Treatment accuracy without rotational setup corrections in intracranial SRT

摘要

The aim of this study was to evaluate the impact of actual rotational setup errors on dose distributions in intracranial stereotactic radiotherapy (SRT) with different alternatives for treatment position selection. A total of 38 SRT fractions from 18 patients were retrospectively evaluated with rotational setup errors obtained from actual treatments. The planning computed tomography (CT) images were rotated according to online cone-beam CT (CBCT) images and the dose distribution was recalculated to the rotated CT images using three different patient positionings derived from: 1) an automatic 6D match neglecting rotation correction ( Auto 6 D ) ; 2) an automatic 3D match ( Auto 3 D ) ; and 3) a manual 3D match from actual treatment ( Treat 3 D ) . The mean conformity index (CI) was 0.92 for the original plans and 0.91 for the Auto 6 D plans. The mean CI decreased significantly ( p 0.01 ) to 0.78 and 0.80 for the Auto 3 D and the Treat 3 D plans, respectively. The mean minimum dose of the planning target volume (PTVmin) was 91.9% of the prescribed dose for the original plans and 92.1% for the Auto 6 D plans, while for the Auto 3 D and the Treat 3 D plans PTVmin decreased significantly ( p 0.01 ) to 78.9% and 80.2%, respectively. No significant differences were seen between the Auto 6 D and the original treatment plans in terms of the dose parameters. However, the Auto 3 D and the Treat 3 D plans were statistically significantly inferior ( p 0.01 ) to the Auto 6 D and the original plans. In addition, a significant negative correlation ( p 0.01 , | r | > 0.38 ) was found in the Auto 3 D and the Treat 3 D cases between the rotation error and CI, PTVmin or minimum dose of gross tumour volume. In SRT, a treatment plan of comparable quality to 6D rotation correction can be achieved by using 6D registration without a rotational correction in the selection of patient positioning. This was demonstrated for typical rotation errors seen in clinical practice.PACS number(s): 87.55, 87.57