniques require high geometric precision of the accelerator. The AAPM142 report recommends that the diameter of the mechanical isocenter (for the gantry, collimator, and treatment table) should not exceed 1mm. We have built an optical system for very precise measurement in 3D of the mechanical isocenter of accelerators. We have measured the isocenter of 5 accelerators installed at our hospital. We will present our measurement system and the results of the measurements we carried out for our accelerators. Materials and Methods The optical system consists of two cameras, a workstation, and a measurement target. Two cameras are mounted on a horizontal bar which is located on the mobile platform. The design enables the measurement of all rotational movements of the accelerator, gantry, collimator, and table. During the measurement, the cameras track the position of the target