Characterization of Oslds For Use In Small Field Photon Beam Dosimetry

<p>The goal of this study was to redesign a Radiological Physics Center (RPC) mailable remote audit tool used for stereotactic radiosurgery (SRS) single beam dosimetry. A prototype phantom was designed and built housing nanoDot (Landauer Inc., Glenwood, IL) Al₂O₃:C optically stimulated luminescence dosimeters (OSLDs) whose visible active luminescent area has been masked. The phantom has two measurement points with two OSLDs at each location and a film insert for localization purposes only. The masked OSLDs were characterized accounting for various correction factors associated with OSLD dose calculations. The uncertainties for each correction factor were also investigated. It was determined that the linearity, depletion, fading, and energy correction factors were identical to the RPC commissioning data for non-masked OSLDs. The element correction factor (ECF) for masked OSLDs must be determined separately. Two new correction factors were introduced to the OSL dose calculation formula, scatter and field size dependence factor. The field size dependence factor was proven to be unity. The minimum field size the masked OSLD system can accommodate as an audit tool was determined to be 10 mm diameter field for circular cones or 1 x 1 cm² field sizes. The overall system uncertainty was 3.72% (95% C.I.) for irradiations performed using a 1 x 1 cm² field size. The uncertainty was suitable in advocating a ±5% acceptance criterion for RPC remote audits. Feasibility studies were performed at various locations on multiple SRS treatment configurations. CyberKnife, linac based cones, and MLC trial audits produced an average RPC OSLD measured to institution reported dose ratio of 0.982 with a standard deviation of 0.036.</p>

Name thesis:degree_name

Masters of Science (MS)

Level thesis:degree_level

Thesis (MS)

Year dc:date.available

2013

Author dc:creator

• Pham, Christopher

Contributors dc:contributor

• David Followill, Ph.D.
• Stephen Kry, Ph.D.
• Paola Alvarez, M.S.

• OSLD
• small field dosimetry
• stereotactic radiosurgery
• RPC
• phantom
• Medicine and Health Sciences

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/401

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-1439