Identifier

etd-11182010-234139

Degree

Master of Science (MS)

Department

Physics and Astronomy

Document Type

Thesis

Abstract

Purpose: To quantify the accuracy and precision of both target positioning and dose delivery for intracranial radiosurgery delivered with the TomoTherapy Hi-Art System using a non-invasive immobilization device. Methods: Techniques developed by Vinci et al (2007) were refined for the measurement of dose distributions in each principal plane using a CIRS head phantom. Pieces of Gafchromic EBT2 film were cut and digitized using a template developed by Vinci et al (2007). A plan was created for a 2 cm diameter x 2 cm long cylindrical target in the TomoTherapy treatment planning system (TPS) version 3.2.1. Intentional misalignments of 5 mm in each of the principal directions were applied to the phantom prior to treatment delivery. The MVCT feature of the TomoTherapy Hi-Art system was used to correct for these misalignments, and then the treatment was delivered. Measured dose distributions (film) were registered to the calculated dose distributions (TPS planar dose) and compared. Results: Alignment errors (displacement between the midpoints of the measured and calculated 70% dose points; mean ± standard deviation) were -0.15 ± 0.47 mm (range: -1.97 to 0.8 mm), -0.36 ± 0.56 mm (range: -1.25 to 0.63 mm), and -0.67 ± 0.93 mm (range: -3.04 to 0.90 mm) in the superior-inferior, anterior-posterior, and lateral directions, respectively. Positional errors of the 80% dose points in millimeters were 1.28 ± 0.91 (range: -0.09 to 3.62), -0.02 ± 0.96 (range: -2.24 to 1.72), -0.04 ± 0.62 (range: -1.24 to 1.25), 0.64 ± 0.52 (range: -0.35 to 1.55), 0.30 ± 0.52 (range: -1.57 to 1.28), and 0.60 ± 0.46 (range: -0.26 to 2.39) for the right, left, posterior, anterior, inferior, and superior directions, respectively. Conclusions: Using a non-invasive immobilization device, 1.98 mm dose voxel size, and manual lateral couch positioning, the spatial accuracy of dose delivery with the TomoTherapy Hi•Art System was not within 1 mm as hypothesized.

Date

2010

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Parker, Brent C.

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