ESTRO 2023 - Abstract Book

S1658

Digital Posters

ESTRO 2023

The Brainlab Exactrac Dynamic system (ED) is composed of two kV X-ray tubes on the floor, two ceiling mounted flat panel detectors and a single ceiling mounted receptacle, which contains a structured light projector, two high resolution cameras and an integrated thermal camera. The system automatically performs the pre-positioning of the patient by matching the live 3D surface with the external contour generated by the treatment planning system. Final positioning is achieved by the fusion of stereoscopic X-Ray images and reference computed tomography images. During treatment, thermal data is combined with surface information to monitor the patient. Materials and Methods The ED system incorporated in a Varian TrueBeam STX linear accelerator was tested using the data from 13 patients who received from 1 to 5 cranial stereotactic radiotherapy fractions. A database of 10 more patients is pending analysis to complete this study. Every treatment day, patients were immobilized with 4PI stereotactic mask system. After performing the pre-positioning of the patients with the ED surface guided system, residual errors calculated from kV X-ray stereoscopic images were registered in vertical, longitudinal and lateral axis. The modulus of the vector composed by the vertical, longitudinal and lateral axis was calculated for each fraction of treatment. Results Figure 1 shows the histogram of the vector modulus from all the registered treatment day. It is observed that most of the displacement are between 3.5 and 4.5 mm. The mean value was 4.4±1.9 mm (k=1). The goal of this work was to evaluate the surface guided pre-positioning system accuracy for cranial treatments.

Figure 2 shows each axis residual errors for all patients and for all treatment day. The mean value was 0.4±1.8 mm, 1±3 mm and -3.2±1.3 mm for lateral, longitudinal and vertical position (k=1), respectively.

Conclusion