Date of Graduation


Document Type

Thesis (MS)

Program Affiliation

Medical Physics

Degree Name

Masters of Science (MS)

Advisor/Committee Chair

David Followill, Ph.D.

Committee Member

Stephen Kry, Ph.D.

Committee Member

Paola Alvarez, M.S.

Committee Member

Peter Balter, Ph.D.

Committee Member

Dershan Luo, Ph.D.

Committee Member

Francesco Stingo, Ph.D.


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.


OSLD, small field dosimetry, stereotactic radiosurgery, RPC, phantom



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