Evaluation of the conventional positioning for patients with prostate neoplasia using the Brainlab Exactrac X-ray 6D system

Special techniques for radiation therapy innovated cancer treatments by improving the dose distribution in a target volume. It is known that the effectiveness of these treatments requires high precision and accuracy in patient positioning and target to be treated. This work evaluated the patient positioning and isocenter location for a conventional treatment system using the BrainLAB ExacTrac X-Ray 6D 5.5.1/NOVALIS. Approximately 748 fractions were analyzed for the treatment of 20 patients. Average translational errors were found to be largest for the anteroposterior direction (3.05 mm) and smallest for the craniocaudal direction (2.02 mm). Regarding rotational corrections, systematic errors were greater for the lateral rotation (1.46 deg) and smaller in angular motion about the vertical axis passing through the isocenter (0.97 deg). The largest value for the translation average random error was found for the anteroposterior direction (2.5 4 mm) and smallest for the craniocaudal direction (1.96 mm). By making the position correction using a low energy beam of the ExacTrac system, one can obtain better image quality and lower dose absorbed by the patient, when compared to radiographic films. Furthermore, the position correction is done daily and automatically by the robotic table, ensuring that the delivered dose is the one prescribed in the treatment planning. (author)