Abstract
BackgroundTo assess the accuracy of fractionated stereotactic radiotherapy (FSRT) using a stereotactic mask fixation system.Patients and MethodsSixteen patients treated with FSRT were involved in the study. A commercial stereotactic mask fixation system (BrainLAB AG) was used for patient immobilization. Serial CT scans obtained before and during FSRT were used to assess the accuracy of patient immobilization by comparing the isocenter position. Daily portal imaging were acquired to establish day to day patient position variation. Displacement errors along the different directions were calculated as combination of systematic and random errors.ResultsThe mean isocenter displacements based on localization and verification CT imaging were 0.1 mm (SD 0.3 mm) in the lateral direction, 0.1 mm (SD 0.4 mm) in the anteroposterior, and 0.3 mm (SD 0.4 mm) in craniocaudal direction. The mean 3D displacement was 0.5 mm (SD 0.4 mm), being maximum 1.4 mm. No significant differences were found during the treatment (P = 0.4). The overall isocenter displacement as calculated by 456 anterior and lateral portal images were 0.3 mm (SD 0.9 mm) in the mediolateral direction, -0.2 mm (SD 1 mm) in the anteroposterior direction, and 0.2 mm (SD 1.1 mm) in the craniocaudal direction. The largest displacement of 2.7 mm was seen in the cranio-caudal direction, with 95% of displacements < 2 mm in any direction.ConclusionsThe results indicate that the setup error of the presented mask system evaluated by CT verification scans and portal imaging are minimal. Reproducibility of the isocenter position is in the best range of positioning reproducibility reported for other stereotactic systems.
Highlights
Stereotactic radiation techniques in form of radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) are frequently employed in patients with skull base tumors in order to increase the precision of radiotherapy and decrease the potential long-term toxicity of treatment [1,2,3].FSRT using a commercially available stereotactic mask fixation system (BrainLAB AG) has been routinely used at University Hospital Sant’Andrea in patients with skull base tumors since 2006
The results indicate that the setup error of the presented mask system evaluated by CT verification scans and portal imaging are minimal
CT verification Sixteen patients were evaluated in the study for a total of 64 verification CT scans
Summary
Stereotactic radiation techniques in form of radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) are frequently employed in patients with skull base tumors in order to increase the precision of radiotherapy and decrease the potential long-term toxicity of treatment [1,2,3]. FSRT using a commercially available stereotactic mask fixation system (BrainLAB AG) has been routinely used at University Hospital Sant’Andrea in patients with skull base tumors since 2006. An essential prerequisite of a frameless system is that patient fixation and positioning are performed with a high degree of accuracy in order to delivery a safe therapeutic radiation dose. Accuracy of patient positioning reproducibility with a stereotactic mask fixation system using both CT and portal images as in current use in our department is reported and discussed. To assess the accuracy of fractionated stereotactic radiotherapy (FSRT) using a stereotactic mask fixation system
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