Evaluation of localization errors for craniospinal axis irradiation delivery using volume modulated arc therapy and proposal of a technique to minimize such errors

Setup errors related to isocenter shifting should be minimized in order to provide the patient with the most dosimetrically accurate treatment possible. Errors of 1-2 mm can negatively affect the quality of the delivered treatment, most notably in the arc junction area, but the deterioration of the treatment plan accuracy is not as problematic as in the cases of larger errors such as 5-10 mm. By employing a new planning technique, the dose differences due to setup errors can be greatly reduced.