Program Information
Use of the TLD-300 Glow Curve Shape to Determine Radiological Magnitudes Inside a BR-12 Phantom Exposed to Mammography Beams
I Munoz1 , I Gamboa-deBuen2 , O Avila3 , ME Brandan1*, (1) I Fisica, Universidad Nacional Autonoma de Mexico, Cd Mx (2) I Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Cd Mx (3) Instituto Nacional de Investigaciones Nucleares, Cd Mx.
Presentations
SU-F-702-4 (Sunday, July 30, 2017) 2:05 PM - 3:00 PM Room: 702
Purpose: To measure percentage depth dose and in-depth photon field effective energy by studying TLD-300 glow curves inside a phantom exposed to mammography beams.
Methods: CaFâ‚‚:Tm chips (TLD-300) were exposed to X-ray beams commonly used in clinical mammography at different depths inside a BR-12 phantom. X-rays were generated with Mo/Mo/25,28, Mo/Rh/28,31 and Rh/Rh/31,34 anode/filter/kV combinations. Glow curves were deconvoluted into 7 peaks plus an exponential background, and the High- to Low-Temperature Ratio (HLTR) was evaluated. In-depth effective energies were calculated using a calibration curve that relates HLTR with the beam effective energy. Percentage depth dose was evaluated using the high temperature peak, P5. Measurements were compared to Monte Carlo simulations performed using PENELOPE-2008.
Results: The HLTR mean change over 3.5 cm of BR-12 was 5%; for the range of studied energies, this corresponds to a change of 2.2 keV in the photon field effective energy. The agreement between effective energies from simulations and measurements is 2% at the phantom surface and 5% at 3.5 cm inside the phantom. Percentage depth dose data shows that dose drops to half the surface value at depths between 0.7 and 1.0 cm, depending on the selected radiological technique. These data agree with simulations and are consistent with independent measurements.
Conclusion: For photon beams with energies similar to those in mammography, in-depth effective energy distributions and percentage depth dose can be established simultaneously in a single measurement, by studying the TLD-300 glow curve. The methods presented, together with the appropriate calibration, could be extended to other radiological techniques involving low energy photon beams. The measured change in effective energy within the phantom might be used to determine other quantities related to the photon field ionization density (such as Linear Energy Transfer).
Funding Support, Disclosures, and Conflict of Interest: Partial funding provided by DGAPA-UNAM, Grants IN105813 and IN107916.
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