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SU‐FF‐J‐26: A Phantom Study to Assess the Feasibility of Using ExacTrac for Patient Setup for Fractionated Stereotactic Radiotherapy (SRT) Technique
Author(s) -
Gete E,
Moiseenko V
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2760531
Subject(s) - imaging phantom , isocenter , radiosurgery , nuclear medicine , absolute deviation , stereotactic radiotherapy , biomedical engineering , medicine , mathematics , radiation therapy , surgery , statistics
Purpose: To investigate the feasibility of using ExacTrac for setup error correction for patients treated with fractionated stereotactic (SRT) technique with the BrainLab relocatable mask system. Method and Materials: A phantom study designed to evaluate setup accuracy of the ExacTrac system was performed. An actual treatment process, from making immobilization mask to treatment setup, was simulated. A 3.8 mm diameter lead bb was inserted in a Rando head phantom to represent a mid‐brain target. The phantom was CT scanned with 1 mm slice thickness and 1 mm slice index. A treatment plan was created using BrainScan, with an isocenter placed at the center of the bb. The phantom was setup for treatment with the following two methods: 1. Phantom setup with the BrainLab localizer box. 2. Phantom setup with ExacTrac. Electronic portal images of a treatment field defined by M3 MLC (12×12 mm 2 ) were taken at various gantry and couch angles. Setup accuracies for the above two methods were calculated from the positions of the bb relative to field center. A Lutz test was performed prior to portal image acquisitions to correct for gantry flex. Results: Setup with ExacTrac showed consistently better accuracy compared with the Localizer box setup. Specifically, in Sup‐Inf direction mean deviations of the center relative to the center of the field were 0.3mm (standard deviation 0.1mm) with ExacTrac setup and 0.4mm (0.5mm) for localizer box. For Left‐Right direction deviations were −0.2 (0.3) and 0.4 (0.5); Ant‐Post 0.2 (0.2) and 0.5 (0.2) mm, for ExacTrac and localizer box, respectively. Conclusions: The BrainLab ExacTrac system has a great potential for setup verification and setup‐ error correction for the fractionated SRT technique with the BrainLab relocatable mask system.