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Fractionated stereotactic radiotherapy for skull base tumors: analysis of treatment accuracy using a stereotactic mask fixation system.

Minniti G, Valeriani M, Clarke E, D'Arienzo M, Ciotti M, Montagnoli R, Saporetti F, Enrici RM - Radiat Oncol (2010)

Bottom Line: No significant differences were found during the treatment (P=0.4).The 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Radiation Oncology, Sant' Andrea Hospital, University La Sapienza, via di Grottarossa 1035-1039, 00189, Rome, Italy. gminniti@ospedalesantandrea.it

ABSTRACT

Background: To assess the accuracy of fractionated stereotactic radiotherapy (FSRT) using a stereotactic mask fixation system.

Patients and methods: Sixteen 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.

Results: The 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.

Conclusions: The 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.

Show MeSH
Verification of isocenter position accuracy. During CT localization (A) and CT verification (B) the patient is positioned on the CT couch with the target positioner box aligned with anterior and lateral lasers using the radio-opaque markers (arrows). The amount of isocenter shift between CT localization (planning CT) (C) and CT verification (D) in relation to anatomical skull base cranial structures was then evaluated directly on the CT scans.
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Figure 2: Verification of isocenter position accuracy. During CT localization (A) and CT verification (B) the patient is positioned on the CT couch with the target positioner box aligned with anterior and lateral lasers using the radio-opaque markers (arrows). The amount of isocenter shift between CT localization (planning CT) (C) and CT verification (D) in relation to anatomical skull base cranial structures was then evaluated directly on the CT scans.

Mentions: During CT localization and CT verification 3 radiopaque markers were positioned outside the surface of the localizer box and aligned with both anterior and lateral lasers in order to reproduce the patient position. This alignment permits to assess the repositioning accuracy of BrainLAB mask by evaluating the shift of isocenter position between CT localization (planning CT) and CT verification in relation to anatomical skull base cranial structures directly on CT slices using the GE 16-slice scanner CT console, and this procedure is currently used in clinical practice before stereotactic treatments (Figure 2).


Fractionated stereotactic radiotherapy for skull base tumors: analysis of treatment accuracy using a stereotactic mask fixation system.

Minniti G, Valeriani M, Clarke E, D'Arienzo M, Ciotti M, Montagnoli R, Saporetti F, Enrici RM - Radiat Oncol (2010)

Verification of isocenter position accuracy. During CT localization (A) and CT verification (B) the patient is positioned on the CT couch with the target positioner box aligned with anterior and lateral lasers using the radio-opaque markers (arrows). The amount of isocenter shift between CT localization (planning CT) (C) and CT verification (D) in relation to anatomical skull base cranial structures was then evaluated directly on the CT scans.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2823752&req=5

Figure 2: Verification of isocenter position accuracy. During CT localization (A) and CT verification (B) the patient is positioned on the CT couch with the target positioner box aligned with anterior and lateral lasers using the radio-opaque markers (arrows). The amount of isocenter shift between CT localization (planning CT) (C) and CT verification (D) in relation to anatomical skull base cranial structures was then evaluated directly on the CT scans.
Mentions: During CT localization and CT verification 3 radiopaque markers were positioned outside the surface of the localizer box and aligned with both anterior and lateral lasers in order to reproduce the patient position. This alignment permits to assess the repositioning accuracy of BrainLAB mask by evaluating the shift of isocenter position between CT localization (planning CT) and CT verification in relation to anatomical skull base cranial structures directly on CT slices using the GE 16-slice scanner CT console, and this procedure is currently used in clinical practice before stereotactic treatments (Figure 2).

Bottom Line: No significant differences were found during the treatment (P=0.4).The 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Radiation Oncology, Sant' Andrea Hospital, University La Sapienza, via di Grottarossa 1035-1039, 00189, Rome, Italy. gminniti@ospedalesantandrea.it

ABSTRACT

Background: To assess the accuracy of fractionated stereotactic radiotherapy (FSRT) using a stereotactic mask fixation system.

Patients and methods: Sixteen 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.

Results: The 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.

Conclusions: The 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.

Show MeSH