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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.

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Related in: MedlinePlus

Patient with mask fixation. The system consists of a semicircular metal frame, an upper and a lower mask conformed to the anterior and posterior surfaces of head, two lateral carbon bars for fixing the thermoplastic mask, and a mouth bite.
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Figure 1: Patient with mask fixation. The system consists of a semicircular metal frame, an upper and a lower mask conformed to the anterior and posterior surfaces of head, two lateral carbon bars for fixing the thermoplastic mask, and a mouth bite.

Mentions: The general procedure for FSRT consisted of different phases: - mask fixation; - CT localization; - treatment planning, - and CT verification. The commercial BrainLab mask fixation system (Figure 1) consisted of - a semicircular metal frame; - an upper and a lower mask conformed to the anterior (fronto-zygomatic area) and posterior surfaces (occipital and neck curvature) of head; - two lateral carbon bars for fixing the thermoplastic mask; - a mouth bite which is applied to the patient's upper dentition to avoid any head tilt movement, - and a plastic head rest. An extra rigid strip of plastic is applied across the nose-bridge, underneath the upper mask, to avoid any head rotation. Following fabrication the patient remained in the mask for 30 minutes to minimize the potential thermoplastic shrinkage during cool.


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)

Patient with mask fixation. The system consists of a semicircular metal frame, an upper and a lower mask conformed to the anterior and posterior surfaces of head, two lateral carbon bars for fixing the thermoplastic mask, and a mouth bite.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Patient with mask fixation. The system consists of a semicircular metal frame, an upper and a lower mask conformed to the anterior and posterior surfaces of head, two lateral carbon bars for fixing the thermoplastic mask, and a mouth bite.
Mentions: The general procedure for FSRT consisted of different phases: - mask fixation; - CT localization; - treatment planning, - and CT verification. The commercial BrainLab mask fixation system (Figure 1) consisted of - a semicircular metal frame; - an upper and a lower mask conformed to the anterior (fronto-zygomatic area) and posterior surfaces (occipital and neck curvature) of head; - two lateral carbon bars for fixing the thermoplastic mask; - a mouth bite which is applied to the patient's upper dentition to avoid any head tilt movement, - and a plastic head rest. An extra rigid strip of plastic is applied across the nose-bridge, underneath the upper mask, to avoid any head rotation. Following fabrication the patient remained in the mask for 30 minutes to minimize the potential thermoplastic shrinkage during cool.

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
Related in: MedlinePlus